UNIVERSITY OF ILLINOIS library book VOLUME Digitized by the Internet Archive in 2016 https://archive.org/details/internationallib02inte INTERNATIONAL LIBRARY OFTECHNOLOGY A SERIES OF TEXTBOOKS FOR PERSONS ENGAGED IN THE ENGINEERING PROFESSIONS AND TRADES OR FOR THOSE WHO DESIRE INFORMATION CONCERNING THEM. FULLY ILLUSTRATED AND CONTAINING NUMEROUS PRACTICAL EXAMPLES AND THEIR SOLUTIONS WORKING CHILLED IRON GEAR CALCULATIONS GEAR CUTTING GRINDING BENCH, VISE, AND FLOOR WORK ERECTING SHOP HINTS TOOLMAKING GAUGES AND GAUGE MAKING DIES AND DIE MAKING JIGS AND JIG MAKING SCRANTON : INTERNATIONAL TEXTBOOK COMPANY 2-B Copyright, 1901, by The Colliery Engineer Company. Copyright, 1903, by International Textbook Company. Entered at Stationers’ Hall, London. Working Chilled Iron : Copyright, 1901, by The Colliery Engineer Company. Entered at Stationers’ Hall, London. Gear Calculations: Copyright, 1901, by The Colliery Engineer Company. Copyright, 1903, by International Textbook Company. Entered at Station- ers’ Hall, London. Gear Cutting : Copyright, 1901, by The Colliery Engineer Company. Copy- right, 1903, by International Textbook Company. Entered at Stationers’ Hall, London. Grinding: Copyright, 1901, by The Colliery Engineer Company. Entered at Stationers’ Hall, London. Bench, Vise, and Floor Work: Copyright, 1901, by The Colliery Engineer Company. Copyright, 1903, by International Textbook Company. En- tered at Stationers’ Hall, London. Erecting: Copyright, 190i, by The Colliery Engineer Company. Copyright, 1903, by International Textbook Company. Entered at Stationers’ Hall, London. Shop Hints: Copyright, 1901, by.THE Colliery Engineer Company. Copyright, 1903, by International Textbook Company. Entered at Stationers’ Hall, London. Toolmaking, Parts 1-3: Copyright, 1901, by The Colliery Engineer Company. Entered at Stationers’ Hall, London. Toolmaking, Part 3 : Copyright, 1903, by INTERNATIONAL TEXTBOOK COMPANY. Entered at Stationers’ Hall, London. Gauges and Gauge Making: Copyright, 1901, by The Colliery Engineer Com- pany. Copyright, 1903, by International TEXTBOOK Company. Entered at Stationers’ Hall, London. Dies and Die Making : Copyright, 1901, by The Colliery Engineer Company. Copyright, 1903, by International Textbook Company. Entered at Sta- tioners’ Hall, London. Jigs and Jig Making: Copyright, 1901, by The Colliery Engineer Company. Copyright, 1903, by International Textbook Company. Entered at Station- ers' Hall, London. All rights reserved. \ lt2Ba BURR PRINTING HOUSE, FRANKFORT AND JACOB STREETS, NEW YORK. Q3.1.1 V. ZL.&opO l PREFACE The International Library of Technology is the outgrowth of a large and increasing demand that has arisen for the Reference Libraries of the International Correspondence Schools on the part of those who are not students of the Schools. As the volumes composing this Library are all printed from the same plates used in printing the Reference Libraries above mentioned, a few words are necessary regarding the scope and purpose of the instruction imparted to the students of — and the class of students taught by — these Schools, in order to afford a clear understanding of their salient and unique features. The only requirement for admission to any of the courses offered by the International Correspondence Schools is that the applicant shall be able to read the English language and to write it sufficiently well to make his written answers to the questions asked him intelligible. Each course is com- plete in itself, and no textbooks are required other than those prepared by the Schools for the particular course selected. The students themselves are from every class, trade, and profession and from every country; they are, almost without exception, busily engaged in some vocation, and can spare but little time for study, and that usually outside of their regular working hours. The information desired is such as can be immediately applied in practice, so that the student may be enabled to exchange his present vocation for a more congenial one or to rise to a higher level in the one he now pursues. Furthermore, he iii *>8216 IV PREFACE wishes to obtain a good working knowledge of the subjects treated in the shortest time and in the most direct manner possible. In meeting these requirements, we have produced a set of books that in many respects, and particularly in the general plan followed, are absolutely unique. In the majority of subjects treated the knowledge of mathematics required is limited to the simplest principles of arithmetic and men- suration, and in no case is any greater knowledge of mathematics needed than the simplest elementary principles of algebra, geometry, and trigonometry, with a thorough, practical acquaintance with the use of the logarithmic table. To effect this result, derivations of rules and formulas are omitted, but thorough and complete instruc- tions are given regarding how, when, and under what circumstances any particular rule, formula, or process should be applied; and whenever possible one or more examples, such as would be likely to arise in actual practice — together with their solutions — are given to illustrate and explain its application. In preparing these textbooks, it has been our constant endeavor to view the matter from the student’s standpoint, and to try and anticipate everything that would cause him trouble. The utmost pains have been taken to avoid and correct any and all ambiguous expressions — both those due to faulty rhetoric and those due to insufficiency of statement or explanation. As the best way to make a statement, explanation, or description clear is to give a picture or a diagram in connection with it, illustrations have been used almost without limit. The illustrations have in all cases been adapted to the requirements of the text, and projec- tions and sections or outline, partially shaded, or full-shaded perspectives have been used, according to which will best produce the desired results. Half-tones have been used rather sparingly, except in those cases where the general effect is desired rather than the actual details. It is obvious that books prepared along the lines men- tioned must not only be clear and concise beyond anything PREFACE v heretofore attempted, but they must also possess unequaled value for reference purposes. They not only give the maximum of information in a minimum space, but this information is so ingeniously arranged and correlated, and the indexes are so full and complete, that it can at once be made available to the reader. The numerous examples and explanatory remarks, together with the absence of long demonstrations and abstruse mathematical calculations, are of great assistance in helping one to select the proper formula, method, or process and in teaching him how and when it should be used. Four of the volumes of this library are devoted to subjects pertaining to shop and foundry practice. The present volume, the second of the series, treats on the following subjects: working chilled iron, gear calculations, gear cutting, grinding, bench and vise work, floor work, erecting, shop hints, toolmaking, gauges, dies, and jigs. All these subjects have been treated very fully and every care has been taken to represent the best modern prac- tice. The papers on Grinding will serve as a guide to those who operate grinding machines and also to manufac- turers in selecting wheels best adapted to the work. The papers entitled Bench, Vise, and Floor Work, and Erec- ting include a thorough treatment on the subject of files and filing, laying out work, and the various types of laying out plates, and the erecting of various classes of machinery. Special attention is called to the papers bear- ing the titles Toolmaking, Gauges and Gauge Making, Dies and Die Making, and Jigs and Jig Making. Each subject has been treated in a very thorough and exhaustive manner and should prove invaluable to any one interested in toolmaking. The method of numbering the pages, cuts, articles, etc. is such that each subject or part, when the subject is divided into two or more parts, is complete in itself ; hence, in order to make the index intelligible, it was necessary to give each subject or part a number. This number is placed at the top of each page, on the headline, opposite VI PREFACE the page number; and to distinguish it from the page number it is preceded by the printer’s section mark (§). Consequently, a reference such as § 37, page 26, will be readily found by looking along the inside edges of the headlines until § 37 is' found, and then through § 37 until page 26 is found. International Textbook Company. CONTENTS Working Chilled Iron Section Page Turning Parallel Rolls 7 1 Turning Rolls With Concentric Grooves 7 9 Grinding Chilled Rolls 7 17 Corrugating Rolls 7 20 Planing Chilled-Iron Dies 7 23 Gear Calculations Gearing 17 1 Spur Gears 17 1 Proportions for Gear-Teeth 17 8 Rules for Spur-Gear Calculations ... 17 9 Laying Out Teeth 17 17 Involute System 17 18 Cycloidal System 17 26 Bevel Gears 17 33 Worm-Wheels and Worms 17 41 Worm-Wheel Calculations 17 44 Worm Calculations 17 46 Gear-Cutting Systems and Processes 18 1 Methods and Processes 18 2 Duplication System 18 5 Formed-Cutter Process 18 5 Templet-Planing Process 18 20 Generation System 18 22 Conjugate-Tooth Method*^ 18 22 vii Vlll CONTENTS Grinding Section Page Introduction 186 1 Grindstones and Oilstones . 18 6 2 Grinding Wheels 186 7 Abrasive Materials 186 7 Manufacture and Use of Emery Wheels 186 11 Polishing and Buffing .... 186 20 Selection of Grinding Wheels . 186 25 Hand Grinding 186 27 Hand Surfacing Machines . 186 28 Tool Grinding 186 32 Hand Tool Grinding .... 186 32 Machine Tool Grinding . 186 34 Machine Grinding 186 41 Grinding Solids of Revolution . 186 42 Advantages of Grinding . . . 19 1 Selection and Use of Grinding Wheel . 19 3 External Grinding 19 16 Internal Grinding 19 37 Surface Grinding Cutter and Reamer Grinding . 19 45 19 47 Purpose of Tool Grinding . 19 47 Tool Grinding Machine . 19 48 Examples of Cutter and Reamer Grinding 19 50 Lapping 19 63 Bench, Vise, and Floor Work Introduction 20 1 Bench and Vise Work .... 20 2 Tools and Fixtures Employed . 20 2 Chipping 20 19 Files and Filing 20 26 Scrapers and Scraping 21 1 Drills and Drilling 21 6 Broaches and Broaching . 21 9 Reamers and Reaming . 21 15 Inside Thread Cutting . . . 21 18 Wrenches . 21 21 CONTENTS . ix Bench, Vise, and Floor Work — Con - tinued Section Page Outside Thread Cutting 21 28 Laying Out Work 21 36 Subdividing Circles 21 42 Laying Out Plates 21 45 Examples of Laying Out 21 53 Erecting Floor Work 22 1 Blocking 22 1 Jack-Screws and Hydraulic Jacks ... 22 7 Machine Foundations 22 13 Erecting Floor 22 14 Floor Pits 22 19 Use of Erecting Pit 22 25 Driving Fits, Press Fits, and Shrink Fits 22 29 Hoists and Cranes 22 38 Machine Erection 23 1 Lathe Erection 23 1 Planer Erection 23 10 Milling-Machine Erection 23 20 Engine Erection 23 26 Erection of a Horizontal Stationary Engine 23 27 Erection of a Vertical Stationary Engine 23 41 Locomotive Erection .... 23 46 Shop Hints Rigging 24 1 Pinch Bars 24 2 Use of Slings 24 3 Use of Lashings 24 4 Chain Hoists 24 5 Splices 24 6 Knots, Bends, and Hitches 24 11 Erection of a Derrick 24 13 Cleaning Work and Castings .... 24 18 X CONTENTS Shop Hints — Continued Section Page The Soda Kettle 24 18 Pickling Solutions 24 19 Compressed Air for Cleaning .... 24 21 Galvanizing 24 21 Tinning 24 26 Filling and Painting Machine Tools . . 24 28 Notes on Shop Economy 24 28 Cost of Construction 24 28 Time Element in Work 24 30 The Scrap Heap 24 32 Lubricants 24 35 Lubricants for Reducing Friction ... 24 35 Lubricants for Carrying Away Heat 24 41 Power Transmission 24 45 Belting and Shafting 24 45 Heat Insulation 24 54 Miscellaneous Devices 24 56 Babbitt Metal 24 61 Babbitting 24 62 Useful Information 24 69 Toolmaking General Tool-Room Work 25 1 Method of Procedure 25 1 Dimensioning Drawings 25 4 Reading Decimals 25 6 Work of the Toolmaker 25 7 Measurements 25 8 Limitations of Toolmaking 25 13 Special Tools Used in Toolmaking . . 25 14 Cutting Tools and Appliances .... 25 21 Design and Construction of Taps ... 25 21 Dies for Thread Cutting 26 1 Reamers 26 11 Counterbores 26 35 Hollow Mills . . 26 39 Milling Cutters 27 1 CONTENTS xi Toolmaking — Continued Section Page Dividing of the Circle 27 23 Division of Lines 27 34 Gauges and Gauge Making Classification of Gauges 28 1 Accuracy Attainable in Gauge Work . 28 2 Materials Used for Gauges 28 4 Gauge Making 28 6 Plug and Ring Gauges 28 6 Snap Gauges 28 15 Angular Gauges 28 20 Taper Gauges 28 22 Special Gauges 28 42 Dies and Die Making Dies and Punches 29 1 Classification of Dies 29 6 Quality and Design of Dies 29 8 Cutting Dies 29 11 Plain Dies 29 11 Progressive Dies 29 15 Compound Dies 29 18 Laying Out Dies 29 21 Making the Die 29 27 Different Forming Operations .... 30 1 Dies for Forming 30 2 Bending Dies 30 6 The Drawing Process 30 13 Drawing Dies 30 15 Size of Blanks for Drawing and Forming 30 26 Redrawing Dies 30 28 Coining Process 30 31 Jigs and Jig Making Classes and Use of Jigs 31 1 Essential Parts of Jigs 31 2 Types of Jigs 31 2 Xll CONTENTS and Jig Making — Continued Section Page General Requirements of Jigs . . 31 3 Jig Details . 31 6 Guide Bushings . 31 6 Clamping Devices ....... . 31 12 Stop-Pins . 31 15 Jig Making . 31 16 Examples of Jig Design . 31 16 Locating Holes . 31 26 Locating Holes From a Drawing . . 31 26 Locating Holes From a Model . . 31 31 Marking and Recording Jigs . . 31 33 WORKING CHILLED IRON. TURNING CHILLED ROLLS. PARALLEL ROLLS. 1. General Consideration. — In working chilled iron, good results are only possible from good castings; it is necessary, therefore, to see that the castings are free from cracks, blowholes, and dirt, and that the chill is deep enough so that the metal turned off will be of even hardness. In turning any chilled-iron rolls it is necessary to employ special lathes, and a few general rules must be observed in order that the work may be successful: First, the cutting speed must be so slow that the tool will hold its edge until it has done a reasonable amount of work; second, the tools and machine must be of very rigid construction and have a large amount of power, as the working of chilled iron pro- duces severe strains on the machine; third, the tool steel employed must be a high-carbon steel tempered as hard as fire and salt water can make it; fourth, the operator must be patient and be content to turn off fine chips that very much resemble gray hair. 2. Lathes for Turning Parallel Rolls. — Rolls for flouring mills, calendering rolls for paper mills, and rolls for similar purposes, in which a broad flat surface is required, are frequently turned in a special type of lathe, the roll being cast as a hollow cylinder chilled on the outside. This §7 For notice of copyright, see page immediately following the title page. 2 WORKING CHILLED IRON. §7 Fig. §7 WORKING CHILLED IRON. 3 cylinder is turned in the lathe and the ends cut off, after which it is bored and fitted on a center carrying the neces- sary shaft and journals. Then, in the case of flouring-mill and calender rolls, it is ground to a perfect finish while run- ning on its own bearings. Fig. 1 illustrates a common type of roll-turning lathe with the roll in place. In this style, both spindles are made hollow and the roll is introduced through the spindles and held by setscrews b passing through the collars a. In the style of lathe shown, both spindles are fitted with gears, and the roll is driven from both ends, thus relieving the strain on the lathe. It will be noticed that this style of lathe is not provided with a carriage having a feed parallel to the length of the lathe, but simply with a broad tool post d fitted upon a cross-slide c that can be fed along the ways e by means of the feed-screw f. A set of gearing designed to give the proper speed reduction is placed on the end of the lathe at j. 3. Lathes driven from one end only are also made for this work; in this case, the tailstock end of the lathe is made with a hollow spindle through which the roll can be intro- duced. Some classes of rolls have narrow necks cast on them, and in this case the rolls are held during turning jn bearings fitting on the necks in the same manner that the rolling-mill rolls are turned. This will be taken up in con- nection with the description of the turning of rolling-mill rolls. 4. Holding and Driving the Work. — Ordinarily, in turning 10- or 12-inch rolls that are to be bored and mounted subsequently, the roll is held by means of eight setscrews at each end, these setscrews also acting as drivers. Fig. 2 illustrates the general method of driving. In Fig. 1 can be seen the collar a through which the setscrews b are passed to hold the work. The same letters have been used for referring to these parts in Fig. 2. The roll r is centered and held by means of the setscrews b. This method of ad- justing and driving the roll enables the workman to center the chilled part very carefully, so that the amount of turning 4 WORKING CHILLED IRON. §7 required will be as little as possible. There is generally about -J to T 3g- inch of stock to be turned off from chilled rolls, and as the turning process is very slow it is important that the centering be done accurately and carefully. 5. Turning Tools. — The tools commonly employed for turning parallel rolls are flat broad-nosed or wide-faced tools. It is probable that \ in. X 5 in. x 5 in. is about an aver- age size for straight work. There are on the market several brands of steel made especially for turning rolls. In turning parallel rolls it is common to operate two tools at a time, thus turning 10 inches of the face of the roll. At first thought it might seem best to use one tool 10 inches wide, but it is difficult to harden so wide a tool without its crack- ing; narrow tools are far less liable to break, and on the whole there is greater economy of steel and less difficulty experienced in adjusting tools when the two 5-inch tools are employed in place of one 10-inch. All tools for turning chilled iron differ radically from those employed on softer b Fig. 2. §7 WORKING CHILLED IRON. 5 metals, and all the turning is of the nature of scraping, the tools being given but little, if any, clearance. Tools for turning chilled iron are never fed into the work and then traversed along the machine, as is done with softer metals, but are fed straight up to their cut, whether turning a par- allel face of a roll or the bottom or the side of a groove. 6. Grinding Turning Tools. — In order to insure a perfectly straight edge on the tool, it should be ground on a grinding machine provided with a a carriage or special tool holder. The ' tool is hardened as hard as fire and salt water can make it and then traversed across the face of an emery wheel to make the face a b of the tool concave, as shown in Fig. 3. This ’ Fig. 3. leaves two sharp corners a and b. The tool is first set to use one corner; when this becomes Fig. 4. 6 WORKING CHILLED IRON. §7 dull the tool is turned over and the other corner utilized. Fig. 4 illustrates a wet-grinding emery wheel fitted with a slide a upon which the tool can be clamped at b and fed back and forth across the face of the emery wheel, the different adjustments being obtained by means of hand wheels c and d. The carriage is traversed across the face of the emery wheel by means of the hand wheel e , which operates a pinion engaging with the rack f on the bottom of the carriage a. By means of such a device as this the tools can be accurately and quickly ground. 7. Cutting-Off Tools. — Special cutting-off tools are employed for cutting off the ends of the chilled-iron rolls after the bodies have been turned to size. Fig. 5 illustrates one of these tools, which is forged from f" X steel and tempered by dipping into salt water. The edge of this tool is about || inch wide and the corners a and b are cut off at an angle of 45°, as shown. Grinding the corners in this man- ner prevents the breaking of the sharp corners that would otherwise occur. The front face of the tool is given a very little clearance, as shown at c. This rarely if ever amounts to more than 5°. This form of cutting-off tool is employed simply for cutting through the chilled iron. After the softer iron at the center of the roll has been encountered, an ordinary cutting-off tool may be substituted for the special one shown. §7 WORKING CHILLED IRON. 7 8. Holding the Tools. — Owing to the great strain to which tools employed for working chilled iron are subject, it is impossible to hold them in any ordinary tool post, and, hence, they must be clamped to the lathe very rigidly. The ordinary methods for holding the tools for turning parallel rolls are clearly shown in Figs. 1 and 2. In Fig. 2 the tool c is set on the carriage h and clamped down by means of the strap e, which is held in position by two bolts f. The tool is forced against the rolls by means of a series of set- screws g. Care must be taken to see that the front face of the rest is close to the roll, as shown at i. The closer this rest is to the roll, the less danger there will be of breaking the front face of the tool. The flat tools employed for this work may be originally \ in. X 5 in. X 5 in., but they are subsequently ground parallel to one axis only. If the tool is ground on one face only, but two cutting edges can be obtained from one grinding. If the tool is ground on both edges, as, for instance^* and k , four cutting edges will be obtained. When these have been dulled, the tool is ground again, and each succeeding grinding makes it narrower. Tools can be used until they become so narrow that they can no longer be held by the clamps e. In Fig. 1, the clamps cafi be seen at g\ in this case very narrow tools are being employed and packing pieces h are placed behind them for the setscrews i to bear against. The upper edge of the tool c f Fig. 2, is set \ inch below the center of the 10-inch roll. This, together with the concave form of the face, will give the proper amount of clearance. In setting cutting-off tools, they are clamped by means of one or more clamps similar to Fig. 2, and the back end of the tool is set against a setscrew or a packing piece held by two or more setscrews. In the case of cutting-off tools, it is necessary to have them overhang the front edge of the rest i 9 Fig. 2, to a greater extent than in the case of turning tools, and, consequently, it is necessary to have the tool deeper from the top to the bottom, so that it may be stronger. This is why the cutting-off tool shown in Fig. 5 is made 1J inches deep, and as the top face d comes above the center of the 8 WORKING CHILLED IRON. §7 roll, clearance must be allowed on the face c, Fig. 5. After the tools have been clamped in place they are fed to the work by means of the feed-screw f, Fig. 1, and are kept parallel with the face of the work by adjusting the setscrews i. The shavings resemble very fine needles or gray hair. 9. Cutting Speeds. — The cutting speed depends to some extent on the character of the chilled iron being turned, the character of the steel employed, and the number of machines run by one man. In the case of job work, or where one man has to give all his time to a single machine, it pays to run at a comparatively high speed and sacrifice the tools more rapidly, thus gaining a greater showing for the man’s time; but, where it is possible to have matters so arranged that one man can operate five or six roll-turning lathes, a speed of 18 inches per minute is usually considered best, as at this speed the tools will last long enough to do a fair amount of work, and as they remain sharp longer they will produce a better surface. By running a number of machines, a man is able to turn out a good day’s work. In some cases, where a limited amount of work is to be done and time is an important factor, work is run as rapidly as 3 feet per minute, but this is probably the maximum speed at which good work can be done on chilled iron. 10. Feed. — As has already been stated, in turning chilled iron a tool is never fed along the length of the work but at right angles to the face being turned; consequently, the motion that corresponds to a feed must be at right angles to the work. When turning rolls, the feeding is usually done by hand at a rate that rarely if ever exceeds inch per revolution. A portion of the surface of the roll corresponding to the faces of the tools in action is turned to the required diameter; the tools are then reset at another place and another part of the surface equal to that already turned is finished. 11. Cutting Off the Ends. — After the face of the roll has been turned to the correct diameter, it is cut off to §7 WORKING CHILLED IRON. 9 the proper length by means of cutting-off tools. The roll is never entirely cut off on the lathe, but is cut down until it has a narrow neck or, in case the roll was cast hollow, a shell about £ inch thick about the core; it is then removed from the lathe and iron wedges driven into the cut made by the cutting-off tool to force the end off. In case the roll is to be bored out and mounted on a bushing, the boring is done with ordinary tools in another machine, because of the fact that the central portion is soft. TURNING ROLLS WITH CONCENTRIC GROOVES. 12. General Consideration. — Rolling-mill rolls are practically all turned with concentric grooves or with con- centric rings about them, these rings being made by turning away the stock between so as to leave the rings projecting. Practically all rolling-mill rolls for moderate-sized work are cast in a parallel chill and are chilled to such a depth that the grooves will not turn through into the soft metal. Roll- ing-mill rolls may be divided into three classes: those made of chilled iron, called chilled rolls ; those made simply of hard iron cast in a sanfl mold, called sand rolls ; and those made of a mixture of cast iron and steel, called sernisteel rolls. The two latter classes are not so hard as the chilled rolls, and are, therefore, turned in a manner more nearly approaching that employed in the turning of hard castings. We shall here deal simply with the turning of chilled-iron rolls. 13. The Lathe. — The exact form of lathe employed must necessarily depend to a large extent on the size of the rolls operated on. Fig. 6 illustrates a representative type of roll-turning lathe. It will be noticed that the lathe is very powerful, and is provided with double helical gears, so that the pull may be constant and that the teeth of the gears cannot cause hammering or backlash. The lathe is Fig. §7 WORKING CHILLED IRON. 11 provided with a short carriage a for turning the bearings or for other similar work when it is necessary to traverse the carriage along the bed. The lathe is also provided with an ordinary tailstock b having a conical center c. This is em- ployed when turning work between centers. The lathe is made very rigid and its bed is firmly bolted to the founda- tion. The supports d that carry the tool rest e , together with the tool rest, are made very rigid and massive, so that all vibration may be absorbed and there may be no lost motion whatever. 14. Holding the Work. — When the casting for a roll first comes from the foundry, it usually has a large riser head on one end that has to be cut off. This is ordinarily done in a regular engine lathe, and both ends of the roll shaft are trued up and centered in the lathe. Care must be taken to true the roll by the outside of the chill, so that dur- ing the subsequent turning of the chilled part there will be the least possible amount of stock to be removed. The surfaces for the bearings are then turned with the roll sup- ported on ordinary conical centers in the ends of the roll shaft. The tailstock b and center c t Fig. 6, may be em- ployed for this purpose, a regular center being introduced into the face plate /"and the bearing turned by means of a tool or tools supported on a carriage a. 15. After the bearings have been turned either in the regular turning lathe or in an ordinary engine lathe, the roll is mounted in special housings, as shown at g and h . The lower half of the bearing g is supported largely on the bridge d that extends across the lathe and carries the tool rest and the upper half of the bearing li is made adjust- able, one end of it being secured to the column i by means of suitable keys j and the other end held in place by the bolt k. This affords ample bearing surface for the support of the roll during turning and insures the turned portion being concentric with the bearings. The roll must not be rigidly attached to the face plate f, but is driven by means 12 WORKING CHILLED IRON. §7 of a universal coupling /. Sometimes, in order to take up any end motion of the roll, a piece is placed in the center in the end m of the roll and the other end of the piece placed against the center c, thus forcing the roll toward the bear- ing g and taking up all end motion. 16. Turning Tools. — The turning tools employed in turning rolling-mill rolls do not differ greatly in principle from those employed in turning parallel rolls; but in most cases the amount of parallel turning is considerably less, and cheaper tools can be used for the purpose. In turning rolling-mill rolls, higher and stiffer tools must be used for the grooving and similar work, and it would not be prac- ticable, therefore, to use the thin tools ordinarily employed for turning the surfaces of parallel rolls, as the cutting edges would be so far below the center of the roll that they would have an excessive amount of clearance and hence become dull very quickly. 17. A good form of tool employed for surfacing rolling- mill rolls preparatory to grooving them is shown in Fig. 7. This consists of a bar of steel from f inch to 1 J inches square with four grooves cut the entire length of the bar along the middle of each face, as shown. The tool is hard- ened as hard as fire and salt water will make it, and is then ground flat across each face, thus giving four cutting edges, one at each of the four corners. The grooves along the sides are made to reduce the amount of grinding necessary to sharpen the corners. Facing tools are also sometimes made by welding a piece of flat steel to the face of a piece of flat iron to bring the thickness up to an inch or more, then hardening and grinding as in the case of an ordinary tool; this method of facing cutters, however, is not as fig. 7. §7 Working chilled iron. 13 advantageous as the one previously given, as it permits of only one edge, or, at the most, two edges, of the steel being employed as cutting edges. 18. Grooving Tools. — For all grooves having a circu- lar cross-section, very efficient grooving tools may be made by turning up short cylinders of tool steel to the desired diam- eter, hardening them, and grinding the ends true. One of these tools is shown in Fig-. 8. When it is desired to turn a groove to roll ovals, one of these circular tools is simply sunk into the face of the roll a short dis- tance; when it is desired to turn grooves for rolling circular rods, a tool of the proper diameter is sunk into the roll to half of its depth. These tools are ground on both ends and can be used in at least four posi- tions before they require regrinding; i. e., both the front and the back edges at the top and the bottom can be used. 19 . For turning rectangular grooves whose sides are either parallel or perpendicular to the length of the roll, a plain rectangular tool similar to a cutting-off tool is em- ployed, as shown in Fig. 9. These tools, when narrow, are i a b Fig. 9. Fig. 10. made wholly of steel; when wide, they may be made partially of steel and partially of iron, as shown in Fig. 10. Apiece of wrought iron a is split open and worked out on the end to Fig. 8. 14 WORKING CHILLED IRON. §? receive the piece of steel b , which is welded into the wrought iron and hardened, after which the tool is ground and used as though it were a solid steel tool. 20 . For turning rectangular or other polygonal grooves in which some of the faces of the grooves are neither par- allel nor perpendicular to the axis of the roll, it becomes necessary to employ tools having special forms. For roughing out grooves for rolling squares, a tool similar to that shown in Fig. 11 may be employed, this tool being made of a wrought-iron body# with a steel cutting face b. It will also be no- ticed that the point c of the tool has been ground off to reduce the liability of its breaking. After this tool has been sunk into the groove to such a depth as to give the groove approximately its right width at the surface of the roll, another tool having a sharp point is introduced to remove the stock left by the point c. 21 . Sometimes it becomes necessary to face up the sides of grooves, in which case a tool of the style shown in Fig. 12 may be employed. This tool may be made of solid steel, as shown in the illustra- tion, or may be made with a piece of steel welded to the top, as shown in Figs. 10 and 11. It will be noticed that the cut- ting edges #, b , and c are all given clearance, so that the tool can cut before itself, or to the right or the left. In turning irregular grooves, it is frequently necessary to make formed cutting tools. They may be made from solid OJ Fig. 12. §7 WORKING CHILLED IRON. 15 steel or by welding steel on iron, as shown in Figs. 10 and 11, and then grinding the cutting edge to the desired form. Sometimes the cutting edge is formed to approximately the desired form before hardening the tool. The tool is then hardened and the cutting edge ground to fit a templet of the desired form. 22. Clamping and Holding the Tools. — The tools employed in turning rolling-mill rolls are held in a manner very similar to those employed in turning parallel rolls, it always being necessary to clamp the tool as firmly as possi- ble. The rest ^of the lathe shown in Fig. 6 is provided with two T slots n and with rectangular holes in its upper surface, as shown. These rectangular holes are fitted with dogs o and p. The dogs o are similar to the ordinary planer; plug, as shown in Fig. 13; the shank a is square or rectangular, depending on the form of the holes in the rest e y Fig. 6. In many cases these holes are rectangular, and, consequently, the point a is rectangular. The point b of the setscrew is brought into contact with the tool or the blocking. The dog /, Fig. 6, is of the general form shown in Fig. 14, and is arranged to fit into a T slot, as indicated by the dotted lines. The lug a is so formed that the dog can be easily removed from the T slot by simply lifting up on the head of the set- screw b , and when the point c of the setscrew is brought against the work, it will cause the lug a to take hold of the T slot and hold the work firmly in place. The tools are held 16 WORKING CHILLED IRON. §7 from behind and at the sides by means of the dogs shown in Figs. 13 and 14, and are held down by means of the clamps or setscrews r in the clamp s shown in Fig. 6. 23. When tools of the general form shown in Fig. 8, intended for turning circular grooves, are to be clamped, they are held against the work by means of special blocks provided for the purpose, as shown in Fig. 15, a being the block and b the cutting tool. in the slot in the end of the piece a. means of the screw r in the clamp s , Fig. 6. A setscrew is brought to bear against the end e of the block a to crowd the edge c of the cut- ting tool against the work, as indicated by the dotted lines f g. The tool rest d is placed as far under the block b as possible, and in some cases no clamp is placed on top of the block b } the resistance along the edge c being depend- ed on to hold it down against the rest d and The piece a is held by 24. Allowance for Hot Iron. — In turning grooves for rolling-mill work, it is necessary to make the grooves somewhat larger than the standard bars they are intended to roll. To meet these requirements, an allowance of inch per inch is usually considered sufficient. For in- stance, a tool to cut a groove for rolling a 1-inch round bar would have to be 1^ ¥ inches in diameter, and a groove for rolling a 3" X i" flat bar would have to be 3g 3 T inches wide, and similar allowances would be required for all shapes. All the tools employed in roll turning may be finished by grinding after tempering, if so desired. §7 WORKING CHILLED IRON. 17 GRINDING CHILLED ROLLS. 25. General Consideration. — Chilled rolls intended for use in flouring mills, calender rolls for paper-making machinery, and rolls for rolling some classes of sheet metal are finished by grinding. This is done to give a smooth surface and to insure the roll being parallel throughout its length. 26. Grinding Machine. — A machine for grinding flouring-mill rolls is illustrated in Fig. 16. The roll a is mounted in bearings b so that it is rigidly supported and revolved on the bearings on which it will ultimately work, thus insuring that the ground surface will be true with the bearings. The roll must be driven by some flexible coupling so as to allow it to run free in the bearings with no danger of cramping or displacement. This is accomplished by means of the universal coupling shown at c and the driving rod d. This driving rod d extends through the spindle e of the grinding machine and is secured by means of a universal joint at the driving-wheel end of the spindle. The grinding is done by means of two emery wheels mounted on opposite sides of the roll, so that they act as a pair of calipers, the roll being ground between them. The emery wheels are driven by belts / /and g, g and are ad- justed by means of hand wheels, one of which is shown at h. The emery wheels are supported on a carriage i, which is traversed backward and forward on the bed j so that the wheels pass over the entire length of the roll. The roll is revolved by means of the belt k running upon a large band- wheel l shown at the end of the machine, and the machine is arranged with suitable mechanism for traversing the car- riage automatically, the length of the traverse being ad- justed by means of stops. The emery wheels are mounted as shown in detail in Fig. 17. The emery wheel a is supported on a spindle b provided with conical endsr, c. These conical ends are carried in Babbitt bearings 00 61-70 6. ■ 52 2.07 71-90 7 . .72 2. 46 91-120 9 ' 00 t'' 3 - II 121-180 I 3-38 4 - 26 181-360 21 . 62 6. CO 00 GEAR CALCULATIONS. 23 § 17 however, and especially with wheels having a small number of teeth, the curve so obtained differs considerably from the correct curve and, in these cases, more satisfactory results are obtained by the method explained in the following articles. 52 . Grant’s Involute Odontograph Table. — By this method, for all gears having fewer than 37 teeth, the curve is approximated by two circular arcs — one extending from the pitch circle to the addendum circle and the other from the pitch circle to the base circle — having different radii, the center of the arc for each being on the base circle. The lengths of the radii with which the two arcs are drawn are obtained by the following method: In Table II, which is taken from Grant’s “Treatise on Gear-Wheels,” are two sets of numbers, a part of each set being in two columns. The first set has the general heading Divide by the Diame- tral Pitch and the two columns in this set have the respect- ive headings Face Radius and Flank Radius. This set is to be used with the diametral-pitch system. To find the radius F , Fig. 8, for the face of a tooth for a gear having less than 37 teeth, divide the number in the column headed Face Radius, opposite the number that corresponds with the number of teeth in the gear, by the diametral pitch. To find the radius G of curved part of the flank, divide the corresponding number in the column headed Flank Radius by the diametral pitch. The second set of two columns of numbers is headed Multiply by the Circular Pitch and is to be used with the circular-pitch system. It is used in the same manner as the first set, except that the numbers taken from the table are to be multiplied by the circular pitch. Applying this method to the diametral-pitch gear of Art. 50 , in which the number of teeth is 24 and the pitch 3, we proceed as follows: To find the radius of the face, we look in the first column for the number 24 and in the same horizontal line in the column headed Face Radius, we find the number 3.64, which, divided by the pitch, gives us 24 GEAR CALCULATIONS. §17 3.64 -r- 3 = 1.21 inches as the radius A of the face. In the same horizontal line and in the column headed Flank Radius, we find the number 2.24; this number divided by 3 gives us 2.24 -f- 3 = .75 inch, nearly, as the radius G of the flank. 53. Odontograph Table for Gears Having More Than 36 Teeth. — An inspection of Table II shows that for gears having more than 36 teeth there is but one column of figures under each of the respective headings of diametral pitch and circular pitch. The reason is that the whole curve is drawn with a single radius, whose length is deter- mined by the general method already explained. It is con- stant for all gears the numbers of whose teeth are included in the several pairs of numbers given in the column headed No. of Teeth; for instance, the length of the radius for all numbers of teeth from 37 to 40 is determined by the use of the numbers in the horizontal line in which these numbers occur. Example. — What is the length of the radius for the curves of the teeth of a gear having 64 teeth, 1.473 circular pitch ? Solution. — Since the number of teeth lies between the num- bers 61-70 in the first column of the table, and the pitch is in the circu- lar-pitch system, we multiply the pitch by the number 2.07, which is found in the second set of figures at the right of the numbers 61-70 and in the same horizontal row. Performing the multiplication, we get 1.473 X 2.07 = 3.05, say 3 in., as the length of the radius. Ans. 54. Completing the Tooth Outline. — With any of the foregoing methods of constructing the tooth outline, the flanks of the teeth are radial between the base circle and the working-depth circle; this part of the outline is therefore made to coincide with the straight line from the center O of the pitch circle to the point where the curved portion of the outline intersects the base circle, as is shown by the line OI in Fig. 8. A fillet from the working-depth circle connects the radial portion of the outline with the root circle and completes the outline of the tooth. Brown & Sharpe make the radius of this fillet equal to one-seventh the width of a space at the addendum circle. GEAR CALCULATIONS. 25 §17 55. Minimum Number of Teeth. — The smallest number of teeth that should be used in a cut gear whose teeth are laid out by the method of single-arc approxima- tion is 30; with a smaller number, the difference between the curve obtained by this method and the correct curve is so great as to cause the teeth to work unsatisfactorily. By using Grant’s odontograph table in the manner explained, it is possible to make satisfactory gears that have as few as 10 teeth. 56. Grant’s Rule for Rack Teeth. — The teeth of a rack that is to mesh with an involute gear of a given pitch may be laid out by the following method, which is known as “Grant’s rule for rack teeth.” First draw the addendum, pitch, and root lines, Fig. 9, making the dis- tances A and B each equal to 1 divided by the diametral pitch, and the distance C equal to one-eighth of A. On the pitch line lay off the pitch distances D, D , and divide them into the two parts t and s , corresponding, respectively, to the thickness of the teeth and the width of the spaces on the pitch line. Draw the sides of the teeth from the working-depth line to the line a a , which is drawn half-way between the pitch line and the addendum line, as straight lines making angles of 15° with lines that pass through the pitch points perpendicular to the pitch line. Draw the; outer half of the addendum as a circular arc having a 26 GEAR CALCULATIONS. 17 radius R whose length is 2.1 divided by the diametral pitch, or .67 multiplied by the circular pitch. A fillet from the working-depth line to the root line completes the outline of each side of the tooth. CYCLOIDAL SYSTEM. 57. Definition of a Cycloid. — In mathematics, a cycloid is a path described by a point on the circumference of a circle as the circle rolls upon a straight line; thus, the curve a be, Fig. 10 (a), described by the point b as the circle j rolls along the line a c is called a cycloid. The circle j is called a describ- ing, or rolling, circle. When the describing circle, as h , Fig. 10 (b), rolls upon the out- side of another circle, as g, the curve e d described by any point on the describing circle, as e , is called an epicycloid. If the describing circle, as i, rolls on the inside of another circle, as g, the curve e f generated by any point of the describ- ing circle, as e , forms what is called a hypocycloid. If the circle i has a diameter just one-half the diameter of the circle g, the hypocycloid will be a straight line, or a diam- eter of the circle g. If the diameter of the circle i is less than half that of the circle g, the hypocycloid will have a curve as shown at e f ’ while if the diameter of i is more than half the diameter of g, the curve will extend to the left from the point e instead of to the right of e. 58. Laying Out Cycloidal Teeth. — The pitch, addendum, working depth, and root circles are drawn, and the pitch, thickness of teeth, and width of spaces on the pitch circle are laid off as described for the involute system. fig. io. GEAR CALCULATIONS. 27 § I? After this the outlines of the teeth may be drawn as theo- retical curves, but the more common method is to draw the curves for the faces and flanks as circular arcs that agree very closely with the theoretical curves. 59. Grant’s Cycloidal Odontograph Table. — One of the most accurate practical methods o£. laying out the approximate curves of cycloidal teeth by means of circular arcs has been devised by Mr. George B. Grant. The lengths of the radii of the arcs and the location of their centers are determined by the pitch and number of teeth of the gear, in conjunction with a table of factors that apply to gears of all sizes from a 10-tooth pinion to a rack. Any two gears with teeth of the same pitch and length laid out by this method will work satisfactorily with each other. The base of the odontograph table is a describing circle whose diameter is equal to the radius of the 12-tooth pinion; a gear laid out by its use will therefore work satisfactorily with any gear having the same pitch and general tooth dimensions, and with theoretical cycloidal curves con- structed with a describing circle whose diameter is equal to the radius of the 12-tooth pinion. GO. Use of Grant’s Cycloidal Odontograph Table. The first step in the use of the odontograph table is the location of the circles on which lie the centers of the arcs, Fig. 11. These circles are concentric with the pitch circle, and their distances from it are determined in the following manner : In Table III, which is taken from Grant’s “ Treatise Divide by the Diametral Pitch. Multiply by the Circular Pitch. 28 GEAR CALCULATIONS. §17 cq O O o o NO On ro O M W Cn| ° £ ) ° M VO ro CM CM CM M M M M c/3 Q 1-1 cm ro cS lO Tt- 0 o VO ro ro O O CM NO o lO VO rO oo VO On NO rh ro CM M o o ON On Rad. CM 1 ro $ 1 } 4 CM w W “ ” “ M M i-i M CM fO 't T in lO VO t^-00 On O M OOOOOOOOOOOOOhhm M ro Tj- io !>. CO 'O 'O 'O vO O 'O ^ MD On fo O ro r^. !>.!>. 00 On On On C/5 M Dis. B. o o O vo p NO to no O ro NO cm ro rj- 00 ^ | "tf rf cm vo w On N no 4 ro to On ro S Q X O.S (0 «2-o §5 0) 0) C < Jj tC +j Ch ►P g S o ■s3«" O & ofe Pi Pi Pi PP o £DPP o i^oao o s j 1/3 ' 4 - r. T3 fc 0 S« s Ph ^ g oo o*pp w pp OOOOOOOOOOOOOOOOOOOOOOOO 0 + J+->4-> + J4->4->'^ J -l->+- , ' , - , + J -*- , ' , - , + J + J » J 'l->4->+->+J4->+J4-> + J-M Ph o o*Ph p4phOPhO££SSO£E o*pp £ Ph o pp S c-o <« ® s ^ . oP ijS'O CO Oj 03 8 °u S« C >^£>‘3 3 & aj $ 3 £ g oj 03fo ooooooooooooooooooooooooo 03 C/3 bO bo d d *3 *43 'ft w C/3 C/3 oo bJO o3 rt c d o o — .d ri 2 03 - ^ 0) 03 o Oj^ O d •a.!? 1 3 g g 2»Srt2 + j-UK.i-i asaas-as^ £PgS|||S « S oi Edk ^ o d hP oi hP oi o > PP Pi O +j ^ o. s§5 s *»£ d d.s 151 o £ 03 d a3 ^03 dR §2 03 — ^ *rt rt £ i-P 01 ’ C/3 * ^ 03 . bo d . ,£ ’Jd ! T3 £ • c « • t£i2 bo— C i 03 03 ^ *o £ C/3 Oh ^T£ o o — o^ 03 - . S-, ,« C/3 C/3 3 03 Jh S-h Ij 03 03 03 — £1*1.1 sis s s d d-c o o ... ^ a &>j3 ^ aT «« P £ O bO 03 _ ’ rt 1 rt 1 ' w ^ ^^P2+jis r d’Q H C 1 5tt Cfi cfi ^ bo £ ^■»5i m.s| 'd'hJ-^gd.£ r dcc! £ 5.5 03 -M bO d d o a £" • £ 03 — C ^ ‘^5 S&aill S ^ .£ 03 — 6/5 o bO £ % £.£ o — bo " o . 03 03 s-h t—t ~ ' ■ f C rt bD. 03 03 T3 i_ H gS ^d c d £ § 03 d'-£ d .< a3 : ££^^WOcowfcPOSu GRINDING. 17 § 18 36. Makers of vitrified wheels use as a system of des- ignating grades, the letters of the alphabet, the first letters indicating the softer wheels. To give an idea of the relations of the grades to the work to which each grade is adapted, Table II, published by The Norton Emery Wheel Company, is given. This table agrees quite closely with the system of grading that is used by most of the makers of vitrified wheels. 37. Testing Emery Wheels. — Emery wheels some- times break or burst while running, which accident, in the case of a large wheel, is liable to do considerable damage, besides endangering the life of the workman using it. In most cases where a wheel breaks when running, a careful examination of the conditions reveals some adequate cause other than the inherent weakness of the wheel. To be sure that the wheel is sound and strong when it leaves the fac- tory, the manufacturer should test it by running it for a short time at a higher rate of speed than will be required when the wheel is in actual use. 38. The machine used for such testing must have a cover for the wheel that will arrest the pieces if the wheel should break. The centrifugal force acting to break a wheel is proportional to the square of the number of revolutions made by the wheel; therefore, if the speed is doubled, the centrifugal force is quadrupled. It is customary, in testing wheels for strength, to run them at nearly double their Working speed, such a test being almost sure to break a wheel if it is not free from cracks or other defects. 39. The following table shows the number of revolutions per minute for specified rates of periphery speed, also the stresses per square inch on vitrified wheels at the specified rates of speed. The usual working surface speed is from 5,000 to 6,000 feet per minute; the number of revolutions corresponding to these surface speeds are given in the table. C. S. III.— 3 SPEEDS OF GRINDING WHEELS, 18 GRINDING. § 18 . 4-> '“'S C/D . a 0 O W O 13* 03 00 CO W H C5 O C3 CO lO M lO M CO 8 °S <13 s 0 . 0^5 •2 s 2 p h io co w r< h i- o i.- o co co o oo oi io w o OO oi OS 05 CO CO 05 CO 00 1.0 I) o 0 o3 pi ft CD OS P? os' t-“ o' o' tT CO*' OP of of of 1-7 1 -T t-7 1-7 1-7 C/3 CT c/3 COHrH <4-1 +J Jh ^ 0 y C/3 . a 0 cj03coriHoiHeo ^ 0 ) ft,5 J 0 « (U '- 1 •2 p p.S COOi-HCO'^JOOrHi.-i.-iOJOOOOOOCOOSOS t- oo os -pn id os i-i t- t- io go os 06 oi ci id ^ u F r-> i- GO lO OS t- Ci 1 -H OS CO O l.o O 1-1 O CO -f lO o F 8 Sgl c/3 a* C/3 03 OJ Pi ft Mr-iiriOQOi.'Cs<:(Tt 0 o S b 53 iL Cj O oS 30 £— GO CO i—i OS O ' — I lO r< 00 O C3 C3 CO i ' n p< P So ®M§ IOOSHCOtHOCOODOOthOSOIOCOWOO) C/3 o' C/3 0 > <3 Pi ft ZD CO CD ZD lO t£ CO CO of of r-7 r-7 1 - 7 1 - 7 1 - 7 1-7 Oi 1-1 8 °| & 2 C/3 . P 0 10«i-iC0l0OC000C0100?0STj S O P 03' COrH'rOOt-QlOOOeOTHWOi^OSrHOSOJ f\5 o ■2 p oo^ost-ii-irooocjooicoosooosHricooiTr 12 P.5 oo os of os 30 co of os t- coi-ii^ooco^rcoos^' 03 b 30 £ og tiCOOSHlO^OOOOJt-OSlO^COOSCOOOl 5 0.1 OJOOQOOiOlHOSlOOJOOS CO.t- CO CD lO "aj^r c/3 cr C/3 03 03 Pi ft no ic~ no co co of of i-7 1-7 1-7 r-7 J-, ^ C/3 . G 0 »O 0 y a) 5 o O ti MCDHOOC0300)05HCOH030J10t-CD£-H a. o • 12 p.S iHioi-t-ooooocooscsiOHOOiaoTfosco ajosos-pHi-ios^ofid^odcdcoofoi^i-Hod 0 _ c/3 J-h K* J-l V 03 Pi ft 30 Oi H CO OS O CO 00 30 i-H t-H CO L- O'? £- 00 1 -H ri (Ux m »I c/3 cr C/3 Hri.-oooooicsco'p.i-HOsooi.'-coioio^rcoco i-7 no co of of i-7 1-7 r-7 1-7 ^4+J tH-P <0 o C/3 . §3 03i-it-lOCOCOiOCOij<0)l>CDrH£iiJ 'pi 1-5 i> oo 'pi of ^ 0 F rfS +3 p c/3 cr C/3 r> S-i 03 S Pi ft CO rH p< O 03 OS IO CO CO Tt< i- 03 00 rH 30 rH "If C0 00 30 0S3O03O03l-C03O'^i#C0C0C00iC3 t- co' of i-T i-7 i-T i-7 (_rP C/3 . P 0 ^ *D S O O + J iHl0'^C0'^03t'C0t'iHT)(e0H0S0!30C3O O d> G h 3 pL, ft 2 12 a>5 •- G j3.S £— 00 03 OS OS CO CD "pH 05 CO 00 £— 03 OS CO i— l CO i — 1 ososcoHrcocdsof^i-Hodoiodoiocoos^co III > ^ THOt-iOCOCOiJ®iHi>COHOSt-lOOlO F cs w +3 p OOOSC3 05 i.iC03C^COCOC30iOiHrH T HrHH ^ rH c/3 cr C/3 0 0 ) Pi ft co' i-7 1-7 •saipui ua^ui’BjQ TH03C0H^ioc0£-00O03Hrc000O03HTOC0 rHHrHrHiHC3O!O3C0M GRINDING. 19 § 18 GRINDING. 40. Applications of Grinding. — Emery wheels are used for grinding all kinds of metals; also glass, porcelain, rubber, wood, and leather, including the dressing of kid skins that are used for making gloves. They are made in a great variety of sizes that range from the small wheel used by the dentist and weighing a fraction of an ounce, to wheels feet or more in diameter and weighing 1,000 pounds. They are also made in a variety of shapes for special machines and work. Iron and steel castings, chilled rolls, hollow ware, stove fittings, plow points, car wheels, armor plate, tools for cutting metals and wood, and such special tools as cutters, reamers, saws, etc. ; also spheres and cyl- inders for roller bearings, and the interior surfaces of cylin- ders that must be accurately formed, such as the “ Triple ” cylinders for the Westinghouse air brake, are all ground with emery wheels. The grinding machine is used successfully on the finest work and also on the coarsest. A fine wheel will remove .00001 of an inch of material from a cylinder, while a coarse wheel will grind inequalities from the rough casting with surprising rapidity and apparent ease. Many persons having seen the rapidity with which a large coarse emery wheel will remove irregularities from a casting have attempted to substitute emery wheels for the lathe tool for roughing out work, but as yet this method has not been a success, as it always takes more power, and up to the present time has cost more to reduce metal to dust than to chips. By the use of very large, heavy, automatic machines using large and heavy wheels, it may be possible to reduce the labor and wheel costs so low that it will enable the grind- ing machine to remove large amounts of stock, not only faster, but cheaper than it can be done in the lathe. 41. Object. — The processes of modern grinding maybe said to have three principal objects ; viz. : First , the re- moval, or cutting away, of stock from the piece to be ground. Second, the bringing of pieces to exact specified 20 GRINDING* § 18 dimensions. Third , the production of a satisfactory finish upon the surfaces ground. 42. Possibilities. — The latest improved automatic grinding machines are demonstrating that large wheels driven on rigid machines and with sufficient power will, in many cases of cylindrical grinding, remove a considerable amount of stock cheaper than it can be removed in a lathe. Grinding machines are, therefore, likely to come into more general use, because they can successfully compete with the lathe where accurate work and smooth finish are required. Indeed, the field for grinding by automatic machines has recently been greatly enlarged by improving the design of the machine and using larger wheels. POLISHING AND BUFFING. POLISHING. 43. Object. — Polishing differs from grinding in that it is not done to remove material or change the size and shape of the work, but simply to create a bright or smooth surface. 44. Polishing Wheels and Belts. — Polishing wheels are usually made by covering the periphery of wooden wheels with leather and gluing to this leather a coating of emery. This is done by coating the leather with hot glue, and before the glue becomes dry rolling the wheel in loose emery until -the emery ceases to adhere to it. When used, such wheels are trued, in a sense, by holding an oilstone or other hard substance against them while they are being run. This levels the rough or projecting places. Flat and curved surfaces are polished on the periphery of wheels and more irregular objects are polished by holding and turning them against leather belts covered with emery and running over pulleys, these belts being wide or narrow, tight or loose, according to the shape of the work. GRINDING. 21 §18 When polishing, the work is held in the hand and moved in such a manner that the desired 'finish is produced. Much practice is re- quired to polish fine work, as it is a matter of skill and touch on the part of the workmen. 45. Enclosed Polishing Wheel. — Polishing-wheel ma- chines are usually of a primitive nature. Sometimes they are com- posed simply of two uprights in which are held wooden plugs hav- ing holes in their ends that receive the points of the polishing spindle. There are, however, a few modern machines for polishing, one of which Fig. 5. is illustrated in Fig. 5. The interior of the base a is so formed that the air-current caused by the rotation of the wheel when running will remove all dust caused in pol- ishing and deposit it on the floor behind the machine or in the water tank c. The wheel b rotates in the direction indicated by the arrow. At the back a shield d is so arranged that it can be adjusted to almost touch the face of the wheel. This shield stops the current of 22 GRINDING. §18 air rotating with the wheel and turns one current down- wards through the passage f t while another current passes downwards through the passage g t but both air-currents are discharged at the back of the machine through the opening h. This machine was devised to polish small work. The wheels used in it are covered with leather and coated with emery. 46. Belt Polishing Machine. — Fig. 6 illustrates one form of mount for a polishing belt. In this case, a pulley <2 has been mounted on one end of an ordinary buffing-wheel or grinding-wheel arbor. The belt b passes over this pulley and the outer end is carried on the pulley c , which is sup- ported upon a swinging arm d that is controlled by a brace f. By means of the brace f, the tension on the belt b may be regulated. This belt is coated with glue and emery, or any other suitable polishing material. BUFFING. 47. Distinction Between Polishing and Buffing. Sometimes buffing and polishing are considered one and the same thing, but it is well to make a distinction between them at the point where the finish becomes grainless. 48. Buffing Wheels. — The buffed or grainless finish is obtained by means of soft wheels. These wheels are sometimes made of felt covered with emery, but usually they are formed of layers of cotton cloth that are cut into round blanks about 12 inches in diameter, which have a hole in the center. These round blanks are piled one above the other until there are enough to form a wheel from 2 to 4 inches thick. These are then placed on the arbor of the machine and bound together at the center by collars and a nut. The larger these collars are, the harder will be the wheel when running; the smaller the collars, the softer will be the wheel when running. 18 GRINDING. 23 It should be understood that when this wheel that consists of layers of cotton cloth is in place on the arbor of the machine, the edges of the cloth are presented to the work, or form the periphery of the wheel. In use, this wheel is revolved (if 12 inches in diameter) from 4,000 to G,000 rev- olutions per minute, according to the practice of the operator who may be using it. 49 . The object of using cloth in this manner is to give a yielding wheel into the periphery of which the operator can press the work, which usually is irregular. In this way the cloth is made to rub every corner and curve of the work and the lines of its motion are in all directions, thereby not only polishing all corners and curves, but also giving a grainless surface. 50 . Cutting or Polishing Material Used in Buff- ing. — The cutting or polishing material is used in the form of a cake that is made by compressing tallow, or other heavy grease, together with emery, crocus, flour emery, rouge, and any other material that may be in vogue with the particular operator, some using one kind and some another; the coarser material is used for roughing and the finer material for finishing and “ coloring, ” as it is known in the workshop. This material is applied to the wheel by holding it firmly against the edges of the cloth, as the wheel revolves, until the edges become saturated ; it is also applied from time to time as the operator wishes to change the cutting quality of the wheel. 51 . Applications of Buffing. — Buffing is used for plated ware and for the peculiar surface that is common on bright vases, culinary articles, and lacquered surfaces. Much buffing is done by first cutting down with a rough material on the wheel, then finishing ready for plating. In the workshop this finishing operation is called coloring. In some of the finer grades of work, this is accomplished by holding it against a very soft cotton-cloth wheel that has no cutting material upon it. If the pressure and speed are 24 GRINDING. § 18 suited to the substance of which the article is made, a very- bright surface will be produced. It is a well-known fact that with plated ware the per- fection of the surface after plating will never be greater than the surface on which the plating is deposited. After the article is plated, it is again taken to the soft buffing wheels and colored, which removes all stains from the plating bath and gives that peculiar luster that the operator calls “ color.” Some work is first polished and then buffed, but in such cases the material is usually hard, such as steel, while brass and softer metals are not so treated. 52. Buffing-Wheel Mount. — Fig. 7 illustrates a light buffing-wheel mount that may also be used for small emery wheels. A rag wheel is shown on the left-hand spindle at a. In the style shown, the wheel is mount- ed on a bench stand. Similar wheels are built that are mounted on posts that stand on the floor. The machine is driven by a belt that runs on the pulley l \ and has provision for a second wheel at c. 53. Brush Wheels. — For polishing purposes, wheels are frequently made that are surrounded by bristle brushes, or brushes made of other materials. In using these wheels, the material is applied to the brush either in the form of a wash or a wax, as in the case of buffing wheels or rag wheels. Brush wheels are more expensive than rag wheels and are not extensively used in machine shops. 54. Leather Wheels. — Wheels for polishing purposes are frequently cut from leather. For very small wheels, disks may be cut from thick saddle skirting, while when larger disks are required they are cut from walrus hide, GRINDING. 25 § 18 which can be obtained an inch or more in thickness and makes an excellent polishing wheel. The polishing material is usually mixed with oil or water, oil being preferred. SELECTION OF GRINDING WHEELS. 55 . General Remarks. — When selecting grinding wheels, it is well to understand that the smoothness of the surface required on the work depends on other conditions as well as the size of grains of which the wheel is composed. A fine-grained wheel does not produce a fine surface simply because the wheel is fine. In fact, it may produce a very coarse surface, and a coarse-grained wheel may produce a fine surface, when of the right grade and used at a speed best adapting it to the material being ground. 56 . Grading of Grinding Wheels. — Emery and corundum wheels are made in different grades of hardness, and according to the standards of the Norton Emery Wheel Company, the grade of vitrified wheels is denoted by letters, A being the softest. The grades most commonly used are J, K, L, M, N, O, P, and Q. The grades of elastic or gum wheels are denoted by numbers, which range from 0 to 6, each number being ^ larger than the preceding one; viz., 0, i, f, 1, etc. Numbers 1 to 5 are those most commonly used. Other companies have other systems of grading. Some grade their wheels from A to Z, A being extremely soft and Z extremely hard. The Carborundum Company grade their wheels from D to Y, D being hard and V being very soft. * 57 . Relation Between Grade of Wheel and Work, — Hard-grade wheels retain their particles longer than softer ones; therefore, the softer grades are said to cut sharp , because the particles are torn out by the act of grinding before they become dull, and thus new ones are constantly being exposed to the work. Some kinds of work 26 GRINDING. § 18 require that these particles shall be torn out before they become at all dull, while other kinds of work require that they shall be retained until they become quite dull and smooth. Between these extremes, there is a great variety of work that requires a variety of grades of wheels. Different materials and different shapes of work require different sizes of grain combined with different bonds and grades of hardness. In general, the harder that the mate- rial to be ground is, the softer must the wheel be, and the coarser may it be. With steel, the hardness of the wheel varies inversely with the softness of the material that is to be ground. Brass, copper, and rubber require soft wheels, and rubber very coarse ones. Hardened steel, cast iron, and chilled iron require soft wheels in order that the parti- cles of emery and corundum may be broken out as they be- come dull and thus constantly present new ones to the work. Brass, copper, and rubber require soft wheels in order that the material being ground may not adhere to the wheel, but that the particles of emery may be torn out be- fore the brass or copper can adhere. Soft steel requires a harder wheel than hardened steel, because the particles of emery are not dulled so soon and, entering deeper into the work, are torn out more readily. Hardened steel, cast iron, and chilled iron require soft wheels because these materials dull the particles of emery and corundum very quickly, making it necessary to throw them away rapidly. 58. Glazing. — When grinding hardened steel with a wheel that is too hard, the wheel will be worn bright and smooth and will cut but little. This is known as glazing. When soft steel is ground with a wheel that is too hard for the work, the wheel will fill with steel; for, since the parti- cles remain sharp and enter deep into the soft steel, they cause the steel to adhere to them, especially if there is con- siderable pressure on the wheel. Fine-grained wheels when hard fill and glaze sooner than coarse ones of the same grade; and, when soft, wear away faster than coarse ones of the same grade when cutting the same depth. GRINDING. 27 § 18 HAND GRINDING. 50. General Consideration. — The term liand grinding is generally understood to cover those operations in which the work is held by liand, pressed against the emery wheel, and moved about either with or without the aid of a rest. There is a class of machines in which the work is large and stands still, while the emery wheel, which is mounted in a swinging frame, is moved about so as to grind the surface of the work. GO. Simple Hand Grinding Machine. — The grind- ing machine used in foundries for smoothing castings, and which is illustrated in Fig. 8, is perhaps the most common type of a hand grinding machine. These machines are made in a great variety of sizes, carrying wheels from 3 inches to 3G inches in diameter. The style shown is provided with fig. 8. rests a upon which the work may be placed while it is being ground. For truing emery wheels, truing devices are per- manently attached to the machine and shown below the rests, € being the axis on which the device works, d the truing wheel, and b the handle by means of which it is con- trolled. Whenever the wheel gets out of true, the truing device can be brought into contact with the face of the 28 GRINDING. §18 wheel and moved across the face on the axis c, thus quickly truing the surface of the wheel e. The wheels e are driven by means of a belt on the pulley f. In some cases, similar machines are used where consider- able skill is required to produce the work, but as a rule this type is used only for comparatively rough work. MACHINES EMPLOYING EMERY WHEELS. 61 . Table Machine. — The machine illustrated in Fig. 8 is intended for rough work. Where approximately bearing for the shaft being carried by the bracket c. Above the emery wheel is mounted a table e through which the upper face of the wheel projects. As shown in the illustra- tion, the table is provided with an adjustable fence f for guiding the work on the surface. The table e can be ad- justed by means of the screw shown at the front of the table, to make allowance for wear in the emery wheel or to adjust the depth of cut taken. This machine will produce approximate flat surfaces and is very useful for removing HAND SURFACING MACHINES. flat surfaces are required without special regard 3 being paid to the angles between the faces, a ma- chine of the class illus- trated in Fig. 9 may be Fig. 9. b employed. The illustra- tion shows one bearing and one emery wheel of a machine provided with a surfacing table. The emery wheel a is mounted on a shaft b driven by a belt on the pulley d , one GRINDING. 29 § 18 rough parts from flat surfaces, but is not especially adapted for producing correct angles. The machine is limited to work of such a size that can be easily handled and placed upon the table. 62. Swinging-Frame Machine. — Where large work is to be ground or polished, as, for instance, portions of engine-frame castings and cylinders, and similar work that frequently requires finishing, and where the work is of such great size that it would be impossible to take it to the emery wheel, a machine of the class illustrated in Fig. 10 may be employed. This machine consists of a bracket a fastened to the ceiling that carries the countershaft on which are placed tight and loose pulleys b and the pulleys c. This countershaft is driven by a belt on the pulley b y while the emery wheel is driven by a belt on the pulley c, which drives the pulley e, which is permanently attached to the pulley f The belt on the pulley /"drives a pulley on the emery-wheel 30 GRINDING. 18 shaft, thus imparting power to the emery wheel h. The swinging frame d is supported from the countershaft bear- ings and the swinging frames is counterbalanced by means of a weight m and a suitable rope passing over the pulleys, as shown. The emery wheel h is mounted on a shaft at the end of the swinging frame g and is provided with a yoke / and handles i and./f, by means of which its motion can be controlled. The connecting portion n below the swinging frame d is so arranged that it can swivel in the frame d , and the portion connecting the swinging frame g with the shaft carrying the pulleys e and f is also arranged so that it can swivel. The result is that the emery wheel h can be turned to any angle or into almost any plane, either horizontal or vertical. This enables the operator to grind both surfaces and edges of the work, or to round corners. This class of machine has found a great field of usefulness, especially in the finishing departments of shops producing rather large work, but considerable skill on the part of the operator is required to produce a smooth surface with it. 63. Upright Surface Grinding. — Flat work may also be ground by holding it against the side of an emery wheel similar to that shown in Fig. 8, but this is rather an awkward and difficult method of procedure and, hence, emery wheels have been mounted on vertical axes so that the work may be placed on the side of the wheel and thus ground flat. Such machines are called upright surface grinders and are used to a considerable extent on some classes of work. DISK GRINDERS. 64. All machines using emery wheels have the com- mon disadvantage that it is difficult to keep the surface of the emery wheel true; hence, accurate work cannot be pro- duced by this class of hand grinding machines without placing the machines under special runners and providing truing devices for the wheels. To overcome this difficulty, the disk surface grinders have been brought out. A GRINDING. 31 §18 type of disk surface grinder is illustrated in Fig. 11. The grinding is done by means of emery cloth secured to the steel disks a. These disks are from inch to j- inch thick, are ground perfectly true and parallel, and are provided with a spiral groove on the side running from the cen- ter to the periphery. Emery cloth is then glued or cemented up- on each side of these disks. In cementing the emery cloth on, it is pressed firmly against the disk so as to bed it into the groove. This provides a space into which any particles of emery or grinding dust will pass and so prevent them from scoring the surface of the work. The disks are used until one side is dull and are then re- versed and used until the other side is dull, when they are replaced by other disks and the worn ones recovered. The machine shown illustrates two principles of grinding that may be employed. At the left-hand side of the machine there is a simple flat table b whose upper surface is scraped at exactly right angles to the disk; by holding any flat surface upon this table, a surface at exactly right angles to it can be ground by the disk. fig. li. 65. The manufacturers claim that it is easily possible to grind small work within the limit of .001 inch on these ma- chines. When it is desired to grind at any other angle than a right angle, an attachment similar to that shown at the right-hand side of the illustration may be used. This is provided with a graduated circle on the piece c by means of 32 GRINDING. §18 which the table can be set at any angle to the disk. It is also provided with a sliding guide d controlled by the han- dle f which operates the feed-screw. By providing a stop or indicator disk upon the handle f, the exact thickness to which the work is ground can be gauged within .001 of an inch; and by means of the graduated circle on the piece c , the angle between the faces can be accurately determined. This head is also provided with a balance weight g by means of which it can be arranged to oscillate within limits, thus swinging the work back and forth across the face of the grinding disk and so reducing the liability of producing scratches upon the surface. The disks are carried upon the shaft h driven by the pulley i. The machine is mounted upon a substantial base, provided with a cupboard for con- taining the grinding disks. The disk grinding machine does not replace any particular machine tool in the shop as much as it serves to do work that is ordinarily done by filing, but it will be found possible to do a large amount of work that is ordinarily done at the bench on a machine of this class. TOOL GRINDING. HAND TOOL GRINDING. 06. General Consideration. — Under the heading of hand grinding may be classed the grinding of tools for turn- ing and planing metal. A number of different machines are made for this purpose on which emery wheels are used ; some of these grind dry and some wet. The wet grinding wheels may be divided into two classes, those that receive their water from the pump system and those in which the wheel runs in a trough or bath into which water may be admitted. The dry grinding machines are comparatively little used for tool grinding, because they are liable to draw the temper of tools; hence, only the wet grinding machines will be described. GRINDING. 33 § is WET GRINDING MACHINE. 67. Methods of Supplying Water. — A representa- tive tool-grinding machine intended for wet grinding is illustrated in Fig. 12. This machine is shown because it is arranged to provide for a supply of water without the use of pumps or pipes, and, also, because it has a truing device arranged in a wheel guard. In Fig. 12 a section of the machine is illustrated, showing the manner in which the water is applied. The water tank d is filled with water while the water trough a is raised to its highest level by means of the screw b and the lever c, this water trough be- ing pivoted at one end. The water trough a surrounds the lower part of the emery wheel and when in its highest position C. IIL—4 34 GRINDING. , § 18 prevents water from wetting the wheel; as the trough a or its forward end is lowered, it sinks into the surrounding water and allows it to flow in around the wheel. The trough is lowered sufficiently to obtain the amount of water desired by the operator; the wheel throws the water out at the rear, but an equal amount, of course, runs in at the forward end of the trough, thus keeping the supply con- stant. 68. Truing Device. — The truing device consists sim- ply of a thread roll h mounted on the end of a rocking lever, so that the operator can force it against the revolv- ing wheel by means of the screw f. This truing device is always ready for use. 69. Tool Rest. — The tool rest and guard in this style of machine are shown at i and e . This rest is surrounded by a guard e so arranged with a balance weight that it normally occupies the position shown. When the operator wishes to grind a tool, he places it on the point g and presses it down- wards until the tool comes in contact with the rest i. When the grinding is being done, the guard rises and prevents water from spattering out in front, no matter how large an amount of water may be supplied to the wheel. MACHINE TOOL GRINDING. TYPE OF MACHINES. 70. General Consideration. — With the growth of machine manufacturing, replacing as it does the older method of machine making, it has become the practice in large machinery establishments to manufacture the lathe and planer cutting tools in large lots^ These tools are all ground to the correct shapes and are ready for the work- man to use. The old ones are reground and sharpened to the standard forms and then placed in the tool room, where they may at any time be obtained by the workman. GRINDING. 35 §18 The shapes of the tools vary in different establishments, but usually each establishment fixes on standard shapes for all their cutting tools and the operator follows the blue- print of standards that is generally placed on the holders shown at the right of the machine in Fig. 13. This matter of machine tool grinding has become of so much importance in the economy of cutting tools that it may be dignified as a trade, requiring (as relating to the establishment of standards and the grinding of these tools commercially) considerable study and care. It is probable that within a few years operators who are skilled in the art of tool shaping and grinding as related to the economy of cutting metal will be in demand. There are two general classes of machines employed for this purpose, one of which uses an ordinary emery wheel and grinds the tools on the face of the emery wheel, while the other employs a disk wheel and grinds the tools on the flat face of the disk. The machine manufactured by Wm. Sellers & Company, Philadelphia, is a good repre- sentative of the first class, and that manufactured by the Gisholt Machine Company, Madison, Wisconsin, is a good representative of the second class. 71 . Sellers Grinding Machine. — The Sellers ma- chine shown in Fig. 13 is called a universal tool-grinding and shaping machine. This machine is so constructed that, with its fixtures and attachments, the accuracy of the form to be ground is not dependent on the skill of the operator, but is obtained by placing the various holders and attach- ments at the angles required, these being graduated and marked so that if the operator places them at the right graduation and angles, the accuracy of the grinding will be insured. When the tools are placed in the various holders, the operator moves them against the wheel by the use of a lever shown at a, Fig. 13. Water is supplied to the emery wheel by means of a rotary pump, and on one side of the machine is attached a diagram of instructions for obtaining the standard shapes. This diagram is shown at b, Fig. 13. 36 GRINDING. §18 The Sellers machine is designed to present a line contact between the emery wheel and the work being ground. The makers believe that it is absolutely necessary, in order to efficiently grind steel tools by means of rapidly cutting wheels, that the contact between the two should be a line and not a surface; hence, if it is desired to grind a plain face of a tool, the wheel must have a cylindrical or conical surface past which the surface to be ground must be moved in a plane. They further state that the plane face of the wheel cannot be used for this purpose because it and the GRINDING. 37 § 18 surface being ground will soon coincide, with the result that no cutting will be done, though considerable heat will be produced. 72 . The style of Sellers tool-grinding machine shown in Fig. 13 is provided with a conical wheel c and the tools are held in a suitable fixture d , one tool being shown at e. Another style of machine manufactured by the Sellers Com- pany is arranged to pass the work across the periphery of an ordinary cylindrical emery wheel. The Sellers machine will not only grind all angles and circles with cone clearance, but it will also, by the use of forms, grind irregularly shaped cutting tools. On this account, it probably has a greater range than any other machine on the market and is remarkably well adapted for shops having a large variety of tools. 73 . Gisliolt Tool-Grinding Machine. — This ma- chine works on an entirely different principle from the Sellers and is intended only for grinding the regular angles and circles with clearance. For this reason, the Gisholt machine will not serve where an extremely large range of tools is required. As in the Sellers machine, the accuracy of the shape of the tool does not depend on the skill of the workman, but is obtained by the different angles at which the parts and various holders and fixtures are set, these angles being read from a chart. Water is supplied to the wheel on this machine by means of a pump, as in the Sellers. The main point of difference between the two machines is in the method of presenting the work to the wheel. The Gisholt machine is illustrated in Fig. 14, where it will be seen that the grinding is done on the face of a cup-shaped wheel, the contact between the tool and the wheel being a surface and not a line contact, as the wheel and the sur- face being ground coincide. In actual practice, the grinding is done rapidly without heating when the right grade and grain of wheel are used and the work is moved past the wheel in the right manner to accomplish the desired results. 38 GRINDING. §18 In this respect both machines are successful. The reason for the success of this style of machine will be shown under the heading “ Selection of Wheels for Tool Grinding.” The depth of cut is regulated by means of a cross-feed controlled Fig. 14. by a hand wheel b and the tool is carried back and forth across the face of the wheel by means of the lever c. The Gisholt machine is very simple and compact, as wdll be seen by the illustration. SELECTION OF WHEELS FOR TOOL GRINDING. 74. Grade of Wheel. — In selecting wheels for tool grinding, as has been stated where the subject was under discussion, it should be understood that the result to be GRINDING. 39 § is obtained is dependent on many conditions in the wheel aside from the size of grain. The grade of the wheel plays a very important part in the manner in which it does its work. A good illustration in this connection is the case of the Gisholt and Sellers tool-grinding machines, which are designed to use diametrically opposite methods, one using a line contact only, to avoid heating and glazing, the other using a surface contact, and also avoiding heating and glazing. 75. In the case of the Gisholt machine, by using a cup- shaped wheel and grinding against its flat surface, advan- tage is taken of the possibilities of proper grading as related to the work in hand; for it is true that as the surface in contact becomes greater, the grade of the wheel should become softer, and may be much coarser. In the case of the Sellers machine, by using a line contact on the periphery or conical portion of the wheel, the wheel can be very much harder, which would be an advantage if the operator was grinding tools of irregular form and wished to preserve the shape of the wheel as long as possible. This is true also in many cases where it is desirable to have the wheel remain intact, without change of form on the face. The Gisholt machine is designed to grind flat surfaces, which are passed entirely across the face of the wheel at each stroke of the lever; hence, the face of the wheel is maintained in correct form and the desired ^result is ob- tained. At the same time, on the Gisholt machine the wheel may be soft enough and coarse enough to cut freely. 76. The emery wheel for tool grinding should be soft enough to cut freely without requiring too great pressure and without glazing. If only very large tools that present broad surfaces to the wheel are to be ground, the wheel should be softer than if only those tools presenting very small surfaces are to be passed over it. The exact number of emery and the grade of wheel to be used in all cases 40 GRINDING. § IB cannot be given, because conditions vary so much. It is safe to assume that wheels for this purpose should be so made that the desired surface on the tool will be dependent on the grade of the wheel rather than the grain;, that is, the wheels should be quite coarse and very porous, for, as has been stated before, a coarse wheel will produce quite a fine finish if of the right grade and run at the right speed for the work in hand. 77. Some workmen prefer to use a coarse wheel for shaping the tool, and a much finer one, quite soft, for a slight cut to give the desired surface for a cutting edge. In most cases, however, only one wheel is necessary, pro- vided the workmen use an oilstone for the finishing touch. 78. The tendency among users of tool grinders is to select wheels much too hard for the purpose. This is owing to the fact that workmen almost universally fail to appre- ciate the emery wheel, and do not understand how light a touch is required to grind work very rapidly on a good wheel. A soft wheel, suitable for grinding tools rapidly, will remove a large amount of material instantly with a very light touch of the tool upon it. But as workmen have invariably acquired their experience by using grindstones, they nearly always bear hard upon the emery wheel when grinding tools. This will wear a good wheel very rapidly and cut holes at intervals in the periphery. Thus it is that the purchasers of emery wheels for machinery establishments must select harder wheels than is necessary in order to preserve them. It is a common complaint among manufacturers of tool grinders that they are obliged to send out wheels that are much harder than the purpose requires. The three wheels that are used quite commonly in tool grinders are the following: Size of grain, No. 30, grade O; size of grain, No. 36, grade N ; size of grain, No. 45, grade N ; all of them being designated by the Norton Emery Wheel Company’s standard. GRINDING. 41 18 MACHINE GRINDING. 79. General Consideration. — Machine grinding may be defined as the art of producing very accurate plane, cylindrical, and conical surfaces by an abrading process performed in an automatic grinding machine. Machine grinding differs essentially from hand grinding in that the accuracy of the surfaces produced by it is dependent almost entirely on the accuracy of the machine in which the grind- ing is done, instead of on the skill of the workman. In the early attempts that were made to produce very accurate plane, cylindrical, and conical surfaces, a common emery wheel was mounted on a metal planer or on a lathe; in fact, the first forms of grinding machines for cylindrical and conical work were called grinding latlies. The early attempts were far from satisfactory, and many persons sup- posed that the errors frequently found in the work were inher- ent to the grinding process, and could not be eliminated; in other words, it was supposed that grinding was incapable of producing true work. Painstaking experiments and a careful study of the conditions convinced the pioneer advocates of machine grinding that the faulty work produced was par- tially due to the selection of wheels illy adapted to the work expected of them, and chiefly to defects inherent to the machinery used. The machinery was gradually improved and the defects were overcome; and with wheels selected to suit the work, the grinding machine of today can be truthfully said to produce round work as accurate as can reasonably be expected and was ever hoped for; in addition to this it was found that some lines of work could be finished to exact size in much less time than by any other method. 80. Classification of Macliine-Grinding Opera- tions. — The different grinding operations for which a grinding machine is used may be classified according to the position of the surface operated on as external grinding and internal grinding ; or they may be classified according to the character of the surface as surface grinding , which 42 GRINDING. §18 term is commonly understood to be an abbreviation for “plane surface” grinding, cylindrical grinding, and conical grinding. 81. External grinding may be defined as a grinding operation performed on the outside surface of a solid; in- ternal grinding, as the grinding of the inside surface of a hole. The term surface grinding is almost invariably understood to denote the grinding of a plane surface in a machine where the work reciprocates in a straight line, while the term radial grinding or disk grinding is applied to the grinding of plane surfaces on work rotating about its axis. Cylindrical grinding, as implied by the name, denotes the grinding of a cylindrical surface, which may be the inside or the outside surface of a solid. Conical grinding is a term that refers to the grinding of a tapering solid of revolution, by solid of revolution being meant a solid generated by the revolution of some plane figure about a line as an axis. Thus, a cylinder is a solid of revolution generated by revolving a rectangle about one of its sides as an axis; a right cone is generated by the revolution of a triangle about one of its sides, etc. GRINDING SOLIDS OF REVOLUTION. 82. Governing Conditions. — The fundamental prin- ciple underlying the grinding of solids of revolution is the application of thousands of cutting points to the surface of the work while it is being slowly revolved about its axis. Each cutting point removes an exceedingly small amount of metal; consequently, the pressure due to the cutting operation is very light. It follows, therefore, that the dis- turbance of the axes of the work and the wheel is corre- spondingly small, owing to which fact the resulting solid of revolution is exceedingly true. If the grinding wheel is traversed along the surface of the revolving solid in a straight line parallel to the axis of rota- tion of the solid, the latter will be ground truly cylindrical; GRINDING. 43 § 18 but if the line of motion of the wheel is at an angle to the axis of rotation of the solid, the latter will be ground conical. It is obvious that the grinding wheel may remain stationary, and that the work may be traversed past it without affecting the result. In practice, the work or the wheel is made to travel in a straight line by mounting either one on a carriage that slides on straight guiding ways that are so designed as to resist wear, and so protected against injury as to remain true as long as the whole machine can reasonably be ex- pected to last without overhauling and repair. When grinding conical work, it is absolutely necessary that the cutting be done along a line lying in the plane containing the axes of the wheel and work, or, as commonly expressed, the wheel and work must be at the same height above the ways. 83. Classes of Machines Used. — There are two gen- eral classes of grinding machines, which are called plain grinding machines and universal grinding machines. The plain grinding machines are designed especially for manufacturing and are made as rigid as possible so as to enable them to do rapid work. All unnecessary adjust- ments are dispensed with and the machine is made with as few joints as possible. This class of machines is intended for grinding plain cylindrical or slightly conical work, such as spindles, rolls, shafts, etc. In all cases the work runs on dead centers. The universal grinding machines are provided with more adjustments, and are adapted for grind- ing internal or external work (either straight or tapered), cutters, reamers, etc. CONSTRUCTION OF GRINDING MACHINES. 84. Plain Grinding Machine. — Fig. 15 shows a front and Fig. 16 a rear view of a plain grinding machine, made by the Brown & Sharpe Manufacturing Company, of Providence, Rhode Island. The entire machine is supported 44 GRINDING. § 18 upon a rigid base a. The carriage b can be moved along the base by the hand wheel c or arranged to move back and forth automatically by setting the stops d and e at the de- sired places. The table f is pivoted upon the carriage b so that it can be brought parallel to the line of travel or set at a slight angle for grinding tapers. One end of the carriage f is graduated either in degrees or inches per foot, so as to assist in setting the work to approximately the right posi- tion, the final setting always being made by trial. The head- stock g and footstock h are clamped to the carriage as shown. The main bearing surface for both headstock and footstock is vertical, as shown at i. One object of this is to have the main bearing for the headstock and the footstock parallel to the center line of the work and so arranged that differences in the pressure used in clamping the parts, wear, etc. will 18 GRINDING. 45 have as little influence on the alinement of the work as pos- sible. Another object of this design is to so locate the bear- ing surfaces that they will be protected from emery dust and water without the use of guards that have to be adjusted for every change in the length of the work being ground. Both centers are dead, that is, they do not revolve. The pulley j is driven by a belt from an overhead drum that is driven by cone pulleys, so that the speed of the work can be adjusted. The dead centers are shown at k and /. To assist in supporting the work, fixed rests m and n may be used or a follower rest may be attached to the arm o. The grinding wheel is carried upon the grinding-wheel slide /, which is well supported from the floor. The grinding-wheel slide p 46 GRINDING. §18 is set on an incline so that it tends to slide away from the work. This removes all danger of the wheel being moved toward the work on account of any vibration. The emery wheel q is provided with a guard r, and provision is Fig. 17. GRINDING. 47 §18 made for flooding the work with water from the pipe s. The water flows back to the tanks /, from which it is pumped to the work again. The emery wheel is driven by belts from an overhead drum, and provision is made for varying the speed of the wheel by a series of cone pulleys. The table feed is driven by a belt on the cone pulley u . The grinding wheel and grinding-wheel stand are moved toward or away from the work by means of the hand wheel v. Back of the hand wheel v is arranged an automatic cross- feed mechanism that will be described later. As previously stated, both the headstock and tailstock centers are dead. This eliminates errors in the roundness of the work due to want of roundness in the live spindle, and any errors that might be caused by the live center running out of true. Work ground carefully on dead centers can be reversed end for end and will then run so true that even a very sensitive indicator will fail to show any error. This test is so rigid that it is very seldom that work done be- tween centers, where one center is a live one, will pass it satisfactorily. In the machine described, the grinding-wheel carriage stands still and the work moves past it. In the machines manufactured by the Landis Tool Company, of Waynesboro, Pennsylvania, the table carrying the work stands still and the grinding-wheel carriage moves along the work. 85. Universal Grinding Machine. — A universal grinding machine, as made by the Brown & Sharpe Manu- facturing Company, Providence, Rhode Island, is shown in Fig. 17. In this particular design of machine, the emery wheel a normally remains stationary during the grinding and the work is traversed past it. The guideways are formed on top of the base b , and serve to guide a long carriage c to which the table d is pivoted. This table carries the head- stock e and footstock which can be clamped' to it in any position throughout its length. The emery-wheel stand g is mounted on a slide that normally is at right angles to the guideways on top of the frame. This stand g can be moved 48 GRINDING. § 18 along its slide toward or away from the work by turning the wheel n. The slide on which the emery-wheel stand is mounted is pivoted to its base, to which it can be clamped at any angle with the guideways that the construction per- mits. This allows short conical work having a large in- cluded angle to be ground; in that case the table d carrying the work will remain stationary while the wheel is traversed past the work. 86. In universal machines the headstock has a live spindle to which a chuck or a face plate. may be fitted; this live spindle is driven by a belt from an overhead drum. Provision is made for grinding on dead centers by placing a loose pulley i on which a belt can be put, on the end of the live spindle, and providing a suitable arrangement for locking this spindle — in this case, a movable pin k that can be inserted into a hole in the pulley /. The headstock is placed on a base to which it is pivoted in order to allow the axis of the live spindle to be placed at any angle with the table that the construction of the machine permits. This adjustment permits conical work held in the chuck or face plate to be ground without disturbing the setting of the table or of the slide carrying the emery-wheel fixture. The headstock base, bottom of grinding-wheel stand, and end of the table are all provided with graduations. These gradu- ations are used in setting the different parts of the machine to approximately the desired angle for any work in hand. The carriage c is moved past the emery wheel by turning the hand wheel m\ it is alsp provided with a feed that can be automatically stopped at any point within the range of motion of the carriage. 87. The footstock of a grinding machine serves the same purpose as the tailstock of a lathe, but differs consid- erably from it in it's general construction. The footstock spindle of a grinding machine, as a general rule, is provided with some form of a spring that operates it and regulates the pressure with which its center is pressed into the center of the work. Such a regulation of the pressure contributes, in GRINDING. 49 § 18 a large measure, to the accuracy of the work, inasmuch as it prevents springing of the work by an excessive setting up of the footstock center which a careless operator is very apt to do. This spring also maintains a constant pressure on the center, even though there may be considerable wear of the center hole, or the work be lengthened by expansion. 88. Fig. 18 shows the construction of the footstock of the grinding machine made by the Landis Tool Company. A lever a is pivoted to the frame of the footstock; it carries a pin b at one end that is placed in a hole cut into the spindle c. The lower arm of this lever is acted on by a plunger d and a helical spring e\ this spring tends to move the footstock spindle forwards. Obviously, the pressure with which the footstock center presses against the work is that caused by the tension of the spring e. The tension of this spring can be regulated by means of the adjusting screw f. For very small work, even the lowest tension of the spring may cause enough pressure to bend the work, in which case the pressure may be relieved to any desired ex- tent by screwing the nurled relieving nut g against the end of the footstock. If this is done, the operator must use great care not to turn the relieving nut so much as to loosen the work, which can be told by tightly grasping the work and, while shaking it, observing if there is any end play. C. S . III. —5 GRINDING. 51 § 18 Footstocks are constructed in a number of ways by the different manufacturers of grinding machines; it is believed that all of them, however, contain a provision of some kind for preventing an excessive pressure on the work in the direction of its axis. 89- Overhead Arrangements. — Figs. 19 and 20 show the arrangement of the countershafts for the universal grinding machine illustrated in Fig. 17. Fig. 19 (a) is a front view, Fig. 19 ( b ) a plan of the overhead arrangements, 13 1 L Fig. 20. 52 GRINDING. § 18 and Fig. 20 an end view of the machine. A tight and a loose pulley a and a' are placed on the countershaft a " , which is driven by belting it to a line shaft, and which can be stopped and started by shifting the driving belt a'" by means of the shifter b. A cone pulley c is keyed to the countershaft a" and is belted to a cone pulley d on the emery-wheel countershaft d\ which carries the cylindrical pulley e that is. belted to and drives the emery-wheel shaft. From this arrangement, it follows that the emery wheel is stopped and started by operating the shifter b. A cone pul- ley g is placed on the countershaft a", to which it can be attached by means of a friction clutch operated by the shifter f. The cone pulley g is belted to a cone pulley h on the headstock countershaft h! , which carries the long cylin- drical drum i that is belted to the headstock. Two separate belts are provided for driving the work, one of which is used for grinding on dead centers and the other for rotating the headstock spindle for chuck work and face-plate work. The belt that is not in use, as the belt m in this case, is removed from the drum and hung up where it is out of the way. The different feeds are driven from the headstock counter- shaft h! by belting the cone pulley k to the feed cone pulley /. By tracing out the belting, it will be seen that the work will have a direction of rotation opposite to that of the emery wheel. A rotary force pump is driven by belting it to the pulley n. It is necessary in any grinding machine to so arrange the countershafts that the speeds of the emery wheel and of the work can be changed independently of each other in order that the best speed may be obtained for each. The changes of speed are usually obtained by placing the belts on differ- ent steps of the cone pulleys. 90. Automatic Cross-Feed. — The best grinding ma- chines are now fitted with automatic cross-feeds. This feed differs essentially from that of a lathe, however, in that its purpose is not a constant movement of the grinding wheel in a direction crossing the axis of the §18 GRINDING. 53 work. Rather, its purpose is to automatically advance the grinding wheel a predetermined distance toward the axis of the work as soon as the wheel or the work has come to the end of its longitudinal traverse; the automatic cross-feed is intended to repeat this operation a prede- termined number of times and then automatically stop the advance of the wheel toward the axis of the work. In other words, the automatic cross-feed relieves the operator from the necessity of feeding the grinding wheel forwards after each cut, and, furthermore, when correctly set will grind the work to the desired diameter and then automatic- ally stop grinding, thus preventing the grinding of work too small. 91 . Automatic cross-feeds are constructed in various ways, but the principle upon which they work can be illus- trated by a description of the one illustrated in Fig. 21, which shows the details of the cross-feed used upon the machine shown in Fig. 17. The length of the table stroke is controlled by the stops i and j f which operate the lever g, thus reversing the table. The cross-feed is operated by the mechanism attached to the lower end of this lever g. When the hand wheel 1 1 , a portion of which is broken away in the illustration to show the details, is rotated in the direction of the arrow, the grinding wheel is moved toward the work, and when rotated in the opposite direction, it is moved away from the work. The ratchet wheel a is attached per- manently to the hand wheel and contains a slot m carrying a loose ring. To this ring is attached a block /, the block being pivoted to the ring at n and being provided with a latch p, which is so arranged that when it is pressed against the stop shown on its right, it will move the ratchet one tooth. The latch p can be disengaged from the ratchet by raising the left-hand end of the block /, provision for this being made by the slot which surrounds the screw, as shown in the illustration. The block / carries a shield r, which, by passing under the point of the pawl b , can prevent its engaging the ratchet wheel. The ratchet wheel is operated 54 GRINDING. §18 by means of the pawl b , which is connected to the lever c , the latter being pivoted at d and being operated by an in- clined block that engages the lower end of the lever g. The amount that this block engages the lever g is controlled by the screw e and stop f. By this means the lever c can be so adjusted that the pawl b will move the wheel through one or more teeth at each end of the stroke, that is, whenever the lower end of g is thrown across the V-shaped stop upon c. 92. Having described the uses of the various parts, the operation of adjusting the cross-feed may be described as follows: The stroke of the table k is adjusted by means of the stops i and /, after which the hand wheel h is carefully turned in the direction of the arrow until the wheel nearly or just touches the work. The stroke of the table is then stopped, and without changing the hand wheel h the screw o GRINDING. 55 § 18 is loosened and the block / raised until the latch p is out of contact with the teeth of the ratchet. The block / is held in this position with the right hand, while with the left hand the pawl b is swung into the notches of the ratchet, after which the block / is moved around until the point of the throw-out shield r is just past the tooth occupied by the pawl b, the pawl being lifted out of the way to allow the shield to pass. The block l is then let down so as to bring the latch p into contact with the ratchet once more, and the thumbscrew o tightened. The pawl b is then thrown back against the shield r, which will prevent its coming in contact with the ratchet. The table stroke is next started, and if the pawl b does not engage the teeth of the ratchet when the lever ^depresses the lever c } it may be made do so by press- ing one or more times upon the latch p. This is done by placing the thumb against the latch and the forefinger against the projection extending up from the block /. The pawl b will then turn the ratchet and hand wheel, thus % feed- ing the emery wheel forwards until it cuts the work, the pawl once more coming to rest upon the shield r. Allow the machine to run until the cut is practically ended, stop- ping the table at the footstock end of the stroke with the shifter and overhead brake. Now measure the work, ascer- taining the quarter-thousandths to be taken off to bring it to the correct size. Press the latch p once for each quarter- thousandth of an inch; thus, for .003 inch, press the latch 12 times, start the table, and the pawl will move the ratchet until the shield r prevents the pawl b catching another tooth Allow the wheel to pass over the work until it shows the same cut as when the measurement was taken and stop the table at the footstock end, as before. If a suitable wheel is used, the diameter will show a reduction of .003 inch. If the work does not show this reduction, the latch p is pressed once for every quarter-thousandth further reduction necessary, and the machine started up once more, as before. When the work is the right size, the pawl b is thrown out and, without changing the position of the block /, the hand wheel h is turned in a direction opposite to 56 GRINDING. § 18 that of the arrow for about one turn. This will remove the emery wheel from the work. When the next piece of work is in place and the table stroke started, the hand wheel is turned in the direction of the arrow until the emery wheel just cuts, then the pawl b is thrown into the notches and the machine allowed to continue its work until the shield r has again stopped the feed by disengaging the pawl b from the ratchet wheel. When the emery wheel shows the same cut that it did when finishing the first piece, the machine is stopped as before and the work measured. If the work is large, the latch p is pressed as many times as the work is quarter-thousandths large and the grinding continued until the right dimension is obtained. After the wear of the wheel has been determined, it is possible to press the latch p the proper number of times before beginning the cut on each new piece and thus finish the piece to the exact size at one operation. 93. When setting the automatic cross-feed, it must be remembered that the depth of each cut is dependent on the number of teeth the ratchet is moved at the end of each stroke. The number of teeth that the ratchet wheel is moved at each stroke is controlled by means of the adjust- ing screw which controls the movement of the lever c and the pawl b. The throw-out shield r , by its position, simply determines the total depth of the successive cuts, that is, the total distance that the grinding wheel is moved toward the work. 94. The diameter of the work produced by the auto- matic cross-feed should be measured after the wheel has stopped cutting, or when the amount of sparks given off shows that it is cutting at the same rate that it did when the previous piece was measured. The reason for this is that the grinding wheel will continue to reduce the diame- ter slowly for some time after the feed has been stopped. 95. The cross-slide on which the wheel of a grinding machine is mounted must move quite freely in order that §18 GRINDING. 57 it may be moved an amount as small as .000125 inch. In order to keep the wheel slide in good condition, it should be oiled with good oil each day and moved throughout its entire length during the operation, so as to insure thorough lubri- cation. If the wheel slide is allowed to remain stationary for some time without lubrication, it may be necessary to clean the parts before they will work freely again, though usually the working of a good quality of oil through the oil holes and the moving of the parts throughout their entire travel several times will put the working parts in good condition. 96. The automatic cross-feed is a valuable addition to the grinding machine, on account of the fact that -it not only enables the operator to attend to other details while the piece is grinding, thus saving much time, but by uniform movement it maintains the proper condition of the emery wheel and increases its sizing power. This latter feature is one that has received very little attention in the past, but is of great importance if it is desired to finish duplicate pieces. GRINDING. (PART 2.) GRINDING SOLIDS OF REVOLUTION. ADVANTAGES OF GRINDING. 1. When grinding machines were first designed, they were used almost entirely for hardened work, the prevailing idea being that grinding was a refined perfecting process suitable only for the finishing of hardened work that re- quired a great degree of accuracy. This idea still prevails in many quarters, but it is incorrect, since experience has shown that whenever a suitable grinding machine is intelli- gently used the accuracy that may be attained when soft work is finished by grinding is accompanied by a reduction in the cost of the work over that which has been accom- plished by other processes. Thus, many kinds of cylin- drical work, such as shafts, spindles, studs, arbors, etc. that are made of soft steel may be turned to nearly the finished size, and then by careful filing, followed by an intelligent application of emery cloth, brought to the correct size. By using a grinding machine, however, most of the cost of the files and emery cloth is eliminated from the charges against the work; furthermore, the quantity of metal left for finish- ing can be removed much faster by grinding than by filing or turning in the lathe, at least on work that is within the capacity of the grinding machine. § 19 For notice of copyright, see page immediately following the title page. 2 GRINDING. §19 2 . It has been shown in actual practice that a grinding machine fitted with a 12-inch grinding wheel, which is a common size, will reduce a cylindrical piece of steel from .005 inch to .012 inch in diameter in less time than would be consumed in reducing the diameter an equal amount in a lathe. With especially heavy and powerful grinding machines, a greater amount than that named above can be removed. 3. While the grinding machine may in the future be developed sufficiently to adapt it for roughing out work, it is not developed enough for that at present, and the work must come to the grinding machine roughed out to within .005 inch to y 1 ^ inch of the finished size in order that the machine may not work at a serious disadvantage. When the amount of metal to be removed is within the limits stated, grinding is not only an economical, but is also a very desirable, finishing process on account of the great accuracy attainable. 4 . An emery wheel having a diameter of 18 inches and a face | inch wide, when running at its ordinary speed, pre- sents approximately 2,500,000 cutting points to the work in 1 minute, and a wheel of the same diameter, but having a face 1^- inches wide, presents about 5,000,000 cutting points to the work in the same period of time. Each of these cutting points removes a very small amount of metal; but when the aggregate amount is considered it is compar- atively large. Furthermore, in modern grinding machines the cutting points pass over from 1 to 4 square feet of sur- face per minute. The statements just made will serve to explain why, within reasonable limits, the grinding machine can remove metal faster than the lathe, with its single cutting point. 5 . The purposes and advantages of machine grinding- may be briefly summed up as follows: In the first place, it is economical to finish work to size by grinding; in the second place, the accuracy attainable is very great. The first advantage named is, today, the most important one, GRINDING. 3 § 19 and fits the grinding machine for manufacturing purposes on work within its range and capacity; accuracy is given the second place, because the accuracy readily attainable by grinding is far beyond that which is necessary on most duplicate work. SELECTION AND USE OF GRINDING WHEEL. SELECTION OF WHEEL. 6. Grade. — In order that the grinding wheel used in machine grinding may cut freely, that is, with little or no pressure, it is desirable that the wheel be “self-sharpening.” A self -sharpening grinding zvheel is one in which the dulled particles of the abrasive material break away readily during the grinding operation, and the ease with which these par- ticles become detached, or the resistance that they offer to breaking out, determines the grade of the wheel. Thus, if the particles break away readily, the wheel is said to be soft, while one that offers considerable resistance to the detaching of the dulled particles is called hard. From this explanation it should be plain that the terms “soft” and “hard,” when applied to a grinding wheel, do not refer to the relative hardness of the abrasive material, but merely to the facility with which the dulled particles become detached. 7 . Causes of Glazing. — It is evident that the longer the dulled particles are retained, the duller will they become, and that, consequently, more pressure will be required to make them cut. Undue dulling of the particles is also caused by an excessive speed. The dulling of the particles manifests itself by the glazed appearance of the cutting sur- face of the grinding wheel, and by considering the causes of this glazing we would be justified in drawing the conclu- sion that a wheel that glazes rapidly is either too hard for the work it is performing or is run too fast. A wheel that 4 GRINDING. § 19 requires much pressure to make it cut will not produce the best results, no matter how rigid the machine in which it is used may be, for the reason that the pressure of the grind- ing will disturb both the axis of the wheel and the axis of the work. 8. Influence of Hardness of Material. — Since dif- ferent materials vary in their hardness, the rate at which they will dull the grinding wheel also varies. Naturally, the harder material will, dull the abrasive substance incorpo- rated in the wheel more rapidly than will the softer material ; from this we may draw the conclusion that the harder the material is, the softer should be the grade of the grinding wheel . Because of this fact, it should be remembered, when considering the working of different grades of steel, that since high-carbon steels are harder than steels containing only a low percentage of carbon, they require a softer grind- ing wheel, while low-carbon steels can be advantageously ground with a wheel that is harder and denser. 9. The different high-carbon steels of the variety known among shopmen as “tool steel” vary but little in their relative hardness, and, consequently, a wheel suitable for one kind of such high-carbon steel will work satisfactorily on most other grades of such steel. Steel that is low in carbon, commonly called “machinery steel” by shopmen, is quite soft, and experience has shown that it can probably be ground best by using a combination wheel, which is a wheel in which several sizes of grains are incorporated. Thus, a wheel in which No. 36, 46, 60, 80, and 100 emery is incorporated is a combination wheel that is suitable for some kinds of work. 10. Influence of Vibration of Work. — The steadi- ness of the revolving work while it is being ground must be considered in deciding on the grade of the wheel that is to be used. If the work vibrates somewhat, the wheel should be harder than if the same work was perfectly free from vi- bration. The reason for using a harder wheel is that the vibration of the work has the same effect on the cutting GRINDING. 5 § surface of the wheel as a succession of hammer-blows, which would break the particles of the abrasive material away too rapidly if a soft wheel were used. DIRECTIONS FOR SELECTING WHEELS. 11. In order to aid the grinding-machine operator in selecting a suitable wheel, the Landis Tool Company publish the directions given below, where the grade of the wheel is given in accordance with the standard of the Norton Emery Wheel Company. 12 . Wheels for External Grinding. — For grinding hardened steel, in roughing it down to nearly the desired size, use a No. GO emery wheel, grades K to M ; for finish- ing hardened steel, according to the degree of finish desired, use a No. 60, 80, 100, 120, or 150 emery wheel of the grades I to M. For roughing soft steel down to nearly the finished size, use wheels from No. 46 to No. 60 of the grades M, N,or O ; and for finishing soft steel, use, according to the degree of finish desired, wheels from No. 60 to No. 180 of the grades L or M. For roughing cast iron down to nearly the finished size, use wheels from No. 46 to No. 60, and of the grades G to K; for finishing cast iron, use wheels from No. 60 to No. 80 of the grades K to M. To finish brass or bronze, use a wheel from No. 60 to No. 120, according to the degree of finish desired, and of the grades F to K. 13. Wheels for Internal Grinding. — -For roughing out soft or hardened steel, use a wheel from No. 46 to No. 60 of the grades G to K, and for finishing soft or hardened steel, use a wheel from No. 60 to No. 100 of the grades E to F. For roughing out brass or bronze, use the same wheels as for roughing out steel; for finishing brass or bronze, use, according to the degree of finish desired, a wheel from No. 80 to flour emery of the grades E to F. 14 . The directions here given should be considered merely as an aid in selecting a wheel. The results must be 6 GRINDING. § 19 observed and the wheel then changed to suit, if found un- satisfactory. The Brown & Sharpe Manufacturing Com- pany recommend that for internal grinding only corundum wheels be used. 1 5. Shapes of Wheels. — Emery wheels and similar grinding wheels are made in various shapes by the different manufacturers; some of the shapes most commonly used in (b) (g) (h) Fig. 1. machine grinding are given in Fig. 1. Wheels having the shape of a flat circular disk with a small central hole, as the one shown in Fig. 1 (a), are used for external grinding, the cutting being done by the periphery. The wheels most commonly used on universal grinding machines have large 19 GRINDING. 7 central holes, as shown in Fig. 1 ( b ). Such wheels are mounted on special arbors or upon bushings on an ordinary arbor. Cupped wheels like the one shown in Fig. 1 (c) are usually mounted directly upon the spindle and are used for surface grinding, the face a being used for this purpose. Sometimes these wheels are made without the shoulder for attaching them to a spindle, in which case they are simply plain cylinders. Such wheels are mounted in a chuck and used for surface grinding. If the wheel shown in Fig. 1 ( b ) had a face several inches wide, it could be used for surface grinding by mounting it in a chuck, the work being done upon the face a. A wheel that has the shape shown in Fig. 1 ( d ) is used for grinding close to the shoulder of work that has a very large flat shoulder; the shape of the wheel permits this to be done since it allows the face of the nut that fastens the wheel to the spindle to come below the face a of the wheel. The grinding is done by the periphery of the wheel. 16. A narrow conical wheel, like the one shown in Fig. 1 (2. Filing Curves. — In filing circular holes, file that is as nearly the size of the hole as it is to obtain should be used. A small file will tend to produce the ridges shown in Fig. 36; with a larger file that conforms more nearly to the curva- ture of the hole, this tendency is greatly reduced. When the filing is to be done on an internally curved surface of a large radius, as shown in Fig. 37, a half-round file is used. As iri the case of the circular hole, there is a tendency to file unevenly, and a file of as large a curvature as is obtainable should be used. The file should be 7777777777?>. ///////////z move d along the cir- cumference of the curve as well as across the work, which gives it a diagonal motion, and in addition to the advantages of diag- onal filing on flat surfaces, prevents the formation of ridges. Fig. 37 63. Filing Into Corners. — When it is necessary to form a sharp corner, or to file up to a finished surface that stands at right angles to the one on which the filing is done, a safe-edge file is used, thereby preventing any injury to the finished part. When the corner is to be extremely sharp, a half-round file may be used, or a flat file may be ground off on one side, to form a safe edge. Either the half-round or a flat file ground in this way has a sharp edge that will permit a sharp angle to be formed. Some forms of triangular files will also make a sharp corner. The other files used in ordinary work are so cut that the corners are either rough or slightly rounded and will not make a clean, sharp angle. When the corners are to be rounded, a round- edge file will give good results. 44 BENCH, VISE, AND FLOOR WORK. 20 04. Filing Slots With Curved Ends. — For filing out slots that have been roughed out by drilling, and where the end of the slot is to be rounded, a flat, round- edged file is the most suitable. When the sides have been machined to size and the end of the slot is to be rounded, a round file with the sides ground off to the width of the slot, as shown in Fig. 38, may be used. Two safe edges a and b are thus formed that will prevent injury to the finished sides. 65. Draw-Filing. — When the filing is done by moving the file sidewise across the work, it is called draw-filing. Fig. 33 illustrates how the file is held, the motion being at right angles to its length. Draw-filing is used very gener- ally in finishing turned work, where it is desired to remove the circular tool marks and lay the marks endwise. Care should be taken to hold the file so that the teeth will cut as it moves away from the body, and to relieve the pressure on the return stroke, as in cross-filing. In draw-filing, the cut is not so deep as in cross-filing, the teeth standing at such an angle to the direction of motion that a light shearing rather than a cutting effect is pro- duced ; very smooth work may be done by this method. A second-cut or smooth file is best suited for draw-filing. On convex surfaces a flat file or the flat side of a half-round file may be used; but in concave work a round file or half-round file will give the best results. When a large amount of metal is to be removed, it should be done by cross-filing, as the cut in draw-filing is so light that a very great amount of time would be required to remove it by this method. 66. Finishing Filed Work. — When a better finish is required than can be produced by draw-filing, the surface may be rubbed with fine or worn emery cloth and oil, the cloth being wrapped about a file or a piece of wood, which is used as in draw-filing. The strokes should be made suc- cessively along the circumference of a cylindrical piece, in order that the finish may be even. When a very fine finish § 20 BENCH, VISE, AND FLOOR WORK. 45 is required, the draw-filing may be followed by cross-filing with a dead-smooth file, after Which it may be rubbed with the emery cloth in the direction in which the draw-filing was done. 67. Position of Body When Filing. — No attempt should be made to keep the body rigidly in one position while filing, especially on heavy work. A free, easy motion of the body, in the direction in which the file is moving, permits a greater force to be exerted without undue strain. In filing right-handed, the workman stands with his left foot toward the work, and as the file is moved forwards, a slight bending of the left knee will tend to throw the body against and upon the file, thus assisting in making the cut. During the return stroke the knee is again straightened as the body returns. A little practice will show the extent to which this motion of the body can be made to assist in the work. 68. Height of Work. — The height of the work largely depends on the class of filing that is to be done. Ordinarily, the surface to be filed should be about as high as the elbow of the workman. When the work is extremely heavy it should be set somewhat lower, in order that a greater pres- sure may be put upon it. If the vise or supporting device is too high, a foot-board or low bench may be used to stand upon. The feet of the bench should be set flush with the ends of the board, in order to prevent tipping when stepping upon the ends. 69. Effect of Oil. — The effect of oil on filing varies greatly with different metals and different classes of work. In finishing broad, smooth surfaces of cast iron, the presence of oil prevents the file from cutting, and causes it to slip over the surface, thus wearing off the sharp points of the teeth. On cast iron, generally, and especially on the class of work mentioned above, oil should never be used. On the other hand, it may be advantageously used when filing wrought iron and steel, and other hard fibrous materials, especially in finishing surfaces, when the file is new and sharp. Oil prevents the file from scratching and cutting too deeply. 46 BENCH, VISE, AND FLOOR WORK. § 20 Sometimes the teeth are filled with chalk, either dry or mixed with oil; this, to a great extent, prevents the filings from clogging between the teeth. New files are usually sent from the factory covered with oil, to prevent their rusting. For work in which oil is objectionable this must be removed, which is sometimes done by first rubbing off the surplus oil, then coating the file with chalk and brushing it off carefully. 70. Selection and Care of Files. — The life of a file may be prolonged very materially by exercising care in selecting a suitable one for each piece of work, and in using it properly. A new file should never be used on rough cast iron from which the sand and scale have not been removed, nor on narrow surfaces. Both these conditions tend to break and dull the teeth. A well-worn file will do excellent service in both these cases. On narrow work, a worn file will give better results than a new one, the teeth on a new file being so sharp that the few teeth in contact will enter so deeply that they are liable to be injured and to scratch the work. A new file should be first used on brass or wide sur- faces on smooth cast iron. The files most commonly used in the machine shop are the 12-inch and 14-inch flat and half-round bastard, the double- cut, and the 12-inch and 14-inch single-cut. The other files mentioned are, of course, needed very frequently for finish- ing, or for special operations, and should be kept in stock. One of the most serious troubles to contend with in filing is the tendency to pin. The cuttings clog between the teeth, forming hard, sharp “ pins ” that scratch the material. fig. 39. This is known as pinning , and occurs more readily in some materials than in others. As soon as the slightest indication of pinning is observed, great care should betaken to prevent it. The teeth should be carefully cleaned. Sometimes this § 20 BENCH, VISE, AND FLOOR WORK. 47 may be done by rapping the file against a wooden block or the work bench, or by rubbing the hand over it. In most cases it is necessary to use a wire brush, called a file card , shown in Fig. 39. Vigorous brushing in the direction of the teeth usually removes the pins, but in cases where the brush will not remove them, a piece of soft sheet brass, or copper or iron wire flattened out at one end, may be used. The end is pressed crosswise upon the teeth and moved in the direction of the length of the teeth. Little grooves will be cut into the soft metal, forming small teeth that clean the file thoroughly. 71. Files should never be thrown upon one another, or upon other tools or hard substances. In too many cases, files, hammers, cold chisels, wrenches, and tools of all kinds are thrown into a box or cupboard promiscuously, resulting in injury to the files and all other cutting edges, to say nothing of the careless and dilapidated appearance of the place and the time wasted in trying to find anything that is wanted. A tool box or cupboard should always be kept in order. There should be “ a place for everything and every- thing in its place” when not in use. Files should be laid either upon shelves or in a drawer that is provided with small divisions so as not to permit them to rub against each other. They should always be carefully cleaned before they are put away, and kept in good condition so as to be ready for use when they are required. 72. Filing Jigs. — These are generally used in the making of duplicate parts, and in a great variety of oper- ations where it is necessary to produce accurate work by filing, and to do this practically independent of the skill of the workman. Such jigs usually consist of hardened steel blocks fastened to the work, and made in suitable shapes to guide the file so as to remove the stock to the proper form in each case. The file will glide over the hardened jig prac- tically uninjured and cut away the softer metal of the piece pf work which projects above it, 48 BENCH, VISE, AND FLOOR WORK. § 20 One form of jig is shown in Fig. 40. This jig is used in making rectangular slots in boring bars, etc. It consists of a hardened steel block < 2 , having a hole for inserting the work b\ a rectangular slot c of the dimensions required to be made in the work ; a series of holes d at right angles to the slot c and circumscribed by a rectangle same as c ; and a setscrew e to hold the jig on the work. In cutting such a slot in a bar, the jig is slipped on to the proper position and clamped by means of the setscrew. The holes are then drilled through the work, those in the jig serving to guide the drill. The setscrew is then loosened and the jig turned 90°, bringing the rectangle over the holes just drilled. A plugger may be used to drive out some of the metal between the holes, after which a file is used to bring the slot to the form of that in the jig. A better way is to move the jig a half hole endwise, then run an end mill through each hole of the jig to remove the metal left between the holes by the drill; the slot may ther be finished by filing as described above. FITTING KEYS. 73. Rectangular Keys. — Keys of a square or rect- angular cross-section are generally planed or milled a little larger than the size of the key seats they are to fill, and are 20 BENCH, VISE, AND FLOOR WORK. 49 then filed to fit. If the key is to fit top and bottom, it should be filed true to a surface plate and made of such width as to fill sidewise the key seats in both shaft and wheel. The corners should be slightly rounded, as well as the ends. The shaft is now put into the bore, with the key seats in line. Red or black marking should be put on the surfaces of the key seat, and the key driven in lightly and taken out and filed where it shows bearing marks. Care should be taken not to drive the key too tightly at first, as it .is easily sprung to conform to the inequalities of the hole, and will show a greater bearing than it should. Care must be taken not to drive the key in dry, as it will surely cut. The marking applied to the seat is sufficient at first, and later the marking material may be put on the key, where it serves the double purpose of marker and lubricant. By repeated trials, the key is brought to fit the seat perfectly, and then may be driven home without danger of throwing the work out of true. A well-fitted hub and shaft may be forced considerably out of true by driving a key that is tight only on one end; and poorly fitted wheels and shafts may be made to run rea- sonably true by using care in fitting the keys and trying the work on lathe centers as it progresses. If means are not at hand for machining keys, as is often the case on repair work, a wooden pattern is first made and the key forged a little large, after which the scale may be ground off on an emery wheel or grindstone and the key filed to fit. 74. Provision for Withdrawing Keys. — Keys that can be driven out by putting a set in the opposite end of the key seat are not pro- vided with heads; but if the seat is so located that only one end is accessible, that end must be provided with FlG - 41 - a head, as shown at a , Fig. 41, for the purpose of withdraw- ing the keys. A pinch bar, or wedge, is used between the head a and the hub, to back this key out. C. S. III .— 13 50 BENCH, VISE, AND FLOOR WORK. § 20 For convenience in fitting, large keys are sometimes made with an extension head 3 or 4 feet long, as shown in Fig. 42. Fig. 42 . While backing out such a key, it should be supported by holding a sledge under the head at the point a , while blows are being struck against the face b. 75. Taper of Keys. — When keys are made with a taper, the taper is generally furnished by the drawing room, but in some shops the workman is left to determine this for himself; in common practice, T * ¥ inch to i inch per foot is found sufficient. 76. Round Keys. — Sometimes a cylindrical or tapered pin is used as a key. In this case a hole is drilled one-half in the shaft and one-half in the hub ; and if the key is to be tapered, the hole is reamed to the proper taper. A key is then turned up to fit the hole, and fitted by filing in the lathe, after which it is driven home. For very small work where there is not much strain on the parts, this style of key may do very well. It is used very generally to fasten the hand wheels of globe valves to the stems. For large work, and especially where there is not a good fit between the hub and the shaft, such a key should never be used, as it has a tendency to burst the hub. 77. Woodruff Keys. — These keys are made by cutting a disk from a piece of cold-rolled stock, and then splitting it into two pieces along its diameter. The keys thus formed are of the form shown in Fig. 43. The key seat in the shaft is made by sinking, a milling cutter, of a diameter corresponding to the curve on the key, Fig. 43. § 20 BENCH, VISE, AND FLOOR WORK. 51 into the shaft to such a depth that the proper amount of the key will be left out of the shaft. The key is driven into the shaft, and the wheel, which has previously been key- seated with a seat whose depth is one-half its width, is driven lightly on the shaft, and, if the work has been cor- rectly done, the key has only to be slightly filed to let the wheel into its place. This key bears sidewise, and should just fill the top and bottom. It is a short key, and when a greater length is required two or more are put in line. BENCH, VISE, AND FLOOR WORK. (PART 2.) BENCH WORK AND LAYING OUT. TOOLS AND FIXTURES EMPLOYED. SCRAPERS. 1. Use of Scrapers. — Scrapers are used in machine construction to fit or correct flat bearing surfaces to each other and to make flat or curved surfaces true. These sur- faces when flat are first planed, or in some cases milled, as true as possible ; but owing to the unequal hardness or tex- ture of the material, the possible springing of the work when clamped on the planer or milling-machine table, and the slight wear of the finishing tool, they are never perfect as they leave the machine. Errors in planed surfaces such as the fitter is called on to correct by scraping are caused in several ways, the most common of which are wind, caused by not having the casting or piece firmly bedded on the table ; out of square, caused by using try-squares that are not true; angles that do not match, caused by carelessness in setting the head to the angle; and by sand holes, spots of scale, and hard spots, that the tool always jumps or slides over. The errors in planed work should not exceed one or two thicknesses of tissue paper, and if found to be greater, § 21 For notice of copyright, see page immediately following the title page. 2 BENCH, VISE, AND FLOOR WORK. § 21 the work should be sent back to the planer, unless it is found that the errors are due to hard spots. 2. Forms of Scrapers. — The scrapers used on flat and angular work are the flat, the hook, the right-hand hook, and the left-hand hook; and for curved work, the half-round and half-round end are much used. For removing burrs and scraping corners and countersunk surfaces, the three- cornered scraper is generally used. The flat scraper is the one most used, as it is the easiest to make, sharpen, and use, and in expert hands it will remove an astonishing amount of surface in a short time with little effort. Scrapers are often made of old files, but they do not work well, because files are made of a grade of steel, called file steel , that can be properly hardened only by the special processes used by the file manufacturers. The half-round and three-cornered scrapers may be made from any good smooth or dead-smooth files that have become too dull to use, by simply grinding off the teeth, thus avoiding the necessity of rehardening. 3. Three-Cornered Scraper. — The three-cornered scraper may be made of a worn-out file of any good make. The file should have all the teeth ground off and the end sharpened at an angle of about 60 degrees. It is best to do Fig. 1. the work on a wet grindstone, for if done on an emery wheel and overheated, the scraper will be spoiled. The appearance of the finished three-cornered scraper is shown in Fig. 1. In some cases the edges from a to b are slightly curved. 4. Flat Scraper. — The flat scraper, Fig. 2 (a) and ($), should be made of any one of the best grades of tool steel, such as Jessop’s, or of the special scraper steel furnished by § 21 BENCH, VISE, AND FLOOR WORK. 3 several American makers. It should be made of stock about inch thick by 1 inch wide, with a tang, similar to that on a file, which is driven into a wooden handle. The cutting edge should be drawn to about inch thick by If to If inches wide, and hardened to the greatest possible degree. (b) Fig 2. The sides should be ground flat, and the end may be slightly rounded. The end should be ground by moving it back and forth along the tool rest, parallel to the face of the grind- stone, thus making two equal cutting edges, as is shown exaggerated in Fig. 3, which shows the end of the scraper as it leaves the grind- c stone. The surfaces a and b are next rubbed on a good oilstone, after which the tool is held in a vertical position so d that both of the points c and d will rest on the stone, in which position it is FlG * 3 - rubbed back and forth, grinding it into the shape shown by the dotted line ef. This makes the thin end of the scraper practically flat. It is now ready for use and has an equally good cutting edge on each side. 5. Bent, or Hook, Scraper. — The bent, or hook, scraper is made in the form shown in Fig. 4 ( a ). It should be made with the same care as the flat scraper, and should be ground to the angles denoted by the lines af and c d, Fig. 4 ( b ), The cutting end is made of the form shown at Fig. 4 ( c ). The cutting is done with the edge e. The face bh is ground to any convenient angle so as to reduce 4 BENCH, VISE, AND FLOOR WORK. § 21 the area of the surface be, which must be finished on an oilstone. For fitting angular surfaces that cannot be reached conveniently by the straight and regular hook scrapers, the right-hand and left-hand hook scrapers are made, as shown in Fig. 4 (d) and (e). 6. Holding the Scraper. — The manner of holding the flat scraper is shown in Fig. 5. The handle is held in the right hand, with the thumb extended along the top, in order to keep the muscles of the hand and arm in line, the §21 BENCH, VISE, AND FLOOR WORK. 5 same as in filing, thus preventing cramping the hand and tiring the arm. The left hand is applied as near the cutting edge as is convenient, and only enough pressure applied as is necessary to remove the required amount of metal. The cutting is done by pushing the scraper away from the oper- ator, except where it is used for frosting, flowering, or finishing, when a long handle may be substituted and rested on the shoulder, while both hands are used to pull the tool toward the operator. The hook scrapers are held in much the same way as the flat scrapers, but are pulled toward the workman. 7. Proper Angle for Holding the Scraper. — The flat scraper is usually held at an angle of about 30 degrees to the surface of the work, but this angle may vary with the material scraped and the condition of the cutting edges. No definite angle can be given for other types of scrapers; it must be determined by trial with each scraper and each class of work. SCRAPING A PLANE SURFACE. 8. Preparation of Surface. — A newly planed sur- face is scraped in the following manner: The piece is placed on any support that will bring it up to a convenient height for the workman, who first brushes off any dust or dirt that may be on the surface. He next runs a smooth or dead- smooth file over the surface, to remove any burrs or fuzz that may be on it, and he also touches off any marks that would indicate that a sand hole or hard spot had left a high spot or spots. 9. Applying the Surface Plate. — A surface plate, prepared by thoroughly cleaning and then coating with marking material , is now placed face down on the work and rubbed back and forth a few times over the entire surface. No pressure is necessary, the weight of the plate being suffi- cient. When the plate is removed, irregular patches of the marking material will be found on the work. These places indicate high spots in the surface, and they are 6 BENCH, VISE, AND FLOOR WORK. § 21 removed with a few strokes of the scraper. The workman now wipes his hand clean of grit and rubs it over the entire face of the surface plate, to smooth the marking, and then rubs the plate over the work again. More bearing spots will be shown- this time, which are removed with the scraper. The work proceeds in this manner until the entire surface of the work is covered with bearing marks, when it may be called true. The marking material, in addition to showing the high spots on the work, acts as a lubricant and prevents undue wear on the plate and the cutting or scoring of both work and plate. The more true the surface operated on becomes, the thinner should be the coating of marking on the plate. For some purposes the marking does not afford sufficient lubrication, and additional oil would prove detrimental to the work. This difficulty may be prevented by using a plentiful supply of turpentine on the surfaces while they are being rubbed together. In addition to lubricating the surfaces, it also facilitates the work of scraping. lO. Marking Mixtures. — These may consist of red lead or Venetian red in lard or machine oil or any similar materials, red or black, that are not gritty. In some cases, special mixtures are furnished by the shop management and their use insisted on. The marking is rubbed with the hand into a thin coating as evenly as possible over the plate, which is now ready for use. It is well to keep the marking mixture in a tin box provided with a cover, so that it can be kept clean and free from grit. Venetian red is better than red lead, on account of the fact that it is much finer in texture. DRILLS AND DRILLING. 11. Drilling Ratchets. — Ratchet drilling is the slowest method of drilling holes, and should not be resorted to if the work can be done by any of the machine processes, such as the drill press, portable drills, and pneumatic drill- ing machine; but there are places where none of these can 7 21 BENCH, VISE, AND FLOOR WORK. be used or are available and in which cases the ratchet must be used. Ratchets are generally made single acting; that is, the drill only cuts during the forward stroke of the handle; but some of the improved ratchets are made to give a forward rotary motion to the drill or cutter during both strokes. Ratchets are made to use both square- and taper-shank drills. The taper-shank twist drill is the better tool, but it often happens that odd sizes are needed by men out on repair work, where it is impossible to get the proper size of twist drill, and a square-shank flat drill can be made by any blacksmith or by the man himself, or a flat drill already on hand may be made into the required size in a few minutes, either by grinding or dressing. 1 2. Use of Drilling Ratchet. — The ratchet is used for drilling in the following manner : The hole to be drilled is laid out in the usual way and center punched. ' Means must be provided to force the drill into the material, which 8 BENCH, VISE, AND FLOOR WORK. § 21 is usually done by providing some sort of brace, or, as it is commonly called in the shop, an old man, or a drilling crow, that will serve to support the ratchet and drill in the correct position and at the same time allow the drill to be forced into the work by the feed-screw. The brace, drilling crow, or old man, is made in a great variety of ways, from a piece of flat iron or steel bent to the proper form to the well-designed adjustable one shown in Fig. 6. This consists of a base a having an upright b carrying an adjustable arm c that is held by the binding screw d. The base is made fast to the work e by means of a bolt f or clamp j, as shown. The arm c , which has a number of center holes in its lower face, is set to such a height that the ratchet i and drill g will go under it. The drill is set square with the work, or it may be set to lean slightly away from the upright, as the pressure upwards on the arm c will spring the upright b back and so draw the drill about perpendicular. The drill is rotated by means of the handle h and is fed into the work by means of the sleeve R. 13. Special Ratchets. — Ratchets for repair work and for use in contracted spaces are often made very short, and have square holes in their spindles, so as to use very short square-shank drills. They are also used in erecting machin- ery to ream holes in line. 14. Crank- Driven Portable Drill. — The crank-drill is a better tool than the ratchet, where there is room enough to use it. This form of drilling machine is clamped to the work and is operated by a crank that gives a continu- ous motion to the drill. The feed is operated either auto- matically or by one hand, and the crank is turned by the other. These drilling machines will work at any angle and form a very useful tool for heavy work. 15. Scotch Drill. — The Scotch drill is a drilling device formed very much like an ordinary carpenter’s brace. It is usually made by bending a piece of steel or § 21 BENCH, VISE, AND FLOOR WORK. 9 iron so that it will form the necessary crank, providing one end of it with a suitable socket for the drill, which may be either square- or taper-shanked. The other end is provided with a pointed center that may be fed out by means of a screw, thus giving the feed to the drill. The crank is rotated like an ordinary carpenter’s brace, the device being held in place by a knee or other suitable clamping device. Some- times the Scotch drill is made with two cranks arranged like a ship auger, so that both hands may be used at the same time, but usually only one hand is employed, as the other is required to operate the feed-nut. 16. Breast Drill. — The breast drill is so named from the fact that it is provided with a suitable guard that may be placed against the breast while drilling, the feed being obtained by a pressure brought to bear on the drill by the body. The drill is usually operated through bevel gears by a crank on the side of the machine. This style of drill is very largely used for drilling small holes for attaching name plates, and for similar light work. BROACHES A\I) BROACHING. 1 7. Broaching. — Broaching, or drifting, is the process of forming holes by forcing a cutter of the exact form required through holes previously drilled. In all broaching operations, the greatest amount of stock possible must be removed by drilling, and if much remains for the broaching tools, they should be so designed that each tool will be given an equal amount of material to take out. 18. Simple Square Broach. — The form of broach depends largely on the nature and quantity of the work to be done. If this is only a small amount, the broach must be as inexpensive as possible. In this case, most of the work is thrown on the drills or other means used for roughing out the hole, and the broach depended on only for finishing the hole. 10 BENCH, VIvSE, AND FLOOR WORK. §21 The simplest form of broaching is illustrated in making a socket to fit a £-inch square in a tap socket or a chuck-screw wrench. The square may be laid out on the end of a piece of round stock, as in Fig. 7. A ^-inch circle a is first drawn from the center mark b, and the square c is laid off. Four ^-inch holes d are now drilled ^ inch deeper than the hole is to be and just touching the lines of the square. The^-inch hole is next drilled, which leaves the hole as shown in Fig. 8 (a). A square piece of steel having the proper temper may now be driven easily to the bottom of the hole. Fig. 8 (b) shows this form of broach; it tapers a little from the cutting edge e to f. 1 9. Use of Several Broaches in a Set. — In cases where there is a con- (a) f (*) Fig. 8. siderable amount of any given class of work to be done, it is best to use several broaches following one another, each removing a portion of the stock. In the case illustrated in Figs. 7 and 8, the greater part of the metal at the corners was removed by drilling small holes, and in some cases some additional metal was chipped out. If there is much of this work to be done, all the metal in the corners may be removed by passing a series of broaches through the work. In Fig. 9, the forms of four broaches for squaring a Linch round hole that extends through the piece are shown at e, f, g, and h. All the broaches should be provided with several cutting edges, as shown between b and c , and a 21 BENCH, VISE, AND FLOOR WORK. 11 guide pin, as shown at a b, in the upper part of Fig. 9, which represents the finishing broach. 20. Making a Set of Broaches. — The pieces of steel to form the set are first centered and milled to the size of the square, after which the guide from a to b is turned to the size of the largest hole that can be drilled inside the square, which in this case is \ inch. The toothed part from Fig. 9. b to c is cut either by milling or planing, or the teeth may be cut in the lathe and afterwards backed off for clearance by hand. The size from c to d should be made slightly smaller than the toothed part, so that it will easily pass through the hole. The various broaches of the set are made of such form that each takes out nearly an equal amount of stock. The broach marked e is driven through first, and is followed in succession by f y g, and //, which finishes the hole to size. 21. Grinding the Teeth. — In a new broach, the teeth from b to c are all of the same size, so that only the leading teeth cut and those behind simply steady the broach. As the front teeth become dull, they are ground on . the front or flat face, and thus are reduced in size, so that the other teeth farther back must be depended on to do the finishing. In preparing the blanks for the broaches shown, the corners in the broaches *?, f, and g can be turned off in the lathe, and if desired both the cylindrical and the flat surfaces 12 BENCH, VISE, AND FLOOR WORK. § 21 can be finished by grinding after hardening. The broaches described are intended to be driven by a hammer, but they may be forced through by a power or hydraulic press. ZZ. Broaching Keyways. — Keyways may be broached more quickly and accurately than they can be chipped by hand. In some cases, quite large and long keyways are formed in this way, the broaches being driven by means of sledges. The necessary tools for broaching keyways are shown in Fig. 10. First there must be a plug, Fig. 10 (a), turned to the proper diameter cd so that it just fits the bore of the hub, and it must be of sufficient length to pass entirely through the hub. The plug is provided with a collar e , which prevents it from passing too far into the hub. A slot or key way having the same taper as the required keyway in the hub is cut in the plug, as indicated by the dotted line a b. § 21 BENCH, VISE, AND FLOOR WORK. 13 The cutting in the hub is done by the tool shown in Fig. 10 ( c ). The cutting edge is at j, and the thickness^/ must be equal to the depth of the narrow end of the slot b d. In order to make the broach cut, liners are placed in the groove behind the broach; one of these liners is shown at Fig. 10 ( b ). The liners are made of sheet metal, and, if the keyway is a large one, after several thin liners are in place they may be removed and replaced by one thick one, after which the thin ones may be replaced one by one, as the suc- cessive cuts are taken. This method of employing some thick liners reduces the number of joints that can be com- pressed as the broach is being driven, and so makes the work more uniform. The broach is provided with a guide gi, which enters the hole first, and the portion g h must be at least equal in length to the slot a b , so that the broach can be driven clear through. The face j k of the broach should be perpendicular to the face to be cut. The broach, if very large, may be made of machine steel and provided with an inserted blade or cutter at j. The cutting edge of a broach should be hardened to a brown or dark straw color. 23 . Machine Broaching. — Broaches for large holes, or for large numbers of similar holes, such as are met with in manufacturing, are forced through the work by power- driven machines or hydraulic presses that support the work and also guide the tool. Broaches used in these machines are designed with special reference to the form of the hole and the quantity of stock to be removed, and a dozen broaches may be made to work out a single form of hole, each one taking a light cut. C. 6-. III .— 14 14 BENCH VISE, AND FLOOR WORK. 21 Broaches for the machine work may be made, as shown in Fig. 11, with a countersunk center in the head and a cor- responding external center on the point. The No. 1, or smaller, broach of a set is forced downwards as far as it will go, and then the No. 2 is placed on it, with its point in the reamed center to guide it; this one, also, is forced down- wards, driving the first one through. This is repeated until all the broaches have been driven through the hole. In some cases, a single broach is forced through by hydraulic pressure and made to finish a hole in one operation. Fig. 12 shows a broach and broached piece. The broach in this case has rounded corners, which illustrates a practice that should be followed wherever practicable, as teeth of this form are much less liable to break than those of square-cornered broaches. The notches a allow the broach to be started without taking the whole cut, and when it has entered far enough to have sufficient support to steady it, the whole teeth b commence cutting and finish the work. 24 . Angle of Broach. Teeth. — The teeth on broaches are sometimes cut diagonally across the sides, but these do not cut as easily as those cut square across, and they also have a tendency to force the ‘broach to one side or to make it take a spiral course, thus causing some of the teeth to run into the stock and make a rough hole. For this reason, the teeth are generally made straight across. 25 . Lubrication of Broaches. — For cutting most metals, broaches require an abundant supply of lard oil. In broaching keyways in cast iron, oil is not required so much for the cutting operation, but the back and sides of the broach should be well lubricated. § 21 BENCH, VISE, AND FLOOR WORK. 15 REAMERS AND REAMING. 26. Object of Hand Reaming. — The continued use of machine reamers dulls their cutting edges and at the same time slightly reduces their diameters. For some work, a hole yoVo- i nc h under size, such as would be produced by a worn reamer, would not be objectionable, but in addition to being small, the hole will be comparatively rough. These defects may be overcome by hand-reaming the hole. 27. Ordinary Hand Reamer. — The hand reamer shown in Fig. 13 illustrates one form of this class of tools. The body a is finished to the correct standard size, and the shank is made of such size that it will act as a guide when Fig. 13. the hole to be reamed is longer than the fluted part a. A groove c, turned about one diameter from the lower end, serves as a stopping place for the wheel while grinding, and below this the diameter is about yqVo inch smaller than at a. From the point c to d, about one diameter, the reamer is tapered up to the full size, and from d up it is parallel. The hand reamer is used, as its name implies, only by hand. The end e is entered into the hole left small by the under- sized machine reamer and acts as a guide, and the taper from c to d removes the stock, while the parallel part a maintains the size. The small amount removed insures the durability of the tool and the smoothness of the hole. For cast iron and brass, the reamer should be entered and twisted through the hole, using enough pressure to force it through quickly. In the case of cast iron, the use of oil will give a smoother hole than can otherwise be obtained. For wrought iron and steel, it should be well lubricated with lard oil. 28. Step Reamer.— The reaming of taper holes, par- ticularly large ones, in tough and hard metals, is greatly 16 BENCH, VISE, AND FLOOR WORK. § 21 facilitated by using the step reamer illustrated in Fig. 14. The small end a of this reamer is made the size of the small end of the hole. A hole of a size corresponding to a is drilled into or through the work as required. The step reamer is then started in and run to the -necessary depth. This reamer cuts only on the end of each step, as at b, c , etc., the diameter of the reamer being slightly less at the top of each step than at the lower end; for instance, the diameter is smaller at e than it is at d , in order that the tool may not bind in the hole. Clearance is also given the cutting edge Fig. 14. from /to g. This reamer is cut with four flutes, and there- fore has four sets of cutting edges. The half-round notches h are cut to make a stopping place for the wheel while grind- ing. The use of this reamer does away with the necessity of using a number of different-sized drills to prepare the hole for reaming. After the step reamer has removed the stock, a notched taper reamer is run in to remove the steps, and after that the finishing reamer smooths the hole. Step and taper reamers intended for use in the lathe or by hand are provided with square shanks, but when made for use in drilling or boring machines they must be provided with taper shanks, so as to fit the sockets. 29 . Taper Reaming. — Taper holes are frequently hand-reamed, to make them of the correct size and smooth- ness. This is done after the stock is removed by the rough- ing and finishing reamers. The taper hand reamer, when not in use, should be kept in a box or tied up in a heavy paper covering, as any nick or dent on its cutting edges will seriously mar the hole. The taper hand reamer must be used with great care. It should be carefully placed in the hole, well oiled if in wrought iron or steel, and turned with § 21 BENCH, VISE, AND FLOOR WORK. 17 enough pressure to insure its cutting from the very first; for turning a taper hand reamer in a hole when it does not cut will soon ruin it. Valve bushings, which must be perfectly smooth and parallel internally, are often reamed with undersized machine reamers and then forced into place, after which a hand reamer is run through them to correct their defects. 30. Advantage of Vertical Reaming. — All ream- ing, whether hand or machine, is better if done in a vertical position. This is so because the weight of the reamer, if working horizontally, tends to ream downwards, and so either carries the reamer out of line or tends to take more out of the bottom side of the hole. Also, any chips or cuttings will fall out of the vertical hole, but in the hori- zontal hole they remain between the teeth of the reamer and often scratch or score the work. 18 BENCH, VISE, AND FLOOR WORK. § 21 31. Example of Vertical Reaming. — Fig. 15 shows the practice of a prominent engine builder. The pulleys for these engines are first put on the boring mill and turned to inch over the finished size; the hole is bored about inch small and then hand-reamed to size, after which the wheel is put on a mandrel and the face turned true and to size. The reaming is done in the following manner: The wheel is placed on blocks, as shown, and the reamer’s shank b is passed up through the bore and hooked to the threaded rod d. A split bush c is placed around the shank b and pushed down into the bore to act as a guide. A double-end wrench is placed on the square of the shank at e , and two men walk around the wheel to turn the reamer. The threaded rod d passes through a nut, not shown in the cut, and this feeds the reamer a upwards through the hole. The reamer a is shown just as it leaves the finished hole. Another finishing reamer is shown at f. 32. Reaming Holes in Line. — Holes may be reamed in line in the following manner: The holes' in two or more castings that are to be bolted together are first laid out as close as possible to their correct location ; all those in one piece are drilled and reamed to size, and the corresponding holes in the next piece are drilled about ^ inch smaller; then the two castings are clamped together in their correct posi- tion, and a reamer the same size as the finished hole, which will cut only on its end, is put through the reamed part of the hole and ratcheted through the smaller hole, thus bring- ing them perfectly in line. This work must often be done in very contracted or limited spaces, and for such work, special reamers, called rose bits or rose reamers, must be made. INSIDE THREAD CUTTING. 33. Methods of Tapping. — Holes are threaded in three ways: first, by cutting in the lathe; second, by using a special tapping fixture in the drilling machine; and third, by hand. The first two methods provide their own means § 21 BENCH, VISE, AND FLOOR WORK. 19 of keeping the tap square with the work, but in hand tapping much depends on the skill of the workman. 34. Squaring Tapped Holes. — Two sorts of hand taps are in common use. The first kind, Fig. 16 ( a ), is made (b) Fig. 16. with a parallel end be the size of the bottom of the thread. This parallel end fits the hole made by the tap drill, so that by the exercise of a little care on the part of the user a squarely tapped hole is the result. The other style, Fig. 16 ( b ), is tapered from d to e\ con- sequently, it will not stand square with the hole. To tap a hole square with (b), the tap should be well oiled, placed in the hole, and given two or three turns with a double- ended wrench. At this point remove the wrench and apply a square to the tap in the man- ner shown at a , Fig. 17. Try the square at the next flute, and if the tap shows out of square apply pressure enough sidewise on it with the wrench while turning to bring it square with the surface. • Repeat these trials until the tap is found to be square. If a square is not at hand, a wide 20 BENCH, VISE, AND FLOOR WORK. § 21 6-inch steel rule may be used instead, as at b , Fig. 17. The tap shown in Fig. 16 (a) will go in reasonably straight, but the beginner will do better work with it by using the same precautions as with the other style. 35. Tapping Jig. — The tapping jig shown in Fig. 18 is sometimes used. It consists of a piece of iron or steel bent to the form shown at a , Fig. 18 (a). The bottom surface be is planed flat, and a hole d the size of the tap shank is drilled square to be. A plug e is turned to fit d and the hole f to be tapped. To use this tool or jig, put the plug into the hole d and then push it into f, as shown ; clamp the jig a fast at the point g, and see that the plug e fits easily in both holes; remove the plug, and replace it with the tap, which will be held in the correct position to tap the hole, as shown in Fig. 18 ( b ). The hole d in the jig may be made as large as the largest tap, and a set of bushings made to adjust it to taps having smaller shanks. 36. Producing Smooth Threads. — It is sometimes desirable to tap holes with particularly smooth threads. § 21 BENCH, VISE, AND FLOOR WORK. 21 This may be done by first tapping the hole with a V-thread tap and then following it with a tap having the United States standard form of thread. The V-tap thread will leave enough material so that the United States standard thread tap will perform the same work in the tapped hole that the hand reamer does in the plain hole. 37. Number of Taps Necessary. — Ordinary holes in thin stock may be tapped in one operation bv running the taper tap clear through the piece; but if the hole is of great depth, or of hard material, a second, or plug, tap must be run down, to relieve the long cut made by the taper tap. By using these two taps alternately, holes may be tapped to any depth that the taps will reach. Neither the taper nor the plug taps will thread a hole clear to the bottom, so when this is necessary, a third tap, called a bottoming tap , is screwed clear to the bottom of the hole. Care should be taken in using this tap, as the end teeth are easily broken by the heavy cut. 38. Pipe Threads. — -The threads on pipe are of the V type, and to insure tight fits the threaded parts are made tapering. The standard taper for the threaded portion of pipe is ^ inch to the inch or |- inch to the foot. The holes to be tapped for small sizes of pipe are usually drilled to the size of the bottom of the thread at the small end of the tap, and then the pipe tap run down to the proper depth ; but for the large work, a reamer having the same taper as the tap is run in to take out some of the stock. This reaming leaves the right amount of stock for threading, and saves unnecessary wear on the tap. WRENCHES. 39. Double-End Wrench. — The wrenches used for turning taps and hand reamers are made in a great variety of forms. Some are made solid, with one or more holes for 22 BENCH, VISE, AND FLOOR WORK. § 21 different-sized shanks, but the best wrenches are made of the form shown in Fig. 19. This wrench is adjustable to several different sizes of tap squares. The length of the handles of different wrenches of this type are proportionate to the diameters of the taps on which they may be safely fig. 19 used. Holes must frequently be tapped in spaces where wrenches of this type cannot be turned, and the single-end wrench must be substituted ; but, where practicable, an exten- sion should be placed on the tap and a double-end wrench used, as by this means holes can be tapped more nearly true and the danger of breaking the tap is reduced to a minimum. 40. Special Double Wrench. — Special forms of wrenches are sometimes made for special work. The wrench shown in Fig. 20, which is commonly used in the boiler shop, and sometimes in the machine shop, may be taken as an illustration of this class, and may suggest others that are Fig. 20. suitable for special operations. The tap wrench illustrated in Fig. 20 is called a stay bolt tap wrench , and is made of -|-inch round steel bent to the form shown. The square hole a is provided for the special staybolt tap shown. Two handles c and d are formed by the bends, and by using both § 21 BENCH, VISE, AND FLOOR WORK. 23 hands, the tap may be given a continuous rotary motion. Whenever possible, these taps are screwed clear through and taken out on the other side, instead of screwing them back again, as is done with the ordinary hand tap. 41. Single-End Wrenches. — Single-end wrenches are made both open and closed ; that is, they are so arranged that they simply enclose three sides of a square nut, or four sides of a hexagonal nut, or are so made that they entirely surround the nut. The open-end wrenches have certain advantages, in that they do not have to be slipped over the end of the bolt or nut; they are made both with the sides of the jaws parallel to the line of the handle and with the sides of the jaws set at an angle to the center line of the handle. For some purposes the straight wrench with the sides of the jaws parallel to the handle, as illustrated in Fig. 21, is suitable, but for work in contracted spaces it is best to give a wrench intended for hexagonal heads or nuts an offset, as shown in Fig. 22. This offset should be 15 degrees. The manner of using the wrench is illustrated in the four views in Fig. 22. In Fig. 22 () wrenches may be made with the FlG - 24 - sides of the opening in the end of the wrench parallel or perpendicular to the handle b, Fig. 24 ( a ), which will give results similar to that shown in the open-end wrench in Fig. 21; or they may be made with a 15-degree offset for hexagonal wrenches, and 22-J- degrees offset for square wrenches, as illustrated in Figs. 22 and 23. The offset is generally not as important in the socket wrench as in the solid-end or open-end wrench, on account of the fact that the shank c , Fig. 24 ( a ), of the wrench is usually made long enough to clear all obstructions. 44. Socket Extensions for Wrenches. — When it becomes necessary to tap holes in contracted spaces, or to screw in studs or bolts in such locations, it is sometimes possible to reach the work by means of a socket extension 26 BENCH, VISE, AND FLOOR WORK. § 21 similar to that shown in Fig. 25. This consists simply of a long stem a having at one end a socket c } of the form required to fit the work, and a square b on the other end intended to fit any ordinary double- end or single-end wrench. Usually, these socket extensions are used only with double-end wrenches. 45. Ratchet Wrenches. — In the case of practically all single-end wrenches, it is neces- sary to remove the wrench and replace it on the nut after a portion of a revolution has been made. As there are a great many places where nothing but a single-end wrench can be used, much valuable time is lost in this changing of the wrench. To overcome this difficulty, ratchet wrenches have been introduced. A good type of adjustable ratchet wrench is illus- trated in Fig. 26, in which the jaws a can be adjusted by means of the screws b so that they will accom- modate a number of sizes. A handle c can be moved for- wards through whatever portion of a stroke the location will permit, and then return for another stroke. It is possible Fig. 26. to make as small a fraction of a revolution as one tooth of the ratchet, shown at d. This style of ratchet wrench has but a single pawl engaging the ratchet, and hence there is bound to be some lost motion before the pawl takes hold of a tooth on the forward stroke. 46. Teeth of Ratchet Wrench. — It is advantageous to have the teeth of the ratchet as coarse as possible, so as to give them the requisite strength; in order to obtain the § 21 BENCH, VISE, AND FLOOR WORK. 27 effect of fine teeth, which give the least amount of lost motion, the multiple-pawl ratchet has been introduced. This is illustrated in Fig. 27. in which the ratchet a has 12 teeth; 5 pawls b are so placed that only one of them will engage a tooth at a time, as shown at c. By moving the pawls back { of a space between th-e teeth, the next pawl will come in contact as at d , and hence the lost motion can- not be greater than \ of y 1 ^, or ^ of a revolution. 47. Studholt Wrench. — For driving studs by means of a ratchet, a special stud holder is provided, as shown in Fig. 28. Fig. 28. The stud a is screwed into the socket b , and then the point of the setscrew c is run down against the end of 28 BENCH, VISE, AND FLOOR WORK. § 21 the stud so as to lock it in the socket. The setscrew c is held in place by means of a locknut d. A stud driver is operated by means of a ratchet on a square e. This style of stud driver is ordinarily used in a very thin ratchet, as shown at c ' . Ratchets may also be applied to socket extension wrenches where these must be used in locations in which a complete revolution cannot be made. The time saved in putting the studs into a single large engine will usually more than pay for the price of a ratchet wrench and suitable stud driver. OUTSIDE THREAD CUTTING AND PIPEWORK. 48 . Die Stock and Square Dies. — Outside threads of various pitches and sizes must often be cut by hand. Dies for such work are made to cut threads on pieces rang- ing from ^ inch to 2 inches in diameter. A form of stock and die that has many advantages is shown in Fig. 29 ( a ). The stock a has an oblong opening b provided with guides for holding the split die c, which is closed by a setscrew. The form of these dies is shown in Fig. 29 (b). They are so constructed that the cutting is done at the points f, which also steady the dies when starting on the work. Bolts can be threaded standard, undersize, or oversize with these dies. For example, a No. 14 screw, a ^-inch, or a -^-inch screw, all 20 threads per inch, can be fitted with one pair BENCH, VISE, AND FLOOR WORK. 29 §21 of dies. They may be made in any size and should be tapped with an oversize tap in order to provide clearance. These dies are especially adapted to repair work where the variety of work is great and the quantity small. With these dies several cuts must be taken to cut a full thread. A pair of blank dies with suitable notches cut in them, used in this stock, makes an excellent tap wrench. 49. Die Stock and Round Dies.* — Standard work is best done with any of the many forms of round dies, one of which is illustrated in Fig. 30 (#), (£), and (^). When in use, the die is held in a die stock, of the form shown in Fig. 31. The die is made of two parts a and b. Fig. 30 (a) showing the two parts in place; Fig. 30 (b), the die with one part removed, and the latter being shown detached in Fig. 30 (c). This die can be adjusted within narrow limits, the screw d being made with a tapered head, and by turning it in, the two halves are forced apart. The die stock, Fig. 31, is provided with a thumbscrew that grips the die when in place. The lower part r, Fig. 30 (b), of this die is bored out to the exact size of the rod to be threaded, C. 6". III .— 15 30 BENCH, VISE, AND FLOOR WORK. 21 and forms a guide for the die in starting. These dies require some pressure to start them, but once started they cut a full thread at one operation. The large sizes are made with inserted chasers that are adjustable for wear and if broken may easily be replaced. 50 . Pipework. — Pipework enters largely into some branches of machine work, and a few of the principal tools used in this connection will be illustrated and described. Pipe is made in lengths of from 15 to 20 feet. It is threaded on both ends at the pipe mill, and a sleeve screwed on one end. Large pipe has a ring screwed on the other end, to protect the threads during shipment and handling. 51 . Cutting Pipe. — Large pipe is generally cut into the proper lengths in a pipe-cutting machine by a cutting-off tool, in the same manner that stock is cut off in the lathe, and afterwards is threaded in the same machine. Some pipe machines are driven by hand, others by power. A great deal of small pipe is cut with a pipe cutter, shown in Fig. 32. The body c of this tool carries a slide e , operated by the screw on the handle f. Three hardened-steel cutting wheels a , b , d are set in the frame and slide. The slide e is drawn back by means of the screw, to allow the pipe to go in between the cutters, which are then forced into the pipe by turning the handle, and at the same time rotating the tool around the pipe. Other cutters of this sort are made that have but one cutting wheel, which is in the slide. A hack saw makes a good pipe cutter, if used carefully, and by using blades having 25 teeth per inch there is little danger of breakage. Thin brass and copper tubing can be cut easier by a hack saw than by any other means. §21 BENCH, VISE, AND FLOOR WORK. 31 52. Threading Pipe. — When the pipe is cut to the correct length, it must be threaded. This is done, as has been said, in power-driven machines for the large sizes, but most of the small-pipe threading is done by hand with one of the various forms of pipe dies. 53. Pipe Stock. — The ordinary pipe stock is shown in Fig. 33. This stock has a body d into which handles c ia) ( h > Fig. 33. are screwed at each end. It has a square recess Fig. 33 (c), in the top to hold the die a , Fig. 33 (a). A cover d , Fig. 33 ( d ), slides over the die to hold it in place. For threading the larger sizes of pipe, the pipe stock is threaded internally and the bushing e, Fig. 33 (d), is screwed into it. The thread is 11^ per inch for sizes up to and including 2 inches, and above that 8 per inch, to correspond to the standard pipe threads. A bushing, or thimble, h having a 32 BENCH, VISE, AND FLOOR WORK. § 21 hole through it of the size of the outside diameter of the pipe is placed in the bushing WRENCHES. 55. Pipe Vises. — Pipe, being round, cannot be screwed together by the ordinary forms of wrenches, and, being hol- low, it cannot be held in the ordinary vise without being crushed. For cutting, threading, or having fittings screwed on, pipe may be held in a pipe vise, Fig. 10, Part 1, or in an ordinary vise having clamps made in the form shown in Fig. 35. The holes a in this clamp are made to fit the out- side diameter of the pipe, and have teeth cut in them to pre- vent the work from slipping. They are held together by the spring b. For putting polished pipe together, some form of clamp or wrench having smooth jaws must be used. 56. Pipe Tongs. — Ordinary iron pipe is screwed together with wrenches’ of various forms. The principal ones are shown in the following illustrations: Fig. 36 shows Fig. 36. the most common form, commonly called pipe tongs, one size being provided for each separate size of pipe. This general style is also made with the jaw a adjustable and controlled by a screw, so as to adapt one pair of tongs to several sizes of pipe. 34 BENCH, VISE, AND FLOOR WORK. § 21 The chain tongs shown in Fig. 37 is especially adapted to work on large pipe. The handle e has two steel jaws a cut on both sides. A chain b made fast to the bolt c per- mits both sides of the jaws to be used. Wrenches of this type are made of various sizes for use on all sizes of pipe. Chain tongs are the most rapid and economical tools of their kind for medium and large work. 57. Pipe Wrenches. — The Stillson pipe wrench, illus- trated in Fig. 38, is an adjustable wrench. It has a movable jaw a moved by the milled nut b, and may be used on Fig. 38. several sizes. It is made particularly for pipework, but finds many other useful applications. Alligator wrenches have a V-shaped opening in one end, and in the smaller sizes in both ends. One side of this opening is left smooth and the Fig. 39. other has teeth cut across it in the form shown in Fig. 39. These wrenches grip all round objects, and are used to grip pipe in places where the other forms of wrenches can get no hold at all. § 21 BENCH, VISE, AND FLOOR WORK. 35 A wedge-shaped piece of steel, as b, Fig. 40, having teeth cut on it similar to those on the jaw of an alligator wrench, may be made for any size of monkeywrench. The jaw may be made in the form of a fork, the two arms of which reach past the bar of the wrench and have a hole through their ends, so that a split pin can be put through them to keep the jaw from falling from its place on the bar. Fig. 40 (a) shows a monkeywrench having a manufac- tured jaw b on its bar. This jaw differs from the shop-made jaw in having only one arm, which is bent at right angles to pass over or around the back of the bar, as shown at c. A thumbscrew d is used in this jaw, instead of the pin, to hold it on the bar. Fig. 40 (b) shows a simple attachment for adapting a monkeywrench to pipework. This consists of a nurled and hardened cylinder, or roller having a wire handle f for convenience in putting it in place. It is placed between the wrench jaw and the pipe, or other round piece, as shown at g. A piece- of 10-inch or 12-inch round file about 1 or 1^ inches long may be used instead of this attachment. 58. Use of Rope as Pipe Wrench. — A rope may be used in place of a pipe wrench, if a suitable wrench or tongs 36 BENCH, VISE, AND FLOOR WORK. §21 is not available. The manner of making and using such a device is shown in Fig. 41. The rope is first doubled, as shown at a, and given enough turns round the pipe to insure gripping. A bar or even a piece of wood bis thrust through the double end of the rope a , and the two loose ends of the rope are brought together and held, as shown at c. Enough strain is put on c to prevent slipping, and the pipe is turned by the bar b, the same as with any pipe wrench. The work- man may walk around the pipe, or by slacking off on both the bar and the rope ends, he may rotate the rope back- wards to get a new hold. LAYING OUT. INTRODUCTORY. 59. Definition. — Laying out is the process of placing such lines on castings, forgings, or partially finished surfaces as will designate the exact location and nature of the opera- tions specified in the drawing. 60. Preliminary Operations. — In many cases, one or more men are regularly employed in laying out work. Occasionally, the same men devote a part of their time to inspecting or testing finished or partly finished work. The 21 BENCH, VISE, AND FLOOR WORK. 37 object of inspecting when partly finished is to prevent additional work, should the first operation be defective to a degree that calls for the rejection of the piece. One great advantage of having the work laid out by an expert who has the drawing of the finished piece before him is that he may determine, before any work is done, whether the for- ging or casting has the required amount of stock, and should there be insufficient stock at any particular point, the piece may either be rejected or perhaps saved by carefully locating the lines so as to permit the finishing of all the holes and surfaces; whereas, if a part of the work is done without the special laying out, it may afterwards be found that there is not sufficient stock for some later operation. 61. Most Economical Method.— The economy of having the laying out done by men set apart for that pur- pose is due to several reasons. Men become expert and quick at this kind of work ; the tools of the shop are not idle while the men running them stop the machine to do the laying out, as was formerly the case; even the vise hands are saved the time of laying out their work ; besides, it can be done on a convenient plate with proper tools to better advantage than otherwise. Then, work can be laid out as soon as the castings or forgings come into the shop, per- haps long before the tools are at liberty to finish the work, and it may be of great advantage to find out early any lack of stock, or any defect that may cause the rejection of the piece, or any change that is to be made, if it is a forging. For instance, a casting may appear to be all right, but a hole may be cored too large, or the core may not have been set correctly, or it may have moved in the mold. After lay- ing out some of the lines and making sure that there is stock enough for finishing, it is often advisable to do part of the finishing before completing the laying out. 62. Divisions of Laying Out. — Laying out may be divided into two parts: the preliminary and the final. The preliminary laying out consists in measuring the piece to see that it is of the proper size and dimensions, and then 38 BENCH, VISE, AND FLOOR WORK. § 21 drawing such lines on its surface as will show where the first machining operations are to be performed. The center lines are so placed, if possible, that they will not be removed by the machining process, and can be used in resetting the piece for future machining. The final laying out consists of placing such lines on the machined surfaces as will indi- cate the further operations to be performed. The preliminary laying out in the case of a steam-chest cover would be to level it on the table and draw such lines on its edges as will indicate its thickness; after which it should go to the planer and be machined to the dimensions denoted by the lines. The final laying out will consist of laying out the holes for the studs and such other operations as may be designated on the drawing. 63. Methods of Laying Out. — Laying out is done in different ways, according to the nature of the work and the accuracy required. The lines are drawn on the surfaces with surface gauges or scribers, and centers are denoted by prick-punch marks. Circles and arcs of circles are drawn with dividers and trammels, and many irregular forms are drawn on the work from accurately filed templets. In some cases, the work is laid out by simply drawing the necessary lines on its surface. In other instances, perma- nence is given the lines by dotting them with prick-punch marks placed directly on the line; or, a thin chisel may be driven into the work on the lines, making a deep cut in the metal. Guard lines are often placed on the work to make sure that the original lines were closely followed, as, in lay- ing out holes to be drilled, some machinists place a circle Yg- inch outside the one worked to, and if the hole is correctly drilled, it will be concentric with this circle. 64. Coatings on Which to Make Lines. — In many cases it would be impossible to scratch lines on an iron sur- face, especially when the latter surface is not perfectly smooth or when it is very hard. This has led to the use of various coatings, on which the lines may be made or in which they may be scratched. Sometimes, chalk is simply rubbed § 21 BENCH, VISE, AND FLOOR WORK. 39 on the surface. In other cases, powdered chalk is mixed with alcohol and applied with a brush, or whiting is mixed with alcohol or water and applied in the same way. Alco- hol has the advantage over water in that it will dry quicker and has no tendency to rust the surface. When the surface has been machined and is fairly smooth, it may be copper-plated by wetting and rubbing the surface with a piece of copper sulphate (blue vitriol), or, better still, by making a saturated solution of copper sulphate and applying this with a brush or swab. As the solution dries, it will be noticed that the surface is covered with a thin layer of copper. This cannot be done if there is any oil on the surface, and surfaces to be thus coppered must be cleaned perfectly before applying the solution. Lines may easily be scratched in this copper and will show very plainly on account of the difference in color between the iron and the copper. In some cases, a light coat of some quick- drying white paint is used, as, for instance, white lead and turpentine. In any case, after the lines are drawn, their location should be permanently established by means of light prick-punch marks. LAYING-OUT TOOLS. 65. Tools and Appliances Used in Laying Out. A variety of tools are used in laying out work. The most common are the surface gauge, scriber, hammer, prick punch, level, square, dividers, trammels, and a line, if large work is handled., In addition to these tools, there should be a supply of quick-drying white paint, chalk, a solution of blue vitriol, a lot of iron wedges, and small pieces of sheet metal of various thicknesses for blocking, parallels of vari- ous sizes, small screw jacks, one or more pairs of V blocks, a pinch bar, and a hack saw. The surface of the laying-out table or plate must be kept as clean as possible; therefore, a bench brush should be pro- vided for the table, and for the large plate, a brush and broom. As a good many drawings are used at the laying- out table, a table or stand of sufficient size to hold them, 40 BENCH, VISE, AND FLOOR WORK. § 21 and drawers in which to place those not in constant use, should be provided near at hand. 66. Surface Plates. — The surface plate is used in machine construction for testing flat surfaces. It is gener- ally made, as shown in Fig. 42, of a hard, close-grained iron casting having a flat top a , Fig. 42 (< a ), supported by a ribbed back b, Fig. 42 (b). Three legs c , d, and e, Fig. 42 (b), Fig. 42. are provided, so that the plate will stand evenly on any sur- face. Handles /" and g are placed on the ends, by which the plate may be lifted. The tops of these plates are first planed as smooth as possible, after which they are filed and scraped perfectly flat. When in use, the surface plate is coated lightly with some marking material, after which the plate is rubbed over the surface that is to be trued. The marking material is left on the high places, thus showing the parts that are to be removed with the scraper. This operation is repeated until the surface shows a good bearing at all points. Small arti- cles are rubbed on the plate. Care should be taken in using- surface plates to use every part of the surface as evenly as possible, for if the work is all done in one place, the plate will soon be spoiled. Surface plates of this form are made in a great variety of sizes for different kinds of work. Spe- cial plates are often made for special work, in places where it is impossible to put a plate having a ribbed back. 67. Straightedges. — A straightedge is used for test- ing flat surfaces and the alinement of machine parts. Most § 21 BENCH, VISE, AND FLOOR WORK. 41 straightedges are made with two edges that must be straight and parallel. The metal of the straightedge must be so placed as to give the greatest stiffness in the direction of the edge to be used. For this reason, straightedges are usually made deeper than they are wide. Straightedges are made in a large variety of forms and lengths, and may vary from 1 inch or so in length up to 10 feet or more. For small work, a graduated steel rule is frequently used as a straightedge, the hardened and ground ones produced by several manufacturers be- ing the best for this purpose. Hardened-steel straightedges having the general form of a knife, so as to reduce the straightedge to a narrow line, are frequently used. Fig. 43 illustrates a common form that is hollowed out on the sides so as to give a better grip to the hand in using it. 68. Long Straightedges. — Where straightedges of considerable length are desired, careful attention should be paid to their design, to see that they are made as stiff as possible, and at the same time that the weight is not unduly increased. Where only one straight surface is required, the form shown in Fig. 44 is very good indeed. These are made of cast iron, and the surface a b is carefully planed and scraped true. Where it is necessary to use a level on the back of the straightedge, or where other straightedges may have to be placed at right angles, it becomes necessary to have both edges true and parallel. For this class of work the tool shown in Fig. 45 is especially useful. The drawing shows the proportions for a 10-foot straightedge. It will be noticed that the general form is that of a box girder, and that the 42 BENCH, VISE, AND FLOOR WORK. § 21 center is cored out, openings being left in the sides to sup- port the core during casting. The metal, in the case of a 10-foot straightedge, should be about \ inch thick, and a a straightedge of this form should be planed all over and allowed to season some time before it is finished, so as to relieve the casting strains as much as possible. b Fig. 45. SUBDIVIDING CIRCLES. 69. Locating the Centers of Circles. — When it is necessary to draw a circle, on work where the center does not occur on the casting, but in the center of an opening or cored hole, it is necessary to locate the center from which the circle may be drawn. This may be done by fitting a strip of wood across the cored opening, and locating the center on this. Owing to the fact that wood is too soft to give a good center to work from, it is usual to place a piece of metal where the center is required. This piece of metal may be a tack driven into the wood, the center being located on the head; or it may be a triangular piece of tin having the corners bent at right angles to the surface, so that they can be driven into the wood, the center being located on the flat surface of the tin. 70. Use of Screw Jacks. — Sometimes, small screw jacks having flat sides on the body of the jack are used to locate centers, the screw jack being placed across the hole and the center located on its side, as shown in Fig. 46 (a). After the center is located, the bolt-hole circle is drawn, and the required holes spaced off on it. If the cored hole is too large for one screw jack to reach across, two screw jacks § 21 BENCH, VISE, AND FLOOR WORK. 43 may be placed with their bases together, as shown in Fig. 46 (b), and the center located on them. 71. Laying Off Subdivisions of a Circle. — In case a circle is to be divided into 4 or 6 parts, or into multiples of 4 or 6 parts, it is usual to draw diameters dividing it into this number of parts first, and then make any additional sub- divisions from these points. Four divisions can be easily obtained by drawing two diameters at right angles, the work being mounted on the laying-out plate, the horizontal diameter being obtained with the surface gauge, and the vertical one by means of a square. To produce 6 divisions, it is only necessary to set the dividers to the radius of the circle and then step them around the circumference of the circle, when it will be found that the radius will just step around 6 times. In order to produce any other number of divisions, up to and including 100, the accompanying table is given. By its use, the dividers may be set very closely, and much of the time and trouble usually spent in getting the dividers properly set by stepping them around with trial distances may be avoided. The numbers in the column headed “N ’’indicate the number of divisions into which the circle is to be divided, and the numbers in the column headed “ S ” are the sines of 44 BENCH, VISE, AND FLOOR WORK. § 21 TABLE FOB DIVIDING CIRCLES. N S N S N S N S i 26 . 1 20540 5 i . 061560 76 .041325 2 27 . 1 16090 52 •060379 77 . 040788 3 . 86603 28 . 1 1 1970 53 •059240 78 . 040267 4 . 707 1 1 29 . 108120 54 •058145 79 •039757 5 • 58779 30 • 104530 55 •057090 80 . 039260 6 . 50000 3 i . 101 1 70 56 .056071 81 •038775 7 • 43388 32 . 098018 57 •055089 82 •038303 8 .38268 33 •095056 58 •054139 83 •037841 9 .34202 34 . 092269 59 •053222 84 • 03739 1 IO .30902 35 . 089640 60 •052336 85 •° 3 6 953 1 1 .28173 36 .087156 61 •051478 86 •036522 12 . 25882 37 . 084804 62 •050649 87 •036103 i 3 .23932 38 . 082580 63 •049845 88 .035692 i 4 .22252 39 . 080466 64 . 049068 89 •035291 15 . 20791 40 . 078460 65 .048312 90 •034899 16 .19509 4 i .076549 66 .047582 9 i .034516 17 ■ i8 375 42 .074731 67 . 046872 92 .034141 18 •i 73 6 5 43 •072995 68 . 046184 93 •033774 1 9 . 16460 44 •071339 69 •045515 94 •033415 20 •15643 45 •069756 70 •044865 95 •033064 2 1 . I 49°4 46 . 068243 7 i •044232 96 •032719 22 .14232 47 •066793 72 • 043 6i 9 97 .032381 23 • 1 36 17 48 . 065401 73 .043022 98 •032051 24 •13053 49 •064073 74 . 042441 99 . 031728 2 5 •12533 5 ° . 062791 75 .041875 100 .031411 half the angles obtained by dividing the circle into the number of parts given in N. The distance between any two points on the circle may be obtained by the formula M — 5 X D t in which M equals the measured distance between two of the points in inches, D the diameter of the circle in inches, and 5 the number found in the column S of the table oppo- site the number of holes required. § 21 BENCH, VISE, AND FLOOR WORK. 45 Example. — If it is required to divide a 62-inch circle into 44 equal parts, what will be the distance to which the dividers should be set ? Solution. — Opposite 44 in the column marked N of the table, and in the column marked S, is found .071339. Substituting in the for- mula, we have M = .071339 X 62 = 4.423018 in. Ans. For ordinary work it would not be necessary to set the dividers closer than to hundredths of an inch ; hence, the dividers may be set to 4.42 inches. On account of the fact that 44 is divisible by 4, the circle may be divided by two diameters drawn at right angles, and the spaces marked off to the four points thus obtained. 72. Laying Out the Square and Hexagon. — It is always best in laying off a circle to locate either 4 or 6 points accurately and to work from these, as this reduces the effect produced by means of a slight mistake in the setting of the dividers; for if the circle were all laid off from one point, and the dividers were set to a distance slightly greater than that required, the last division would be smaller than the others by an amount equal to this error multiplied by the number of spaces in the circle. But by dividing the circle into 4 or 6 parts, and then stepping off the spaces each way from each of these points, the total error at any given point will only amount to the error in setting the dividers multiplied by the number of spaces marked off from the given point, which will be from -J- to of that in the previous case, depending on whether the circle has been divided into 4 or 6 parts. LAYING-OUT PLATES. 73. Plate for Light Work. — For laying out light or small work, the size and character of the plate used may vary greatly. In some cases a flat casting, as the base of an old machine, is taken from the scrap pile and planed up; this is placed on a bench or on suitable trestles. In other cases, a well-designed casting is made. Fig. 47 illustrates a general form of laying-out plate. The plate a may vary in size from 2 or 3 feet on each side up to considerable C. S. III . — 16 46 BENCH, VISE, AND FLOOR WORK. § 21 size, about 7 feet by 10 feet being the largest size practicable for this design of plate. In the larger size, the top a should be made 1^ inches thick, the ribs b should be carried around the sides of the plate and cross-ribs placed across the back of the plate about every 24 inches; the depth of these ribs for a plate 7 feet by 10 feet should not be less than 8 inches, and they should be of the same thickness as the body of the plate. The casting should be planed on the upper surface# and on the faces of the ribs b , so that the faces b will be at right angles to the surface #, thus ijiaking it possible to use surface gauges or other tools from the faces b. In a plate of this style, it is well to draw parallel lines both lengthwise and crosswise of the plate, the lines being 3 or 6 inches apart. As shown in the illustration, the plate is mounted on trestles c , and care should be taken to keep the upper surface of the plate level and out of wind, by adjusting wedges under the legs of the trestles, as shown at d. For ordinary working, it is well to have the upper surface of the plate about 30 inches from the floor. Such a plate as this may be placed under the main traveling crane, and it is also well to have an auxiliary air lift, or similar hoisting device, for handling the work when the crane is not available. § 21 BENCH, VISE, AND FLOOR WORK. 47 74. The advantages of this style of plate are that it is not a permanent fixture in any one place, and hence can be easily moved from one part of the shop to another, if it should be more advantageous to have it in a different position. Then, too, if the plate is not needed for some time, but the floor space is, it can be turned up on one edge and set against the wall, and the space that it formerly occupied utilized for erecting or for other work. 75. The disadvantages of this style of plate are that owing to its support on trestles it is not suitable for laying off heavy work that requires great accuracy, on account of the fact that it is impossible to keep the plate true and out of wind when heavy weights are being placed on or taken from it, as the stresses on both the plate and the trestles are constantly changing. Sometimes, a plate of this general style is mounted on a concrete or brick foundation, but if the latter expense is to be incurred, it is usually best to have a more elaborate one, such as is described in Arts. 76 and 77. 76. Plate for Heavy Work. — For laying off heavy work, the plate must have a very firm foundation, and the ribs must be of such a depth that there is no danger of the plate springing under the weight of the piece being laid off. Plates for heavy work are usually made lower than those for light work, the top of the plate being placed from 18 to 24 inches above the floor. Fig. 48 illustrates a very good plate for heavy work that is in use in one large shop. The top of this plate is 24 inches above the floor, and it is composed *of two pieces A and B that are joined together with a tongue and groove, as shown at C. This plate is 8 feet by 15 feet, and the ribs around the outside and along the center are made to extend clear to the foundation, which is only 2 inches above the floor, thus making the plate 22 inches deep. Parallel grooves 6 inches apart are planed the entire length of the top surface, and at right angles to these lines are ruled on the surface 6 inches apart. The grooves are especially handy, on account of the fact that 48 BENCH, VISE, AND FLOOR WORK. 21 § 21 BENCH, VISE, AND FLOOR WORK. 49 parallels can be slipped into them and pieces brought against these parallels for lining up, after which measure- ments may be made from either grooves or lines. In the case of all heavy plates, care should be taken to see that the plate has a good bearing on the foundation, and that the foundation is made deep and strong enough that it will not settle or be broken under any weight that is liable to be put on the plate. 77. Plate for General Work. — In shops handling a variety of work, varying from heavy to light, a plate of Fig. 49. the form illustrated in Fig. 49 may be used. This plate is about 8 feet by 12 feet, and the details are shown in Fig. 50. Fig. 50. The foundation consists of a concrete base on which are built three brick walls running lengthwise of the plate and 50 BENCH, VIvSE, AND FLOOR WORK. § 21 a cross-wall at each end. The plate is supported on these walls, as shown in Fig. 50. A hole in the plate, at least 18 inches by 24 inches, together with an opening in the middle wall, affords access to the space beneath the plate for the purpose of cementing between the iron and brickwork. This hole in the plate is also useful, on account of the fact that it permits parts of the work to hang below the surface ; as, for instance, one crank of a three-throw crank, or an arm on a rocker-shaft. The hole is cast with a ledge to receive a wooden cover. This cover is necessary to prevent objects from falling through the hole and being lost under the plate. The top of the wooden cover should be inch below the surface of the plate. It will be noticed that the plate overhangs the foundation 7 inches all around, to allow foot-room on the floor. Grooves \ inch wide and J- inch deep are planed length- wise every 6 inches, and lines made crosswise every 6 inches; or grooves may be planed both lengthwise and crosswise. A number of short parallels ^ inch square should be pro- vided to drop into the grooves to aid in locating the work or tools. The proportions or size of the plate may, of course, be varied to suit the character of the work being done. It is not good practice to mount a plate on brick walls all running in one direction, when heavy work is to be placed on or taken off the plate ; for if work were to strike the end, there would be danger of racking the walls, while' the tying of the longitudinal walls together at the ends tends to overcome this difficulty, and also prevents dirt from col- lecting beneath the plate. 78. Revolving Laying-Out Plate.— In many cases it is quite important to have the light fall on the work from a certain direction, so as to enable the operator to see the lines being drawn, and also in the case of small work, it is often necessary to operate on several sides of the piece. If this work were placed on a large plate, the work would have to be turned and reset several times, or the operator would have to climb around over the plate. To overcome 21 BENCH, VISE, AND FLOOR WORK. 51 this difficulty, a plate of the general form shown in Fig. 51 may be employed. This consists of a circular table a mounted on a suitable foot, or base, b. The back of the plate a is ribbed, as shown in Fig. 52, and a ball bearing is inserted between the plate a and the base b , as shown at c. In order to facilitate the centering of work having a hole in it, a plug d , Fig. 51, may be inserted in the center of the 52 BENCH, VISE, AND FLOOR WORK. § 21 table and a ring e of suitable diameter placed over the plug. Work thus dropped over a ring of the proper size can be quickly centered. To facilitate the dividing of work, two grooves f and g are planed across the table at right angles. These grooves are so located that one edge of the groove passes through the center of the table. For convenience in measuring, other grooves may be located at any specified distances from the center, and parallel to either one of the main grooves, as shown at h. Small parallels are introduced into the grooves for adjusting squares or other tools, or to bring the work into the desired position. These parallels are shown in position at i, i. By means of these two grooves and the parallels, work can very quickly be divided into four equal parts by dropping the parallels into the grooves, and bringing a square against the sides of the parallels in contact with the edges of the grooves that pass through the center of the plate. The top of the table illustrated is 31 inches above the floor, and the rim is 2 inches thick. For some classes of work it is convenient to have circular lines, 1 inch apart, turned on the table before the plate is taken from the lathe. This form of table can be easily taken to the work, in place of bringing the work to the table, in cases where there is a large amount to be handled, and especially when it is advantageous to have it done near the same machine. For convenience in moving the table, an extension of the hole that receives the pin d in the base b may be tapped, and a strong eyebolt fitted to it. This bolt will form a ready means of attaching the crane hook to the table. 79. Special Laying-Out Appliances. — On the lay- ing-out table illustrated in Fig. 48 are shown several special laying-out appliances. First may be mentioned the parallel shown at m . These parallels are made in various heights, differing by even feet, and smaller solid parallels or hollow rectangular parallels are made, varying by inches, so that any height, varying by inches, can be obtained from a series of them. The edges n and /, and r and ^ should be in the § 21 BENCH, VISE, AND FLOOR WORK. 53 same vertical planes, so that when one of the edges n or r is brought against a certain parallel or line on the plate, the corresponding edge p or s will be in the same vertical plane. This enables the man doing the work to obtain horizontal measurements from the edges of the upper surfaces of the parallels. With the use of these parallels, it is unnecessary to use the old-fashioned high surface gauge, which could never be depended on because of the spring of its parts. At the front of the plate are shown two V blocks o , o that are extremely useful in laying out pieces having turned ends, or any form that has to be supported in this manner. At h is shown a special T square, which, for some classes of work, is more useful than an ordinary square for drawing vertical lines, owing to the fact that there is little, if any, danger of the portion in contact with the plate becoming displaced ; while if an ordinary square were used, it would be necessary to make the arm or beam in contact with the plate very heavy to balance the long blade. EXAMPLES OF LAYING OUT. 80 . Laying Out Bolt Holes for Pipe Flanges. In Fig. 48 at the right-hand side of the plate is shown a casting for a branch pipe in which it is required to lay out bolt holes for the different flanges. The pipe is leveled by blocking up the small end t until the large end a stands square with the plate or table. The .branch, or arm, u is next raised until the surface b is square with the table. Wooden strips are fitted across the ends of the pipe, as shown at c , this fitting usually being done before leveling up the pipe, so as not to displace the setting by driving in the wooden strips. After the wooden strips are in place and the pipe is leveled up, the trammels are set to approximately the radius of the circle e that has been turned on the end of the pipe while in the machine. With these trammels, the arcs at d are drawn and a center located between them. Usually, a small piece of tin or other metal is placed at the center of the wooden strip, to receive the center when located. 54 BENCH, VISE, AND FLOOR WORK. § 21 After this, trammels or dividers are set to the radius of the bolt circle /"and this circle drawn. If the drawing calls for an even number of holes, a surface gauge is set to the center and a line drawn across the flange, as shown at v x. This line may be continued across all three of the flanges. If the number of holes is a multiple of 4, a vertical line is also drawn by means of a square, or a T square similar to that shown at /*, thus locating the top and bottom holes y and z. The other holes are spaced off from these by means of dividers. In case of any number of holes, whether odd or even, the setting of the dividers can be obtained by the method described in Art. 71. In the illustration, 12 holes are shown in the flange a. When the holes in the three flanges must have some fixed relation to one another, the horizontal line v x is carried around all three faces, and the holes laid off from this as required. 81 . Laying Out a Large Journal Cap. — At the left-hand corner of the plate, Fig. 48, is shown a journal cap in the process of being laid off. The casting is blocked up on the plate so that the front and back faces are approxi- mately square to the surface, and the center line i is drawn § 21 BENCH, VISE, AND FLOOR WORK. 55 midway between the points j\j. The shoulders k , k are laid off at equal distances from the center line i, and a proper allowance for finish is made at the top of the box, after which the lines /, l are drawn, so that the vertical distance from the horizontal plane passing through /, / to the point determined at the top of the box is equal to the radius of the finished box. The lines < 7 , q on the flanges of the cap are next drawn the proper distance above the lines /, /. After this, the cap is planed before the holes for bolting down the cap are laid out or drilled. 82. Laying Out a Crank-Arm. — The crank-arm shown in Fig. 53 may be laid out as follows: The piece is first placed on its side, with the parallel a under the small end. A surface gauge is set to the center of the hub, which has been determined by placing a wooden strip g across the hub and locating a center h on it by means of dividers. After this, the parallel a is pushed under the end of the arm 56 BENCH, VISE, AND FLOOR WORK. 21 until the small end is raised so that the point of the dividers is level with the center of the arm. Then the line b b' b" is drawn. After this the arm is clamped to an angle plate, as shown in Fig. 54, the line b b' being brought vertical by means of a square. The surface gauge is set to the center^ and the line cc' drawn. The surface gauge is next set so that its point will be above the line c c' an amount equal to the distance between the two holes in the arm, and the line d d' is drawn. This locates the center of the hole f, after which the circles at e and f may be drawn with dividers and marked off with prick-punch marks, as shown, ready for drilling or boring. 83. laying Out a Crossliead. — The method of lay- ing out a crosshead is governed principally by the design of the crosshead. The form shown in Fig. 55 is one provided with adjustable shoes, the end hh! of the crosshead being considerably narrower than the end a a ' , so that as the shoes are moved along on these inclined surfaces they will be expanded. The method of laying out is as follows : The cross- head is placed on the table, with blocking under the piston- rod end, and wedges under both sides of the connecting-rod end, as shown in the illustration. If the piston-rod end is § 21 BENCH, VISE, AND FLOOR WORK. 57 to be turned at the part marked d , the casting is usually made with a metal bridge which is cut out after the rest of the machine work has been done. In case no such metal bridge exists, it is necessary to insert a wooden strip at this point on which to locate the center f. Wooden blocks are also placed in the holes, as shown at e, and in the center of the piston-rod hole in the end d. Chalk or white paint is applied in a broad line wherever the laying-off lines are to be placed, as shown by the' broad, dark marks in the illustration. The centers of the holes for the connecting-rod pin and for the piston rod are now found, and the casting is leveled up by them and brought square with the table at the connecting-rod end. If it is found that the cored holes for the piston-rod or crosshead pin are not in the correct relative position, the body of the casting may be shifted somewhat, to bring them into such a location that all can be finished to the required dimensions. When these points are definitely located, the center line ij is drawn on all sides of the work. The centers, at each end of the cross- head pinholes e are laid off the proper distance from the piston-rod end d , and a circle is drawn at each end of the cross-head pin. A circle is also drawn for the piston-rod hole. The slot g for the piston-rod key is next laid off the proper distance from the end d. This slot is sometimes made with round ends and sometimes with square ends, depending on the conditions specified in the drawing. The line a a' is drawn the correct distance from the cen- ter e, this line being located by means of a square that is set on the table. The lines a h and a’ h' are not parallel to the table, on account of the tapered form of the crosshead body, and in order to determine these lines, the following process may be used: The taper is usually given as so much per foot on the drawing, and this amount may be marked off from a and a' , as shown at b and b' . After this, short ver- tical lines are located at c and c r , 1 foot from the line a a' , and the surface gauge is set to the point b, and a mark made at c. It is then set to b\ and the mark made at c', thus establishing two points on the inclined lines. After this Fig. § 21 BENCH, VISE, AND FLOOR WORK. 59 a straightedge may be laid through the points a and c and the line ah drawn, and then through the points a' c' and the line a' h drawn. The lugs k must be drilled for screws to operate the crosshead shoes. These screw holes may be located by drawing horizontal lines on the piston-rod end of the lugs by means of the surface gauge. These lines must be the proper distance from the center line of the crosshead. After this, the center of the lugs may be found by means of dividers, and the circles representing the holes laid out. 84. Laying Out an Engine Bed. — The method of laying out an engine bed differs according to the type of bed, but the essential features of the process are the same. Usually, the work has to be done in two or three operations, owing to the fact that some of the surfaces have to be machined before the last part of the laying out can be done. The bed chosen for illustration is shown in Fig. 56 and is of the solid cast variety, having bored guides, the bearing for the crank-shaft being cast solid with the bed . and the cylinder being arranged to bolt to the end of the bed. The bed casting a is placed on the laying-out or machine table, right side up, with blocks under it at intervals, as shown at b, b. Wooden strips are fitted across the ends of the guides, as shown at r, and across the sides of the jaws for the crank- shaft bearing, as shown at c. The centers of the guides are located on the wooden strips at both ends, and those of the jaws at both sides. The bed is now tested with the surface gauge, and set level by driving wedges between the bed and the blocks b. If either of the points located does not come true, the centers may be shifted slightly, care being taken to allow stock enough so that the guides and the jaws of the main bearing can be finished. Some beds of this type have their bottoms planed. If the bottom is not to be planed, it should be left as nearly parallel with the center line dd as possible. After having adjusted the centers of the guides and the jaws so that they all come level, and so that there is sufficient stock for finishing these parts, a sur- face gauge is set to the height of the center of the guides, 60 BENCH, VISE, AND FLOOR WORK. § 21 and the line dd is drawn on painted strips or spots on both sides and ends of thecasting. If the bottom is to be planed, the line /'/'should be drawn parallel to dd, and at the proper distance from it. After this, the blocks r, r at the ends of the guides are removed, and a line (either a piece of piano wire or a sea-grass fish line) is stretched through the guides along the line ee. The distance from this line ee to the center of the crank-shaft bearing is measured, and the line gg established and marked off on the jaws of the bearing. Then the distances h , h are determined, and the lines i i and i' i drawn so as to determine the amount of stock to be removed from each end of the bearing. The height of the governor pad from the bottom of the bedplate is marked off at /, and the amount to be removed from the rocker-arm hub is laid off at k. After this, the ( end of the bed to which the cylinder is to be bolted is also laid off, the line m n being drawn, thus determining the amount to be faced from this end. The distance from the end of this face to the center of the bearing should agree with the drawing. It will next be necessary to machine most of the faces already determined, after which the lines o p, s t, and o t may be laid off on the jaws of the bear- ing, and the center of the rocker-shaft hub at k may be laid off the proper distance below the center line. After the guides are bored and the end faced off to the line m n , the bolt circle may be drawn on this end, and the bolt holes laid out in a manner similar to that described for the laying out of bolts and flanges, Art. 80. If the laying out is done on a table having lines running both lengthwise a.nd crosswise, it will simplify matters to adjust the bed so that some one line corresponds with the center line d d-, after which many of the measurements may be obtained from the other lines. 85. Gauges for Laying Out Key Seats. — Differ- ent types of gauges have been adopted for laying out key seats, but for the ordinary run of work the form shown in Fig. 57 will be found very useful. This consists of a ring § 21 BENCH, VISE, AND FLOOR WORK. 61 of cast iron a that is bored to the correct diameter b, and that has the necessary keyways laid out in it, as shown at c and d. This ring may be slipped over the shaft, and the keyways marked from it; it may then be removed and placed on a hub of the crank or wheel, and the keyways on it also marked out, thus insuring the accurate location of these keyways. fig. 57 . 86, Faying Out Ends for Small Rods. — A conve- nient method of laying out the ends of small rods is shown in Fig. 58. In this, the piston rod a is placed on V blocks that bring it level. A stake or post b is put into a hole in the plate or table, to which it has been fitted, so that it stands perpendicular, as shown, with its upper end through the holes in the fork c , fitting it accurately. The top end of the post b has a small center-punch mark in it, which pro- vides a convenient center from which to draw the circle d for the rounded end of the fork. The parallel edge lines from e and e tangent to this circle are drawn by means of a surface gauge, after the fork has been revolved to a vertical position and set to a square. C. S. III .— 17 ■ ERECTING. (PART 1.) FLOOR WORK. BLOCKING. INTRODUCTION. 1. Definition. — The term blocking ds applied to the various pieces of material that are employed for temporarily supporting work that is being done on the erecting floor or in the field. The purpose of the temporary supports is either the alining of the work in some particular direction or direc- tions, or the raising of the work above a certain position in order to make it more accessible. 2. The form of the blocking depends on the character of the work for which it is to be used and the service it is intended to perform. In a great many cases the simplest form and the most elaborate form of blocking can be and are advantageously used alongside of each other on the same piece of work. 3. The simpler forms of blocking merely serve to sup- port the work; while the more elaborate forms can, in ad- dition, be employed for moving the work to an extent depending on their construction. Among the simpler forms of blocking may be mentioned wooden blocks , trestles , and iron parallel blocks. Trestles are known by the name of horses in many localities. Screzv jacks and stone jacks are §22 For notice of copyright, see page immediately following the title page. 2 ERECTING. §22 examples of the more elaborate forms of blocking, and hydraulic jacks are often used for lifting work, but not for blocking or holding it. WOOD BLOCKING. 4. Wooden Blocks. — For supporting the heavier classes of work, either on the erecting floor or in the field, wooden blocks are extensively used. The blocks are gen- erally made square; they may have a thickness that varies from 2 to 14 inches, and a length that varies from 2 to 6 feet or more. Pine and similar soft woods are often used for blocking, on account of their low price; there is no partic- ular objection to the use of the softer woods for work done away from the shop, where the chances are that the blocking will not be in use for any great length of time. Hard wood is preferable for work on the erecting floor, since it will keep its shape better and last much longer than the softer woods. 5. Wooden blocks are sometimes used for packing blocks that are to be placed under the clamps that secure work to the table of a machine tool. When used for this purpose, it is recommended that hard wood which has been sawed square across the grain be used. The block should then be placed on end so that the grain is at right angles to the table, on account of the fact that wood is less easily com- pressed in the direction of its length than across the grain. 6. Trestles. — The trestle is used as a support for large, but comparatively light, work. It may be made as is shown in Fig. 1. The legs should be cut so as to leave a shoulder a , and should be bolted to the beam b by bolts passing through the legs and the beam. Lagscrews are often used instead 22 ERECTING. 3 of through bolts, but their use for this purpose is not recom- mended. When great stiffness is desired, or when the weight to be supported is rather heavy, the legs may be tied together near the bottom by boards nailed across them. The only objection to this is that the trestles then cannot be stacked on top of one another when not in use. Trestles may be made of any convenient size; when they are used frequently they should be constructed of hard wood. IRON BLOCKING. 7. Rectangular Iron Blocking. — The simplest and the most common forms of iron blocking are the solid par- allel bars used in connection with machine tools. Large parallel bars, or parallel blocks, as they are often called, are usually made hollow, and are then well ribbed in order to safely carry the great weight often placed upon them. 8. Two excellent styles of parallel blocks are shown in Figs. 2 and 3. The block shown in Fig. 2 has a form that combines considerable strength with lightness. It is planed all over so that „ F , JL opposite sides are parallel and adjacent sides are at right angles. When a number of such blocks are made, it is advisable to make their corresponding dimensions equal, in order that the G blocks may be used in pairs. The block shown in Fig. 2 is so constructed that a number of equal blocks may be piled up to suit the requirements of the work and then form practically a single block. Holes for dowel-pins are drilled in corresponding positions in the four faces of each block. The dowel-pins are made a good fit; they prevent the blocks from slipping on each other and at the same time permit them to be readily separated. One of the dowel-pins is shown at a. Jr 4 ERECTING. 22 9 . The block shown in Fig. 3 has the general form of a box; it is finished all over and is provided with T slots and V grooves, as shown.. The V grooves in the sides permit the block to be used with either side up for round work; the Fig. 3 T slots permit the work to be fastened to the block, or the block to be fastened in position by bolfs. Blocks of this type may be used singly, or they may be piled up to any height that the work may require. 1 0. When making cast-iron parallel blocks, it is recom- mended that they be made in sets, in which all the blocks that are used together are exact duplicates. Blocks of dif- ferent sizes may be made with a rectangular cross-section and with the short side of the large block equal to the long side of the next smaller size, and the long side of each from two to three times as long as the short side. 11. Cylindrical Iron Blocking. — A kind of blocking that is quite convenient for some classes of work, together with its application to a piece of work, is shown in Fig. 4. The blocking greatly resembles a short section of flanged cast-iron pipe; the sections may have the flanges strength- ened by ribs, as, for instance, the sections a , a\ or, the flanges may be plain, as those of the sections b, b. The flanges should be faced straight and parallel with each other, and the different sections should all have the same length. 22 ERECTING. 5 12. A lighter form of pipe blocking is made of wrought iron or steel pipe that is threaded at both ends to receive flanges. The latter should be faced after they are screwed on the pipe. 13. Adjustable Parallel Blocks. — The adjustable parallel block is illustrated in Fig. 5 (a). Its first cost is greater than that of ordinary parallel blocks, but it will be found both a time-saving and money-saving device on ac- count of the fact that one adjustable parallel block displaces a number of the ordinary non-ad justable type. By far the greatest advantage of the adjustable parallel block lies in the fact that any thickness within the range of the block can be obtained. In other words, it can be adjusted exactly 6 ERECTING. §22 to the requirements in any particular case. It consists of two separate pieces a and b that are movably connected to- gether by a dovetail, which is clearly shown in the end view. After the two pieces have been carefully fitted together, the a a iT b -fch b JVWWWWVVV| 0 » Fig. 5. block is planed so that its surfaces are square with one an- other, and opposite surfaces are parallel. The dovetailed slide being at an angle to the surfaces a' and b\ the distances between these two surfaces may be varied by sliding the pieces upon each other. In order that the pieces may not slide under a heavy load, the inclination of the slide to the surfaces a' and b' should not exceed 10°. 14. An adjustable parallel block constructed as shown in Fig. 5 (a) may be made any convenient size and will be found a very useful appliance for the various machine tools. The block may be, and often is, used as a gauge by which to set a planer tool for planing work to an exact height above the planer or shaper table. 15. If the base b is extended to two and one-half times its ordinary length, as shown in Fig. 5 ( b ), and rack teeth are cut the whole length of a good gauge for getting the exact thickness of the racks used for various machine tools is obtained. The teeth in the part a are placed in mesh with the pinion and the part b is set so as to give just the right fit between the pinion and the rack seat. After the gauge is set, it may be removed; the pieces of rack, which ERECTING. 7 § 22 are generally left too thick, are now finished to the size in- dicated by the gauge. The pitch of the teeth cut in this gauge must, of course, be the same in every case as that of the pinion. JACK-SCREWS AND HYDRAULIC JACKS. 16 . Jacks. — In addition to the parallel blocks just de- scribed, the lifting device known as a jack is almost indis- pensable in all kinds of floor work, especially in erecting. Jacks are made in a large variety of styles and sizes, from those intended for leveling up light work on the tables of machine tools, to the heavy jack-screws and hydraulic jacks capable of raising or supporting 150 tons or more, and con- sequently are used for a wide range of work. 17 . Simple Leveling; Jack. — The simplest form of jack consists of a circular cast-iron foot, which is faced at the bottom and has a tapped hole through it. A square-headed screw with a slightly rounded top, as shown in Fig. 6, is used for raising the work. This style of a jack-screw is used principally in leveling up work on the tables of machine tools, although it will be seen later that jacks resembling this are sometimes made in large sizes and used in erecting. 18 . Adjustable-Top Leveling Jacks. — A good little case-hardened jack, with an adjustable cap, which is very serviceable for machine-tool work and light assembling, is shown in Fig. 7 (a). The body a is tapped to re- ceive the adjusting screw b , which has a square top and holes for the rod c. The cap d is attached to the screw by a ball- and-socket joint, so as to permit the cap to accommodate itself to the angle of the work. When a solid or conical top 8 ERECTING. §22 is more suitable for the work, a second screw ^is substituted for b. The foot of the body a is counterbored to fit the (a) (b) Fig. 7. projection on the auxiliary base f, which may be placed under the jack when a greater height is required. Auxiliary bases of different heights may be used as needed. A special base g is also furnished with the jack and is used where this form of base is more suitable. 19 . Another very serviceable jack for light erecting and for setting work on ma- chine-tool tables is shown in Fig. 7 ( b ). A steel screw a having a square thread is screwed /A *7? >5 guare r* (a) Fig. 8. Fig. 9. into a cast-iron base b , the bottom of which is faced. A cap c is attached to the screw by means of a ball-and-socket §22 ERECTING. 9 joint. This jack serves the same purpose as the one shown in Fig. 7 ( r n m !%□ -%r^* 5 r J? 1 fie si \/ h L f i iy I / r b b y^_ u i Fig. 9. §23 ERECTING. 17 The cross-rail is moved up and down by two screws oper- ated by the gears k and k' . When one end of the rail is found to be low, it should be raised the proper amount. In Fig. 9 this can be accomplished by loosening the screw n and turning the gear in' the desired amount. By repeating these trials the cross-rail can be brought into such a posi- tion that the tool and feeling piece, or indicator, will give the same reading over both cylinders b and b ' . The vertical screws carrying the cross-rail should always be adjusted in such a manner as to raise the cross-rail, on account of the fact that this will take up any lost motion or backlash between the nuts, the feed-screws, and the uprights. For this reason it is always better to raise the low end of the cross-rail rather than to lower the high end. The feed- mechanism and the mechanism for raising the cross-rail by power, together with the oiling device, are all put in place and tested, after which the machine is tested to see that it is within the allowable limits of error. After the cross-rail has been adjusted parallel to the V‘s, a light cut should be taken over the top of the table. The head g should then be set vertically by means of a square. In the case of very large planers the table is not trued in place by the manufacturer. 24. Preparation of Planer for Shipment. — Small and medium-sized planers are generally shipped with the principal parts in place and all bright parts coated with a slush of oil, or some other protective coating, to prevent rusting. The lighter and small parts are crated to prevent breakage and the whole mounted on skids for convenience in handling. Larger planers are taken apart, the smaller pieces being boxed and the fitted faces of the larger ones crated. All finished surfaces, in all cases, are slushed or given a protective coating before shipping. The smaller planers have their tables carefully trued in place before leaving the manufacturers, but the larger ones are usually shipped with the table just as it comes from the planer on which it was finished. C. S. III.— 21 18 ERECTING. §23 ERECTION OF PLANERS IN PLACE. 25. Large Planers. — In the case of all large planers, the beds of which rest on the foundation, the bed is placed on the foundation and leveled by means of wedges or jacks. The housings are bolted in place and the bed leveled by the process described in Art. 20. The housings are also set perpendicular to the bed. The cross-rail and its elevating mechanism are then placed in position. The cross-rail may then be tested to see that it is parallel with the V’s, as described in Art. 23. The feed-mechanism may be put in by other men while these operations have been going on, and after the cross-rail is adjusted parallel to the V’s, the table should be tested. If it is found that the table is not parallel with the cross-rail, a light cut should be taken over it. After this is accomplished, the head g, Fig. 9, must be set to plane perpendicular. In the case of a large planer there will probably be two heads on the cross- rail. They are both set as near perpendicular as possible by means of a square. After this, the sides f, f of the table may be trued down by means of tools set in the heads, and the angle at the edge of the table tested by a square. If this is found to be true, the mark h is placed on the saddle opposite the zero mark of the graduations on the head, as practically all planers are shipped from the factory with their heads graduated, but without the zero mark on the saddle being located. If the planer is provided with side heads on the uprights i and i\ they may be tested by bolting a casting as indicated by the dotted lines at j to the face e of the table and then taking cuts from the sides of this casting by means of the side heads, the upper face of the casting having been trued by means of a tool in one of the heads on the cross-rail. 2(5. Securing tlie Planer to the Foundation. After the planer is erected and all the tests have been made and everything adjusted correctly, it should be secured to the foundation. This may be accomplished by ramming any suitable cement between the bottom of the bed and the ERECTING. 19 §23 top of the foundation. Sometimes iron chips and sal ammo- niac are used. In other cases a regular Portland cement mortar is employed, while in some cases melted sulphur is poured under the bed. After the cement is in place the planer should not be used until time has been given for the cement to harden. In cases where the foundation is on yielding ground, and it is not practicable to obtain a perma- nent foundation, planers are sometimes left set on wedges or jacks and are leveled up frequently to keep them in line. The bed of the planer should be tested lengthwise with a straightedge to see whether or not it is planing concave or crowning. This precaution is especially necessary in the case of very long planers. It is convenient to have the planer table set level so that a spirit level may be used on any part of it. In this case, by applying the spirit level to different parts of the table it will indicate whether the planer is planing convex or concave. 27. Planers Having Legs. — Small and medium-sized planers are shipped from the factory with all their parts in place, and hence do not need as careful attention in erec- tion as do the larger sizes, which have to be assembled on their foundations. It is usually sufficient to drive wedges under the legs until the table is level. The cross-rail is then tested to see that it is parallel to the top of the table, and if found so, no further adjustment need be made. If it is not parallel, the table should be run back, and the cross-rail set parallel to the V’s, as described in Art. 23. After this, a light cut should be taken over the table and the heads set to plane vertically. In the case of very small planers, the beds are usually stiff enough so that very little, if any, adjusting is necessary when setting them up, all the adjustment being made by the manufacturer; but even in this case it is well to go through the entire series of tests, if accurate work is to be required from the machine. 28. Setting Planer Heads. — The amount of accuracy required in setting the heads, either on a large or small 20 ERECTING. §23 planer, depends very largely on the character of the work to be done on the machine. If the work will all be simply roughing and surfacing, the zero mark h, Fig. 9, may be placed accurately enough by adjusting the head to any available square and scribing or cutting the mark on the saddle; while if a large amount of angular work is to be done on the planer, it will be necessary to face down one or more castings to see that the mark is accurately located. Sometimes it is well to put on a provisional or temporary mark and then test each piece of work as it comes from the planer until sufficient information has been obtained to locate the mark accurately. MILLING-MACHINE ERECTION. 29. Introduction. — There is a large class of machines in which the erection cannot all be done at one time, but must be carried on between the various operations in the machine work. This is on account of the fact that some parts of the machine must be completed before other parts can be machined or fitted. This is especially true of very large machines and of some comparatively simple machines in which a number of parts are interdependent. The milling machine as erected in at least one large shop forms a good example of this class of erection. 30. Planing the Column. — The column a, Fig. 10, is first fastened on a planer table with the face b up. Great care must be taken to see that the casting is not sprung by clamping. The face b and the inclined surfaces c, c' are carefully planed to a standard gauge. The general form of these parts is shown in Fig. 11. 31. First Drilling Operation. — After the planing is complete, the frame is taken to a drill press and all the holes that do not require exact location drilled. This includes those for fastening the column to the floor, for the tool shelf, the tool-cupboard door, etc. A special jig that clamps on to the face b by means of the surfaces c and c' is used to guide drills and reamers for forming the holes for §23 ERECTING. 21 the elevating screw d ', the knee , stop-rod e , and the vertical feed-shaft f. This jig must not be confused with the large drilling and boring jig described later, but is simply an angle plate that is clamped to the face b and carries bush- ings for locating the holes mentioned. 32. Fitting the Surface for Carrying the Knee. After the first drilling operation is completed, the column is 22 ERECTING. g 23 laid on its back and the surface b, Fig. 10, scraped to a surface plate. After this, the angular surfaces c and c ' , Figs. 10 and 11, are scraped to a special surface plate or straightedge of the pattern shown in Fig. 12. The exact angle between the surfaces has to be determined by means of a gauge. The surfaces a and a' b Fig. 11. of the straightedge are scraped and fitted perfectly true. 33 . Painting the Column. — After the scraping is complete, the surface of the casting is filled, rubbed down, and painted, all but the finishing coat being applied at this time. The finishing coat is not given until after the machine has been inspected. 34 . Boring Operations on the Column. — After the scraping is completed, the column a is placed in the jig b , Fig. 13. The surface b, Fig. 10, rests on a scraped surface in the jig, and the surfaces c and c\ Figs. 10 and 11, are brought in contact with the gibs in the jig, the fixed gib being shown at c, Fig. 13, and on the opposite side there is an adjustable gib that is held in position by means of set- screws. This secures the column in its proper relation to the jig, after which the holes for the spindle^', for the sup- porting arm //, and the back gear-shaft z, Fig. 10, are all bored in their proper positions. While these holes are being bored, the boring bar is supported at each end in hardened- steel bushings, and is driven by means of a floating driver carrying two universal couplings. This method of driving the boring bar prevents all danger of the spindle of the drill press springing it out of line with the bushings. The holes ERECTING. 23 § 23 are both bored and reamed while the column is held in the jig. This method of procedure insures the holes mentioned being at right angles to the face b, Fig. 10, and hence in the proper relation to the table. 35. Fitting the Various Parts. — After the holes for the spindle g t the supporting arm /z, and the back gear- shaft -S', Fig. 10, have been bored and reamed, the column is removed from the jig and placed in an upright position on the floor. The boxes in which the spindle runs are then fitted in place by grinding. The knee j, Fig. 10, is planed up and its upper face scraped to surface plates in a manner similar to that used in scraping the surfaces b , c, and c ' , Figs. 10 and 11. The face that is to fit the upright of the column is also fitted, and care must be taken to see that these two surfaces are at right angles to each other. After this the knee is fitted to the upright by scraping the upright face of the knee until the horizontal face comes square with the surface b , Fig. 10. The spindle that has been accurately ground with tapered bearings is now fitted into its place by scraping the boxes to bring the spindle true with the top of the knee. Care should be taken to see that the spindle is true in both the 24 ERECTING. § 23 horizontal and vertical planes. The scraping also serves to give the spindle a good bearing in the boxes. After the knee and spindle have been fitted up, the clamp bed k and the table q , Fig. 10, are fitted in place, each one being adjusted to the parts already in place. The index head o and tail-stock center p are fitted up elsewhere and placed on the table after it has been accurately fitted. The overhanging arm h is fitted parallel with the spindle by scraping the holes in the casting through which it passes. The outboard bearing or support r is fitted to the arm h and the hole n drilled and reamed by means of tools in the spindle. This insures the hole in the outboard bearing being in line with the spindle. The diagonal braces s for the arm and all other minor details are fitted as opportunity offers. 36. Erecting Trucks. — For erecting any machine, such as a milling machine, it is handy to have erecting trucks fitted to contain all the small parts of the machine. When an order for a number of machines is placed in a shop, many of the small parts are made and kept in stock. When the larger castings come on the floor and the work of erec- tion begins, the man in charge of the erection takes to the stock room as many trucks as he has machines to erect, and puts the necessary stock for each machine on the trucks. These trucks are then placed opposite the castings for the machine with which they are to go. When this practice is followed much time will be saved, as the erector will always have the necessary parts at hand. 37. Inspection of Milling Machines. — The machine now goes to the inspector, who carefully tests all parts and motions for accuracy, testing the knee at the highest and lowest positions; also the clamp bed at its inner and outer positions and the table at both ends of its travel. A carefully ground steel testing bar, one end of which is ground to fit the tapered center hole of the spindle, is placed in the spindle, care being taken to see that both the hole and the test bar are clean before it is introduced. The parallel part of the bar projects from the spindle to the outer end of the knee. ERECTING. 25 § 33 No. Universal Milling Machine. Lot Construction No Serial No. Spindle runs at mouth, ; end, “ with knee in Ver ; Hor “ “ frame in drop, ; width, “ “ overhanging arm, in inches. “ “ center in O. H. arm, high ; low. . “ “ bushing in O. H. arm, high ; low “ “ surface of platen, length ; width. Slot with ways of platen, Spiral Head Spindle runs at mouth, ; end, “ “ “ with slot, “ “ “ “ center of slot, “ “ “ “ back center in Hor ;Ver. ... “ “ “ “ platen when at 90°, “ “ “ “ main spindle when at 90°, .... . Eccentricity of swivel bed with main spindle, Collet runs at. mouth, ; end, ( Main Spindle, Chuck runs out on -! ( Spiral Head Spindle, Vise out of parallel with platen in its width, Back gears run, Passed, 190. . .by Brown & Sharpe Mfg. Co. Inspector. * • • REMARKS : 26 ERECTING. §23 The spindle and the test bar are then revolved, and the amount that the test bar runs out of true both at the spindle and at the outer end is carefully noted by means of an indi- cator reading to thousandths of an inch. The test bar may also be used for measuring, by means of an indicator, to see that both ends of the table are the same distance from the spindle. The inspector is given a list of the allowable vari- ations in the different parts of the machine, and he must not pass a machine until all errors have been corrected so that the variation shall not exceed the allowable limit. In the case of a universal milling machine, the universal head and tail-stock .center are also tested. In testing the universal head, a test bar similar to the one used in testing the spindle is employed, in order to determine whether or not the spindle of the universal or spiral head runs true. The vise and chuck are also tested to see whether or not they are true. 38. Inspector’s Report. — All information obtained from the inspection should be entered on a report similar to the accompanying one. Each machine is given a serial num- ber, and these reports are filed at the office, so that in the case of any trouble arising or any repairs being required for a given machine, an exact record of its condition when it left the shop is available. ENGINE ERECTION. 39. Equipment Necessary. — The manner of erecting an engine depends both on the equipment at hand and the style of the engine. Where medium-sized or heavy engines are to be erected, traveling cranes should be provided for handling the heavy parts, as they can accomplish the work much more quickly and easily than any other system of handling device. Another advantage of the traveling- crane system is that the traveling crane commands the entire erecting floor. The crane should have sufficient height of lift to place in position the highest parts of any machine built in the shop. Where very high work is to be erected, it is sometimes necessary to set the base in a pit so §23 ERECTING. 27 that the highest parts will not come above the crane. This is especially true in erecting vertical engines. Some shops making a specialty of vertical engines have two sets of traveling cranes, one above the other, the lower one intended for handling the heavier pieces and the upper one for handling the upper portion of the engine and the light pieces. If an engine should be so high as to interfere with the travel of the lower cranes, it will be necessary to see that there is a crane set on each side of the engine before cylinders are put up, so as not to cut off the rest of the erecting floor from the crane service during the time that the high engine is in the shop. One advantage of having light quick-motion traveling cranes placed well above the heavier cranes is that the upper cranes can take light pieces and lift them above the lower cranes and carry them to any place on the erecting floor without interfering with the heavy work of the larger cranes. All floors on which erecting is done should be firm and solid, so that there is no danger of the work being thrown out of line by settling when heavy parts are added. Before beginning work, the erecting floor should be cleared of all unnecessary obstructions and swept. The influence of the style of engine on the manner of erection will be brought out in the description of the three principal types of horizontal, vertical, and locomotive engines. For the erection of small engines an iron-plate erecting floor on which the engine can be bolted down and tested is a great convenience. ERECTION OF A HORIZONTAL STATIONARY ENGINE. 40. Preparation of tlie Engine Heel. — Before the engine bed is brought to the erecting floor it should be machined as far as possible, including the boring of the main bearing, if this is cast with the bed, and the scraping of the guides. The guides are usually scraped to a special surface plate, or in some cases to the crosshead itself, before the 28 ERECTING. §23 work is brought to the erect- ing floor. The method of erecting a horizontal engine is not influenced greatly by the type of engine; that is, the work of erecting both Corliss and slide-valve en- gines is very similar. It is best to carefully level up the bed on the erecting floor. This may be done by placing levels on the guides and in the pillow-block bearings. 41 . Fitting tlie Main Bearing and Cylinder to the Bed. — In case the main bearing is cast separately from the bed and attached by bolts, it is necessary to bring it approximately square with the bed. This may be ac- complished by placing a line through the crosshead guides and another one through the pillow-block and testing them to see that they are at right angles. This method will only set the bearing approx- imately square with the bed, though it will usually set it so nearly square that any further adjustment can be made by scraping the shaft bearing. The bed with the pillow-block attached should be carefully leveled by means of leveling jacks or wedges. ERECTING. 29 §23 The cylinder is bolted to the bed or frame and a line or wire fastened to a piece of wood bolted to one of the studs in the end of the cylinder, as shown at a , Fig. 14. This line is carried through the cylinder, piston-rod stuffingbox, and guides, and fastened to the end of the frame in case the pillow-block is cast solid with the frame; or in the case of an engine in which the pillow-block is bolted to the frame, the line may be fastened to any suitable object, as, for instance, the angle plate and stick shown at b , Fig. 14. The line should be set central with the bore of the cylinder at the back end by calipering from the inside of the cylinder to the line. This may be done \yith an inside adjustable gauge or micrometer, but in most cases it is better to use a light pine stick like that shown in Fig. 15. The stick a Fig. 15. is tapered at both ends and may have a pin b driven in at each end. The advantages of the stick in calipering are that it is lighter than the inside micrometer and is not affected by expansion and contraction as much as a metal gauge would be. The line must also be brought central with the stuffingbox at the other end of the cylinder. This may be done by means of a stick similar to that shown in Fig. 15, but it may be done more quickly by means of the device shown in Fig. 16. This consists of a hard- c wood block a, which is turned to just fit the stuffingbox and has a |--inch hole b drilled in the center. The face of the block is turned square with the outside, and two center lines c d and e f are drawn across the face at right angles to each other. By sighting along the lines cd and ef, it is easy to determine when the line or wire c d, Fig. 14, is central with the stuffingbox. 30 ERECTING. § 23 42. Lining the Guides to the Cylinder. — After this the guides may be lined to the cylinder by measuring from the inside of the guides to the line at the top and bot- tom, as at f, Figs. 14 and 16, which will determine whether the line is central to the guides in a vertical plane. This test should be made at each end of the guides. In order to see whether or not the line is central horizontally, spots g, Fig. 14, are cast on the frame and faced off by the boring tool at the same time that the guides are bored. Another and quicker method of lining the guides with the cylinder is to use special devices similar to that illustrated in Fig. 17. This consists of a casting a that is turned to fit the inside of the guides. At the center there is a small hole b through which the line passes, and the lines c d and e f drawn at right angles to each other serve to locate the center line in its proper position, this being done in a manner similar to that described in Art. 41. When the device shown in Fig. 17 is used, the spotting plates^*, Fig. 14, are not necessary. 43. Bringing the Cylinder in Line Witli the Guides. — If it is found that the cylinder is not in line with the guides, it is necessary to fit the joint between the cylin- der and guides so as to bring them in line. The amount of ERECTING. 31 § 23 adjustment necessary may be determined by slacking off the nuts on one side and introducing pieces of sheet metal until the cylinder and guides are brought into exact alinement. After this an amount equal to the thickness of the metal introduced may be removed from the other side of the end of the cylinder or guides. Where this amount is very small, it is sometimes removed by filing or scraping; when it is greater, by machining. It has been found practically impossible to machine parts so accurately that the cylinder of a large engine can be brought in line with the guides without fitting, and on this account many manufacturers place a loose ring or spacing piece between the cylinder and the guides, and in the case of a tandem compound engine, between the high-pressure and low-pressure cylinders. After the amount of adjust- ment necessary has been determined, this distance piece is taken out and the proper amount removed from the high side. , When this method is followed, care must be taken to mark the distance piece so that it cannot be placed in a wrong position. To insure this, it is well to have at least one of the stud or bolt holes uniting the parts not located accord- ing to the regular spacing system, so that it will be impos- sible to put the castings together in any but the correct position. This may also be accomplished by using guides or dowel-pins. Many engine builders bore all their cylinders and guides in a vertical boring mill and so reduce the difficulty of fitting the parts, but in the case of a horizontal engine, the parts will spring out of round when placed in a horizontal position. 44. Fitting the Crank-Shaft. — After the cylinder and guides have been brought into perfect alinement, the crank-shaft must be fitted. The outboard bearing may be located by stretching a line through the shaft bearings at right angles to the lines through the cylinder and guides. This will serve to locate the outboard bearing very closely. After this has been done, the journals of the shaft should be wiped clean and given a coat of marking material. The 32 ERECTING. 23 shaft should then be placed in its bearings with the lower half of the boxes in position and given a few revolutions. The shaft is then lifted out of the bearings and the high spots scraped off with a half-round scraper. This operation is repeated until the shaft shows a good bearing in both the main pillow-block and the outboard bearing. After the lower half of each box is scraped, the upper halves may be put in place and fitted in like manner. The shaft is then taken from the bearings and the cranks pressed or shrunk on and keyed. The eccentrics and governor-driving device are also placed in position, after which tffe shaft is returned to its place. In order to make sure that the crank-shaft is exactly at right angles to the center line of the engine, and that it is also horizontal, the following course may be pursued: The crankpin a , Fig. 18, is brought up to the center line c d of the engine and a piece of wood b is fitted between the face of the crank e and the head of the crankpin f. A mark is made on this piece of wood in the middle, and this mark should coincide with the line c d. If they do not coincide, the outer end must be moved until they do. The shaft is now given a half revolution to bring the crankpin under the line at the other end of its travel, as shown by the dotted lines at a ' . If the line on the stick b again coincides with the center line c d, the shaft is at right angles to the center line of the engine. In order to test the shaft to see whether it is level or not, a fine plumb-line may be hung ERECTING. 33 §23 vertically before the shaft and the crankpin a brought in contact with it at the upper portion of its revolution, and then tested again at the bottom of the revolution. If the crankpin just touches the line at both the top and the bottom, the shaft is horizontal. 45 . Fitting the Reciprocating Parts. — After the engine is lined up and the shaft square and level, the recip- rocating parts may be put in place. The piston, with its piston rod attached, is slipped into the cylinder and the crosshead into the end of the guides. The piston rod passes through the bushing in the head of the cylinder and is secured to the crosshead. These parts should be tested as they are put in place, to see that they line up properly. Some makers use a crosshead of such a pattern that the line c d, Fig. 14, may be carried through the crosshead and used in testing the crosshead to see that it lines up prop- erly. After the crosshead and piston rod are in place, the connecting-rod may be put on. Before any of the surfaces that are to slide or move on one another are placed in con- tact, care should be taken to see that they are well oiled. The oiling devices are put in place as fast as the parts are ready for them. The control of the movements of the engine depends on the governor; consequently, great care should be taken to see that there is no danger whatever of the governor stick- ing or failing to act. In order to insure this, the governor should be assembled separately and belted up so as to run at about its normal speed. The gears should be fitted so as to run as quietly and as smoothly as possible, and the dashpots, weights, and all parts properly adjusted during this prelim- inary run. It is usually best to run the governor one or two days in this way. After the governor has been fully adjusted, it may be taken down and placed on the engine. If the engine is a Corliss engine, the dashpots are responsi- ble for the closing of the valves, and hence they should be assembled and tested before being placed on the engine. Shops building this class of engines usually have some C. S. III.— 22 ERECTING. 34 § 23 device in which they can place a dashpot and run it for some time while adjusting it. After the dashpots are fully adjusted they are placed on the engine. 4(3. Oiling Devices and Other Small Parts. — The oiling devices for the crankpin, eccentrics, crosshead, gov- ernor, and all other parts are put in place as fast as the parts are ready to receive them and they should all be tested before steam is let into the engine. 47. I itti ng the Flywheel. — Flywheels for small engines are made either solid or in halves. If the flywheel is made solid, it must be placed on the crank-shaft before this is lowered into the bearings. In some cases there is not room in the shop to put the flywheel in position, and hence the engine is assembled without the flywheel being placed on the shaft. Where it is possible, it is best to erect the fly- wheel with the engine. In erecting a large built-up flywheel, the hubs and hub flanges are placed on the shaft first. The arms and segments of the rim are then attached one at a time. By beginning the work on one side, the arms and sections of the rim may be attached to the hub flanges near the floor level, thus doing away with the necessity of raising them to any great height. After one arm and section of the rim are put in place, they may be lowered into the pit and the next one in order connected. This process may be continued until the wheel is completed. When the work is done under a traveling crane, it is usually more convenient to place each of the arms and segments at the top of the wheel and then lower them far enough to make room for the next. 48. Use of Dowel-Pins. — Whenever it is necessary to make the bed of an engine in sections, or whenever there arg any parts that require accurate alinement, they should be doweled together This is done by drilling holes through the pieces and reaming them out with a taper reamer after the work is erected. After the holes are drilled and reamed, taper pins are fitted to them. These pins are usually given a taper of from £ to J inch per foot. As each part is put in place, it should be clearly and distinctly marked by ERECTING. 35 § 23 letters, figures, and lines, so that it may be easily returned to its position when erecting in the field. If the work is complicated, it is well to keep a record of the marks used so as to avoid confusion in the final erecting. 49 . Lagging* — When the cylinder attachments have all been put in place and the cylinder tested, the jacket or lagging is put on. This, in the case of small engines, may consist simply of a sheet of Russian iron cut to the proper form, bent, and screwed to the flanges of the cylinder. In the case of large engines, a framework of flat or angle iron is fitted to the cylinder and wooden strips or sheet-steel lagging fitted to this framework. If the lagging is com- posed of iron or steel, it is put in place by a machinist, while if it is made of wood, a carpenter or patternmaker is called on to do the fitting. 50 . Placing the Engine on Dead Center. — It is often necessary to place the crank on the dead center when setting the valve, and this is done in the following manner: The crank is turned so that the connecting-rod will stand in the position shown by the full lines a , Fig. 19, and a line b is drawn on the crosshead and guide. A scriber or tram similar to that shown in Fig. 20 should be placed in a prick mark c on the bed, and a line g drawn on the crank. The crank should now be rotated so as to bring the rod into the posi- tion shown by the dotted lines c, and when the lines b on the crosshead and guide coincide, another line d is drawn on the crank. The distance from g to d may be bisected with fig. so. 30 ERECTING. §23 a pair of dividers, which will give the line yon the crank, and when this line is set to the tram, the engine is on the dead center. This operation may be repeated when it is desirable to get the dead center on the other end. If the crank is of such form that it is not convenient to use it in this manner, the flywheel may be used instead. 51. Valve Setting. — No definite rule can be given for setting the valves of steam engines, as the work is largely a matter of judgment. The valves and valve gear are designed in the drawing room, and the details are worked out in the machine shop according to the drawings, which, in the case of complicated valve gears, give full directions for setting them. The slide valve is the one most commonly met, and a description of the manner of setting this will be given. As a valve gear is generally constructed, there are two ways of adjustment provided. The first consists of a change in the length of the valve stem and the second consists in rota- ting the eccentric on the shaft. By altering the length of the valve stem, the valve may be made to travel equally each way from mid-position; that is, if the valve travels \ inch too far toward the head end, shortening the stem half that amount pulls the valve \ inch nearer the crank and makes it travel equal each way, and any movement of the eccentric hastens or retards the valve action as it may be moved ahead or back. The valve must be made to move centrally by adjusting the valve stem and at the right time, by moving the eccentric. To accomplish this, set the crank on one of the dead points and set the eccentric so as to give as nearly the proper angle of advance as can be judged. The lead may now be meas- ured and the crank set on the other dead point and another measurement of the lead made. The valve may now be moved half the difference of the two leads and be given the correct lead by moving the eccentric, which should bring the lead the same at each end. No general method can be given for the detailed setting of all forms of valves, as this depends largely on the design. §23 ERECTING. 37 52. Painting and Finishing. — All rough places on the bed are smoothed off by chipping and filing before painting, or in some cases the bed is given a coating of filling material that fills all depressions. After the bed has been filled and rubbed down with sandstone or sandpaper, it is painted. In some cases the specifications call for the testing and acceptance of the engine before painting. 53. Dismantling the Engine. — When the work is passed or pronounced correct by the superintendent or inspector, the man that has had charge of the erection of the engine oversees the taking down and prepares the parts for shipment. The lagging is usually removed and boxed. All small parts are also boxed. These boxes should be num- bered and a careful record kept of their contents. The cylinder, in the case of large engines, is mounted on skids. In some cases the cylinder is covered with non-conducting material, so as to prevent the radiation of heat when the lagging is in place. This non-conducting covering may be applied in the shop previous to shipment, or may be applied in the field. All finished parts of the work are given a coating of some protective material that will prevent rust- ing. The bearings or fitted surfaces are boxed or covered with boards to protect them from injury. Crankpins and main shafts are sometimes wrapped with burlap or rope, and if large and finely finished, they may be lagged with wooden strips. In the case of comparatively small engines, the entire engine is sometimes placed on skids. In case the machinery is to be shipped by rail, care should be taken to see that the heavy parts of the load come over the trucks, the lighter parts, boxes, etc. being located near the center of the car. All parts should be securely fastened, so that they cannot shift during shipment. 54. Foundation-Bolt Templet. — While the engine is being erected in the shop, a templet for locating the anchor bolts in the foundation is made. This templet should include the correct location of all bolts for securing the engine bed, cylinders, and outboard bearing to the 38 ERECTING. §23 foundation, and in the case of a large and complicated plant like a hoisting engine, should also include the bolts for the steam brake, steam reverse, drum-shaft bearings, etc. The templet is usually laid out from the drawing, after which ali the dimensions should be checked by actual measurements of castings, in order to see that there is no discrepancy between the drawing and the casting. After the holes have been properly laid out, they are bored the same size as the anchor bolts. This templet is usually made of 1-inch white- pine lumber and must be thoroughly braced. The parts should be put together in a substantial manner with screws or bolts, or both, and also marked so that after being taken apart for packing and shipment, the templet can be easily and accurately assembled at the foundation pit. Fig. 21 shows a plan of such a templet. ERECTION OF ENGINE ON FOUNDATION. 55. Foundations. — The foundations may be composed of masonry, brick, or concrete. Stone and brick should be laid in good cement mortar. The bolts may be built into the foundation or pockets may be left at the bottom for the washers and nuts, and holes left for introducing the bolts later. In some cases, these holes may be made by building wooden boxes or iron pipe into the foundation. In still other cases, the foundations are built with pockets near the ERECTING. 39 §23 bottom, and then the masonry or concrete built up solid, after which the bolt holes are drilled with a diamond drill. When the foundation is made of concrete, it is usually better to build the bolts into the foundation. In small work a bunch of burlap may be wrapped around each bolt and these bunches are then raised along the bolts as the brick- work or masonry progresses, thus leaving clearance spaces around the bolts. The anchor bolts may be held down in a variety of ways. Sometimes a large washer is placed on the lower end of each bolt. In other cases a stirrup is formed at the lower ends of the bolts and pieces of railroad iron passed through these, as shown at #, Fig. 22. The pieces of iron may be long enough to extend through the stirrups of two or more bolts at once. The foundation-bolt templet b , Fig. 22, is supported on suitable blocking in a level position and rigidly braced to support the bolts. Sometimes it is necessary and best to suspend the templet by braces from overhead sup- ports. The rails a should be wedged against the bottom of the stirrups c by driving wedges on top, as shown at d. In order to allow some adjustment of the bolts, a piece of pipe may be placed about them, as shown at e. 56. Appliances for Erecting tlie Engine on the Foundation. — The engine is sometimes erected on the foun- dation by the same man that did the erecting in the shop. In the shop, the erector has the advantage of all the shop tools and appliances, including cranes, special tools, etc. When the engine is shipped from the works, the man that is to go with it selects such tools as he requires. The b Fig. 22 . 40 ERECTING. 23 tools needed vary greatly with the work and with the locality in which the engine is to be erected. Most modern power houses have traveling cranes in the engine rooms that can be used in erecting the engine or for any future repair work. In this case very few tools will be required. If the engine is to go into a region a long distance from any shop, as, for instance, a mining camp, the erector must take practically everything with him that he will require. Usually one or two hydraulic or stone jacks, a few screw jacks, and some pinch bars will be all of the larger tools necessary, and, in addition to this, a liberal stock of heavy ropes, wrenches, hammers, chisels, and other tools that may be necessary should be taken. All the small tools, together with supplies, waste, oil, etc., should be kept in locked tool chests. In case heavy parts have to be hoisted some distance, it maybe necessary to take a chain block or a hand windlass, crab, or winch, to be used in connection with a block and tackle. Sometimes it is convenient to take a stock of rollers and blocking, but usually these can be obtained in the field. 57. Setting Engine on Foundation. — The engine bed and cylinder are placed on the foundation and bolted together. All the dowel-pins are fitted and the engine is lined up by stretching a line through the cylinder and beyond the crank, just as was done in the shop. The engine can be supported on iron wedges during this opera- tion. The outboard bearing can be put in place and squared by means of the crank, as described in Art. 44. After the bedplate is properly located over the anchor bolts, the clear- ance spaces left around the bolts in the masonry should be filled with cement. This is mixed the same as that used under the engine bed, as noted below. Enough water is added to the cement mixture so that it will flow readily into the holes. In large work with removable bolts, the cement- ing is not required. After the engine has been bolted together and lined up, the space between the bottom of the bedplate and the foundation may be filled with some suitable com- pound. In some cases melted sulphur is used, in others a ERECTING. 41 § 23 mixture of iron chips and sal ammoniac is rammed in with a calking chisel, while in still other cases Portland cement mixed in a proportion of 1 part cement to 2 parts sand is employed. When the cement has hardened, the flywheel or pulley may be put in place and the caps over the bearings adjusted. All parts that are subjected to friction should be thoroughly oiled before being put into place, as an unoiled surface sometimes cuts during the first few revolutions before the oil reaches it through the oil hole. The piston, cross- head, connecting-rod, cylinder head, governor, valve gear, oiling devices, lagging, and piping are assembled in the order named. The engine may now be turned a full revolution by hand to make sure that all is clear. Next, care should be taken to see that everything is in adjustment; then the steam may be turned on and the engine started very slowly. After the engine is started with steam, a thorough inspection of all working parts should be made and all the oiling devices properly adjusted. Any parts that have been left too loose may now be tightened to proper running fits, and any part that shows a tendency to heat should be examined and adjusted. After the engine has been running at full speed for some time, it may be belted up and kept at work while the indicator test is being made. This test will usually show any defect in adjustment of valve setting, which may be corrected at this time. ERECTING A VERTICAL STATIONARY ENGINE. 58. General Consideration. — The method followed in erecting a vertical engine does not differ materially from that used in the horizontal engine, but as the parts are differently arranged, and in most cases some additional parts are required, a description showing the principal points of difference may be of interest. As a rule, it is more difficult to erect a vertical engine without the aid of cranes or hoists than a horizontal engine. Very large horizontal engines are frequently erected in the field without 42 ERECTING. §23 any hoisting tackle whatever, all the parts being moved on rollers and lined up by means of jack-screws. In the case of a vertical engine, it is usually necessary to rig a derrick, shear legs, or some hoist when in the field. 59. Work Necessary on the Bed. — The bed a, Fig. 23, is leveled by means of wedges or erecting jacks, as in the case of a horizontal engine. The bearings for the crank-shaft may be scraped either before or after the guides fig. 23 . are in place. Sometimes, to aid in scraping these bearings, a hollow cast-iron shaft is made of the same diameter as the crank-shaft. This is lighter than the crank-shaft and serves as a surface plate for scraping the bearings into line. 60. Fitting the Guides and Cylinders. — The frames and guides d and d ' are placed on the bed and temporarily bolted down. A center line along the center of the shaft is §23 ERECTING. 43 established by placing blocks across the bearings, as shown * at e. A piece of tin is fastened to the center of each one of these and a center line marked on it. A long straightedge is then laid across both blocks and a center line established. A line, as fghi, is stretched through each cylinder. The line is secured at the bottom to a plank /, which is blocked or clamped to the bottom of the bedplate and has a hole in the center through which the line passes. At the upper end, above the cylinders, the line is secured to the plank k. The line passes over pulleys at g and //, and is kept taut by a heavy weight at i; a piano wire capable of standing a break- ing stress of 400 pounds is usually used for this purpose, and the weight at i may vary from 100 to 200 pounds. This weight should be located so that it will do no damage if the wire should break. After the line is established, the guides and cylinders are adjusted to it. If desired, the weight at i may be hung under the cylinders in place of the plank f. It is best to suspend the weight in a vessel of water to prevent vibration. Great care must be taken to see that the lines fg and f'g' are the same distance apart, both top and bottom, and are in the same vertical plane. If it is found that the cylinder does not come in line with the guides, packing pieces must be placed between the cylinder and the guides, as in the case of a horizontal engine, after which a sufficient amount must be dressed from the end of the cylinder or the intermediate piece, bringing the two into alinement. In measuring from the line to the cylinders, or from the line to the guides, a wooden measuring piece may be used, as described in Art. -41. After the cylinders and guides are properly located, they are securely clamped, in place, and the bolt holes for holding the uprights to the bed, the guides to the uprights, if the latter are made separate, and the cylinders to the guides, are reamed ready for the bolts, and the holes for the dowel-pins are drilled and reamed and the pins fitted. 61. Placing Reciprocating Parts. — The placing of the reciprocating parts of vertical engines does not differ 44 ERECTING. 23 materially from that of horizontal engines, and the method of squaring the crank-shaft to the center line that is used in the horizontal engine can also be employed in the vertical engine. 62. Oiling Devices and Smaller Parts. — In some cases, vertical engines are fitted with separate oiling devices for each bearing, while in other cases an oil tank is arranged at or near the cylinder from which pipes lead to the various bearings. Another system provides a reservoir with a pump, either attached to the engine or as a separate machine, which distributes the oil through a suitable arrangement of piping. All these devices are placed in position during erection. Owing to the fact that many parts of the engine are not accessible from the floor, it becomes necessary to provide some device by means of which the attendant can reach any part of the engine. To accomplish this, plat- forms or floors are built around the engine at different elevations. These platforms are usually iron plates sup- ported on brackets, and are reached by staircases leading from the floor of the engine room. These brackets and plates are all placed in position as the various parts of the engine are being assembled. In the outer edge of the plates, provision is made for standards, which carry a hand rail, usually composed of a piece of brass or iron pipe. Large vertical engines are often provided with hand or similar turning gear for turning the engine around a portion of a revolution in starting or when fitting belts. They are also supplied with steam, vacuum, and revolution gauges, and a clock. Provision must be made for attaching these to the engine frame, though they are not generally assembled in place until the engine is erected upon its foundation ; or they may be erected on a board entirely separate from the engine. Provision must also be made on all engines for attaching the steam indicator. 63. Dismantling Vertical Engines. — After an engine has been erected and tested, it is dismantled in a 46 ERECTING. §23 manner similar to that used in taking down large horizontal engines, except that it must be done to a greater extent. 64. Erecting on Foundation. — The erection of a vertical engine on the foundation does not differ materially from that of a horizontal engine, with the exception of the fact that in some cases a line is not stretched through the engine when it is erected on the foundation. When no line is used, bolts and dowel-pins are depended on entirely for bringing the parts into line. Care must be taken in erect- ing a vertical engine to see that the bedplate is carefully leveled and has a firm bearing before the other heavy parts are assembled on it. LOCOMOTIVE ERECTION. METHOD BY PLACING THE BOILER FIRST. 65. Methods of Erection. — The erection of locomo- tives varies in different shops, not only owing to the different ideas possessed by the men in charge, but also on account of the varying equipment of the shops. In one method the locomotive boiler is placed first and all the parts assembled about it, the principal argument in favor of this method being that the boiler is the stiffest thing about a locomotive engine, and hence everything should be lined up to fit it. In the other method, the frames and working parts are erected first and the boiler placed on them. The first method will be now considered. 66. Placing the Boiler. — In Fig. 24, a locomotive boiler is shown ready for assembling the other parts about it. The length of the top part of the blocking at a under the firebox end must be less than the distance between the two frames, so as not to interfere with the other placing. The barrel or shell of the boiler is supported by a strong trestle b that rests on the block c. It is not necessary that the boiler be level endwise, but care should be taken to have §23 ERECTING. 47 it plumb sidewise. The center of the dome d should come over the center line of the bottom of the firebox, and each side of the barrel of the boiler should be equally distant from the vertical center line. Should there be any slight dis- crepancies in the shape of the boiler, they should be averaged in the setting. In other words, in case it is found that with the center of the dome over the center of the bottom of the firebox the barrel of the boiler projects more on one side of the vertical line than on the other, the sides of the boiler may be brought equidistant, or nearly so, from the center of the bottom of the firebox, even if the dome is thrown slightly to one side. 67. Placing the Cylinders. — The cylinders are brought under the boiler and approximately to their places, the saddle a , Fig. 25, being in contact with the barrel of the boiler. Lines b and b' are then run through each cylinder and fastened to some fixed object, as the post d near the back of the firebox. The lines b and b' should be parallel and equidistant from the sides of the front end of the boiler shell, as shown by the line c , hung over the top of the boiler shell and having the weights f attached to each end. The two center lines are brought to the desired distance, plus the amount to be chipped off the saddle, below the firebox at the point e. This is accomplished by placing a straight- edge under the firebox at e and measuring to the lines. The horizontal distance from the sides of the firebox to the center lines may also be determined and made equal on both sides. The erector then scribes a chipping line all around the saddle by means of a pair of dividers or a small surface gauge. The cylinders are next moved out in front of the boiler and the saddle chipped to the line referred to. The cylinders are then returned to their positions in contact with the boiler shell and tested by the lines. In some cases it may be necessary to remove them and make any slight corrections that may be required by further chipping and filing. A narrow chipping strip is provided all the way around the saddle a to facilitate this work of fitting. 48 ERECTING. §23 Fig. 25. C. S. III.— 23 Fig. 50 ERECTING. §23 The space above the upper surface of the saddle a and between the chipping strips is then filled with cement to give a solid bearing between the saddle and the boiler. Different materials are used for this purpose, as, for instance, asbestos, stove putty, red and white lead cements with or without iron chips incorporated in them, and in some cases iron chips and sal ammoniac have been used to form a rust joint. In all cases considerable care is necessary to use just the right amount of material, on account of the fact that there is no chance to calk or drive it into place. After the space in the saddle has been filled, the cylinders are bolted to the shell and blocking placed under them to support the weight of the front end of the locomotive. The trestle b , Fig. 24, is then removed from under the barrel of the boiler, as it would be in the way during the latter operation. G8. Placing the Frames. — The frames are next placed in position, as shown in Fig. 26. They are bolted to the cylinders at the front end, and the foot-plate a is bolted across the back ends, which spaces them properly. The waste plate b is attached to the frames, but not to the barrel of the boiler. The guides c and d are bolted to the cylinders and blocked in place. In Fig. 26 the lower guide is sup- ported by a jack-screw and the upper one by blocking. While this work has been in progress other men have put in the tubes and dry pipe, drilling and tapping the holes for the gauge cocks and cleaning plug holes, also the holes for the studs for the running-board brackets, sand box and bell, the combination globe or steam turret, and any other holes that may be required. G9. Lining tlie Guides. — The guides are supported at the back end by the yoke a , Fig. 27. A line b is passed through each cylinder to a piece of board held in one of the pedestals, as shown at c. These lines are centered in the front ends of the cylinders and in the piston-rod glands at the back ends. After the lines are in place, the guides are set parallel to the lines and the guide yoke adjusted. About this time the waste sheet d, Fig. 27, is secured to the barrel ERECTING. 51 § *3 Fig. 52 ERECTING. §23 of the boiler by the angle e. After the guides and guide yoke are in place the yoke is secured to the frames by proper attachments and to the boiler by a sheet and angle, as shown at a , Fig. 28. While this work is going on the holes for the furnace pads (also called expansion pads or bearers) are drilled, as shown at f, Fig. 27, and the pads and links put on, as shown at b and c , Fig. 28. At the same time other men are placing other details, such as the bell, stack, oil pipes, etc.- 70. Testing the Boiler. — The firing or testing of the boiler in some shops is done without taking the engine from the erecting floor. A better way is to run two temporary trucks, made expressly for the purpose, under the locomo- tive, as shown at d and e , Fig. 28. This enables it to be hauled to the transfer table and moved to the firing room. Locomotive boilers are sometimes tested by using steam piped to them from a high-pressure stationary boiler installed for this purpose, but the better practice is to use a fire in the firebox of the boiler, as this makes the test under actual working conditions. The boiler is first filled to the top of the dome with hot water, through an injector. Any leaks that may appear are tightened by calking, and a water pressure sufficiently high is slowly applied. In ordinary practice this is about 240 pounds. While the pressure is on, if any leaks appear, they are marked with chalk. The pressure is then taken off, and the leaks that have been marked are carefully calked. The water is lowered to one gauge and a fire started in the firebox. The water will rise to two gauges by expansion. Steam is raised to the desired pressure, usually equal to the water pressure used. For instance, if the steam pressure were 240 pounds when this limit had been reached, the pressure would be reduced to 50 pounds, which process is repeated three times. The oil pipes are tested at the same time to see that they are all right before they are covered with the jackets. The jacket is not placed on the boiler until the engine is returned to the erecting shop after firing. Fig. Fig. 29. §23 ERECTING. 55 71. Placing the Wheels, Valve Gear, and Details. The locomotive is now brought back to the erecting shop and lifted from the temporary trucks by the traveling crane, and is ready for its own wheels to be run under it, including the truck. The engine is then lowered into place, as shown in Fig. 29. The links and motion work are next put up and the valves set. At the same time the boiler is being covered or lagged with a non-conducting material, and the planished iron jacket, running boards, cab, and pilot are placed in position. The running boards, cab, and pilot are made in a different shop and brought to the erecting floor ready for placing. The painters have been following the machine work most of the time, as opportunity offers. The cab, sand box, and some other parts are painted before being brought to the erecting shop. To enable men to work under. the locomotive, an erecting pit about 38 feet long, 47 inches wide, and 32 inches deep is usually provided between the tracks of each erecting stall. This pit usually begins about 14 feet from the door. The tender is made complete in another department, and is ready to be attached to the locomotive after it is run out from the erecting shop. METHOD OF ERECTING BY PLACING THE CYLINDERS AND FRAME FIRST. 72. Placing tlie Cylinders and Frame. — In this method the cylinders are first placed on four jack-screws, the saddle having been machined to the same radius as the smokebox. The frames, guides and guide yokes, foot-plate, buffer beam, and some other parts are put in place, the cylinders jacketed, and the parts adjusted to one another. During this work the frames are supported at the back end by jack-screws. The cylinders are brought into the proper relation to the frames by means of lines, as described in the other method of erection. 56 ERECTING. 23 73. Placing tlie Boiler. — After the frames and cylin- ders are joined, the boiler is brought by the traveling crane and lowered to its place, and the connections between the boiler, frame, and cylinders are made. If the boiler is not perfectly round, it will not fit the saddles perfectly. After all the parts that have been erected together have been attached to the boiler, the entire engine is lifted by a crane in readiness to receive the wheels that are now rolled under and placed in their proper positions. After this the stack and pilot are put on, the boiler tested, lagged, and jack- eted, and the rods, valve work, running board, cab, fixtures, and other parts are put in place very much as in the first method described. 74. Comparison of tlie Two Methods. — The main difference between the two plans described is, briefly, as follows: In the first plan, the boiler is the starting point, or backbone, and all other parts are built around it. In the last-mentioned method, the main part, or skeleton of the engine, is assembled and the boiler added, after which the running gear and the remainder of the engine are put in place. When the second method is used, no erecting pit is required. SHOP HINTS. (PART 1.) RIGGING. DEVICES FOR HOISTING AND MOVING. LIST OF APPLIANCES. 1. For the handling of heavy pieces of machinery in the field, or in buildings where they are to be erected, tools and appliances known by the general name of rig- ging are used. The appliances ordinarily required are the following: 1. The winding winch, or windlass, which is a machine with a rope drum and appliances for turning the same. 2. A set of different sized tackles, in which the rope, or line, should be long enough to reach the windlass or to allow a number ^of men to grasp it when the blocks are the greatest required distance apart. 3. One or more screw jacks and hydraulic jacks are indis- pensable. 4. Slings or straps made of rope spliced together to form an endless rope. § 24 For notice of copyright, see page immediately following the title page. 2 SHOP HINTS. §24 5. Lashings, these being pieces of rope of different sizes and lengths, with the ends stopped up, by tying or binding, to prevent their unraveling. 6. Blocks of wood, rectangular in shape and of different sizes, and timber for the construction of derricks and gin poles. 7. Wedges, both of iron and of hard wood. 8. Crowbars and pinch bars. 9. Chains and chain hoists. 10. Rollers, which are generally short pieces of iron pipe. The articles enumerated in the first, second, third, eighth, and ninth paragraphs can usually be bought cheaper and better than they can be made. Slings, lashings, blocks, wedges, and rollers are rarely bought in the market, but are usually made. PINCH BARS. 2. The most common form of pinch bar is a straight iron or steel bar, square on one end, with a flat, wedge- shaped point turned slightly to one side and the other end round and slightly tapering to form a handle, as shown in Fig. l. Fig. 1 (a). This form of bar is usually about 4 feet long, and is commonly called a crowbar. The smaller pinch bars, used in machine shops and in erecting machinery, are 24 SHOP HINTS. 3 from 2 to 4 feet long, and are made of -f-inch or f-inch octagonal steel, as shown at ( b ). A rather convenient form of pinch bar that is well adapted for lifting and moving quite heavy weights is shown in (c). As will be seen by referring to the illustration, the bar is mounted on two wheels, and consequently, when the bar supports a heavy weight, the bar and weight can be easily shifted. This form of pinch bar is sometimes called a cow bar. USE OF SLINGS. 3. Slings are loops of rope or chain used for attaching weights to the hook of a tackle or for fastening a tackle block to some support. In order that a sling may best serve its purpose, one of several methods of fastening it to the block has to be chosen, the choice of method being influenced to some extent by the weight of the load to be lifted. For instance, the resistance of the sling is least if used single, as shown in Fig. 2 (a), but its greatest possible strength may be obtained by looping it over the hook as shown in Fig. 2 (b), thus increas- ing the surface of the sling in contact with the hook of the tackle block. The sling may be applied to the piece of work to be moved in the same manner in which it is fastened to the hook of the tackle block; that is, it may be either passed around singly, as in Fig. 2 (a), or doubled, as in Fig. 2 (6), the latter method being preferable owing to the absence of any danger from slipping of the sli|ng. It is obvious that if the sling is fas- tened by doubling over, a noose is formed and the sling is thus tightened on the work when the free end is pulled; hence, the preference of riggers for this half-hitch arrangement. (a) (b) Fig. 2. 4 SHOP HINTS. § 24 USE OF LASHINGS. 4. Where headroom is limited, the tackle may be attached to the work by means of lashing. This is simply over the hook, the ends of the line being fastened by a knot. Another advantage of lashing lies in the fact that a small rope may be used ; the necessary strength is then obtained by increasing the number of turns. INSPECTING ROPES, SLINGS, AND LASHINGS. 5. There will come a time when, from repeated use and occasional abuse, the strength of ropes, slings, and lashings will be impaired; in order to prevent any accident that may occur on account of this loss of the strength, it is necessary to know how to detect a weakened rope. The first thing to be done is to inspect the outside carefully, running over the lines from end to end, and noting if any of the strands, or yarns composing the strands, are damaged. If nothing wrong is discovered about the outside of the rope, the inside should be inspected, for the reason that a rope will Fig. 3. a piece of rope suffi- ciently long to admit of its being passed several times around the piece to be moved. Work is fastened to the tackle by first bringing the back of the hook of the tackle block in contact with the piece to be hoisted, as shown in Fig. 3, and then passing several turns of the line around the work and §24 SHOP HINTS. 5 often be perfectly sound on the outside, but utterly bad inside. The inside may be inspected by taking the rope in both hands and untwisting it sufficiently to expose the inner surfaces that have been chafing against one another. Then, if the life or utility of the line has been impaired by long use, a considerable number of broken fibers will be found; if in a bad state, they may have been reduced to powder. If broken fibers are discovered, the use of the rope should be confined to loads not heavier than half the load it for- merly could stand; if a considerable quantity of powder is found, the line should be condemned at once as unfit for use. Slings and lashings, as a general rule, are ruined by exter- nal chafing received when moving rough castings, etc., and hence their safety can be determined from their external appearance. Ropes or lines, on the other hand, when used for tackle blocks, receive the greatest wear on the inside, owing to the chafing and grinding of the strands when passing over small pulleys under heavy strains. CHAIN HOISTS. 6. Chain hoists, as a general rule, are best adapted to lifting heavy loads where the help available is scarce, since, owing to the way in which they are geared, they require very little power. There is, however, a great range in the effi- ciency of chain blocks, varying from 18 per cent, with the common differential chain hoist , where it takes considerable power to lower the load, to 79 per cent, efficiency in the case of the triplex hoist. One great advantage of chain hoists lies in the fact that they may be stopped at any point; that is, theToad will remain in a state of rest, without secur- ing the chain in any way, until set in motion again by the operator. With a tackle this cannot be done, since it is necessary to fasten the free end of the line to some station- ary object in order to hold the load; this, of course, is often a drawback to the use of a tackle, and a great point in favor 6 SHOP HINTS. § 24 of the chain hoists. To offset this, we have the fact that, with long usage, the iron in the chain links becomes crystal- lized, and hence is liable to break suddenly even under a moderate load. The effects of crystallization can, however, be rem’edied to a large extent by a thorough annealing of the chain. This can most readily be done by coiling the chain after removing it from the blocks, and then building a charcoal fire around it. This should be done in the open air; no blast should be applied to the fire. After the chain has been heated cherry red, it should be placed in an iron vessel, the bottom of which has been covered with' powdered charcoal. Then cover the chain with the same substance, close the box, and allow the chain to remain there until cold. It may then be rove through the blocks again, and will be nearly as good as when new. SPLICES. 7 . Definitions. — Splicing is the operation of so join- ing two pieces of rope as to obtain one continuous piece with no appreciable increase of diameter at the splice. There are several kinds of splices, but the principal ones are the short splice, the lo7ig splice, and the eye splice. The principle of all splicing consists of joining, or marry- ing, the strands, thinning them out and tapering them so that the diameter at the splice is the same or only slightly greater than that of the rope itself. In the long splice, no increase in diameter is allowed. 8. Materials Used for Ropes. — Until comparatively recent years, all ropes were made of vegetable fiber teased out and spun into suitable form either by hand or machinery ; but since the introduction of iron, and particularly of mild steel, into the rope-manufacturing industry, steel rope is rapidly superseding all other kinds of rope for certain classes of work. For many purposes, however, fiber ropes are still used and can never be replaced by steel ones; they are made, §24 SHOP HINTS. 7 for the most part, either of hemp, manila, or coir (cocoanut husk fiber). First, the fibers are spun into yarns, then the yarns into strands, and, finally, the strands into rope. The methods of splicing described and illustrated here apply only to these fiber ropes. 9. Splicing Instruments. — The only instruments necessary for making a splice are a marl inspike and a knife. The former is made of either iron or hard wood, is from 12 to 14 inches long, and about 1 inch in diameter at the thick end, the other end being sharpened to a blunt Fig. 4. point about as shown in Fig. 4; it is always operated by the right hand, while the left encircles the rope. After pushing the point through the rope, between the strands that are to be separated, the thick end is placed against the body of the operator; then, using both hands, the rope is untwisted so as to rendor the work of opening the strands compara- tively easy. 1 O. Making a Short Splice. — Unlay, that is, split open, the strands at the end of each rope for a distance about as shown in Fig. 5; this distance depends entirely on 8 SHOP HINTS. §24 the diameter of the rope, but as the proportion will be the same for all diameters, the illustration serves as a general guide. Be sure to unlay enough; a few inches too much is better than too little, as the ends have to be cut off anyway. Then, place the two ends together as shown at ( a ), so that each strand lies between two strands of the other rope. Now, hold the strands x , y 9 z and the rope A in the left hand; if the ropes are too large to hold in this manner, fasten them together with twine; then take one of the strands, say n, and pass it over strand y, and having made an opening, either with the thumb or with a marlin- spike in the manner illustrated in Fig. 4, push the strand n through x and pull it taut ; this operation is known as stick- ing. Proceed similarly with strands m and o , passing each over the immediately adjoining strand and under the next one. Perform precisely the same operation with the strands of the other rope, passing each strand over the adjoining one and under the next, thus making the splice appear as at ( b ). Now, in order to insure security and strength, this work must be repeated by passing each strand over the third and through under the fourth ; then, after subjecting the splice to a good stout pull, cut off the ends of the strands, and the finished splice as shown at ( c ) is obtained. In slings and straps used for heavy work, the strands should be passed twice each way, and one-half of each strand should be whipped , or bound, with twine to one-half X in pole. When the upper end of the mast and boom are tied together by a horizontal member, the whole device is called a crane, 14 SHOP HINTS. §24 and is usually fitted with a traveling carriage on the horizontal part, or gib. 15. Erecting the Gin Pole. — When it is desired to erect a tall derrick, it will generally be necessary to put up a gin pole first to assist in raising the mast, but if the der- rick is low, its boom may be used for this purpose. One method of erecting the gin pole is to slip a bar of iron a through the hole in the lower end and secure it to suitable stakes c, as shown in Fig. 10. The free end of the gin pole is then lifted from the ground and placed on the X-shaped brace e. The guys f, g, h , and i are then attached to the 24 SHOP HINTS. 15 upper end d and are laid out on the ground ready for use. The men now raise the gin pole b by means of pike poles and advance the support e toward the lower end. When the free end has been raised some distance from the ground, the ropes f and i may be pulled, and thus help to raise the fig. 10 . gin pole to a vertical position; at the same time, the men who attend to the guys g and h must see that it does not shift from the desired position. Usually only one man is required for each end of the guys g and Ji, since he can wind the rope about a stake, and then easily prevent the gin pole from moving too far. 16. Erecting the Mast. — After the gin pole has been raised into an upright position and the guys have been fast- ened, it may be used for lifting the mast, as is shown in Fig. 11, in which a represents the gin pole, the lower end of which is' lashed to the stakes c. The base for the der- rick having been located and fastened to the timbers b , b , the mast <3^4s hoisted into position by means of a rope fastened a little above its center and passed over the pulley e on the end of the gin pole. The other end of this rope f may be handled by hand if the mast is not too heavy, or by a suitably located winch or crab if the mast is of consid- erable weight. The derrick head g should be placed in 16 SHOP HINTS. §24 position and the guys attached before the mast is raised. The lower end of the mast is now lowered into the base, Fig. 11. after which the guys attached to the head g are tightened and fastened in position. The temporary guys /i, i,j \ and k SHOP HINTS. 1 ? § 24 for the gin pole are usually of manila or hemp rope, while the permanent guys for the mast are made of wire rope. 1 7. Placing the Boom. — After the mast has been properly guyed and the gin pole has been taken down, a hoisting rope is passed over the pulleys at the top of the mast; a hitch is then made around the boom and it is raised until the bottom end can be swung into the knee, where it is secured by its pin. The ropes are then all reeved through their proper pulleys and the derrick is ready for work. Large derricks are generally erected by the aid of a sepa- rate gin pole, as just described. In the case of a very large derrick it is sometimes necessary to erect a gin pole of a height such that the men can handle it, and use this for set- ting the boom on end, which is then used as a gin pole for lifting the mast. In some cases two separate sticks of timber are used as gin poles, a short one, less than one-half the height of the mast, being used to set a gin pole about two- thirds the height of the mast; this second gin pole is then employed for setting both the mast and the boom. Derricks so large as to require two gin poles for their erection are rarely used except on permanent work. 18. Erecting a Small Derrick. — With small der- ricks, it is rarely necessary to use a gin pole for raising the mast, as the boom is generally light enough to be erected as a gin pole, and is then used for raising the mast. After the mast has been raised and securely guyed, the mast itself is used for swinging the boom, which up to this time has served as a gin pole, into position. 19. Dismantling tlie Derrick. — When the work has been finished and it becomes necessary to dismantle the der- rick, the boom is hoisted up to the mast, and is detached from the knee. Stakes are then driven into the ground and the lower end of (the boom is lashed to them; the boom is then used as a gin pole for lowering the mast. The boom itself is lowered afterwards by paying out two of its tempo- rary guys until it can be caught on a support similar to that shown at e } Fig. 10. 18 SHOP HINTS. 24 MISCELLANEOUS OPERATIONS. CLEANING WORK ANI) CASTINGS. THE SODA KETTLE. 20. Description of tlie Kettle. — All shops have x more or less work that must be cleaned so as to be free from grease. This is often a troublesome task, involving the expenditure of time and energy. The greater the irregularity of the pieces, the more trouble there is experi- enced in cleaning them. A very convenient method of quickly and easily cleaning small parts of machines, tools, or machined parts is to wash them in hot soda water. The most convenient receptacle for this mix- ture is known in the shop as a soda kettle. This is often a shop- made affair, but e m - bodies the main features of the kettle illustrated in Fig. 12. This soda kettle, which is built by a well-known tool builder, consists of a cast-iron kettle a con- taining a coil of steam pipe for heating the soda water. Live steam enters the coil when the globe valve b is opened, and the exhaust steam leaves through the pipe c , which is provided with a globe valve. A by-pass pipe d having a globe valve is connected to the exhaust pipe; if the globe valve in the exhaust pipe is closed and the valve in the by-pass pipe is opened, the pressure of the live steam will force the water 24 SHOP HINTS. 19 of condensation in the bottom of the coil into the kettle. A drain cock e is used for emptying the kettle. 21. Operation of the Kettle. — In use, the kettle is filled about three-fourths full of clean water to which is added about its volume of sal soda; the mixture is then heated as hot as the steam will heat it. A wire basket, or an iron pail or bucket having the bottom punched full of holes, is provided for holding small pieces while dipping them into the soda mixture. Suitable hooks made of small iron rod may be used to dip single pieces into the kettle. A pair of pick-up tongs and one or two hooks should be kept near the kettle, since pieces are sometimes dropped into it and must be fished out. Work covered with soft grease or oil and chips is cleaned by putting it into the basket, which is then dipped into the hot water. Work that may be covered with oil that has dried on it often has to be soaked in the solution for some time, and a part of the dried oil then has to be scraped off ; the work is now given a further soaking, which is generally sufficient to remove the rest of the dried oil. Work cleaned in the hot soda water dries quickly and will not rust. PICKLING SOLUTIONS. 22. Sulpll uric Acid for Pickling. — The surfaces of castings, drop forgings, and many of the materials used in the construction of machinery require cleaning or prep- aration before they can be used. Much of this cleaning is done by pickling the work in such mixtures as, by experi- ment, have been found to be most effective. Several of these solutions are given below, and the user can, by experi- ment, determine which of these is best adapted to his needs. Oil of vitriol, oi^sulphuric acid, is one of the most common acids used for pickling. It is generally transported in glass carboys, which are securely boxed up. The acid is handled in small quantities around the works in glass, earthen, or lead vessels It is used in the proportion of about 1 part of acid to 4 parts of water, for cleaning sand and scale from 20 SHOP HINTS. §24 iron castings, although some use a larger proportion of water. Pure sulphuric acid will not attack iron, but the dilute acid, or the acid mixed with water, will do so. 23. The Pickle Bed. — The cleaning is generally done in what is called a pickle bed, which consists of a lead- lined trough for holding the solution. At one side of it is a sloping wooden platform, so that the solution will flow from it to the trough. The castings are piled upon this platform and the solution is poured, over them with a ladle. They are allowed to lay over night ; it will then be found that the acid has attacked the surface of the iron suffi- ciently to loosen the sand, much of which is washed away with water. The castings are further cleaned with wire brushes and old files. 24. Hydrofluoric Acid as a Pickling Mixture. Wrought iron that is badly scaled in forging may be cleaned with a solution of 1 part of sulphuric acid to 10 parts of water ; after pickling, the work should be cleaned in hot lime water. Another, and in many respects, better, solution is composed of 1 part of hydrofluoric acid to 10 parts of water. This is kept in a wooden vat ; the castings are immersed in it for 2 or 3 hours. Hydrofluoric acid does not, like sulphuric acid, attack iron, but, instead, attac'ks the sand directly and eats it, as well as the hard magnetic oxide (the scale). About half as much hydrofluoric acid is used as would be needed of the sulphuric acid, and the work is done in about one-fourth the time. The pickling vat may be filled and used two or three times before adding more acid. Drop forgings are often covered with a thick, hard scale that may be removed by dipping them in this mixture, then washing them in clear water. Care should be taken to keep this acid from the hands, as it burns severely in a few hours. If it is spilled upon the hands, they should be washed in water mixed with aqua ammonia, or some other alkali, in order to prevent injury. Brass castings are pickled in a mixture of 1 part of nitric acid to 5 parts of water and washed thoroughly after pickling. §24 SHOP HINTS. 21 COMPRESSED All? FOR CLEANING. 25. In shops having compressed-air service, a |~inch rubber hose with a -|-inch nozzle attached to it forms a con- venient means of cleaning many pieces of work that are so shaped that it is difficult to reach every part with the hand. The blast is simply turned on the piece to be cleaned, and most, if not all, of the loose dirt is blown off. An air hose will be found very useful in the tool room for cleaning the shelves, racks, and drawers, and may even be used advan- tageously for rapid cleaning of some tools. The disadvan- tage of the air blast lies in the fact that it scatters the dirt all over the vicinity. PROTECTIVE COVERINGS FOR METALS. GALVANIZING. 26. Preparing tlie Iron for Galvanizing. — Gal- vanizing iron consists in providing it with a tightly adher- ing coating of zinc. This makes it practically waterproof, and it is of good advantage even if afterwards coated with protective paint. All castings that are continually exposed to the weather should be galvanized, unless otherwise protected. The process consists in the preparation of the casting or other articles to receive the coating, and the actual immer- sion in the bath of melted zinc. The castings are first freed from as much sand as possible in the foundry. Malleable castings are usually clean enough for this purpose when they leave the soft-casting cleaning room. Next, they are placed in large vats containing dilute sulphuric or hydrofluoric acid, the latter being used only in obstinate cases, as a rule. Here they remain until the coating of oxide is thoroughly removed. Ror large work, the vats are sometimes 30 feet long, 6 feet wide, and 4 feet deep, and have steam pipes to warm the solution in cold weather, though usually the chemical reactions warm the pickle sufficiently. The castings may remain in the pickle over night, being stirred frequently so that pockets of gas that have formed may not 22 SHOP HINTS. 24 cover a spot and prevent the acid from touching it, as these spots would not galvanize properly. Castings are also repeat- edly taken out and scratched with a chisel or old file to note how the action of the acid progresses. When the process is finished, the acid maybe drawn off into another tank, prefer- ably by means of a steam siphon, or it may, as is usually the case, be left in the tank, and the castings transferred into a second tank containing clean, warm water. Small castings are always wired together or put into perforated wooden boxes so that they cannot be lost. In this second tank the acid is washed off, and the pieces should be thoroughly examined. The work could now go to the drying oven and then into the zinc pots, but an improved method introduces another pickling in dilute hydrochloric acid, in which the work remains long enough to be again attacked thoroughly. When lifted from this solution the castings are placed in a large drying oven, shown in Fig. 13, to be dried and heated preparatory to the galvanizing process. These drying and heating ovens are usually constructed of brick and have doors, as shown at a, a , of sheet iron on each end, each door being the full width of the oven. This facilitates the placing and removing of the material and enables the operation to be performed so quickly that little heat is lost. The fire is §24 SHOP HINTS. 23 built on the grate at b, from which the gases with the heat pass through the chamber c , heating the oven from below, and into the oven through the opening d , and finally out again through e. 27. Coating the Work With Zinc. — It seems that the second pickling in hydrochloric acid impregnates the sur- face of the iron with a chloride of iron, which, on being dried, protects the iron surface from rusting. Again, the dried chloride of iron, on touching the melted zinc, is volatilized, leaving a clean surface of pure iron behind, and this surface in a rough state increases the tendency of alloying with zinc. The consequence is that no difficulty is experienced in fig. 14. getting the zinc to adhere; hence, when the castings come from the heating oven, they go directly into the bath of melted zinc. This bath is practically a tank furnace, one form of which is shown in Fig. 14 (a) and ( b ). A tank of suitable size, according to the character of the work treated, is made of heavy steel plates riveted to an angle-iron frame, as shown at b , Fig. 14 (a). This tank is bricked into a furnace arranged with fire-pots at regular intervals, as shown at c , c, which are required to keep the zinc at the proper temperature. Air drafts, as shown at d , are provided for each fire-pot. It is important that the castings coming from the drying oven lose no %at, for such a loss has the effect of chilling the bath, which means delay in getting out the work. Small castings are also kept wired together in the zinc bath. When taken out, the surplus zinc is shaken off and the castings are sometimes quenched in cold water, although this may injure the castings, sometimes cracking or breaking them. Large castings are handled with a tackle suspended above 24 SHOP HINTS. §24 the tank, while the surplus zinc is taken off with a trowel and wet broom. . Small castings, if it is impossible or unde- sirable to wire them together, are placed in large dippers made of coarse wire-screen material, and all dipped into the molten zinc. Some galvanizing works do not use drying and heating ovens, but take their castings in small quanti- ties directly from the acid bath to the zinc bath, and let this heat them. This practice -is not a very good one, as it dete- riorates the zinc in the bath and leaves a bad looking sur- face on the casting. After the castings are.galvanized they are sometimes carried through the quenching water on a chain carrier, and at this point the inspection should be made and faulty work returned to the tanks for regalvani- zing. During the galvanizing process, dry sal ammoniac is thrown on the work as it is dipped in and out of the bath of zinc, to help the alloying process. Dense fumes of sal ammoniac fill the room, but they are not seriously dangerous to health. It is well to have some grease on the zinc bath, as this keeps the zinc from oxidizing rapidly and also assists in the alloying of the zinc with the iron surface to be coated. The castings finally go to the warehouse for shipment. 28. Recovering tlie Waste Zinc. — The oxidation of the zinc is one of the most serious things with which the galvanizer has to contend, as it gradually renders the zinc unfit for use. A certain amount of iron is removed from the castings and from the tank. This iron enters the zinc bath, and, uniting with the zinc, forms an alloy called dross, which settles to the bottom of the tank, and if left there will soon form a hard cake and ruin the tank. The continuous application of excessive heat will result in the blistering and burning out of the steel plates. Once or twice a week, there- fore, a large iron scoop, shaped like a large snow shovel, and operated from above by the tackle, is pushed down into the tank, and the dross lifted out. Perforations in the scoop allow the good zinc to drain off, and the dross is poured into iron molds, where it quickly solidifies. It is then dumped and piled for sale to the zinc-refining companies. When it is understood that sometimes one-fourth of the SHOP HINTS. 25 §24 whole bath-is dross at the end of a week of continuous gal- vanizing - , and that the dross is 90 per cent, zinc, the serious- ness of the loss becomes apparent. The dross can be refined again by melting with lead and rabbling with green poles, but it hardly pays galvanizers to attempt this, as the zinc-refining companies have special facilities for the pur- pose and do the work at moderate cost. The skimmings of the zinc bath and floor sweepings should also be preserved, as they contain considerable zinc. Much of the zinc is recovered from them by treating the material in a special roast- ing furnace, as shown in Fig. 15, with an inclined hearth, shown at a. Small quantities are treated at a time, the particles of scat- tered zinc collecting as they run down in the little well shown at b , at the bottom of the pan, from whence the zinc is tapped through the opening shown at c into the vessel shown at d. What re- mains of the roasted ma- terial is barreled and sold. The furnace here illus- trated has a firing door an ash door grates g , a flue y^a hood i, and an opening froitp the hood j, through which the fumes from the zinc pass. This process is very trying to the immediate neighborhood on account of the fat used to cover the bath of the zinc, much of which finds its way into the skim- mings and results in very bad-smelling fumes. The roast- ing should therefore be done only at night, unless some provision is made for the disposal of the fumes. C. S. III .— 25 26 SHOP HINTS. §24 29. Some Precautions and Suggestions in Gal- vanizing. — With hollow castings, pipe, etc., great precau- tion must be taken to keep out of the way, for if any moisture has remained in the pipe and comes in contact with the hot zinc, it will cause an explosion, throwing quantities of the melted zinc from the end of the casting with great force. The same holds true in quenching a pipe in cold water, although here the projected water is not so serious. Glycer- ine is often used to add to the .grease on the melted zinc, as it is said to give fine results when good color and crystalliza- tion on the surface are wanted. A good way to prevent the dross from adhering to the bottom of the tank, as well as to facilitate its removal, is to introduce a quantity of lead into the zinc bath. Lead does not alloy with either zinc or iron; it has a greater density than either, and, therefore, sinks to the bottom, forming a liquid cushion on which the dross and other impurities float. TIXMXG. 30. Tinning by Dipping the Work Into Molten Tin. — Tinning castings differs from galvanizing only in the substitution of tin for zinc and in general carrying on the process on a much smaller scale. The work when small is all put into wire baskets and pickled, after which the basket with the well-pickled cast- ings is slowly lowered into the bath of tin. This is usually done with a small tackle, and when thor- oughly tinned the basket is raisedandthetin allowed FlG ' 16 ' to drip off. The castings are then dumped into a wooden chute, shown in Fig. 16, [ ^ J 1 !, §24 SHOP HINTS. 27 which has inclined wooden shelves, as shown at a, which throw the castings violently against each other as they descend. The consequence is that the remaining surplus tin is jarred off, the pieces cool without remaining in contact with each other, and are quenched practi- cally singly as they fall into the water shown at b. They are finally rolled in sawdust in order to dry them thoroughly, and are then packed for shipment. The tinning furnace ordi- narily used resembles a crucible furnace, and is illustrated in Fig. 17. A firebox is shown at a , with its ash-pit at b and flue for escaping gases at c. The iron kettle shown at c/isin direct contact with the flame, thus heating readily. Above the kettle is the hood shown at e for collecting the fumes and directing them toward the opening, shown at /, into the chimney. 31. Tinning by tlie Cold Process. — When block tin is dissolved in hydrochloric acid and a little mercury, an alloy is formed that can be readily used in tinning articles without heating either the tin or the work. Some make the alloy of 1 part of tin, 6 of mercury, and 2 of zinc, by weight. The tin and mercury are mixed together until a soft paste is formed. The articles to be tinned should be cleaned by some of the methods previously explained, and then rubbed with a rag dampened in hydrochloric acid. The alloy should be applied to the surface at once and rubbed with the hydrochloric acid. By this method it is very easy to cover iron, steel, or copper with a complete, but thin, coating of tin. 28 SHOP HINTS. 24 FILLING AM) FAINTING MACHINE TOOLS. 32. Most machine tools are finished by giving them a coat of paint. The surfaces of the castings are cleaned first in the foundry scratch room, and any remaining dirt or irregularities and unevennesses of joined parts are removed during erection by chipping and filing so far as may be necessary to make a good surface. The shop painter next goes over the surfaces with a filler, which is a kind of thick, heavy paint, very adhesive and quick- drying. It is applied with a putty knife, as it is about as thick as very soft putty or freshly opened white lead. This filler hardens rapidly when exposed to the air. The filled surfaces are then smoothed by wetting and rubbing them with a piece of grindstone or a piece of a broken emery wheel, or by simply rubbing them with coarse sandpaper. When the smoothing has been finished, one or two coats of paint having the desired color are applied. Green paint is preferred by some builders and shop superintendents, as it gives a lighter appearance to the shop than black paint. Green and even lighter paints are much used for machine tools, and if the painted surfaces are covered with a varnish that will resist oils, they are easily kept clean and the general appearance of the shop is thus much improved. Steel-gray metallic paint is a favorite paint with many builders on account of the handsome appearance it gives to the machines. NOTES ON SHOP ECONOMY. COST OF CONSTRUCTION. 33. Large Quantities Can Be Made at Low Prices. The question of cost in constructing a machine or device is one of great importance in machine-shop operations, since the question of whether to build or not to build depends on it. It is an every-day occurrence for men to go to a machine shop and ask to have a part of a tool or a machine made, and to be told that the piece would cost more than the price paid §24 SHOP HINTS. 29 for the whole tool or machine when it was new. The reason for the low cost of the whole machine and the seeming high price for the single piece lies in the fact that the maker of the machine or device had special tools for every operation and trained help to do the work, which was done in large lots, perhaps hundreds at a time, and could thus be produced very cheaply. But the man that is called on to make single parts, one at a time, either has to use such tools as he happens to have, or has to make special ones that will be of no use on any other work, and that must be paid for by the customer. The cost of constructing the model of a typewriter, bicycle, sewing machine, or any similar piece of mechanism frequently runs up into thousands of dollars, since every part is made by hand ; but, the manufactured article, where every part is made in large quantities on the interchange- able plan, and with special tools, fixtures, and workers, is built for a few dollars. 34. Cost of Pattern Work. — In foundry work the same condition exists. A customer frequently wants some comparatively simple casting, weighing perhaps only a few pounds, but which requires the making of a special pattern. Evidently the cost of the pattern must be included in the price charged for the casting. Then, though the value of the iron may be only ten cents or less, it may cost five or ten dollars to make the pattern for this small casting; and this must be paid for by the customer. As a matter of course, if a large number of castings are to be made from one pattern, the cost of the pattern is distributed among so many castings that the cost of each is quite low. For instance, it costs several thousand dollars to make the pattern for a stove, but the finished stove can be sold at a very low price on account of the large number of castings made from each pattern. 35. Cheapening by Duplication. — If only one machine or engine of a kind is to be built, the work must be done with such tools as are at hand and such other ordinary 30 SHOP HINTS. § 24 tools as may be bought or made on the premises; but, if a large number of the same kind of engine or machine is to be built, special tools can be provided for the different oper- ations and the same operation can be performed on all the pieces in succession, thus saving the time that would be required for changing tools and machines if each separate piece were finished all over at one time. It should be kept in mind that it costs just about as much to rig up a machine or get it ready to perform an operation for a single piece as it does to do the same thing for a dozen ora hundred pieces; hence, wherever it can be done, the whole number of the same operations should be performed before making a change. This statement applies to all parts and all stages of the work, from starting on the rough forgings and cast- ings to inspecting and painting. TIME ELEMENT IN WORK. 36. Rate of Speed in Doing Work. — Any one engaged in mechanical work, be he apprentice or journey- man, should always have the clock in mind. This state- ment does not refer to watching the clock for quitting time, which comes quickly enough to those really interested in their work, but to the time element in connection with the work. No doubt the principal object is to do the work right, but between two men, each doing it equally well, the one that completes the work in the shorter time is the better man, the one who should and generally will receive the higher wages, and the one who is less liable to be “ laid off ” when business is dull. It is well, therefore, for a person to cultivate the habit of working as rapidly as the character of the work will permit, first making up his mind as to the time a piece of work should take, and then doing his best to shorten that time. Some think that they will first learn to do the work well regardless of time, and afterwards learn to do it quickly; but this plan is open to the practical objection that having once learned a rate of doing work it is hard for us to change that rate. While the quality of the work must §24 SHOP HINTS. 31 always be the first consideration, the time element should never be disregarded. Thus, an apprentice may think, because his pay is small, that only a small amount of work should be expected of him, and, hence, may conclude that he will increase his speed when he becomes a journeyman or receives a higher compensation. He should consider, how- ever, that the money he receives is the smallest part of his compensation, and that the trade he is learning, the manual and mental training, and the experience that he is receiving form the greater part. Such a boy may learn to do a piece of work well, but is not likely to receive the high- est rate of compensation when he becomes a journeyman, since his rate of speed generally remains abnormally low. 37. Standard of Quality and Speed of Work. — In performing a certain operation on a piece of work, or in fact in doing any kind of work, it must always be remembered that work, and, consequently, the value of the producer, is measured by two different standards, the mechanical and the commercial. The mechanical standard measures the degree of skill with which the work is executed and the excellence of the design ; in other words, it is a measure of the quality of the work. The commercial standard takes account of the labor cost, and the person that reduces this factor to the lowest limit Compatible with the degree of mechanical excellence that the nature and purpose of the work requires, is the one that will, and properly should, receive a higher compensation for his services than the person that can do a good job only when he is given an unlimited amount of time. An old proverb states that “what is worth doing at all is worth doing well.” This proverb is applicable to many cases and conditions, but a blind adherence to it is liable to be a serious detriment to a person engaged in commercial work. For such a person the proverb might profitably be changed to read “ what is worth doing at all is worth doing as well as the circumstances of each case require.” That is, the quality of the workmanship should be suited to the 32 SHOP HINTS. §24 purpose to which the work is to be put, and unnecessary refinements and ornamentation that neither add to appear- ance nor usefulness should be omitted. THE SCRAP HEAP. 38. Lessons From the Scrap Heap. — The final rest- ing place of all the metallic appurtenances of the machine shop, smith shop, and boiler shop is the scrap heap. In this universal receptacle are found all kinds of metallic objects in all conditions, from the new special machine left on the builder’s hands by some turn of fortune to that mass of metal so thickly coated with rust or grease that only a cold-chisel test will determine whether it is brass, steel, or lead. A scrap heap is a kind of shop barometer, telling in its own mute fashion of the general shop management of the place and of the use or misuse of materials in other places. A scrap heap represents employed capital, and for this reason it should be run through the cupola or furnace as soon as possible, and thus be reduced to available assets. Many valuable lessons can be learned by an intelligent inspection of the various pieces to be found in a scrap heap. The undue weakness of compotent parts of machinery is here shown by the presence of the broken parts, and a care- ful inspection of the appearance of the breaks will not only show where the parts need strengthening, but, also, whether or not the break was due to an abuse of the machine. The presence of a large number of broken small tools of the same kind may safely be considered as an indication of a defect in their design, although in isolated cases, especially in shops where much unskilled labor is employed, it may indicate bad management on the part of some responsible person. 39. Patching Chipped Castings. — In the handling of heavy castings it frequently happens that chips or flakes are knocked off by accidental collisions with other work. While these may not weaken the machine appreciably, they are unsightly, and for the sake of appearances such defects SHOP HINTS. 33 § 24 should be remedied. There are compounds on the market especially prepared for this work. The dry compound is moistened until it has the consistency of putty, and is then pressed over the defacement and allowed to harden. When once hard, it adheres firmly and may be filed precisely like iron. It then presents a metallic surface. 40. Brazing Broken Castings. — Commonly, a broken iron casting is consigned to the scrap heap, but it is possible in many cases to prevent this loss by brazing the broken parts together. This is done by using a patented brazing composition or flux called “ Borafix,” which is spread evenly over the fractured surfaces. These are then placed together properly, and brought to a cherry-red heat, which melts the flux. Spelter or brazing material is added, after which the piece is allowed to cool in the air. This method recommends itself in cases where the castings are not sub- jected to extraordinary strains and are not excessively large. The process is a comparatively new one, but it has a valu- able place in the work of the shop. Castings should not, however, be repaired in this way or in any other when it will cost more to do the repairing than it would to make a new casting. 41. Repairing a Leaky Cylinder. — To repair a leaky cylinder caused by open-grained iron, make a saturated solu- tion of hydrochloric acid and iron drillings, and pour this into the cylinder, or wash the interior of the cylinder with the solution. Next apply ammonia water, and then steam or air pressure, which will drive the iron hydroxide into every pore of the cylinder walls. When dry, the cylinder will be steam-tight. SHOP HINTS. (PART 2.) LUBRICANTS. INTRODUCTION. 1. Two Uses of Lubricants. — A lubricant may serve for either one of two entirely different purposes, and should consequently be selected accordingly. In practice, a lubricant is used either in order to reduce the friction between two bodies, one of which moves on the other, or in order to carry away the heat generated by a cutting operation. LUBRICANTS FOR REDUCING FRICTION. 2. Selecting a Lubricant. — A lubricant reduces fric- tion by interposing itself in the form of a thin film, which may be considered as being composed of a large number of minute globules, between the rubbing surfaces of the mov- ing bodies. These globules act as rollers or balls, and con- vert the sliding friction into a rolling friction to an extent depending on their deformation under the load they carry. The deformation of the globules of the lubricant depends on its consistency, and is greater for a thin lubricant than for a heavy thick one. For this reason a thick oil should be selected for heavy pressures, while for light pressures a thin oil may be used. The contact between the rubbing surfaces must also be duly considered in connection with the selec- tion of a lubricant, and one used that is fluid enough to flow § 24 For notice of copyright, see page immediately following the title page. 36 SHOP HINTS. § 24 in between the surfaces. Thus, in machine tools and fine machinery, the rubbing surfaces are usually fitted very closely to each other, and hence fluid mineral oil having sufficient body to last a reasonable length of time must generally be used. 3. Oil for General Shop Use. — For general shop use, a mineral oil having considerable body is well adapted. It should be thin enough to run freely through the oil holes and oil channels of bearings. Animal oils are generally objected to on account of the fact that decomposition by age is liable to develop fatty acids that attack most metals. Furthermore, animal oils are very liable to gum, i. e., some of their constituent parts will collect into a sticky mass and close the oil channels of bearings. All oil intended for lubrication should be entirely free from grit. By examining a drop of the oil with a strong magnifying glass, its presence is readily discovered. 4. Cylinder Oil. — A special grade of heavy oil known to the trade as cylinder oil, is intended to be used for the lubrication of parts subjected to fairly high temper- atures, as the valves and pistons of steam engines. It has the property of standing considerable heating without vola- tilizing or being decomposed. Owing to its heavy body, it is used sometimes for bearings subjected to heavy pressures. r>. Grease. — For very heavy work and relatively low rubbing speeds, one of the many forms of manufactured grease is frequently used. The bearings must then be fitted loosely enough to admit the grease. The great body, which is the characteristic feature of a grease, prevents its being crushed or squeezed out by the weight of the moving parts. G. Grease for Rail Bearings. — Grease of the best quality may be used to advantage in putting ball-bearing work together, when difficulty is experienced in keeping the balls in place while assembling the bearing. The ball races, or seats, are filled with the grease and the balls are then pressed into it. The grease will hold the balls in place while §24 SHOP HINTS. 37 the parts are being put together, and will serve to lubricate them for a long time afterwards. This is a very convenient aid in assembling the ball bearings of the pneufnatic drilling machines now so commonly used in large shops, and also of bicycles. 7. Grease for Shafting. — Bearings of shaftings and machines that are subject to great wear and are not at all times under the eye of the attendant, or easily within reach, and hence are liable to run dry with the ordinary methods of oiling, are provided for in the following manner: Grease cups are screwed, or grease pockets are cast, on places where bearings are liable to heat; these are filled with a grease that will not melt at the ordinary temperature of the bearing, but as the bearing becomes warm, this grease melts and runs down through the oil holes to the surfaces needing lubrication. 8. Light Oils for Cleaning Bearings. — Refined petroleum (also called kerosene, coal oil, or paraffin oil, in different localities) and mineral sperm oil are among the most fluid commercial oils, and will flow into smaller spaces than heavier oils ; both have the disadvantage, however, that they lack body, i. e., they evaporate quickly, and consequently are of little value as a lubricant. They are of great value however in cleaning rubbing surfaces, as they will dissolve or thin down almost any heavier oil, and can be used for cleaning bearings, etc., where it is suspected that the oil channels have become clogged by the gumming of the regular oil that is used. In such a case, a copious and constant supply of kerosene or mineral sperm oil may be applied to the bearing until the oil comes out clear; it must then immediately be followed by a copious application of the heavier oil generally used for lubrication, in order to prevent any cutting of the rubbing surfaces owing to their becoming dry through the rapid evaporation of the light oil. f). Thinning Oils. — The lighter oils can often be used advantageously for thinning down the heavier oils in order to make a grade suitable for some special purpose. Most of 38 SHOP HINTS. § 24 the lighter oils are quite inflammable, and consequently due care must be taken to prevent their ignition. 1 O. Volatile Oils. — Benzine, naphtha, and tur- pentine are used considerably in shops for cleaning pur- poses ; these oils evaporate very rapidly and form vapors that are highly inflammable. If these vapors are mixed with air in certain proportions, they form explosive mixtures that need but a spark to ignite them. For this reason, great care should be taken not to have a naked light or any fire close to a place where any of these volatile oils are stored or used. 11. Graphite. — The mineral substance known tech- nically as graphite, and in shop parlance as black lead, or plumbago, forms an excellent lubricant, which when ground fine may be used either dry or may be mixed with some fluid lubricant or grease to a consistency considered suitable for the work. Graphite is one of the most refrac- tory substances known; this fact makes it an invaluable lubricant for bearings subjected to high temperatures. Its lubricating qualities at all temperatures are so high that it forms a very valuable addition to almost any oil. 12. Curing Hot Bearings. — A bearing will get hot by reason of friction due to an insufficient or interrupted supply of the lubricant, or by reason of the journal fitting so closely that the lubricant cannot pass between the rubbing surfaces. The first thing to do when a bearing gets hot is to supply it with a liberal quantity of oil, repeating the appli- cation frequently until the bearing commences to cool. If, the bearing becomes so hot that it smokes before it is dis- covered, and it is not advisable to stop the machine, water may be turned on the bearing, pouring it down the oil hole, or playing a hose on it until it is cool. When a hot bearing is discovered, the cap may be slacked back somewhat so as to allow a free circulation of the lubricant. As soon as the bearing is cool, a copious and constant supply of oil, which may have some graphite mixed with it, should be provided and the results noted. If the bearing refuses to keep cool §24 SHOP HINTS. 39 after this, it generally shows that the rubbing surfaces are in such a bad condition as to need refitting. If the hot bearing is rigid, i. e., not self-adjusting to the shaft, observe if one end is hotter than the other; also test the shaft for alinement, as the heating of the bearing may not be caused by a defect in the hot box, but by the bearing next to it getting out of line, thus bringing all the load on one end of the bearing that is heating. 13. Oil Holes and Oil Channels. — Various means are provided to make sure that the lubricant reaches the place or surface it is intended to cover. In the first place, oil holes are drilled through the metal from the high side so that the oil will reach its proper place by gravity. The size of the oil holes should vary with the kind of lubricant that is to be used, drilling small holes in small work and for a fluid lubricant, and larger ones as the density of the oil and the length of the hole increase. Bearings that are not easily reached must have tubing or pipe run to them as directly as possible; this oil piping should be supplied with fittings that allow it to be easily taken down and cleaned. 14. Cutting Oil Channels. — Oil channels should be cut so as to distribute the oil over the whole length of the bearing; also, such other channels should be provided as may be needed to insure an even distribution of the lubri- cant. In order to insure thorough lubrication, the oil chan- nels must have a liberal width and must be deep enough so as not to become filled too rapidly with the impurities some lubricants contain. Furthermore, the direction in which the oil channels run from the point of supply (the bottom of the oil hole) should be the same as the direction of rotation of the journal, in order that the latter may tend to draw in the oil rather than to repel it. A lubricant will not flow up hill any more than any other liquid; hence, the lubricant should always be applied at the highest point permitted by circumstances. 1 5. Special Methods of Oiling. — Small planers have their ways oiled by hand whenever they show any indication 40 SHOP HINTS. 24 of becoming dry. Large planers are usually provided with means for a constant lubrication, as, for instance, oil wells cored out in several places in the ways. These wells are filled with oil that is delivered to the ways by conical brass rollers that are pressed against the V’s of the platen by springs. This method of oiling is perfect as long as reason- able care is used to prevent an accumulation of dust and dirt in the oil wells, which would finally interfere with the free action of the rollers. 16. Use of Waste. — Enough lubricant should be applied to machinery, and in the right place, to insure a thorough lubrication; and any dirty surface should be wiped off so as to keep the machine as neat as possible. Waste is generally used for this purpose; when dirty, it is often thrown on the floor or into out-of-the-way places; or it is left lying on the work or machine. This is an extremely bad practice, being not only wasteful and dirty, but also very dangerous on account of the liability of the waste to take fire either from spontaneous combustion or otherwise. 1 7. Disposition of Greasy Waste. — All waste or greasy material of this sort should be put into sheet-iron tanks or barrels located at convenient points throughout the shop. These tanks should be made of heavy galvanized iron or steel, and should have legs to keep their bottoms 2 or 3 inches above the floor. They should be riveted together, instead of being soldered, so that if the material in them does get on fire, they will not come apart and set fire to the building. A good tight-fitting cover should be kept on the tank at all times, so that if fire does start in the waste, it will be smothered before gaining much headway. These tanks should be taken out and emptied at stated times. In some shops the dirty waste is washed and used again. The cleaning is done by putting it into a tank of water with soda, cheap soap, or some washing compound, and boiling it for a few hours by either live or exhaust steam entering the tank through a suitably arranged pipe. SHOP HINTS. 41 § 24 LUBRICANTS FOR CARRYING AWAY HEAT. I 8. Reason for Removing Heat Generated. — The cutting speed of a tool may often be considerably increased by the application of some kind of lubricant, such as oil or water. When oil is used, it reduces the friction between the shaving and the face of the tool, and thus reduces the heat- ing. If a sufficient quantity is used, it also carries off a great deal of the heat generated by the cutting operation and keeps the tool from getting as hot as it otherwise would ; consequently, it is possible to increase the .cutting speed without overheating the cutting edge. 1 9. Lubricants for Steel and Wrought Iron. The best lubricants for cutting steel or wrought iron are the best grades of lard oil and sperm oil. One of these oils should be used for all tapping or reaming operations. For turning shafts, soda water is used, or in some cases a mixture of soft soap and water. Soda water is an excellent medium for absorbing heat; the soda also keeps the water from rust- ing the machines or the work. Soft soap dissolved in water is used in some shops instead of soda water and possesses some lubricating quality. When a finishing cut is taken on soft iron or steel with a keen tool, and a supply of water is kept on the tool, a very bright smooth surface is produced. Such a cut is called a zvater cut; some kinds of work are thus finished with sufficient smoothness to make polishing unnecessary. 20. Conditions Under Which Lubricants Should Not Be Used. — Cast iron is usually worked dry. The dirt caused by mixing fine cast-iron turnings with oil or water on the machine is an objectionable feature that more than over- balances the increased cutting speed that might be obtained. Furthermore, it is difficult to take a light cut on cast iron when it is oily. The oil soaks into the surface of the iron for a short distance and seems, to form a skin that is not easily broken. If the cut is deeper than a finishing cut, the oil on the surface will not impede the cutting. Brass, copper, and Babbitt metal are generally cut without a lubricant, C. 5. I 11.-26 42 SHOP HINTS. § 24 although it is becoming the practice to flood work composed of these metals with lard oil in automatic screw-machine work so as to reduce friction and increase the life of the tools. 21. A Cheap Lubricant for Tools. — For some classes of work, a cheap and satisfactory lubricant may be made by combining oil with other ingredients. There are many such mixtures in use in which an oil is first thinned down by mixing it with a cheap liquid-like soda water, and then add- ing some ingredient that will give body to the lubricant, i. e., thicken it enough to make it somewhat adhesive. A good mixture may be made by mixing together \ pound of sal soda, -J pint of lard oil, 4 pint of soft soap, and enough water to make 10 quarts. This should be boiled ^ hour and well stirred. When cool, ft is ready for use. This mixture can easily be handled by a pump, and is quite satisfactory for general use. 22. A Pipe System of Lubrication. — When a large number of machine tools are kept busy on work where con- stant lubrication is deemed essential, it is often convenient to place the tank containing the lubricant in some warm out- of-the-way place, as in the boiler room. A system of piping having branch pipes leading to the different machines may then be laid through the shops. A force pump of some kind should be placed near the tank and have its suction pipe connected to it, while its discharge pipe connects with the pipe system. All the drippings may be automatically returned to another tank near the first through a separate pipe system so arranged that they will flow back by gravity. By grouping together all the machines requiring lubrication, the piping system can be made relatively inexpensive. The placing of the tank in the boiler room is especially con- venient in the case of mixtures that require boiling, since a steam coil can then be placed in the tank at small expense. Another arrangement of the pipe system has the supply tank located at a height that will cause the lubricant to flow to the machines by gravity, and the pump is used to raise it SHOP HINTS. 43 § 24 from the lower to the upper tank. The oil should always pass through a strainer or a filter before being used again. 23. Lubricants in Cutting Babbitt Metal. — Bab- bitt metal may be worked dry in most cases, but when bushings of this material are being bored in the lathe or when boxes are machined in position, it is often found that a lubricant is necessary. This is especially true of bushings that are being bored in the lathe, since the chip has a ten- dency to wind around the boring tool and form a compact ball. Boxes that have been bored and are to be reamed will sometimes be scored or roughened in the reaming if the work is done dry. Lard oil is sometimes used in working Babbitt metal, but a copious supply of kerosene oil will give far better results than any other lubricant. 24. Lubricants for Drilling Rawhide. — It is some- times necessary to drill rawhide with a twist drill ; this, in general, will be found a trying and tedious job, on account of the clogging up of the flutes of the drill when the drilling is done dry. If a cake of ordinary laundry soap is held against the drill every little while, however, no trouble will be experienced. The drill should be run quite fast for drilling rawhide. 25. Turpentine as a Lubricant. — It is sometimes necessary for fitters who are working on cast-iron work to use a lubricant, other than the marking material, when they are rubbing two parts together in order to obtain bearing marks. Oil will prevent the seizing and cutting of the sur- faces, but it will leave no bearing marks, and, besides, it will interfere with the scraping. Turpentine may be used freely on such work, however, instead of oil, and will prove bene- ficial rather than otherwise. PREVENTING WASTE OF LUBRICANTS. 26. The Oil Separator* — Shops in which a great deal of screw-machine work, milling, and tapping of wrought iron or steel is done, use correspondingly large quantities of 44 SHOP HINTS. §24 oil to lubricate the cutting tools. This oil becomes mixed with the cuttings or chips from the work, and while most of this oil can be drained off, a large amount adheres firmly to the chips and is usually thrown away. Much of this oil may be saved by collecting the oily chips, and running them through a centrifugal separator. This separator consists of a circular tank that is open at the top and is provided with a cock in the bottom, in order to allow the extracted oil to be drained off. A vertical spindle passing up through the center of the tank carries a strong conical steel pan pro- vided with an equally strong cover that is held on, when in use, by a locknut. The edge of the pan has small openings for the escape of the oil. A pulley is provided on the lower end of the spindle to drive the extracting pan, and is belted to an overhead countershaft. The pan is filled with the oily chips, th£ cover securely fastened, and the machine started slowly and allowed to come up to its full speed, which should give about 7,000 feet per minute at the periphery. The oil is thrown from the chips by the centrifugal force and finds its way out through the small openings in the top edge of the pan. As the oil flies from the pan it is caught by the wall of the tank and flows down to the oil well. 27. The Oil Filter. — Oil that has been used over a number of times is liable to be filled with very fine chips that separators will fail to remove. Such oil may be filtered through a regular oil filter ; in the absence of such a device, blotting paper will be a fair substitute. Some of the heavier particles of metal in the oil can be gotten rid of by letting the oil stand in a quiet place for some time, when the heavy foreign matter will settle to the bottom of the vessel. The clear oil may then be poured off into another vessel. This settling process will fail to clean the oil as effectually as an oil filter will do. Oil cleaned by the settling process should never be used for lubricating bearings, but only for the cutting tools. An oil filter or settling tank will not work well if kept in a cold place. SHOP HINTS. 45 § 24 TRANSMISSION OF POWER. BELTING ANI) SHAFTING. BELTING. 28. Length of Belts.— One of the most common cal- culations in shop work is that concerning the length of belt that is required for a certain position. If the shafts and pulleys are already in place, the simplest way to find the necessary length is to stretch a tape line around the pulleys in the position in which it is desired to place the belt and thus to obtain the length directly. In such a case, the stretch of the tape line is taken to be the same as that neces- sary for the belt. However, in case the pulleys are not in position, so that a tape line cannot be used, the length of the belt must be cal- culated, and this can be done by the following rule: Dule. — To find the length of a direct open belt , multiply one-half the sum of the pulley diameters by S\ and add to this product twice the distance between the centers of the shafts . This sum will be the approximate length of the belt required. The above rule, expressed as a formula, would read * . * (£+*) + ,4 in which B — length of belt in inches; D — diameter of one pulley in inches; d — diameter of other pulley in inches; L — distance between centers of shafts in inches. Example. — The distance between the centers of two shafts is 10 feet; the diameter of the larger pulley is 36 inches and of the smaller pulley ~28 inches. What is the length of belt required ? Solution. — The distance between shaft centers is 10 ft., or 12 x 10 = 120 in. Then, by the rule given, ( o fi _i_ OQ\ — T — j + 2 x 120 = 3| x 32 + 2 x 120 = 344 in. Ans. 40 SHOP HINTS. 29. The approximate length of a crossed belt is given by the formula 30. Arc of Contact. — The arc on which the belt touches the pulley is called the arc of contact. If it were possible for the belt to extend once completely around the pulley, the arc of contact would be 360°. If ,the belt touches the pulley along half of its surface, the arc of contact is 180°; if it touches the pulley along quarter of its face, the arc of contact is 90°; and similarly for any portion of surface covered by the belt on the pulley. To find the arc of contact, stretch a string tightly over the pulleys in the position the belt is to occupy. Then take another string and wrap it once around the pulley and cut it so that the ends meet. The length of this string represents the distance around the pulley. Now take a third string and hold one end at the point where the arc of contact on the pulley begins, as shown by the string stretched over the pulleys representing the belt. Wrap this third string around the pulley alongside the string that represents the belt, to the point where the latter leaves the pulley. Cut the third string at this point. The length thus cut off is the distance covered by the belt on the pulley. Then, the arc of contact is equal to the length of this third string multiplied by 360, divided by the length of the second string, which represented the distance around the pulley. The above rule applies to cases where the pulleys are in position. If the arc of contact is to be taken from a draw- ing, it can be quickly found by the use of a protractor. 31. Effective Pull. — The driving side of a belt is always under greater tension than the slack side. The difference in tension of the two sides is the force that tends to turn the driven pulley, or the effective pull. The tension, or pull in pounds, on the driving side of the belt is governed by three things: the effective pull, the coefficient of friction between the belt and pulley, and the length of the arc of SHOP HINTS. 47 § 24 contact. The effective arc of contact is that on the smaller pulley. The effective pull that may be allowed per inch of width of a single leather belt varies according to the arc of contact. Table I gives the allowable effective pull per inch of width for different arcs of contact of a single belt. TABLE I. ALLOWABLE EFFECTIVE BELT FULL. Arc Covered by Belt. Allowable Effective Pull Per Inch Degrees. Fraction of Whole Face. of Width. Pounds. 9° i = -250 23.0 H2i ITT = -3i2 27.4 120 ^ = *333 28.8 I 35 1 = -375 3 1 • 3 !5° T2 = -417 33-8 !57i it? = -437 34-9 180, or over i = • 5°° 38.1 Table I enables one to calculate the horsepower that a given belt can transmit, or to find the width of a belt required to transmit a given horsepower. The allowable effective pull per inch of width varies greatly in practice; in some cases it is as much as 50 per cent, greater than that given in the table. 32. Horsepower. — The term horsepower represents a rate of doing work. If a man lifts a weight of 100 pounds vertically a distance of 1 foot, he does 100 X 1 = 100 foot- pounds of work. If he lifts a weight of 25 pounds a distance of 4 feet, he still does 25 X 4 = 100 foot-pounds of work. One horsepower represents 33,000 foot-pounds of work done in 1 minute, or 550 foot-pounds per second. That is, if a belt has an effective pull, of 55 pounds and runs at a speed of 10 feet per second, then the force of 55 pounds acts through SHOP HINTS. §24 48 a distance of 10 feet each second, and the power developed is 10 X 55 = 550 foot-pounds per second, or 1 horsepower. 33. Belt Speed. — The speed at which the belt runs determines the horsepower transmitted. In order to find the speed of any belt use the following rule: Rule. — Multiply the diameter of the pulley in inches by 3.1Jfl6, and this by the number of revolutions per minute of the pulley , and divide the product by 12. The result is the speed of the belt in feet per minute. No allowance is made in this rule for the slip of the belt. All belts slip some; hence a slip of 2 per cent, is allowed in most belting problems. Belts sometimes run as slow as 1.000 feet per minute, or even slower, and a speed of 6.000 feet per minute should never be exceeded.. 34. Horsepower of Belts. — In order to find the horsepower that a single leather belt under given conditions will transmit, use the following rule: Rule. — Find the arc of contact on the smaller pulley and from Table I obtain the corresponding effective pull. Then multiply together the effective pull, the width of the belt in inches , and the speed of the belt in feet per minute, and divide the product by 33,000. Example.— A 4-inch belt runs on two pulleys 36 inches in diameter that make 200 revolutions per minute, (a) What is the speed of the belt ? (b) What horsepower will it transmit ? Solution. — ( a ) By Art. 33, the speed of the belt in feet per minute . 36 X 3.1416 X ‘200 , 00 , x , . » is — = 1,884.96 ft. per min. Ans. (b) As the pulleys are of the same size, the arc of contact is 180°, and from Table I the pull is 38.1 lb. From Art. 34, the horsepower is 38.1 X 4 X 1,884.96 33,000 m 8.7 H. P. Ans. 35. Width of Belts. — In case it is desired to know what width of single leather belt is required to transmit a given horsepower, the following rule may be used : Rule . — Multiply the horsepozver to be transmitted by 33,000 and divide this product by the product of the speed in feet per §24 SHOP HINTS. 49 minute and the effective pull. The result will be the width of the belt in inches. Example. — What width of belt would be required to transmit 16 horsepower when the belt is running at a speed of 2,000 feet per minute and has an effective pull of 38.1 pounds per inch of width. Solution. — 38 l^x ^ ^Oo!) ~ ^ ^ Tinch belt would be selected for this work. Ans. 36. Double Belts. — Double belts are made by cement- ing and riveting together two single belts, one upon the other. They are used to transmit powers that would strain or break a single belt. Naturally, the double belt is the stronger per inch of width. It is commonly assumed that a single belt has T \ the strength of a double belt of equal width, because the thickness of a double belt is about T 7 ¥ that of two single belts. Then, to find the horsepower that a double leather belt will transmit, we have the following rule: Rule. — Multiply together the effective pull , the width of the belt in, inches, and its velocity in feet per minute, and divide the product by -fa of 33, 000, or 23,100. Example. — How many horsepower will be transmitted by a double belt, 24 inches wide, if the arc of contact on the smaller pulley is 150° and the belt runs at 2,500 feet per minute ? Solution. — From Table I, ^ 33.8 X 24 X 2,500 or , Q TT „ then 23.100 ~ 87.8 H. P. the allowable effective pull is 33.8 lb., Ans. 37. If it is desired to. find the width of a double leather belt required for a certain horsepower, use the following rule: Rule. — Multiply the horsepower to be transmitted by 23,100. Divide this product by the product of the velocity in feet per minute and the effective pull as found from Table I. The result is the width in inches. Example. — What width of double belt would be required to trans- mit 160 horsepower with the belt running at 2,500 feet per minute and having an arc of contact on the smaller pulley of 150° ? Solution. — From Table I, the effective pull is 33.8 lb. per inch of width ; hence, 160 X 23,100 2,500 X 33.8 43.74 in. A 44-inch belt would be used. Ans. 50 SHOP HINTS. §24 SHAFTING. B8. Distance Between Bearings. — For a medium steel shaft having no pulleys whatever, and used for trans- mission of power only, the greatest allowable distance between adjacent bearings, for shafts up to and including 4 inches in diameter, is given by the following rule: Rule. — Multiply the diameter of the shaft in inches by 55 and add 55 to the product . The result is the greatest allow - able distance , in inches , between adjacent bearmgs . For an iron shaft the maximum distance is somewhat less than that given by the above rule. Example. — What is the greatest allowable distance between bear- ings for a 3-inch shaft of medium steel, used only to transmit power ? Solution. — According to the rule, the maximum distance is (55 X 3) + 55 = 220 in., or 18 ft. 4 in. Ans. TABLE II. TURNED-IRON HEAD-SHAFTS, BEARINGS CLOSE TO PULLEYS. Revolutions Per Minute. Diameter of Shaft. Inches. 6o 80 100 150 200 250 300 Horsepower. 2. .6 3-4 4 •3 6, 4 8.6 10 •7 12.9 2 3 . .8 5-i 6 ■4 9 .6 12.8 16 .0 19.2 2 i 5. ■ 4 7-3 8. . 1 12. .0 16.0 20, .0 24.0 2 i 7 . •5 10.0 12 • 5 18. ,0 25.0 3i .0 37 -o 2f IO. .0 13.0 16 .0 24. ,0 32.0 40. .0 48.0 3 13 .0 17.0 20 .0 30. .0 40.0 50 , .0 60.0 3 i 16, ,0 22.0 27 .0 40. ,0 54-0 67. .0 81.0 3 i 20. .0 27.0 34 .0 5 i ,0 68.0 35 . ,0 102.0 3 t 25. ,0 33-0 42 .0 63. ,0 84.0 105, .0 126.0 4 30. .0 41.0 5i .0 76. ,0 102.0 127. .0 153-0 4 i 43. ,0 58.0 72 . .0 108 . ,0 144.0 180. ,0 216.0 5 60, ,0 80.0 100. ,0 150. ,0 200.0 250. 0 300.0 5 i 80, .0 106.0 133 .0 r 99 .0 266.0 333 . .0 400.0 SHOP HINTS. 51 § 24 39. For a countershaft or line shaft having many pul- leys, and' consequently subjected to both bending and torsion due to belt pulls, the distance from bearing to bearing should be not more than 8 feet. For a head-shaft, with a main driving pulley or gear, the bearings should be placed very near the driving wheel or wheels. 40. Horsepower and Size of Shafting. — The horse- power that a shaft of given size will safely transmit depends on its duty. If it is a plain shaft, used to transmit power from one point to another at a considerable distance, with no pulleys or gears at intermediate points, it will transmit considerably more than a shaft of the same size used as a countershaft or line shaft, loaded with pulleys, and still more than a head-shaft carrying a main driving pulley or gear. TABLE III. COLD-ROLLED IRON HEAD-SHAFTS, BEARINGS CLOSE TO PULLEYS. Diameter of Shaft. Inches. Revolutions Per Minute. 6o 80 IOO 150 200 250 300 Horsepower. 4 2.7 3-6 4-5 .'•7 9 0 11 13 if 4-3 5-6 7 -i 10.6 14.2 18 21 2 6.4. 8.5 10.7 16.0 21.0 26 32 2 \ 9.0 12.0 15.0 23.0 30.0 38 46 2 I 12.0 17.0 21 .0 31.0 41.0 52 62 2f 16.0 22.0 27.0 41.0 55 -o 70 82 3 21 .0 29.0 36.0 54-0 72.0 90 108 3 i 27.0 . 36.0 45-0 68.0 91 .0 1 14 136 3 '* 34-0 45-0 57 -o 86.0 114.0 142 172 3 f 42.0 56.0 70.0 105.0 140.0 174 210 4 510 69.0 85.0 128.0 170.0 212 256 4 i 73-0 97.0 121 .0 182.0 243.0 302 364 52 SHOP HINTS. § 24 The horsepower that shafting of various sizes will safely transmit is given in Tables II, III, IV, and V. These tables may be used to find the horsepower that a given shaft will transmit, or they may be used to find the size of shaft required to transmit a given horsepower. TABLE IV. TURNED-IRON LINE SHAFTING WITH BEARINGS 8 FEET APART. Revolutions Per Minute. u laiiicici yt l Shaft. Inches. IOO 125 ! 5 ° 200 250 300 350 Horsepower. If 6.0 7-4 0 CO 11 9 14.9 17.9 20.9 7-3 9 - 1 IO.9 14-5 18.2 21.8 25-4 2 8.9 11 . 1 13-3 17.7 22.2 26.6 31 .0 2l 10.6 13.2 15-9 21.2 26.5 31.8 37-0 2 i 12 . 6 15-8 19.0 25.0 31.0 38.0 44-0 2 I 15-0 18.0 22.0 29.0 37 -o 44-0 52.0 2 i 17.0 ' '21.0 26.0 34-0 43-0 52.0 60.0 2 I 23.0 29.O 34-0 46.0 58.0 69.0 81.0 3 30.0 37 -o 45-0 60.0 75 -o 90.0 105.0 3l 38.0 47.0 57-0 76.0 95-0 114.0 133-0 3 | 47-0 59 ° 71.0 95-0 119.0 143 0 167.0 3 f 58.0 73 -o 88.0 117.0 146.0 176.0 205.0 4 71.0 89.0 107.0 142.0 0 CO 213.0 249.0 Example 1. — What horsepower will be transmitted by a turned-iron line shaft 2| inches in diameter, running at 250 revolutions per minute ? Solution. — From Table IV, for turned-iron line shafting, we find the diameter in. in the first column. Following out horizontally from 2| until we reach the column headed 250 revolutions per minute, we find 43. Therefore, the 2|-inch shaft will transmit 43 H. P. at 250 rev. per min. Ans. Example 2. — Let it be required to find the horsepower of a cold- rolled head-shaft 4 inches in diameter, making 300 revolutions per minute ? §24 SHOP HINTS. 53 Solution. — In Table III, for cold-rolled shafting, locate the diam- eter, 4 inches, in the first column, and follow this line horizontally to the column headed 300, where 256 is found. The 4-inch head-shaft will therefore transmit 256 H. P. at 300 rev. per min. Ans. Example 3. — What size of cold-rolled line shaft will be required to transmit 200 horsepower at 300 revolutions per minute ? Solution. — In Table V, of cold-rolled line shafts, locate the column headed 300 rev. per min. Following down this column to the value 205 H. P. , which is the nearest to 200 that is given, we find that the corresponding diameter of shaft, in the first column, is 3£ in. Ans. TABLE V. COLD-ROLLEI) IRON LINE SHAFTING, WITH BEARINGS 8 FEET APART. Revolutions Per Minute. Diameter of Shaft. Inches. IOO 125 150 200 250 300 350 Horsepower. I-g! 6. • 7 8. 4 IO 1 13 • 5 16.8 20. , 2 23.6 If 8. ,6 IO . 7 12 . .8 17 . 1 21.5 25 . •7 31 .0 If IO. ■ 7 13 4 16 .0 21 ■5 26.8 32 . , 1 39 -° If 13 .2 16. 5 19. ■7 26. ■ 4 32.9 39 • • 5 46.0 2 16. 0 20. 0 24 .0 32 .0 40.0 48. .0 56.0 19 .0 24. 0 29 .0 00 .0 48.0 57 . .0 67.0 2 i 22 . .0 28. 0 34 .0 45 .0 56.0 68, .0 80. O' ry 3 2 8 27 . .0 33 - 0 40 .0 53 .0 67.0 80 .0 94.0 2 i 3 1 .0 39 - .0 47 .0 62 .0 78.0 93 .0 109.0 ry 3 2 t 41 .0 52 . 0 62 .0 83 .0 104.0 125 .0 145-0 3 54 .0 67. .0 81 .0 108 0 0 -t- co 162 .0 189.0 34 68. . 0 86. .0 io 3 .0 137 .0 172.0 205 .0 240.0 3 i 85 . 0 107 .0 128 .0 171 .0 214.0 257 .0 300.0 Example 4. — Suppose it is required to find the size of a turned- iron head-shaft capable of transmitting 200 horsepower at 200 revolu- tions per minute. Solution. — In Table II, for turned-iron head-shafts, locate the column headed 200 rev. per min. Following down this column to the value 200 H. P., the corresponding diameter of shaft, from the first column, is found to be 5 in. Ans. 54 SHOP HINTS. §24 HEAT INSULATION. 41. Lagging Steam Cylinders and Pipes. — Cylin- ders of steam engines and main steam connections need to be as thoroughly protected from the cold as possible, in order that the condensation of steam may be reduced to the lowest point. For this purpose the cylinder is often coated with a cement, or mortar, composed largely of asbestos. This is mixed, tempered, and applied to the cylinder in much the same manner that mortar is put on by a mason. The work is done after the supports for the lagging are in place, and the material is applied in such thickness as not to interfere with the lagging. The cylinders are generally heated by steam when this work is done, so as to dry the material. Steam pipes for conveying live steam are protected in a variety of ways. Sometimes the pipe is surrounded with wire netting of about f-inch mesh, which is held some dis- tance away from the pipe by distance pieces that are fastened to the wire netting and butt against the pipe. Non-con- ducting mortar is applied to this netting and pressed in on the pipe; when the pipe is outdoors, it is usually boxed in order to further protect it. If the pipe is indoors, it is often lagged to match the cylinder. Several kinds of sectional covering are made that are easily applied to such pipes, and are held in place by clamps or straps. The object of jacketing or covering cylinders and pipes in this manner is to retain the heat, except in refrigerating machinery, where the object is to keep out the heat. 42. Cutting and Fitting Sheet Lagging. — Many steam-engine cylinders are covered with sheet-steel or Russia- iron lagging. This lagging, when possible, is cut to the right dimensions and rolled into a cylindrical form ; or it is sheared to the proper dimensions, if the cylinder is to be lagged square. There still remains a great deal of fitting on the sheet, or sheets, which is generally done by hand, but which may be done on a machine similar to that illustrated in Fig. 1 ( a ). This machine has a column a that carries a SHOP HINTS. 00 §34 table b. A movable slide c working in guides formed on the column carries a cutter d, which is attached to the slide by the clamp e. The guide bar f has a slot in its front side in which the cutter d slides; it is held in position by a screw and a hand wheel g. The machine is driven by means of the belt //, and an up-and-down motion is imparted to the cut- ter d by means of the crank i and rod j. Fig. 1 ( b ) is a detail of the square cutter used, in which k is the cutting edge. The sheets to be cut are laid on the table and pushed into the notch / ; the cutter then shears out a chip on the 5G SHOP HINTS. § 24 down stroke. Fig. 1 (c) shows a section of the cutter in the plane indicated by the lines a, b , c , Fig. 1 ( b ). Cutters of any section may be made for following curved lines as well as straight lines. The lagging sheets are worked out on this machine to nearly the right form and the remainder of the fitting is done by hand. The screw holes in the sheets are generally drilled in a power-driven machine. Finally, the sheet is clamped in place while the holes are marked off on the cylin- der or lagging frame; these are then drilled into the sup- porting surfaces on the cylinder or the lagging frame. MISCELLANEOUS DEVICES. 43. Boxes, Pans, and Trays. — All shops and manu- facturing establishments doing small work have more or less trouble in moving small parts from place to place. This is generally done by using such boxes, kegs, and barrels as happen to be at hand. These soon become dirty or are broken, and must then be replaced. An excellent substitute for these makeshift devices is found in the metallic articles illustrated in Fig. 2. The one shown in Fig. 2 (a) is a steel box that can be used in- stead of a wooden one for many shop purposes. The pressed- steel pan illustrated in Fig. 2 ( b ) may be used instead of the box, and has the advantage that it will hold water or oil. These pans, when not in use, may be stacked up, so as to occupy very little space. These boxes are commonly called tote boxes. Another useful and cleanly device is the tray rack, illustrated in Fig. 3. It consists of three iron trays, the §24 SHOP HINTS. 57 upper one of which carries a drawer. For shop use, casters are added so that it may be moved from place to place. It is especially useful where a number of operations have to b e performed o n pieces by different machines. The trays may be used by the machine-tool man to hold both his tools and work, while the drawer may contain his in- dividual tools. 44. Keeping Machine-Shop Tools. — Various methods are followed in caring for machine-shop tools. In the simplest method, the tools are thrown down where used and left there until they are wanted for another job, when they are hunted for until found, and are then cleaned and again made ready for use. This method is probably the worst that could possibly be devised, and is a direct evidence of mismanagement. The modern and proper plan of caring for tools is to require all tools to be cleaned by the user, and to be returned to such a place as may be designated for their storage and care. Tool rooms are built in most shops for the storage and care of all the tools used in the place, or, if the shop is divided into departments, each head of a department may have his own tool room and a man to care for it, who, in addition, also does such other work as he may have time for. The tool room may be used only as a storeroom for tools, or it may be equipped with such a varied selection of machine tools that any tool or appliance needed on the work may be made there, and tools and light machinery may be repaired. C\ S. III.— 27 58 SHOP HINTS. §24 Large shops usually have, in addition to the tool room, such storerooms or vaults as may be needed for the storage of any large and valuable jigs, tools, or fixtures that are seldom needed, but that require protection from fire. Tools should be kept in such a manner that they may be gotten out and returned in the least time, and should also, while in their places, be as well protected from dust and rust as possible. Drawers are extensively used for holding tools, and for many purposes they answer admirably. They are, however, very liable to be overloaded, which soon racks them to pieces. This may be avoided by making them extra heavy, or providing rollers for them to run on. They may also be easily handled if the sliding surfaces are of hard wood or are metal-faced, and the contact surfaces greased occasion- ally with a good lubricating grease. Drawers are used to the best advantage for tools that are seldom needed, but require protection from injury and dirt. Shelves or pigeon- holes furnish the most ready means of keep- ing tools that are much used. These should be as shallow as possible in order that the tools may not be pushed in out of sight, and that they may be easily brushed out, or blown out if an air hose is used for cleaning. Cupboards containing numerous shelves are useful for special tools that are used less fre- quently than standard ones, since the cup- board doors protect them from dirt and the atmosphere. SHOP HINTS. 59 §24 The walls of tool storerooms are often covered with boards, which should be painted and have hard-wood pegs put into them on which to hang milling cutters and similar tools; in some cases, nails are used instead of the wooden pegs. A better method of keeping cutters is shown in Fig. 4, which consists of a cabinet having a series of shelves a to which boards b are hinged. These boards are provided with hooks c on which to hang the cutters. This cabinet provides a clean, convenient, and space-economizing place for a large number of milling cutters and gear-cutters. Racks of various kinds furnish a convenient and clean place for keeping a large class of tools, such as pipe stocks, wrenches, long taps, reamers, drills, boring bars, cutter bars, sockets, and other similar long tools, in such a manner that they are easily put away or gotten out, and are kept clean when in their places. A rack of this description is shown in Fig. 5. It consists of four uprights a that* are braced by wrought-iron tie-bars b. These are held by long bolts c, which pass through the tie-bars b at each end, and are surrounded by distance pieces d made of iron pipe. Racks that are constructed in the manner shown in Fig. 5 may be made 7 feet high and 3J feet wide at the base, with the upright spaced at such dis- tances as will accommodate the shortest tools that may be kept on them. Light and frequently used tools are piled on the arms, while less used and heavier tools are placed on the cross- pieces b. These racks may stand against the wall, but are preferably placed on the floor where they can be reached from all sides. Racks of special design are usually provided GO SHOP HINTS. §24 for such tools as ratchets, tapping attachments, air drills, and other portable drilling and grinding fixtures. Boxes are sometimes used for storing tools, and when so used they should be plainly marked; a convenient record should also be kept of their exact contents. 45. The Ram. — It is sometimes necessary when taking old machinery apart, as, for instance, when trying to remove an old shaft from a wheel or crank, to strike the heaviest blow possible. The heavy blow carries the object struck before it, while lighter blows will simply upset the end of the piece and thus rivet it into place. When heavy sledge hammers are used on light work, the surfaces hammered should be protected by a piece of Babbitt metal or copper held or laid on them. Where heavier blows are required than can be struck with a sledge, a ram is used. This is a long bar of iron sus- pended at its center of gravity, in order that it may hang in a horizontal position, and hung in front of the piece to be rammed. The rope suspending the ram is made fast to an overhead point, after which the operators draw the bar, or ram, backwards as far as possible, and then run with it toward the piece to be struck. The ram is often used when a hydraulic press is not available or would be unfit for the work. Care should be taken in using the ram not to upset the face of the part that is being rammed, which will only tighten the parts in their places. Since several men are required to operate a heavy ram, it is an expensive operation that should not be resorted to if a press can be used. 46. A Sectional Key. — In shrinking to- gether two pieces that have key seats that must be in line with each other, a device known as a sectional key may be advantageously used for alining the pieces. One form of this device is shown in Fig. 6. Two tapered side keys a and b, having handles a ' and b' of suitable length, are placed into m SHOP HINTS. 61 § 24 the two key seats of the two parts that are being shrunk together; and when these parts are in place, a tapered cen- tered key c, with a long handle c ' , is then driven in between them, thus forcing the side keys against the sides of the key seats and alining them. When the work has cooled off, the device is removed, and the permanent key fitted and driven home. BABBITT METAL AND BABBITTING. BABBITT METAL. 47 . Composition of Babbitt Metal. — Babbitt metal is an anti-friction alloy named after its originator, who used it in a form of journal-box that he invented. Bab- bitt metal is composed of tin, copper, and antimony. The proportions of these elements as originally used are given by the best authorities as follows: For heavy duty, 50 parts tin, 2 parts copper, 8 parts antimony; or, 96 parts tin, 4 parts copper, 8 parts antimony; and for light duty, 50 parts tin, 1 part copper, 5 parts antimony. The term Babbitt metal is also applied to a great number of alloys on the market that are used to line journal-boxes. If the user wishes to insure himself against the purchase of worthless imitations, he should either make the Babbitt himself or have it made after correct specifications by a reliable manufacturer. The melting points of these three metals may be taken as follows: Copper, 1,930° F. ; antimony, 1,000° F. ; tin, 445° F. 48 . Making Babbitt Metal.- — In making Babbitt metal, it is necessary to melt the copper first, as its fusing point is higher than that of either of the other two elements of the compound. Add the antimony to the melted copper, and then put in about one-third of the tin. The copper should be covered with a layer of powdered charcoal, to prevent oxidation and vaporization of the tin and antimony. Keep 62 SHOP HINTS. § 24 the mass well stirred with a dry pine stick; add the remain- der of the tin, and cast into small ingots. These usually vary in weight from 1 pound to 10 pounds, depending on the quantity to be used on the work. It does not necessarily follow that genuine Babbitt metal is required for all such work. In fact, it should not be used in boxes for all speeds and pressures. The legitimate cost of anti-friction linings for journal-boxes will vary, of course, with the prices of their constituent elements, and this cost should be proportioned according to the needs of the case. From the standpoint of cheapness, ease in handling, anti- friction properties, etc., lead would be ideal as a bearing metal. For this reason it forms the basis of a great number of the alloys used for lining journal-boxes, in which other metals, such as antimony, copper, tin, and zinc, are added to correct the softness and the shrinkage of the pure lead. In melting Babbitt, care must be taken to heat it slowly. Cover the surface of the melting metal with powdered char- coal, to prevent oxidation of the tin and antimony, and stir with a dry pine stick. This stick serves as a guide to the correct temperature of the Babbitt, since the molten metal must not become so hot as to char the pine. 49. Old type metal makes an excellent bearing metal for ordinary work, in fact all except heavy work, and for light work it will carry some additional lead. In one case the back pillow-block of a 60-horsepower engine babbitted with type metal, when taken out after 25 years’ use, showed little or no signs of wear. BABBITTING. 50. Melting Babbitt Metal. — Babbitting is not considered fine work, but at the same time it requires con- siderable experience and skill in order to do it well. The amount of babbitting done in a shop varies. An occasional box can be babbitted by metal melted in an iron ladle over a blacksmith’s fire, but in larger establishments the steady SHOP HINTS. 6 3 § 24 employment of several men with special fires and appliances are often required. Babbitt metal should never be melted over a blacksmith’s fire that is to be used for welding, for if a little of it gets into the fire, it is likely to spoil the welds. Therefore, it is well to have a fire set apart for melting Babbitt. A portable forge is especially useful for this work, as it can be moved to the place where the work is to be done. Coke is preferable to coal for melting Babbitt on account of the fact that it makes less smoke. Natural gas is an excel- lent fuel for this purpose. The ladles may be either of wrought iron, steel, or cast iron, and should be discarded when worn thin in the bottom, as metal may be lost by an unnoticed leak. For large work, the melting is usually done in either a cast-iron kettle or a boiler-iron ladle set in a brick furnace. The surface of the metal when melting should be covered with powdered charcoal to exclude the air in order to prevent excessive oxidization. The melted metal is dipped out of the melting pot in hand ladles, from which it is poured into the boxes. Care should be taken to heat the ladles so that they may not chill the metal. A little powdered rosin should be scattered on the surface of the metal and the metal stirred with a stick just before pouring. The rosin acts as a flux and leaves the metal cleaner and more fluid. 51 . Form of Box for Babbitting. — The Babbitt metal in boxes or bearings is generally held in place by raised strips or projections cast in the box, which enclose it on all sides, for the purpose of restraining the tendency of the metal to stretch or flow under the pressure or pounding of the shaft. The strips should be cut below the surface of the bearing, so as not to come in contact with the journal. In the case of large boxes, dovetail grooves are sometimes cast in the surface of the casting to aid the strips in holding the Babbitt, and in some cases the strips are omitted, and the dovetail grooves only are relied on to hold the metal. Important journal-boxes like those in the pillow blocks of an engine are generally babbitted from -J to \ inch smaller than the finished bore. The metal is then hammered into the 64 SHOP HINTS. §24 box by using the round peen of a hammer to either compress or expand it firmly into place, after which the journal is bored to the required diameter. Roller tools such as are used for expanding copper linings into pump and hydraulic cylinders, as illustrated in Fig. 7, may be used to advantage for expanding Babbitt into place. If the Babbitt bearing is chucked in a lathe, the tool (a) is used in the tool post and fed through the work after the manner of a boring tool; or, if a boring bar is used, the tool ( b ) may be in- serted in the bar or cutter head and takes the place of a boring tool. The feed and speed of the roll may be considerably faster than in the case of a boring tool. The surface to be rolled may be lubricated with soda or soap, water or oil. In the case of small bear- ings, the metal is compressed by driving or forcing one or more polished steel drift plugs through the bearing. 52. Mandrels for Babbitting. — A mandrel of the same, or approximately of the same diameter as the shaft for which the box is made, is placed in the box when the Babbitt is poured. The mandrels are often made hollow, as shown in Fig. 8, and consist of a cylindrical portion a with a bar b across each end. The bars b carry the centers c for turning the mandrel in a lathe. The hollow mandrel is not only cheaper than a solid one, but is also lighter to handle and quicker to heat in case it is desired to warm it before pouring the Babbitt. Man- drels are also made of wood. Iron mandrels should always be warmed before the metal is poured into the box. SHOP HINTS. 65 § 24 The mandrels are often made a little larger than the jour- nal that is to be used in the box, both to allow for the shrinkage of the box and to insure that the bearing will not bind the shaft sidewise; a box that bears in the bottom is less likely to heat than one that pinches the shaft sidewise. Sometimes paper is. wrapped about the journal, which is used instead of a mandrel; this is not advisable except in the case of temporary work. Strips of pasteboard or wood may be placed between the mandrel and the strips that retain the Babbitt in the box to insure a proper thickness of Babbitt. To prevent the Bab- bitt from running out at the ends and joints of the box, the openings should be closed with clay or putty; care should be taken that they are not too wet, as water in the mold is likely to form steam and blow out the metal. A pouring basin leading to the box may also be made of clay or putty; large boxes are sometimes poured from several ladles simul- taneously. In all cases, ample vents should be left for the air to escape from the box, and the metal should be poured at a low heat and as rapidly as possible. The surface of the mandrel should be slightly oiled. 53 . In case a large number of boxes with machined ends are to be babbitted, a mandrel of the form shown in Fig. 9 may be used and both parts of the box poured at once. The mandrel consists of a cyl- inder a of the required diameter and length, with a disk b at each end to fit against the machined ends of the box. One disk is held in place by a cap screw c and is removable. The mandrel is put in position in the bottom of the box, and a liner d of pasteboard or sheet iron placed against each side of it and the cap bolted on. The Babbitt is poured through the oil holes or slot in the cap and reaches the lower part of the box through the fig. 9. SHOP HINTS. 60 § 24 notches e in the liners d that are in contact with the sides of the mandrel a. The two parts of the box are separated by driving a wedge under the cap. 54 . In Fig. 10 ( a ) and ( b ) is shown a rig for babbitting the pillow blocks of a center-crank engine. The engine (b) Fig. 10. bed a rests on the parallels b, b , which are supported by a cast-iron floor plate c. The parallel b under the pillow- block d is set square across the plate c and bolted to it, and the engine frame a is set to a center line on the plate c. A standard e rests on the cross-bar b under each end of the engine shaft f The bottom of the standard e has a SHOP HINTS. 67 §24 projection g, that fits in the groove in the bar b , and a bracket h with vertical adjustment is bolted to the top of the bracket and has a V-shaped top that embraces arid supports the shaft of the engine or a mandrel f\ when the mandrel is properly adjusted, the Babbitt is poured in the two boxes i, i. 55. A more elaborate fixture for holding the mandrel, and one that is self-centering, is shown in Fig. 11. The I 1 o 1 1 n 1 1 O b O o b O c > H) a TEf \A=p b vdi Fig. 11. lower guide bars on the engine bed a having been planed, a fixture shown at b is placed at each end of the engine guides and these support a bar c with a casting d on the end to hold the babbitting mandrel e. Different sized boxes may be babbitted by having several mandrels all the same size in the center d , but of smaller diameter in the journals f, f. The center of the hole in d for holding the mandrel e can be bored, if desired, -J- inch or so higher than the center of the hole for the bar c. This will allow for the spring of the bar c and also bring the cen- ter of the journals a little above the center line of the engine, so that the first wear will be down toward the center line 68 SHOP HINTS. 24 and not away from it. Keys may be fitted in the shaft c and the castings b and d to level the mandrel e, or the keys may be omitted and the mandrel e leveled by a surface gauge on the floor plate under the engine bed, or a spirit level may be used on the mandrel e. The rig shown in Fig. 11 can be made to serve for babbitting two sizes of engine by making the casting b with two sets of shoulders g, g and h, h to fit the guides of two sizes of engine. 5 ( 4 . When a large number of engines are to be built, a babbitting jig may be made for each size, as shown in Fig. 12, which is a single casting a with a rib b to stiffen it. The casting is planed under the lugs c, c to fit the engine guides and bored at the end d so as to receive and support the babbitting mandrel. Many other forms of mandrels may be designed to meet the requirements of the case in hand. 57 . Rebabbitting a Box. — In case a babbitted box is so worn down as to require renewal, first chip out the old Babbitt metal and then proceed to rebabbitt as nearly in the way described for a new box as the appliances at hand will permit. 58 . Babbitting Journal Brasses. — Journal-box brasses are sometimes lined with Babbitt metal. It is neces- sary to tin the surface of the brass so that the Babbitt will adhere to it. The surface must first be made bright and clean by machining, grinding, or pickling; it is then heated a little above the melting point of tin, 445° F., moistened with tinning solution, and a stick of tin rubbed on the sur- face. The tinning solution is made by dissolving zinc in §24 SHOP HINTS. 69 muriatic acid; sometimes sal ammoniac is added. Tinning salts are also on the market. After the surface is thoroughly tinned, the Babbitt is poured in the usual way, but in this case unites with the tin and is held firmly to the brass. 59 . A special mandrel for babbitting brasses is shown in Fig. 13. The mandrel consists of a hollow cast-iron cylin- der a resting on a base b bolted to a table c. The cylin- der a is turned to the proper diameter to fit the brasses d, and has two lugs e , e for the edges of the brasses to rest against, leaving a space f between the mandrel and the sur- face of the brass that is to be filled with Bab- bitt. The brass d stands on the base b and is held against the lugs e, e of the mandrel a by means of a curved lever g hinged to the frame at h. The Babbitt is poured from a dipper into the space f 9 and the brass is removed as soon as the metal sets. The cast-iron mandrel a is cooled by means of a circulation of water that enters through a pipe i attached to the center at the bottom. Fig. 13. USEFUL INFORMATION. Of). Putting in Wood Screws. — The machinist is sometimes obliged to put in wood screws. These can be screwed home easier if they are rubbed with, or stuck into, a cake of tallow, while in the absence of tallow any heavy grease or oil may be used. Screws that are thus lubricated may be easily taken out again. Wood screws may be put into the hardest wood by the following process: A screw of 70 SHOP HINTS. §24 the size to be used is filed or ground to the form of a half- round bit, thus making a tap of it. A hole, equal in diam- eter to the size of the screw at the bottom of the thread, is drilled or bored into the wood and the half-round tap is screwed in. This cuts a good thread into which the screw, which should be well greased, may be easily screwed. 61. Cutting Soft Rubber. — Soft rubber is very hard to cut smoothly, even when the knife is very sharp. It can be cut quite easily, however, if the knife, which must be sharp, is dipped frequently into water, or wet with saliva. 62. Working Vulcanized Rubber. — Vulcanized rubber, which is more frequently called hard rubber, is a material that is hard to machine smoothly on account of the fact that it dulls the tool very rapidly. The tool used for turning or planing it may be a little keener than that used for steel, and should be left just as hard as fire and water can make it. Hard rubber can be machined to the best advantage with a diamond-tipped tool. Vulcanized rubber will take a high finish, which is obtained by buffing it on an ordinary buffing wheel. 63. Bluing Iron and Steel. — Polished work made of iron or steel may be given a beautiful blue color by heating it in hot sand, in wood ashes, or in pulverized charcoal. The substance in which the article is to be blued may be put into an iron kettle that is placed over a fire. The substance must be constantly stirred while it is being heated in order that the whole of it may be brought to an even temperature. The article or articles to be blued must be absolutely free from grease if an even color is desired ; they may be placed into a wire basket or may be suspended by wires and then immersed in the heated substance until the desired color is obtained. A light-blue color can be obtained by heating in sand or wood ashes, but a dark-blue color requires the article to be heated in pulverized charcoal. The brightness of the color depends largely on the finish; the higher the polish upon the work, the more brilliant the color which will be obtained. The substance in which the 24 SHOP HINTS. 71 heating is done should be just hot enough to char a dry pine stick. By this manner of bluing, a piece of work having thick and thin parts can be given an even color all over. (->4. Blacking Iron and Steel. — Polished articles of iron and steel can be given a deep lustrous black color by immersing them into a heated mixture composed of 1 part of black oxide of manganese and 10 parts of saltpeter, by weight. This mixture should be heated in an iron kettle until it is hot enough to char a pine stick. The articles to be blackened must be scrupulously clean; the excellence of the color will depend on the degree of finish of the work. When bluing or blacking articles in a heated substance, it must be remembered that the articles will themselves become heated, and that if they are hardened, the temper will be drawn. 65. Browning Iron and Steel Chemically. — Many articles of iron and steel can be given a color varying from a light brown to a deep black by a chemical treatment. For this purpose a solution composed of 1 part of corrosive sub- limate dissolved in a mixture of 16 parts of sweet spirits of niter and 16 parts of alcohol, by weight, is used. The article to be browned is cleaned thoroughly, so as to be free from grease, and is then washed with wet lime, and finally rubbed down with dry lime, in order to eliminate all traces of grease, as the success of the treatment depends on it. Care must also be taken not to touch the article with the fingers after it has been cleaned, by fitting wooden handles to it by which it can be held. The article having been cleaned, the browning solution is applied with a sponge and the article is put in a dark, dry place until a dry rust has formed on it. This will take from 8 to 48 hours, depending on the condition of the weather and the hardness of the material. When the rust has become dry enough to fly when a file card is applied to it, the article is carded off with a card that must be absolutely free from grease; it will now be found to have a light-yellow color. Another coat of the browning solution is now applied and after the dry rust has CAPSCREW HEADS 72 SHOP HINTS. §24 *The angle of the conical head of the flat or countersunk head is 72°. f No. 4 wire. SHOP HINTS. 73 § 24 formed, the article is again carded off, when it will be found to have a dark-yellow color. The next repetition of the process will give it a light-brown color, then a dark-brown, and finally, a deep-brown. The deep-brown color is changed to a black color by immersing the article in boiling water for a few minutes. After the article has dried, and while still hot, it should be given a coat of oil and be allowed to cool slowly. A more lasting black color can be obtained if the article is put into an oven that is heated by steam to a temperature of 300° F., and keeping it there for about 8 hours. Instead of the file card, a rotary steel-wire brush may be used to advantage when much browning is to be done. The barrels of firearms are browned by the process just described, or by modifications of it. Capscrews. — It is frequently desirable to know the diameter and the length of the head of a capscrew of given form. Table VI gives these dimensions for five different forms of capscrew heads, for screws ranging from inch to inches in diameter. C. S. III. 28 TOOLMAKING. (PART 1.) GENERAL TOOL-ROOM WORK. INTRODUCTION. 1. Definition. — Toolmaking may, in general, be defined as the making of tools. A tool in its broadest sense may be any device, instrument, appliance, machine, or apparatus that is intended to perform some essential func- tion in the production or transformation of raw material into a finished product or that aids in the performance of some function required for the change. Custom, however, has narrowed this definition until the term toolmaking now comprises only the production of tools by the aid of which the integral parts of devices, instru- ments, appliances, machines, or apparatus can be formed through cutting, drawing, compressing, or abrading opera- tions performed on bodies susceptible to these operations. The most important subdivision of toolmaking relates to the production of tools for the working of metals, and is the one that will be treated of here. METHOD OF PROCEDURE. 2. There are several stages in the production of tools; it is rather difficult, however, to draw a distinct line of demarkation between the ending of one stage and the beginning of the other, since they frequently blend more or less together, according to the circumstances of each § 25 For notice of copyright, see page immediately following the title page. 2 TOOLMAKING. 25 individual case. Generally speaking, these stages are as follows: conception ; commercial consideration ; design ; and, finally, construction. The stages follow in the order named. 3. Conception of tlie Possibility of Improve- ment. — This may be considered as the foundation of prog- ress. Ability to conceive possibilities requires not only intimate knowledge of every stage of the particular process or operation under consideration, but also full knowledge of the good points, defects, capabilities, and limitations of the tools used for this process or operation. 4. Study of tlie Commercial Considerations. — Will the improvement pay ? This question must be asked in each and every case, and must have been answered in the affirmative before any further step is taken. Naturally, each case must be investigated by itself and decided upon its own merits. First of all, the probable cost of improve- ment must be estimated; the saving that the improvement will effect must then be carefully investigated. Finally, it must be determined if the ratio that the saving bears to the investment required to effect it is sufficient to warrant the expenditure. It is always to be remembered that the pri- mary object of tool improvement is the lessening of the cost of production, or the analogous object of raising the quality of the output without increasing the selling price. 5. Design. — Since the cost of a tool depends largely on its design, and since the latter also directly determines its ultimate value, it will be apparent that the design is a very important matter. It must always be remembered that there are usually quite a number of different ways in which an object can be accomplished; then, in order that the first cost of a tool shall be within reasonable limits, it is neces- sary to carefully study the facilities at command. This con- sideration shows the importance of a thorough knowledge of tool-room operations, appliances, and special processes. For this reason, in the majority of manufacturing establish- ments, the design of special tools is left entirely to the tool- maker or to special designers. TOOLMAKING. 3 § 25 When designing a tool, various ways of accomplishing the object sought will present themselves successively; unless special considerations prevent it, the design that will accom- plish the object in the most direct manner is the one to be chosen. A good tool designer will never introduce compli- cated mechanical movements or such special modifications of relatively simple ones as are not only expensive to pro- duce but difficult to keep in proper alinement. Simplicity, accessibility, compactness, rigidity, durability, and handi- ness are the prime factors requisite in a successful tool, whether it be a boring machine for boring the largest sizes of steam-engine cylinders, or a box tool for a small automatic screw machine. 6. Construction. — In the construction of tools, the toolmaker is very frequently called on to solve problems that, while not essentially different from those of the ma- chinist, still require entirely different methocls of procedure to accomplish the object sought. Thus, the problem of locating and drilling a couple of bolt holes 3 inches apart, when the bolts have a clearance of inch or more, is solved in an entirely different manner from that of producing two holes with their axes parallel and in the same plane, and 3 inches apart, within a limit of variation not to exceed it innr inch. In the first case, the combination of a drill press, center punch, hammer, 2-foot rule, a drill, and a laborer will usually be sufficient; in the second case, an accurate lathe kept in the best of condition, fine measuring tools, standard test gauges, an extremely sensitive indicator, and other special appliances used by a highly skilled toolmaker, will be needed to locate the holes within the given limit of variation. In the construction of a tool, the purpose of every part of it must be taken into consideration in order to prevent undue accuracy and unnecessary expense consequent thereto. It is a mistake to accurately machine, scrape, and finish parts that may be said to “ fit a hole in the air.” The time needed for this can be spent more profitably on those parts that 4 TOOLMAKING. §25 accomplish a useful purpose; likewise, it is unnecessary and a direct waste of time to go to the utmost refinement of meas- urement in a gauge that may be “plenty good enough ” if accurate within fa inch — as a gauge for the blacksmith, for instance. Before constructing a tool, the purpose and the accuracy required for each integral part of it should be studied; the operations necessary to produce it can then be regulated accordingly. 7. The design and construction of a tool are intimately correlated, as becomes painfully apparent when special meth- ods needed for its construction have not been taken into ac- count and it becomes necessary to devise expensive makeshifts in order that the whole work previously done on the tool may not be lost. For this reason, no matter by whom the tool has been designed, it is good practice to go over the whole design and see if every operation required in the production of the tool can be actually performed with the facilities at hand. If not, and when circumstances permit it, the design should be changed; provided, of course, that the change will not affect the efficiency. DIMENSIONING DRAWINGS. 8. In dimensioning a drawing, it should always be the aim to give all dimensions with special reference to the manner in which the tool must be constructed. If the tool- maker will have to work from some certain surface in order to lay out the different parts of the tool, and will have to make all his measurements from it, let all dimensions on the drawing or sketch read from that surface. If this plan is followed, a great deal of needless work is obviated. When giving the distance between holes that have to be accurately located in reference to each other and in reference to some fixed point of the tool, put in all the dimensions that the toolmaker needs to thus locate them ; this is better than expecting him to make these calculations himself. §25 TOOLMAKING. 5 A case in point is shown in Fig. 1. In view (a), part of a jig is shown in which the three holes are to be located with reference to one another and to the finished surfaces a and b, as shown by the dimensions. The dimen- sions given would be sufficient for work not requiring any great de- gree of accuracy, say for ordinary machinist’s work. With these di- mensions, the aid of a surface gauge, a surface plate, an angle block, and by extremely careful work, the centers may be laid out within a limit of error of 1 0 3 0 0 inch, and an expert may even bore the holes within that limit of variation. But suppose that a greater degree of accuracy is required; assume that the limit of variation is not to exceed one-half of yoVo* ^ch- in order to obtain this degree of accuracy, which must not be imagined to be anything extraordinary, the toolmaker must substitute contact measurements for measurements taken from a scale and then transferred by scribed lines to the work. . In order to make these contact measurements, the toolmaker needs the dimensions marked x, y, and z in Fig. 1 (b) ; if these are not given, he cannot conclude the work until they are supplied. 9. Referring again to Fig. 1 (a), it will be noticed that the dimensions locating the holes with reference to one another and to the surfaces a and b are given in decimal parts of an inch, and the other dimensions in common frac- tions. This is done in accordance with a method of dimen- sioning that, while not universal, is well deserving of wider application. It simply signifies that all dimensions given decimally are accurate dimensions, and that the parts are to (a) G TOOLMAKING. § 25 be located or made to those dimensions as closely as can be measured with a micrometer, vernier calipers, or similar measuring instrument decimally graduated. On the other hand, for those dimensions that are expressed in common fractions, no great accuracy in machining or fitting is required. If this system of dimensioning is adopted, it usually results in the reduction of needless accuracy, which, in turn, means a decided saving in the labor cost. On good work it is often advisable to specify on the draw- ing the limit of variation permissible; this prevents choice of methods entailing a vast amount of work when less elab- orate methods will produce a job that is “good enough for the purpose.” READING DECIMALS. lO. Since, with very rare exceptions, the measuring instruments of the toolmaker are graduated to read to the one-thousandth part of an inch, and some to the one ten- thousandth part of an inch, dimensions on drawings for tool work are in many cases given decimally. Trouble is expe- rienced occasionally in reading them correctly, hence a short explanation of how to read decimals is here given. The method given, while differing from that laid down in works on arithmetic, is in common use in shops, and is especially adapted to the needs of the toolmaker on account of the graduations of his measuring instruments reading directly to thousandths of an inch. As decimals containing more than four figures are very rarely met with in tool work, their reading will not be considered here. Rule . — Read the first three figures to the right of the deci- mal point .as a common fraction having one thousand for its denominator , and read the fourth figure as a fraction having ten for its denominator and one one-thousandth of an inch as a unit. Figures to the left of the decimal point are whole num- bers and are to be read as such. Commence reading the TOOLMAKING. § 25 7 decimal at the first figure greater than zero, reading from left to right. For example, 1.0567* would be read, one and fifty-six one-thousandths and seven-tenths of a thousandth of an inch ; .0005'' may be read, five-tenths of a thousandth of an inch; .072" would be, seventy-two one-thousandths of an inch. When there are less than three figures to the right of the decimal point, annex enough ciphers mentally to make three figures. Thus, .07" would be read as though it were written .070" and may be expressed as seventy one- thousandths of an inch, and .4" would be read as though it were written .400", i. e., four hundred one-thousandths of an inch. Suppose a micrometer graduated to read to ten-thou- sandths of an inch is to be set to read .7653 inch. Then, since on all portable micrometers the one-thousandth of an inch graduations are independent of the vernier by which the tenth part of a one-thousandth is obtained, the microm- eter would be set first to seven hundred sixty-five one- thousandths, and then, by the aid of the vernier, set ahead three-tenths of one-thousandth of an inch. By accustom- ing himself to read decimals in this manner, a person is less liable to make an error in setting or in reading the micrometer. WORK OF THE TOOLMAKER. 11. In its broadest sense, the work of the toolmaker comprises the design and construction of machine tools, such as lathes, planers, shapers, etc., in addition to that of the small general tools, such as taps, dies, reamers, milling cutters, and the special tools, such as jigs, gauges, and similar implements used in the production of duplicate work. It being the tendency to specialize in every direc- tion of machine-shop work, the journeyman toolmaker today does not generally build the machine tools himself, but, instead, produces the tools and special appliances for the construction of the machine tools in an economical manner. The making of taps, dies, reamers, milling cutters, and 8 TOOLMAKING. 25 similar cutting 1 tools forms, in most shops, but a relatively small part of the toolmaker’s work, since there are many concerns making a specialty of this work. In consequence thereof, all such tools can be bought of the makers for a small fraction of what their cost would be if made singly and with the facilities usually found in tool rooms. Many of these tools thus bought are really superior to home-made tools, simply on account of the makers having the proper facilities. As far as cutting tools are concerned, the work of the individual toolmaker is confined, except in relatively rare instances, to the making of special cutting tools differing in one or more dimensions or in design from the standard sizes in which the makers supply them. The production of the special tools used where articles are manufactured in quan- tities under the interchangeable system, and such special tools as tend to cheapen the cost of manufacture where machinery is not built in large quantities, form, in general, by far the greater part of the toolmaker’s work. MEASUREMENTS. 12. Classification of Measurements. — The meas- urements to be made in tool construction may be divided into two general classes: (1) Approximate measurements; (2) precise measurements. The adoption of one or the other class of measurement depends on the accuracy required. In most cases, both classes of measurement are used on a job, since a tool is rarely of such shape as to require measurements of precision for each and every part of it. 13. Approximate measurements are those made with the aid of an ordinary graduated steel scale and a caliper, dividers, scribing block, surface gauge, etc., or measurements that may be classified as direct visual meas- urements. While an expert using the greatest care and TOOLMAKING. 0 § 25 working with a magnifying glass can set calipers by a steel scale within a limit of variation of .001 inch of the true size, there are rather few people that can do so. Generally speaking, the limit of variation, that is, the degree of accu- racy attainable, may be placed at .002 inch; it requires quite close work to attain this accuracy. 14. Precise measurements depend primarily on gauges of various kinds that represent commercially accu- rate subdivisions of the standard yard. These gauges, among which may be mentioned the standard end-measure pieces made by Pratt & Whitney, and the reference disks made by Brown & Sharpe, are carefully ground and lapped to a size not Varying more than i nc h from the true size. Gauges of this degree of accuracy are naturally quite expensive, and hence are not intended for use in the machine shop, but rather for the testing of micrometers, vernier calipers, and similar shop-measuring instruments. The precise measurements that the toolmaker is usually called on to make depend for their precision on his sense of touch, they being chiefly measurements of contact. As a matter of course, it is here assumed that the measuring instrument used — as a micrometer, for instance — is com- mercially correct. With an accurate instrument and a finely developed sense of touch, a surprising degree of accuracy can be obtained by direct-contact measurement. Instances are numerous where toolmakers have finished work that, upon testing by more refined methods, was shown to be accurate within -g-o^or inch. To attain this degree of accuracy, a long training is required ; however, very little work that the toolmaker is called on to do will need to be within this limit. To attain accuracy within a limit of variation of .0001 inch is possible for almost any one that possesses a sensitive touch. It may sound like a very small amount, but its magnitude will be realized very forcibly when a hardened, ground, and lapped cylindrical plug is placed between the anvils of a microm- eter set to just touch the plug. Let the micrometer be 10 TOOLMAKING. § 25 screwed up .0001 inch and let the difference in the force required to push the plug through the opening be noted. The difference will prove a surprise to any one that has never felt this demonstration of the magnitude of the tenth part of one-thousandth of an inch. While granting that an expert may attain a greater accuracy, generally speaking, the limit of accuracy of ordinary contact measurements may be placed at that figure. 1 5. Accumulation of Errors. — It must not be inferred, however, that all work can be done or is done within this limit of variation ; while it is possible to attain this accuracy for one contact measurement, it is unreasonable to expect to get it when a number of successive contact meas- urements have to be made in order to obtain a precise over- all dimension. Naturally, the total error will very likely be more than the error of each individual measurement. A case illustrating this is shown in Fig. 2. The problem given is one that frequently arises in one form or another. In this case, a row of six holes is to be bored in some part of a jig; the holes are to be in a straight line, equidistant, and 1 inch apart. It is required that the holes be bored with the greatest possible degree of accuracy attainable with the measuring instruments at hand, which are limited to a 1-inch micrometer. Under the circumstances, some toolmakers would locate the centers of the holes by temporarily attach- ing small annular circular steel disks of known diameter to the work by fillister-headed screws and placing them the re- quired distance apart by the aid of a temporary gauge filed TOOLMAKING. 11 §25 up to a length equal to the center distance of two adjacent holes diminished by the sum of the radii of the two adjacent disks. If all disks are alike, the same temporary gauge will answer for each division. The disks are placed in line by being brought up against a true straightedge. The work is then placed on the face plate of the lathe and trued up until one disk runs true; the disk is now removed and the hole bored. This operation is repeated until all the holes have been bored. Now, while each hole may have been located originally within say yowo ^ nc ^’ th e errors °f each meas- urement may have accumulated until the center-to-center distance between the end holes may vary an amount consid- erably in excess of the limit of variation of a single contact measurement. 16 . In a job of the kind here shown, the errors that prevent absolute accuracy are as follows: 1. The error of the measuring instrument. This, with an instrument purchased of a reliable maker, is usually exceed- ingly small. 2. Error in measuring the size of the disks. This should not exceed .0001 inch. 3. Error in making the temporary gauge. This need not be more than the previous error. 4. Error in placing the disks equidistant and at the re- quired distance. Its magnitude will be a combination of errors 2, 3, and 4. These errors may accumulate or neu- tralize, partially or entirely. 5. Error in chucking the disk to run true. This error need not exceed .0001 inch if a sensitive indicator is used. 6. Error in boring. Its magnitude depends on the skill of the toolmaker; it may be infinitesimal or quite appreciable. Examining into these errors and knowing that some of them cannot be obviated entirely, it is seen that the best that can be done is to reduce each individual error to TOOLMAKING. §25 12 the lowest possible limit. The better the sense of touch is trained and the more skill is used, the closer a final result may be attained. 1 7. Reduction of Accumulating Errors. — We will now investigate the elimination of errors for this particular case. Suppose that a 2-inch micrometer is at the disposal of the toolmaker. Then error 3 can be eliminated entirely, since the micrometer can be used directly over any two adjacent disks. Error 4 will also be reduced, since there is one measurement less to be made for the location of any two adjacent disks; that is, there are now three contact measurements instead of four. Error 2 can be diminished when the disks are exactly alike by placing three or four of them on a surface plate, pushing them all in contact with a straightedge and one another, and then measuring their combined size, finally dividing the measurement by the number of disks. Error 1 cannot readily be eliminated by any means at the command of the toolmaker. Errors 5 and 6 can be minimized by careful work. From the preceding discussion, it is seen that a careful study of the way in which the measurements can be made is advisable in order to secure accuracy. In general, it may be stated that, in order to secure the greatest accuracy where a number of successive contact measurements are necessary, the number of the measurements should be reduced to the smallest number feasible with the measuring instruments at disposal. When a number of successive measurements are needed for intermediate parts and the object sought is accuracy of the combined length of these intermediate parts, in addition to their own accurate location, make, first of all, the longest measurement circumstances permit, and from it obtain the subdivisions. This applies not only to precise measurements, but to approximate meas- urements as well. For illustration, assume that, in the job shown in Fig. 2, the distance between the end holes is re- quired to be as precise as it can be made. Then, facilities permitting, the two disks locating them should be adjusted §25 TOOLMAKING. 13 first of all, and the intermediate disks from these in turn. The following may be laid down as a general rule: Rule. — Where several methods of measurement are fea- sible , the method that involves the fewest and most direct measurements should always be chosen. 18 . Considering the different methods of measure- ment that are feasible, it will be seen upon reflection that no rules can be given. The toolmaker must consider the means of measurement at hand and the nature of the job; he must then use his ingenuity and be guided by his prac- tical experience. 19. For measurements that have to be made within a smaller limit of variation than is attainable by direct-contact measurements, special forms of measuring instruments based on the principle of the micrometer are used. In these machines, special devices show the degree of contact of the measuring surfaces with the work. They are to be found in a few of the leading shops where accurate work is done, being intended for measurements within a limit of variation of g 0 loo i nc h. They are used rarely for work other than making standard gauges intended for testing the ordinary measuring instruments. For measurements closer than the above, a machine known asa “ comparator” is used. Since it can scarcely be considered as a measuring instrument suitable for tool-room work, it will not be described here. LIMITATIONS OF TOOLMAIvING* 20 . The limitations of toolmaking are twofold ; they are limitations of accuracy and limitations of com- merce. The first depend ultimately on the degree of skill, knowledge, and ingenuity of the individual and the mechan- ical resources at disposal. In many cases, a sharply defined limit is set by restriction as to cost. The second depend on the conditions of each particular case; theoretically, they 14 TOOLMAKING. § 25 may be said to have been reached when further toolmaking fails to reduce the cost of production or to improve the quality. As a general rule, the commercial limitations are reached in practice when the cost of production has been reduced below that of competitors. At this period, in most cases, a halt is called to the devising of new tools or the improving of old ones until further advance is made neces- sary by competitors lowering the selling price or bettering the quality of the product. SPECIAL TOOLS USED IN TOOLMAKING. 21 . In addition to the ordinary measuring instruments and similar devices used by the machinist, the toolmaker needs an indicator for showing the truth of cylindrical work, and also a center indicator. There is quite a variety of other tools of great use to the toolmaker, but since these are fully described in the catalogues of concerns making a specialty of measuring instruments, no space will be given to them here. The lathe indicator and center indicator have been com- paratively unknown and have heretofore been made by the toolmaker himself; as a consequence there is a great variety of designs. The two instruments shown in Figs. 3 and 5 and the holder for them shown in Fig. 6 were designed by the writer and have been used by him constantly for fine work. Their construction is not covered by patents. Sev- eral firms are now making good indicators. 22 . Construction of a Lathe Indicator. — The lathe indicator is shown in Fig. 3, the illustration being full size. The purpose of the indicator is to magnify any untruth of the work in order to make the error more visible ; the most obvious and direct method is to use a lever with a long and a short arm. The short arm bears against the work. When the latter is revolved in the lathe, any error, due either to the work not being round or to its not being set centrally, §25 TOOLMAKING. 15 causes the end of the long arm to describe an arc, the length of which is directly proportional to the ratio between the lengths of the two arms. In other words, the longer the long arm is made in proportion to the length of the short arm, the more sensitive the indicator will be. In practice, it is rarely necessary or advisable to make the ratio more than 1 to 50; with this ratio, an error in the work amounting to only .0001 inch will cause a movement of the long arm r, — j~ oil |! b i) i Syirr 1 — r_— ... .jvn- 'l *= a 1 6 (b) — Fig. 3. through an arc fifty times as long, or .005 inch in length. This is an amount that can plainly be seen with the naked eye. If the indicator is made more sensitive than this, it is too liable to be affected by the vibrations of the floor and machinery that exist to a greater or less degree in all shops. For special work requiring the greatest of accuracy, an indi- cator may be constructed with a greater degree of sensitive- ness than that here recommended as the limit for general C. S'. III .— 29 16 TOOLMAKING. 25 work; in that case, it must be used in a place free from vibrations. 23. Referring to Fig. 3, views ( a ) and (b) are, respect- ively, a side elevation and a plan view of the indicator. It consists essentially of four parts. These are the body the lever b , the feeler c , and the spring^. For convenience, the lever is divided into two parts b and b' . They are so joined that b\ which forms part of the long arm of the lever, can be swiveled to any convenient position within range. By means of the locknut e, the two parts may be locked together after adjustment. The division of the lever into two sep- arate parts also allows the degree of sensitiveness to be increased or decreased by the substitution of different arms. The end carrying the feeler is hardened; the hole that receives it is lapped true and smooth. The feeler itself is hardened, ground, and lapped so as to be a good sliding fit in the hole. Both of its ends are hemispherical; the upper end is enlarged to form a stop. The chief peculiarity of the lever is the manner in which it is fulcrumed, the ful- crum being so designed that not only is all wear taken up automatically, but also the possibility of any lost motion at the fulcrum is done away with. This is done without the introduction of any complicated device. Referring to view (r), which is a detail drawing of the main part of the lever, it is seen that the fulcrum pin f is held by its ends in the two wings that straddle the end of the body a. This pin is hardened and lapped smooth ; it is then driven home. The seat or bearing for the fulcrum pin is shown in view (e). A slot g, about two-thirds the diam- eter of the pin in width, is cut to a depth sufficient to have the pin clear the bottom of it. The upper edges of the slot are slightly beveled; the fulcrum pin rests on these two edges. It is held down to its seat by the straddle spring which, by reason of its bearing on the lever between the fulcrum and the point of contact at the feeler, holds the fulcrum pin down, prevents any lost motion, takes up any wear, and also causes the lever to follow any sliding motion TOOLMAKING. 17 § 25 of the feeler. The straddle spring is shown in view (d). It should be a rather stiff spring; if made of the size shown in the drawing, it should be made from sheet steel tV inch thick. 24 . Testing Work. — Suppose it is desired to test a piece of work to find out if it runs true on dead centers. Place the work between the centers of the lathe, and, after attaching the indicator to its holder, which is shown in Fig. 6, adjust it so that the feeler will bear hard on the work to be tested and be about perpendicular to the surface of the work. Rotate the work between the centers by hand and watch the end of the long arm. If it moves, it indicates one or both of two things: (1) The work may not be cylindrical; (2) the work may be eccentric in regard to the centers on which it has been finished. A good idea of the kind of error may be formed by care- fully watching the movement of the end of the lever. If it vibrates steadily just once for each revolution of the work, the latter is most likely to be round, but not central in regard to its centers. If the pointer moves in jumps, i. e., makes several vibrations during one revolution, the work is most likely to be out of round and it may also be eccentric. To test its roundness, caliper it in a number of directions, preferably with a micrometer. When the work is eccentric, it can often be made central in regard to its centers by care- fully lapping the center or centers with a brass lap charged with emery, provided the error is very small, say .0005 inch. When the end of the long arm remains stationary, it shows the work to be both round and concentric with its centers. 25 . The indicator may be applied to a hole in a piece of work held in the chuck or on the face plate, for the purpose of finding out if the axis of the hole coincides exactly with the axis of the spindle; in other words, to find out if the hole runs true. If the hole is too small to admit the feeler of the indicator, grind up a cylindrical plug to fit the hole nicely, and apply the indicator to the outside of the cylinder. The indicator may also be applied to the face of 18 TOOLMAKING. 25 work, to see if it has been faced true or runs true sidewise. Likewise, it is of great assistance in rechucking or resetting cylindrical work that is required to be chucked with great accuracy. 26. The particular design of indicator here shown, being removable from its holder, can be attached to a sur- face gauge and may then be used for testing the parallelism of straight surfaces. As is well known, it is very difficult to measure the parallelism of straight surfaces when they are far apart; in many cases calipers cannot be applied at all. For instance, consider the piece shown in Fig. 4. The question arises as to whether the plane of the circular ring at a is parallel to the plane of b. Evidently, this cannot be measured by calipering. But if the indicator is attached to a surface gauge, the work may be placed on a surface plate and the feeler brought in contact with the ring a. If its pointer remains stationary while the feeler is moved around the ring, the surfaces are parallel. 27. In order that a small motion of the end of the pointer will be visible, it is necessary to have some station- ary point near it. The writer has used for this purpose a thin metal disk with a piece of soft brass wire, pointed at the end, soldered to it. The disk was placed between the joint of the holder and the joint end of the indicator; the brass wire was then bent to the shape required. If desired, some more elaborate construction may be employed. 28. Construction of a Center Indicator. — The cen- ter indicator shown full size in Fig. 5 is intended to aid in the proper location of work that is to be chucked so that a center punch mark will coincide with the axis of the live spindle of the lathe; that is, run true. The tool is essen- tially a lever with a long and a short arm turning about a TOOLMAKING. 19 § 25 ball joint as a fulcrum. The indicator is clamped to the tool holder shown in Fig. 6, which is held in the tool post of the lathe; the carriage is then run forwards until the pointed end of the short arm bears lightly in the center punch mark in the work. The part a is made thin so as to form a spring that will hold the pointer in the center punch mark. If, on revolving the headstock spindle, it is found, that the end of the long arm moves in a circle, it shows the center punch mark is not in the axis of the spindle, and the work needs moving until the end of the pointer remains stationary when the spindle with work attached to it is revolved. It is necessary to have some stationary point by which to observe the motion of the pointer; the dead center is the most convenient point to use. 20 TOOLMAKING. 25 29. If the indicator is connected to a holder in such a manner that it can be swiveled up and down, it can readily be used in all sizes of lathes. The center indicator shown possesses the advantage that there are no joints, and its accuracy is not disturbed by wearing of the joints. Fur- thermore, the pointer is adjustable for different degrees of sensitiveness; a small setscrew in the ball, a section of which is shown separately, is used for clamping the pointer and ball together. It is scarcely advisable to make the pointer longer than 15 inches; this length will be found to answer very well indeed. If made longer, the tool will be affected too much by the vibration of the machine. The pointer., the clamping bolt c y by means of bail, and the head a should be made of tool steel and afterwards hardened. The head a must be drawn to a spring temper, since it serves as a spring. The ball and the end of the pointer may be drawn to a straw color. Grind together the ball and the seat in the head, using the finest flour emery. The shank b may be made of machinery steel and case-hardened. 30. Holder for In- dicators. — The hold- er shown in Fig. 6 is made of tool steel. Its head a has a cylindrical hole b to receive the which the indicators are TOOLMAKING. 21 §25 attached. The head has a cylindrical shank closely fitted to a hole in the holder proper. The holder is split at the front end; a clamping bolt d allows the head a to be locked in any position after rotation to the desired place. The combina- tion of two joints allows a movement of the indicator in two planes perpendicular to each other; hence, the indicator can be swung through a very wide range of positions, and is thus adapted to almost any size of lathe and any kind of work conceivable. It is advisable to harden the holder at a rather low heat, and then draw it to a spring temper. CUTTING TOOLS AND APPLIANCES. DESIGN AND CONSTRUCTION OF TAPS. FLUTES. 31 . Number of Flutes. — In order to provide cutting edges, and also to provide a place for the reception of the chips, taps are fluted. It is almost the universal practice today to cut taps, independent of their size, up to and including 2-J- inches diameter, with four flutes. For larger sizes, practice varies. Some toolmakers advocate five or more flutes for sizes above; others retain four flutes for all sizes. Generally speaking, four flutes will usually prove sufficient and satisfactory for all taps that cut a full thread of the right diameter in one operation. Special taps, or hobs, as they are often called, for tapping screw-cutting dies are made with from six to eight flutes; they are not intended to cut a full thread at one passage, but rather to finish out to size the hole in the die that has previously been tapped with a slightly smaller tap. 32 . Forms of Flutes. — There are two different forms of fluting in common use, shown in Fig. 7 at ( a ) and ( b ), respectively. The form shown at (a) is considered by many 22 TOOLMAKING. 25 as the better form, since it makes not only the stronger tap, but also prevents the cracking of the tap lengthwise in hardening, owing to the absence of relatively sharp corners where a crack could start. The curve of the groove is com- posed of two arcs tangent to each other; the large arc, as b , may, for a four-fluted tap, have a radius equal to the diameter of the tap, and the small arc c may have a radius of one-sixth of the diameter. These proportions are approx- imate and vary somewhat, not only with different makers, but also on account of the inexpediency of having a different cutter for each different size of tap. In practice, one cutter will be made to answer for several sizes. The fluting shown at ( b ) is probably the one in most com- mon use, although it does not make as strong nor as easy working a tap. In order not to weaken the tap too much, the land a must be left wider than it is in Fig. 7 (a ) ; this produces a greater friction in tapping. The sides of the flute are perpendicular to each other; the corner may have a radius of one- eighth of the diameter of the tap. In both forms of fluting, it is the common practice to make the cut- ting edges radial, as shown by the dotted lines in Fig. 7. This answers very well indeed for general work. If a tap is to be used entirely for brass, and especially for brass castings, the TOOLMAKING. 23 § 25 cutting’ edge may be slightly advanced in the direction of cutting parallel to a radial line, as shown in Fig. 8. This will give it a slight negative rake and cause it to cut more smoothly and with less liability of chattering. The amount that the cutting edge is advanced need not be very large; it may be from one-sixteenth to one-tenth of the diameter of the tap. Taps that are to be used for general work on all kinds of metal usually have their cutting edges radial. HAND TADS. 33. Design. — As the name implies, liand taps are intended for tapping holes by hand. Since it is rather dif- ficult to use the tap without throwing a sideward strain on it, in consequence of which the tapped hole will be larger at the end where the tap was started, the construction should be such that it will counteract this tendency as much as possible. This is done by making the lands rather wide and giving no relief to the thread back of the cutting edge. The width of the lands for a four-fluted tap when made with flutes, as shown in Fig. 7 (a), may be two-tenths the diam- eter of the tap. When fluted with four flutes, as shown in Fig. 7 ( b ) and Fig. 8, the width a of the lands may be about one-fourth the diameter of the tap. The square on the end of the tap intended to receive the tap wrench is generally placed so that the corners are in line with the cutting edges. 34. Making a Hand Tap. — For a straight tap, select steel slightly larger in diameter, say y 1 ^- inch, for sizes up to ^-inch; -J. inch for sizes up to 1 ^ inches; and T 3 y to \ inch larger for sizes above. Have it well annealed, preferably in slaked lime. Turn the shank and tap body to size, then mill or file the square and cut the thread in the lathe. The thread should be cut as smooth as possible ; many tool- makers prefer to use the single-pointed tool for roughing out to within .002 or .003 inch of the correct size and then 24 TOOLMAKING. 25 finish it with a chaser. On small taps, but only when accu- racy of pitch is not essential, the thread may be cut with a die. If the die is in good condition, a very good thread can be cut if plenty of oil is used in cutting; however, as with all dies that feed themselves, the pitch of the thread cut will be coarser than the pitch of the thread of the die. The thread having been cut, chamfer the end in the lathe an amount depending on whether the tap is to be a taper tap, plug tap, or bottoming tap. The tap is now ready for fluting. This can best be done in the milling machine, holding the tap between the centers or in the universal chuck, accord- ing to size. The cutter is set, by trial, to cut the correct depth of flute; large taps may require several cuts. The flutes having been cut, the cutting edges will have to be filed up a little on the face with a rather fine file to remove the burrs left by the milling cutter, and if the tap is over \ inch, it had better be backed off by filing. The chamfered ends must be given clearance by filing. The size, and, preferably, the number of threads also, having been stamped on the shank, the tap is ready for hardening. To harden it, the safest way is to heat it inside of a piece of gas pipe, frequently turning the latter and changing its position. The danger of overheating and burning the steel, and of unequal heating, is greatly lessened thereby. The tap should be hardened at as low a heat as will make it hard enough so that a file will not “touch.” it, dipping it ver- tically into clear water a little beyond the threaded part. It may then be ground in the flutes on an emery wheel to sharpen the teeth and make it bright for tempering. Draw it to a good straw color evenly all over, holding it some distance above the fire. When an emery wheel is not available, the cutting edges must be made sharp before hardening by filing with a fine file. The tap may be brightened in the flutes, after hardening, by grinding or by emery cloth, using care that the emery cloth does not touch the cutting edges; if it does, it will dull them more or less. It is best, however, not to use any emery cloth on a tap. 25 TOOLMAKING. 25 35. Effect of Hardening. — If the pitch of the thread and its diameter are measured after hardening, it will usu- ally be found that the pitch and the diameter have changed a small amount. In a few instances, the tap will measure the same as before. There is no known way of preventing this change, which is due to hardening. It can be mini- mized by a slow, careful, and even heating, combined with a hardening at as low a heat as will be sufficient to make the tap hard. Fortunately, the amount of change rarely exceeds two-thousandths of the length and diameter, and is negligible for nearly all work. 36. Straightening Taps. — When taps are rather long, they will usually become crooked in hardening and Fig. 9. tempering. They can be straightened as follows: Place the tap between the centers of the lathe; fasten a piece of metal with a square end in the tool post and place it against the 26 TOOLMAKING. § 25 highest point of the convex side, as shown in Fig. 9. Now, with a Bunsen burner or an alcohol lamp, heat the tap, which has been previously covered with lard oil, until the oil commences to smoke. Then, by means of the cross-feed, slowly force the tap over until it is a little crooked the other way and quickly cool it while between the centers. By repeating this operation, it may be straightened very nicely. The amount the tap must be forced over can only be ascer- tained by practical experience. No attempt can be made to give a rule for it. Other hardened and sprung work may be straightened in the same manner. The tap should be straightened before drawing the tem- per. String solder may be used in place of oil to test the temperature when heating the tap. As quick as the solder melts, the tap is hot enough. MACHINE TAPS. 37. Machine taps are intended for use in tapping ma- chines, in the turret lathe, and for similar work. Since these taps are intended to be guided axially by their attachments, the lands can be made narrower than in hand taps, and relief can be given to the teeth, which causes them to cut more freely. Relief is given by filing the thread back of the cutting edge until the tap has the form shown in Fig. 10. Very little filing is fig. io. necessary; it is not advisable to give too much relief, since, in backing the tap out, chips are liable to be drawn in between the work and the lands. TAPER TAPS. 38. Relief. — In making a taper tap, attention must be paid to two points that are frequently overlooked, and in consequence of which the tap, though finely made otherwise, will produce poor work. These points are: (1) The teeth must be relieved back of the cutting edge; and (2) a taper §25 TOOLMAKING. 27 tap cannot be cut to correct pitch by setting the tailstock over and gearing up for the right number of threads per inch. A trial of a taper tap not relieved in the thread, especially if the taper is large, will immediately show that the tap, instead of cutting the metal, will squeeze it. This is due to the fact that the sides of the thread at the back of the lands drag against the work, thus preventing the cut- ting edges from cutting. The threads are usually backed off with a three-square file; manufacturers of taps use a special machine that relieves the thread in the process of cutting it. 39. Errors. — In order that the tap may have the cor- rect pitch of thread, it must be cut by the use of a taper attachment. When a taper tap is cut in a lathe not fitted with a taper attachment, it is done by setting over the tail- stock center. Two errors are then introduced that become more pronounced as the taper is made larger. In the first place, the pitch will be finer; in the second place, the thread, instead of being true, will be drunken. Neither one of these errors can be corrected very readily. The second error is due to the fact that, in taper turning with the tail- stock set over, the work does not turn with a uniform angular velocity, while the cutting tool advances along the work with a uniform linear velocity. When the taper is slight, the change in pitch and the drunkenness of the thread is ordinarily imperceptible to the eye ; with tapers of f inch per foot, the errors become sen- sible and increase rapidly as the taper becomes larger. For these reasons, taper taps should always be cut with the taper attachment. If none is available, there is nothing left except to set the tailstock over. The thread should then be well relieved; this will make the tap cut free, but will correct neither the pitch nor the drunkenness of the thread. In cutting the thread on a taper tap, the threading tool should be set square with the axis of the tap. This is the practice of manufacturers and is well worthy of general adoption. 28 TOOLMAKING. §25 40. In order that the toolmaker may determine whether the error in pitch introduced by setting over the tailstock is of sufficient importance to prohibit this method, the table below is given. In this table, the figures in the second col- umn represent the length along the center line of the tap, in ten-thousandths of an inch, for 1 inch measured along the surface of the tap. TABLE OF ERRORS IN TAPER TAPS. Taper. Length Along Axis. Taper. Length Along Axis. | inch per foot. .9999 l£ inches per foot. .9980 £ inch per foot. .9999 If inches per foot. .9973 T 5 g inch per foot. .9999 2 inches per foot. .9965 f inch per foot. .9998 2£ inches per foot. .9946 -fa inch per foot. .9998 8 inches per foot. .9922 inch per foot. .9997 3| inches per foot. .9895 £ inch per foot. .9995 4 inches per foot. .9863 1 inch per foot. .9991 Note. — The word taper is defined in a different manner by different persons; it will here be taken to mean the difference in diameters per foot of length measured along the axis. This definition is in accord- ance with the most general practice. HOBS. 41. Design and Use. — Taps made for cutting the threads in solid and split dies for screw cutting are called hobs. They differ from ordinary taps chiefly in having more flutes; they are usually given from six to eight flutes. When hobs are to be used for solid dies, they must, of course, be of exact diameter. When used for dies adjustable through quite a range, it is advisable to make them larger. Their diameter may then be twice the depth of thread plus the diameter of bolt. It is recommended that the diameter of the hob should not be made larger than just given. Cut- ting an adjustable die with a hob larger than the screw to be cut with it, will have the effect of giving relief to the TOOLMAKING. 29 § 25 threads of the die back of the cutting edges. In conse- quence of this relief, which in ordinary dies cannot readily be given in any other manner, the die will cut much more easily and cleanly. Hobs are advantageously used in con- nection with a leading tap slightly smaller in diameter. This relieves the hob of the most severe duty, and hence a smoother and truer hole will be tapped by it. When making a hob, it must always be remembered that the perfection of the screw made by the die the hob is in- tended for, depends primarily on the hob; and hence this should be made as perfect as conditions permit. ' Any poor workmanship in the thread of the hob will be duplicated in the die, and usually in a more emphatic manner. A poorly cut die will naturally produce a poor screw thread. When tapping a die with a hob, plenty of oil should be used and care should be taken to see that the flutes do not be- come clogged with chips. Some persons do not relieve the hobs that are intended for straight dies, but taper hobs should always be relieved, for the same reason as taper taps. The term “ hob ” is also applied to the milling cutter used for cutting the teeth of worm-wheels to correct shape. This style of hob will be treated of under the heading of “ Mill- ing Cutters.” 42 . Chaser Hobs. — Hobs for making chasers are made straight. They need not be longer than three times the width of the widest chaser that is to be cut by them. Nu- merous flutes are required, and, preferably, should be spaced a little unevenly. As they are intended to be used between the centers of a hand lathe, they should be provided with liberal-sized centers. A shank long enough to take a dog should be provided. For threads from 40 per inch to 8 per inch, a good size is 1^ inches diameter, with the thread about 2 inches long, and the shank 1|- inches long. About twenty flutes may be cut with a 60-degree cutter, making the cut- ting edges radial. Since the excellence of the chaser de- pends on the hob, the thread should be cut as perfect and smooth as possible. After hardening at a low heat, draw TOOLMAKING. 30 § 25 the hob uniformly to a full straw color. When using it, adjust the rest to such a height that the upper side of the chaser will be about y 1 ^ inch above the height of the cen- ter. The hob will then cut the teeth into the chaser with sufficient relief to make it cut free. The chaser itself may be drawn to a pale straw color. ADJUSTABLE TAPS. 43. Design. — Where holes have to be tapped to a very exact size, as is often required in work done in large quan- tities under the interchangeable system, it is rather hard to produce solid taps that will tap the holes within the limit of variation permissible. While it is quite feasible to make them accurate within .0001 inch when soft, the change in diameter when hardening them will often go beyond the per- missible limit of variation, especially when the tap is larger than inch. It is of very little use to try to make allow- ance for this change of diameter, since nobody can tell whether the steel will contract, expand, or remain the same diameter in hardening. For these reasons, adjustable taps have been designed. Some of these will cut a full thread in one passage through the work ; others again can be used only for finishing a hole that has previously been tapped by a leading tap of slightly smaller diameter. 44. Examples of Adjustable Taps. — Adjustable taps may be made as shown in Fig. 11. There are four a a a Fig. 11. tool-steel blades a, a inserted in dovetail slots; the bottom of the slots makes an angle with the center line, or axis, of the tap. The blades are confined axially by two nuts, one TOOLMAKING. 31 § 25 at each end. By varying the position of these nuts, the tap may be expanded or contracted a slight amount. Taps of this kind cannot ordinarily be made for sizes smaller than 1 inch, since the shank will become too small if made smaller. 45- In making such a tap, the body should be turned first. In the smaller sizes the body may be made of tool steel, and for large taps, of machinery steel. The slots can generally be cut faster and better in the shaper than in the milling machine. Cut a fine thread for the two nuts in the lathe ; the diameter of the tap body, at the points where the nuts are located, is sometimes made small enough to clear the bottom of the slots. Thread and face each one of the two nuts at the same chucking, in order that the faces will be true with the thread, and make the nuts a good snug fit. The blades may now be milled or planed out of well-annealed tool steel and then carefully fitted to the slots. In order to make them of equal length, drive them into the slots and face their ends in the lathe. They should fit tightly enough not to slip during facing. Put the nuts on and screw the nut at the shank end up until it is within a short distance of the shoulder. Then tighten up the front end nut. Now turn the blades to correct size (approximately) ; cut the thread on the blades, using the lathe, and chamfer the front end with a square-nosed tool. Remove the nuts, mark the blades and slots with corresponding marks, drive tlie blades out, re- lieve the chamfered parts, and slightly back off the threads with a fine three-square file. The threads require backing off on account of the springing of the tap during thread cutting causing the back edge of each blade to be slightly higher than the front or cutting edge. After relieving, harden and temper the blades carefully, drawing them to a straw color. If the blades should spring very much, they must be straightened before inserting them again. Assu- ming the body to be of machinery steel, it may be well to case- harden the square at the end. An adjustable tap is usually set to correct size by actual trial. C. S. III.— 30 32 TOOLMAKING. 25 46 . A very simple form of adjustable tap is shown in Fig. 12. This method of construction is covered by a Fig. 12. patent; the J. M. Carpenter Tap and Die Company, Pawtucket, Rhode Island, are the exclusive manufacturers of these taps. As shown in the figure, the tap is split. Taper-headed screws b allow it to be expanded, and binding screws a , a serve to lock the two halves together. 47 . Another design of adjustable tap suitable for holes that pass clear through the work, or do not need to be tapped close to the bottom, is shown in Fig. 13. The Fig. 13. tap is split longitudinally; the two halves can be forced apart by a centrally located screw a having a tapering head. After setting it, the two halves of the tap are locked to- gether by setting up the nut b , which has a beveled recess that engages the conical projection at the front end of the tap. While locking the nut, the central screw must be pre- vented from turning by inserting a screwdriver into its slot and holding it. The nut may be made hexagonal in form at its front part, as shown, or have radial holes drilled in its circumference. In the latter case, a spanner must be made for it. In making such a tap, it is advisable to cut the thread and flute the tap before splitting it. It may be slot- ted slightly beyond its threaded part, the slot terminating in &hole drilled perpendicular to the axis, §25 TOOLMAKING. 33 MULTIPLE-THREADED TAPS. 48. Occasionally, multiple-threaded taps are re- quired. If these are intended to cut a full thread in one operation, the lands back of the cutting edges must be well relieved to allow the tap to cut freely; if this is not done, the force required for tapping may be sufficient to break the tap. Generally speaking, it is better to chase the threads in the hole to be tapped and use the tap for finishing only. SQUARE-THREADED TAPS. 49. Square-threaded taps may be fluted in the same manner as V-threaded taps. If intended to cut a full thread in one operation, the lands must be well backed off, other- wise the amount of force required for tapping will be exces- sive. When used merely for sizing holes in which the thread has been roughed out, very little backing off is necessary. LEFT-HANDED TAPS. 50. If a left-handed tap is . required, it may be designed and made in the same manner as a right-handed tap, except that the flutes are to be cut in a way the reverse of that used for a right-handed tap. All remarks previously made regarding the number of flutes and the backing off of the lands apply to left-handed taps as well. It is a good plan to stamp left-handed taps with a large L on the shank, to call attention to the fact of their being left-handed. This is to be done not on account of machinists not being able to detect the difference, but rather on account of unskilled helpers failing to distinguish between right-handed and left- handed taps COLLAPSING TAPS. 51. Purpose of Collapsing; Taps. — Taps so con- structed that the blades forming the cutting edges can be moved radially at will toward or from the center, are called collapsing taps. They are used quite largely for work 34 TOOLMAKING. §25 done in the turret lathe, when the hole to be tapped exceeds inches in diameter. Their chief advantage is that they need not be turned back to withdraw them from the tapped hole; the blades are drawn in enough toward the center to clear the thread, and the tap can then be withdrawn by an axial motion. As a matter of course, nearly all the time required to wind an ordinary tap back is saved. Since a collapsing tap is quite an expensive tool, its use is limited by commercial considerations to work done in large quantities. 52. Design of a Collapsing Tap. — A simple collaps- ing tap designed for tapping a taper hole in brass castings is shown in Fig. 14. For this reason, the cutting edges of the blades are advanced in the direc- tion of cutting ; that is, theyare given negative rake. The shank A is fitted to the turret. The end of the shank is bored out cylindrical to receive the tap body £, in which four dovetail grooves are cut, to which the blades or chasers are fitted. A circular groove d\ having a square cross- section [see Fig. 14 (r)] , receives the lugs d , d and confines the chasers longitudi- nally. The body of the tap is prevented from rotating, by a pin C passing through it. This pin, while the tap is cutting, rests against the lower ends of the helical slots F and F'. When the hole has been tapped to the desired depth, the pin C is turned in the direction of the arrow. The pin then follows the helical slots and the body B Fig. 14. § 25 TOOLMAKING. 35 is drawn into the shank; since the dovetail grooves in which the chasers work are at an inclination to the axis, the chasers are drawn together and the tap' can be withdrawn. To get it ready for work again, the pin C is turned back. A tap of the design shown in Fig. 14 may be used in a chuck in the lathQ. When used for a turret lathe, it is almost always necessary that the hole is to be tapped to the same depth in every piece operated upon. If this is the case, it should be used in connection with an adjustable dis- connecting tap holder. 53. Making the Tap Shank. — When making a col- lapsing tap of the kind shown, the only thing that may prove difficult will be the two helical slots. They are rather difficult to produce by hand, but if care is taken to use a helix that can be cut in the milling machine by an end mill, the slots are easily cut. If no milling machine adapted for spiral work is available, the slots may be cut in the lathe as follows: Gear the lathe to cut a thread having a pitch equal to one turn of the helix adopted. Then, with a scriber fastened in the tool post and the tap shank between the centers and forced to turn with the spindle, scribe a fine line on the shank in the proper place to represent the center line of the slot. Turn the work 180° between the centers without moving the headstock spindle; scribe a line again. Now throw the leadscrew out of gear and at the beginning and end of the slots scribe fine circles around the tap body. At the intersection of these circles with the helical lines, make fine center-punch marks, and divide along these lines into a sufficient number of divisions to drill out most of the stock. Center punch well, and drill out the stock, remov- ing most of the stock between the holes with a keen-edged cape chisel. The slots may now be finished by a suitable planing tool to be held in the tool post of the lathe. The tap body is placed between the centers, and the dog prop- erly adjusted to have the tool match the slot. A wooden wedge is then driven in between the tail of the dog and the side of the slot in the face plate that drives it; rotating the 36 TOOLMAKING. §25 leadscrew by hand will then cause the tool to travel along the tap body, and, if fed in by means of the cross feed-screw, it will cut out the slot. The planing tool is preferably made so as to plane both sides of the slot at once. The opposite slot may be finished in the same manner. 54. Collapsing taps may be made in a variety of de- signs to suit different kinds of work. Thus, where bottom- ing holes are to be tapped, the blades may be arranged to collapse by means of a centrally located movable stop within the tap body coming in contact with the bottom of the hole; the stop when moving back then draws the blades inward. For some work it may be advantageous to design a col- lapsing tap on the lines of the ordinary scroll chuck, or the geared three-jawed or four-jawed automatic chuck. These designs will readily suggest others. RELEASING TAP HOLDERS. 55. Purpose and Design. — In screw-machine and turret-lathe work, when holes are to be tapped to a uniform depth, it is advisable to use a tap holder that will automatic- ally release the tap from the holder as soon as the hole has been tapped to the proper depth. Such a holder will allow fig. 15. of rapid tapping, and, when properly adjusted, obviates breakage of taps through striking the bottom of the hole. A very common and highly efficient releasing tap holder is that shown in Fig. 15, which is especially adapted to screw- machine and turret-lathe work. It consists essentially of TOOLMAKING. 37 §25 two pieces. The sleeve a has a shank that fits one of the tool holes of the turret. The tap holder proper is free to slide longitudinally within the sleeve a certain amount; when the clutch pinsc and d are disengaged, it is free to rotate within the sleeve. The end of the tap-holder shank carries the backing-out pin e, which is so located that when the clutch pins c and d will just clear each other, it will be from ■§■ to J inch away from the helically formed end of a. The end b of the tap holder may be made in a variety of ways to suit the purpose. The simplest way is to make it as shown; the tap shank fits the hole and is held from turning by the set- screw. If thus made, its use is obviously limited to taps having the same shank diameter. To make it adapted to all sizes of taps, the end b may be a universal chuck; the holder then becomes a universal releasing tap holder. 56. Operation. — The operation is as follows: The shank a being fastened in the turret and the stop-pin c but- ting against the flange of a and the stop-pin d preventing b from turning, the slide of the turret is advanced and the tap then engages the revolving work. As soon as the tur- ret slide comes against its stop, the tap, by reason of being entered in the work, is drawn forwards until c and d are dis- engaged, when it is free to revolve. This stops further tap- ping. The spindle of the machine is now reversed, which causes the work, and hence the tap, to turn in an opposite direction. The turret slide is then withdrawn to the rear; the backing pin e during the backward motion is guided by the helical end into the recess of the sleeve shank, and any further revolution of the tap is thus arrested. In conse- quence of this, the tap is backed out by the revolving work. 57. Forming the Helical End. — When making a releasing tap holder, it is well to remember that the helix at the end of the sleeve shank must be right-handed for a right- hand tap and left-handed for a left-hand tap. The pitch of the helix may be about one and one-half times the diameter of the stop-pin. The helix is most readily produced in the lathe, gearingthe lathe to give the proper pitch and using a 38 TOOLMAKING. §25 square-nosed tool for cutting the helix. A line may first be scribed to mark the position of the helix and then most of the stock removed by drilling and chipping, leaving to the lathe tool the finishing only. 58. Proportions. — The diameter of the sleeve shank is fixed by the size of the holes in the turret for which it is intended, as is also its length. The shank of the tap holder may be about five-eighths the diameter of the sleeve shank. The three stop-pins may have a diameter equal to about’ one-third the diameter of the tap-holder shank. For small work, it is usually advisable to make the whole device of tool steel. NUMBER OF TAPS IN SPECIAL CASES. 59. Taps for Square Threads. — In tapping square threads several taps are sometimes used in a set, especially where the hole is small and the pitch of the thread coarse. When the hole is long the flutes in the ordinary tap are too small to carry off the cuttings, hence more taps are used, taking smaller cuts and having larger flutes. Sometimes as many as six taps are used in a set and if they run with, plenty of oil they will clear themselves readily, cut more rapidly, and last longer without dulling. The fir$t tap is sometimes a V-thread tap with the correct pitch, and the other taps take out the balance of the stock, gradually approaching the square shape until the correct size and form is reached. 60. Square-Tliread Taps in Brass. — Where square- thread taps do not readily clear themselves of chips, it has been found advantageous to remove some of the teeth, or lands, of the tap. Sometimes every other tooth is removed, and even more than half may be removed with good effect. This is especially true when cutting square threads in brass. The reason for this is that when there is little difference §25 TOOLMAKING. 39 in the height of the cutting edges, they sometimes rub over the surface of the brass with a glazing effect, making the cutting more difficult. Removing part of the teeth reduces the cutting surface and permits the others to do more effective service. TOOLMAKING. (PART a.> CUTTING TOOLS AND APPLIANCES. DIES FOR THREAD CUTTING. CUTTING EDGES. 1. Number of Cutting Edges. — It is now the uni- versal practice to give dies four cutting edges for all sizes up to and including 4 inches. Beyond that size, prac- tice varies. Some toolmakers advocate five cutting edges for dies above 4 inches; others prefer four cutting edges for all sizes. There is no particular objection to making large dies with five or more cutting edges beyond the fact that it slightly increases the first cost. It is generally admitted that the only instance in which it is absolutely necessary to give more than four cutting edges to a thread-cutting die is that in which part of the circum- ference of the work to be threaded is cut away. More cut- ting edges are then needed in order to steady the die and thus prevent crowding into the work on the side where the metal is cut away. The number of cutting edges may then be as given in the following table: §26 For notice of copyright, see page immediately following the title page. 2 TOOLMAKING. §26 TABLE OF CUTTING EDGES FOR SCREW-CUTTING DIES. Circumference Cut Away. Cutting Edges. none 4 is 5 tV 6 i 7 8 When more than one-sixth of the circumference is cut away, dies usually will fail to cut a satisfactory thread. Attention is called to the fact that it is customary to denote the size of a die by the diameter of the screw it will cut; thus, a die that will cut a l|--inch screw is called a 1^-inch die, irrespective of the outside diameter of the die itself. 2. Rake of Cutting Edges. — For general work and for dies that are to be used indiscriminately for iron, steel, brass and other copper alloys, it is advisable to make the cutting edges radial. For dies that are to be used entirely for brass castings, the cutting edge may recede some from a radial line, thus giving a slight negative rake. NON- AD JUST ABLE DIES. 3. Making a Solid Die. — Owing to the difficulty of sharpening the cutting edges, and also owing to the diffi- culty of making them to an accurate size, solid dies, i. e., dies made out of one piece, are used comparatively little nowadays in machine-shop work. Being inexpensive in comparison with adjustable dies, they may sometimes be used with advantage for special work when only compara- tively few threads are to be cut and no great accuracy as to size is required. When only one die of a special size or pitch of thread is to be made, it will scarcely pay to make a hob for cutting the §26 TOOLMAKING. 3 thread in it. The usual way, which is also the cheapest, is to cut the thread in the lathe, provided of course the die is large enough to permit this to be done. Since it is very difficult to measure an internal thread, a male thread gauge of the required diameter and pitch of thread is first made, unless a tap is in existence that will serve as a male gauge. The thread having been cut, the beginning of the thread in the die is chamfered while still in the chuck. Cutting edges and clearance spaces are then produced by drilling and filing, and, after relieving the chamfered threads, the die is ready for hardening. The die may be made as shown in Fig. 1. The die illus- trated is round, being intended for use in the die holder of a screw machine. It may be made of any other form, how- ever. The outside diameter of a solid die is usually fixed by the diameter of the holder that it is intended for, but should not be made less than 2.5 times the diameter of the screw it is to cut. The depth a of the die may be 1.25 times the diameter of the screw, and slightly more for very small screws, such as machine screws. If four cutting edges are used, the clearance holes, as b , b } should be spaced equidis- tant and with their centers on a circle having a diameter equal to the diameter of the screw to be cut. The diame- ter c of the clearance holes is usually made one-half the size 4 TOOLMAKING. §26 of the die, and the top d of the lands about one-twentieth the circumference of the circle tangent to the lands. The cutting end of the die is to be chamfered out about three to four threads deep, as shown in the cross-section. The cham- fered parts must be relieved in order to give keen cutting edges. 4. When making a solid die, cut the thread first. Then screw in a piece of steel the full length of the die and face it off flush with the faces of the die. The temporary male thread gauge previously mentioned may be used for this purpose to advantage when only one special size die is to be made. Lay out the centers of the clearance holes on the back face of the die and drill through. After drilling the first hole, insert a plug that fits tightly into the clearance hole just drilled, in order to prevent the screw within the die from turning while drilling the other clearance holes. After drilling, remove the screw and finish the back edge of the lands by filing. File the front edge carefully with a fine file to remove the burrs, relieve the chamfered parts, then harden and temper, drawing to a good straw color. 5. When a large number of solid dies of the same size are to be made, it is cheaper to cut the thread by tapping, finishing with a hob of correct size. The chamfering should be done with a suitable taper reamer prior to tapping. The clearance holes may then be drilled in a jig; with a substan- tial jig, if the drilling is carefully done, there will be no need of inserting a screw in the tapped hole. The holes in the jig will steady the drill sufficiently for drilling. For rapid finishing of the clearance spaces, a hardened filing jig will be found of great service. The relieving of the cham- fered cutting edges is usually done by hand. While it can be done by special tools, this will rarely pay except when the number of dies is very large. 6. Inserted-Blade Dies. — When dies are required for screws larger than 2-inch, it is usually advisable to make them with blades inserted in a ring made of cast iron, wrought iron, or machinery steel. There are several §26 TOOLMAKING. 5 benefits gained by tnis construction. In the first place, it obviates all danger of losing the die by cracking while hard- ening; in the second place, it allows the die to be readily sharpened, since the blades are removable ; and, again, after the ring or die body is once made, new blades can be made at a fraction of the cost of a solid die. The first cost of an inserted-blade solid die of small size is probably a little higher than that of a solid die up to 2£ inches in diameter; above this size, the inserted-blade solid die is usually cheaper to construct and will give better satisfaction on account of ease of sharpening and repair. 7. A very solid and simple inserted-blade solid die is shown in Fig. 2. Dovetailed slots, with the sides radial, are ^vvVVWVVVS Fig. 2. planed in a ring of suitable inexpensive material and dove- tailed blades are well fitted to the slots, being made a driving fit therein. The blades are then faced flush with the sides of the holder ; the thread is now cut in the lathe, the beginning of the thread chamfered off for three to four threads, as shown in the partial cross-section, and the blades, after being properly marked, are driven out. They are then relieved on the chamfered part, hardened, tem- pered, and driven home again in their proper places as marked. For dies larger than 2-inch, the following proportions will serve as a guide, where d— diameter of screw ; outside 6 TOOLMAKING. §26 diameter of die body = 2.4 to 2.5 d ; inside diameter of die body =1.3- < 2 ^; length of blade =1.25 d ; width of lands, when four blades are used, as is recommended for general work, about one-sixteenth the circumference of the screw to be cut. When more blades are used, the lands must be made narrower. If the nature of the work demands it, the blades of an inserted-blade die may project somewhat beyond the faces of the die body. They should not project more than the width of the lands, however; otherwise they are liable to break off under the strain of cutting. ADJUSTABLE DIES. 8. There is a great variety of adjustable dies made for general work. Since special sizes of these, for use in the ordinary die stocks, can be obtained of the makers for less than they can generally be made in the tool room, the tool- maker is rarely called on to make them. If such should be the case, there are generally dies at hand that will serve as a guide in making a special die. 9. Spring Die. — In many cases spring dies for screw- machine work are, for various reasons, made in the tool room, although, generally speaking, they may be bought more cheaply from concerns making a specialty of taps and dies. These dies are always used with a clamp col- lar that serves to adjust them. When a spring die is to be made, it is good practice to fit it to one of the clamp collars at hand, thus saving the expense of making a new clamp collar. Provide four cutting edges for gen- eral work, making the lands about one-six- teenth the circumference. Chamfer about three to three and one-half threads and re- lieve to give keen cutting edges. The depth of the thread may be about one and one- quarter times the diameter of the screw to be cut. For the cutting edges, use a 45° milling cutter that will split the die as shown in Fig. 3. Tap the die with a hob the same size as 26 TOOLMAKING. 7 the screw to be cut. After splitting the die, the burrs thrown up on the threads may be removed by running the hob through again. Finish the cutting edges by filing with a fine file, stamp the size and the number of threads on the die, and then harden as far as the end of the thread and temper to a deep straw color. For accurate uniform threads, two dies must be used, one for roughing out and the other for the finishing cut. To do good work, the cutting edges must be kept sharp; dies made as shown in Fig. 3 can readily be sharpened by grind- ing the face of the lands on a suitable emery wheel. lO. Average proportions of spring dies are given in the following table, where all dimensions are given in inches. It is to be understood that the proportions given are in- tended only as a guide, and, hence, may be departed from to some extent to suit special requirements. TABLE OF SPRING-DIE PROPORTIONS. Size of Screw. Outside Diameter. Length. i to ¥ i ito f i if t to \ l 2 ito t li H f to 1 If 2} 1 to li 2 3 li to 1^- H H H to if H 4 If to 2 H When spring dies are to be used for work whose circum- ference is partly cut away, make the number of cutting edges as given in the table of Art. 1. A cutter to suit the increased number of cutting edges will then have to be se- lected for slitting the die. The spring die is probably the cheapest adjustable die for screw-machine and turret-lathe work up to and including 2 inches in diameter, as far as C. 6*. III.-v 8 TOOLMAKING. §26 first cost is concerned. When threads larger in diameter are to be cut, it is usually more economical to use some form of adjustable die with inserted blades. 11. Inserted-Blade Adjustable Die. — One of the simplest designs of an adjustable die with inserted blades is that shown in Fig. 4. The blades are inserted exactly as in the die shown in Fig. 2; the die body is then split, as shown, and an adjusting screw put in. When this die is used in its holder, the setscrews of the holder will lock the die firmly together. Its only drawback is the necessity of removing the die from the holder every time it is desired to adjust it.\ This may be overcome, however, by cutting a hole through the holder in the proper place to allow the adjusting screw to be reached with a screwdriver. For very large dies, two adjusting screws may be provided, locating each near one of the faces. The only thing that may prove difficult to one that has never done this before is the drilling and counterboring of the hole for the adjusting screw. This job may be done in a jig if a large number of dies are to be made; in case of a limited number, it may be done in a lathe or a milling ma- chine, strapping the die body to the top of the slide rest or to the milling-machine platen. Using a two-lipped mill- ing cutter of correct size, the counterbore can, by careful 26 TOOLMAKING. 9 feeding, be cut without much trouble. Drilling is then done while the die body is still strapped down, catching the drill in a chuck. If the die body has been split prior to drilling the hole for the adjusting screw, an iron or wooden shim should be inserted in the slot. 13IE HOLDERS. 12. For screw-machine and turret-lathe work, solid and adjustable dies are inserted in releasing die holders made on the same principle as a releasing tap- holder. The die is held in the holder by three or four pointed setscrews that enter conical depressions, as shown in Fig. 5. These fig. 5. depressions are so located that the tightening up of the set- screws will draw the die against the shoulder of the holder. The length of the die holder naturally depends on the length of the screw to be cut. One or two liberal-sized openings should be cut through the holder back of the die, to provide for free escape of the chips. Practical considerations pro- hibit the use of the holder shown for very long screws. For these a releasing holder may be constructed in a somewhat 10 TOOLMAKING. 26 different manner, retaining the same principle of releasing and clutching for backing the die off. 13 . A design for such a holder is shown in Fig. 6. It consists essentially of two parts, a shank a to fit the turret and a die holder b. The clutching and releasing mechanism is contained in the front part of the device. For releasing, two stop-pins are employed; the one is driven into the holder and the other into the shank, as shown. The for- ward part of the shank is enlarged and grooved to receive the end of the backing pin c, which in the design here illus- trated is firmly screwed into the holder proper. The for- ward side of the cylindrical groove forms a helix that serves to guide the backing pin into its place. The die holder proper is bored to be a good sliding fit on the front end of the shank. In the position shown, the clutch pins are disen- gaged and the holder is free to rotate about the shank. If the turret is now withdrawn while the work just threaded is revolving in a reverse direction, the backing pin c is guided into place, clutches the shank, and the die is unscrewed from the work. The shank has a hole drilled through it to admit the threaded work. §26 TOOLMAKING. 11 In designing such a holder, care should be taken to locate the backing pin and the groove so that the groove will not be uncovered when the backing pin clutches the shank. If the die holder is to be used for a right-hand die, the helical side of the groove must be right-handed, that is, as shown in the illustration. For a left-handed die, it must be left- handed. If desired, the device may be adapted to both right- handed and left-handed threads. To do this, the enlarged end of the shank is made long enough to receive two grooves ; the front side of one is then made a right-handed helix, and the front side of the other a left-handed helix. A hole to receive the* backing pin is drilled and tapped for each groove ; the backing pin may then be changed from one groove to the other. A blank screw should be provided to fill the backing-pin hole not in use. Also provide one or two open- ings for the escape of chips. The helical side of the groove is most conveniently cut in an engine lathe geared to the correct pitch, which may be about one and one-half times the diameter of the backing pin. REAMERS. CLASSIFICATION OF REAMERS. 14. Reamers may, in accordance with their shape, be divided into three general classes. These are straight reamers, taper reamers, and formed reamers. Each of these classes may be divided into three subclasses, in accordance with their construction. These are solid ream- ers, inserted-blade reamers, and adjustable reamers. Reamers are generally intended for the production of round smooth holes of accurate size. In some cases, they are merely intended to enlarge holes without particular reference to the holes being true and straight. Experience has shown that, in order to produce round and smooth holes, reamers must have their cutting edges spaced and formed 12 TOOLMAKING. §26 correctly. It must not be inferred from this statement, however, that there is but one correct way of spacing and forming the cutting edges; the required result may be arrived at in various ways. CHATTERING. 1 5. Chattering, which is a common fault of reamers, is in itself an evidence of incorrect design or construction of the reamer. It is due to several entirely preventable causes, any one of which, when present alone or in combi- nation with one or more of the others, will induce it. Whether a chattering reamer can be cured or not depends on its design and construction. A knowledge of the causes that induce chattering of a reamer will indicate whether it can be cured or not. The causes of chattering are as follows: 1. Equidistant spacing of the cutting edges. 2. Excessive front rake of the cutting edges. 3. Excessive clearance of the lands. If the cutting edges- are spaced equidistant around the circumference, each edge will follow in the track of the others. Experience has shown that this condition is not conducive to the production of a round hole. Excessive front rake will cause the reamer to cut too freely, or “ take a greedy -bite,” as it is called. This precludes the possibility of producing a smooth hole, since smoothness can be attained more readily by a scraping cut. Excessive clearance, or relief, of the lands robs the reamer of the support it should derive from them; consequently, it works unsteadily and with a wobbling motion. SPACING OF CUTTING EDGES. 16. Two different systems of spacing are in general use, either one of which will tend to prevent chattering. One system is shown in Fig. 7. In this, the cutting edges §26 TOOLMAKING. 13 are spaced irregularly and opposite each other. In ularity of the spacing, a supplementary dotted circle has been drawn and divided into equidistant divisions. Since no two edges are opposite each other, the diameter of the reamer cannot be meas- ured by calipering and it can only be brought to size by fitting it to a ring gauge of correct size. This drawback is over- come in the system of spacing shown in Fig. 8. no two edges are diametrically order to show clearly the irreg- Here Fig. 7- the spacing is so arranged that any two opposite cut- ting edges are on the same diameter. Hence, the reamer can be calipered, and, for this reason, the general adoption of this system of spacing is recommended. While Figs. 7 and 8 show a sec- tion of a solid reamer, the methods of spacing shown apply to inserted-blade and adjustable reamers as well. NUMBER OF CUTTING EDGES. 17 . Fluted reamers for lathe and handwork, with the exception of rose reamers and special reamers designed to rapidly remove a relatively large amount of metal, are rarely given less than six cutting edges. For solid reamers, the num- ber of cutting edges may be as given in the following table: 14 TOOLMAKING. §26 TABLE OF CUTTING EDGES FOR REAMERS. Diameter of Reamer. Cutting Edges. i to i G i to 1 8 1 to H 10 li to 2± 12 2J to 3 14 Generally speaking, there is nothing to be gained by giving a larger number of cutting edges than that given in the table. 18. In inserted-blade reamers, the largest number of cutting edges that can be given depends on the thickness of the blades. They are usually made with less cutting edges than solid reamers. It was believed formerly, and the view is still held by many, that a reamer must have an odd number of cutting edges in order to work well. Actual experience with properly formed reamers has demonstrated conclusively that, as far as truth, ease of working, and smoothness are concerned, it does not make the slightest difference whether the number of cutting edges is odd or even. On account of being able to caliper the reamer, an even number of cutting edges is really preferable. Rose reamers may be given from three to seven flutes, according to size. In the small sizes, they may be made without any teeth between the flutes, and, in the large sizes, may have one or two teeth between each flute. FLUTING. 19. A form of flute that is very satisfactory is that shown in Figs. 7 and 8. This form of flute leaves the reamer very strong and, at the same time, by the absence of a sharp corner, reduces the possibility of the reamer cracking in the corner of the flutes in hardening. Another §26 TOOLMAKING. 15 good form of flute is that recommended by Brown & Sharpe, which is shown in Fig. 9. This form gives a greater clearance space than the flute with sides at right angles to each other. Milling-machine cutters for this form of flute may be obtained from the Brown & Sharpe Manufacturing Company. These cutters are to be set so as to give a slight nega- tive rake to the cutting edge. To allow the nega- tive rake to be seen plainly, two dotted diameters have been drawn in Fig. 9. When using this form of flute, the cut- ter must be set to such a depth that the land will be about one-fifth the average distance from one cutting edge to the next. If the flute is cut deeper, the cutting edges become too springy for good work. When flutes of the form shown in Figs. 7 and 8 are used, the lands may be about one-eighth the average distance from one cutting edge to the next. In general, a reamer will work more smoothly if the cutting edge is given a slight negative rake, since it will then take a scraping cut. The amount of negative rake need not exceed that shown in Fig. 9, which is about 5°. If the reamer is to be used entirely for steel, the cutting edges may be radial, like in Figs. 7 and 8. CLEARANCE. 20. In order that the reamer may cut freely, the lands must be relieved back of the cutting edge. This relief can be given either by grinding the reamer with an emery wheel in a suitable fixture, or by oilstoning. The amount of clearance to be given depends on the purpose of the reamer. If it is to be used for roughing out, the clearance should be 16 TOOLMAKING. §26 more than is given to a finishing reamer. It should be least for a finishing reamer that is intended to keep its size for a long time. Fig. 10 shows the appearance of reamer teeth properly relieved for different purposes. In Fig. 10 ( a ), the relief to be given to a roughing reamer is shown. If the lands are thus relieved, the reamer will Fig. io. cut freely, but cannot be expected to make as true a hole or last as long as the reamer having its teeth relieved as shown in Fig. 10 ( b ). This latter form of relief leaves the cutting edge better supported, and, consequently, the reamer will work more smoothly and keep its size longer than with the form first shown. It will not cut as freely, however. Fig. 10 (c) shows the form of clearance to be adopted when it is important to reduce the wear of the reamer to a mini- mum in order to produce a large number of holes of the same size. As shown, the land is backed off on the arc of a circle. The amount of clearance at the back edge is made the same as in Fig. 10 ( b ), but, owing to the circular form of the relief, the cutting edge is supported better. If desired, roughing reamers may be backed off on the arc of a circle; however, this is more expensive than the flat backing off shown. The amount that the back edge of the land should clear cannot be definitely expressed by any simple rule, since it §26 TOOLMAKING. 17 depends on several variable factors. As an aid in deciding what clearance to give, it may be stated that, for a roughing reamer, the angle b , see Fig. 10, may be about 80°. For a finishing reamer, the angle b may be from 85° to 88°, using the smaller angle for brass, which, in general, requires more clearance. HELICAL CUTTING EDGES. 21 . In order to prevent a reamer from drawing into the work, the cutting edges may be cut helically, choosing a left-handed helix for a straight reamer that is to turn right- handed. The helix should be such that the cutting edges will make an angle of about 15° with a plane passing through the axis of the reamer. Right-handed helical cutting edges are of advantage for taper reamers having a very coarse taper, and for formed reamers that differ considerably in their various diameters, as it will assist them to cut. Fin- ishing taper reamers and finishing formed reamers may have their cutting edges left-handed, if made helical. Some tool- makers claim that if thus formed, owing to the shaving cut taken, they will produce a smoother and truer hole than can be obtained otherwise. The advantages of helical cutting edges for straight reamers are somewhat doubtful, at least for general work; many toolmakers believe that the extra expense involved in making them is not justified by the results, claiming that, with reasonable care, just as true and smooth a straight hole can be obtained with a reamer having its cutting edges straight. Helical cutting edges for straight reamers are recommended when holes are to be reamed that are pierced crosswise by openings. All remarks previously made in regard to spacing, number, and clearance of cutting edges apply to helical cutting edges as well. ALLOWANCE FOR GRINDING. 22. Since there is no way of preventing a reamer from warping in hardening, an allowance must be made to allow it to be finished by grinding. The amount to be allowed 18 TOOLMAKING. §26 for grinding depends on the length and diameter of the reamer; it is least for a short and most for a long reamer. For reamers up to f- inch, and not over 6 inches long, ex- clusive of shank, an allowance of .025 inch will usually prove ample, since there is no particular difficulty in straightening the reamer sufficiently to allow it to be trued with this allowance. For every \ inch the reamer is above this size, the allowance may be increased .01 inch, provided the reamer is not over 8 diameters long. If longer, the allowance for grinding should be increased. GRINDING REAMERS. 2 > 3. For grinding reamers, a grinding machine is most convenient, although straight and taper reamers can be ground true by other means if the shop has no grinding machine or grinding fixture for converting a lathe tem- porarily into a grinding machine. The reamer should first be ground to run true, revolving it between the centers. It §26 TOOLMAKING. 19 may be ground, according to its size, to within xgVrr or t ttW inch of the finished size. The clearance is then ground with the emery wheel so set that its periphery will clear the front edge of the tooth succeeding the one being ground. The reamer is kept from rotating by a finger so adjusted that the correct clearance will be ground. The relative position of emery wheel, reamer, and guiding finger is shown in Fig. 11. The guiding finger a is fastened right in front of the wheel to the carriage that carries the emery wheel and travels along with it, thus always supporting the reamer tooth directly at the point where the wheel is cutting. The emery wheel should always rotate in such a direction that in grinding it tends to press the reamer tooth down on the finger, thus preventing rotation of the reamer during grinding. The arrow x shows the correct direction of rotation of the emery wheel. As shown in the figure, the height of the finger is so adjusted that the cutting edge is below the line joining the centers of the reamer and emery wheel. The farther the cutting edge is placed below the center line, the greater the clearance produced by the wheel; conversely, the nearer to the center line, the less the clearance. From this, it is seen that varying amounts of clearance can be obtained with the same wheel and on the same reamer by varying the height of the finger. 24. In grinding the clearance, the metal must be re- moved by a succession of light cuts, going successively around the reamer. It is of the utmost importance that the temper of the cutting edge should be preserved ; a heavy cut taken with a dry emery wheel is almost certain to anneal the cutting edge, thus rendering the reamer worthless. The clearance must not be ground up to the cutting edge; according to the size of the reamer, it may be ground to within from .01 to .02 inch of the edge. The reamer is then brought to a sharp edge and to correct size by oilstoning. For grinding the clearance, as large an emery wheel as the machine will handle should be used, since the larger the 20 TOOLMAKING. §26 wheel, the less concave the clearance will be. A small wheel will grind the clearance so hollow that the cutting edge will be deprived of support. 25. If no grinding machine or fixture is available, a straight or taper reamer may be ground in a lathe to run true. A piece of free-cutting oilstone, preferably of Washita stone, is held in the tool post. The reamer is revolved backwards at a high speed and the oilstone brought up by means of the cross feed-screw until it slightly engages the reamer. The carriage is then rapidly moved back and forth by hand ; if freely lubricated, the oilstone will gradually cut the reamer down until it is round and true. Clearance is given entirely by oilstoning at a right angle to the axis of the reamer. The method here given is naturally very slow and expensive and is to be recommended only as a makeshift. It is doubt- ful whether a reamer can be made as round and true by it as can be done by a grinding machine, or by means of a proper grinding fixture. GROOVING REAMERS. 26. A reamer can be grooved most rapidly in a milling machine with a suitable cutter. As a makeshift, the grooves can be planed in the lathe, shaper, or planer. This is not recommended, however, except when no milling machine is available. Suppose the method of spacing in which any two opposite teeth are on the same diameter has been selected. Then, the grooves are most advantageously cut in pairs; that is, after milling one groove, the one diametrically opposite is cut before passing to the adjoining one. This is recommended on account of the saving in labor accomplished by it. In the method of spacing selected, any two opposite grooves will have the same depth, and any two adjoining grooves will differ in depth. Consequently, by adopting the method of cutting the grooves in pairs, the number of times the cutter must be reset is reduced to one-half of what it would be when cutting one groove after another. §26 TOOLMAKING. 21 27 . The irregularity of spacing is obtained by moving the index pin a different number of holes for each adjoining pair of grooves. The irregularity introduced need not be very large; one that will cause the cutting edge to diverge by 2° to 4° from the angle corresponding to an equal divi- sion will be sufficient. An example will show how the irregularity is introduced. Suppose we wish to cut a reamer with 8 cutting edges, and that the milling machine available requires 40 turns of the index pin for one revolution of the index-head spindle. Then, with the index pin adjusted to the circle having 20 holes, 20 X 40 = 800 holes must be passed over for a complete revolution of the reamer, and 800 -f8 = 100 holes for dividing into eight equal divisions. As a movement of 800 holes causes the work to revolve through 360°, the angle through which it is revolved by a movement of 1 hole is = say -j-°, or .5°. If we wish to introduce an irregularity of 2°, it needs a 2 movement of — = 4 holes. Then, by a judicious selection, we arrange the number of holes to be passed over for each division. For instance, we may use successively 95, 99, 105, and 101 holes for adjoining grooves, and, after cutting each groove, give 20 turns to pass to the opposite one. With this number, the greatest difference between adjoining gooves is that corresponding to 101 — 95 = 6 holes, which is about 6 X i = 3°. If the number of holes selected for successive grooves had been 98, 102, 106, and 94, the greatest difference between adjoining holes would have been that correspond- ing to 106 — 94 = 12 holes; or 12 X y — 6°. In selecting the holes, it must be remembered that the sum of the holes must be equal to one-half the number of holes required for a whole revolution of the reamer. Consequently, the number of holes required for the last groove is equal to the difference between the sum of the preceding ones and the number of holes required for one-half of a revolution of the work. The moves that are to be made successively in order tQ 22 TOOLMAKING. 26 obtain the spacing are as follows for the particular division and spacing selected: Referring to Fig. 12, to cut the first groove, none; to cut the fifth groove, 20 complete turns of the index pin; to cut the fourth groove, 95 holes, or 4 turns and 15 holes; to cut the eighth groove, 20 complete turns; to cut the seventh groove, 99 holes, or 4 turns and 19 holes ; to cut the third groove, 20 complete turns ; to cut the second groove, 103 holes, or 5 turns and 3 holes; and to cut the sixth groove, 20 complete turns. A movement of 101 holes, or 5 turns and 1 hole, will bring the cutter to the fifth groove again, and 20 complete turns to the first groove. When making a solid reamer, it is necessary to go around twice, sinking the cutter in deep enough the first time to distinctly mark the position of the cutting edge. When back to the first groove, the cutter may be sunk deep enough to give the proper width of land, which can be determined readily if the position of the cutting edge of the adjoining groove is known. Then, after cutting grooves 1 and 5, the cutter must be reset to the proper depth for grooves ^ and 8 , 7 and 3 , and, finally, 2 and 6 . If the grooves are helical, the spacing is obtained in just the same manner. 28 . It must not be inferred that it is necessary to use the 20-hole circle for an 8-grooved reamer, or that the num- ber of holes passed over for each division must be just as given in the preceding discussion. The numbers of holes and the 20-hole circle have been arbitrarily selected in order to illustrate the principle involved. TEMPER OF REAMERS. 29 . The cutting edges of a reamer may be tempered to suit the service to be performed. When the reamer is to remove a relatively large amount of metal in one operation, the cutting edges should be soft and tough enough to stand TOOLMAKING. 23 § 26 the strain of cutting; when a reamer is intended for finish- ing and accurate sizing of holes, where it has to remove only a very small amount of metal, it can advantageously be made quite hard. A roughing reamer, after being hardened so that a file will not touch it, may be drawn to a full straw color, while a finishing reamer may be left a pale straw color. If the finishing reamer is intended for very light service, and if it is essential that the wear of the reamer be reduced to its lowest limit in order to make a large number of holes uniform in size, it may even be left as hard as fire and water can make it, provided, of course, that the steel is not heated hot enough to burn it. TAPER REAMERS. 30 . If intended for finishing, taper reamers are made on the same principles that govern the construction of straight reamers. Roughing taper reamers are often made in the same manner, but with right-handed helical cutting edges. If the taper of the reamer is at all large, the rough- ing reamer may be made as shown in Fig. 13. This con- FlG. 13. struction is an extension of the principle on which a counter- bore is based; in fact, each step in conjunction with the adjoining one forms a counterbore. All cutting is done at the forward end of the steps; the cutting edges, as a , a , are formed by backing off with a file. The parts of the cylin- drical surface of each step, which remain after the grooves are cut, are left cylindrical; no clearance is given, as they serve the purpose of guiding the succeeding cutting edges. C. S . 111.-32 24 TOOLMAKING. § 20 The reamer may be given four cutting edges, which may be cut with a milling cutter suitable for a tap of the same size. If the reamer is to be used for brass or cast iron, the flutes may be made straight, as shown in the figure; if it is to be used for roughing wrought iron and steel, the flutes may be helical, using a right-handed helix of such a pitch that it will make an angle of about 15° with a plane passing through the axis. The reamer being intended to turn right-handed, the cutting of right-handed helical flutes has the effect of giving keen cutting edges, which will make the reamer work easily; at the same time, the chips are crowded back toward the shank. When turning up a stepped reamer, it is advisable to neck it down a little with a round-nosed tool at the end of each step. When grinding, the grooves allow the grinding wheel to pass entirely over the surfaces, and, furthermore, they make it easier to sharpen the cutting edges. The cut- ting edges are backed off by filing before hardening; when grinding the steps, the extremity of the cutting edges of each step can be trued at the same time, removing as little metal as possible. They are finally brought to a sharp edge again by careful hand grinding on a beveled emery wheel, or by oilstoning. Stepped reamers may also be made of suitable form to rough out holes that are to be finished with formed reamers. The number of steps that are to be used for a stepped reamer must be decided separately for each particular case, bearing in mind that the greater the number of steps for a given length of reamer, the less work will be left for the finishing reamer. 31 . If a number of taper reamers of the same size and taper are required, and especially if they are constantly in use and must frequently be reground or replaced, a gauge to which they can be fitted becomes an absolute necessity. The gauge may be a hole of proper size and taper in a cylin- drical piece of tool steel that has been hardened and ground. With careful use, such a gauge will last practically a lifetime. 26 TOOLMAKING. 25 ENLARGING WORN SOLID REAMERS. 32. In spite of the most careful use, reamers will wear, and hence will ream holes smaller than the standard size for which they were made. The question of when a reamer has worn enough to become unserviceable must be decided on its own merits in each particular case ; it is utterly impos- sible to lay down any rule for it. When a finishing reamer has worn down too much, it may either be converted into a roughing reamer, or be restored to its former size by, anneal- ing it and then upsetting it sufficiently with a round-nosed calking tool to allow it to be reground to its former size after hardening. To upset it, the reamer may be held between lead jaws in a vise; the calking tool is then applied to the face of the cutting edges, a little below the edge. When driven into the face with a hammer, it forces the edge outwards, thus making the reamer larger in diameter. This operation of enlarging a worn reamer can rarely be done more than once. SHELL REAMERS. 33. Shell reamers may be given the same number of teeth, and have their cutting edges formed in the same man- ner, as any solid reamer. In making a shell reamer, it is well to make the hole slightly smaller and then grind it to correct size after hardening and tempering. The hardening process is likely to change the diameter of the hole, and is sure to throw it out of round ; hence, in order that the reamer may fit its arbor well, the hole must be ground. The cutting edges may then be ground while the reamer is mounted on its arbor. If the reamer is worn below size, it may often be restored by the means described in Art. 32 ; however, since it is not possible to tell whether the hole will enlarge or become smaller, there is no certainty about whether it can be used on the same arbor afterwards. If the hole is made tapering, it can usually be done; if the hole is straight, this is rather uncertain. 26 TOOLMAKING. §26 ROSE REAMERS. 34. As rose reamers cut on the end only, the grooves with which they are to be provided along their cylindrical surface need not be of the same shape as those of other reamers. A semicircular milling cutter having a width equal to about one-quarter the diameter of the rose reamer will cut an excellent groove, the depth of which may be about two-thirds the width of the cutter. After hardening and tempering, grind and leave the cylindrical part truly circular. True up the extreme cutting edges at the same time and bring to a sharp cutting edge again by careful grinding on a beveled grinding wheel, or by oilstoning. 35. Rose reamers for small work can be made advan- tageously of drill rod, which can be obtained very closely agreeing with the diameter corresponding to its nominal size. Commercial drill rod in sizes up to No. 1, Brown & Sharpe drill gauge,will rarely vary more than T qVo' inch from its true size and be surprisingly straight. Such small rose reamers are often made without flutes, and answer quite well where extreme accuracy is not required. Furthermore, they are quite cheaply made in a speed lathe and, since they are hardened only at the very cutting end, need no grinding for ordinary work. When making small reamers from drill rod, it is advisable to neck them down back of the cutting edge, as shown in Fig. 14; the diameter at the neck may be from yoVo t° tf6t inch smaller than the rod. It has been Fig. 14. observed when hardening drill rod at the end, that it will often swell, that is, become slightly larger in diameter, directly back of the hardening. By necking down the rose reamer 'where the swelling is likely to occur, any danger of having the reamer bind in the hole is obviated. §26 TOOLMAKING. 27 Rose reamers made of drill rod up to and including No. 1 gauge size may be given three cutting edges. After bevel- ing the end of the reamer in the lathe, the flutes may be filed in with a three-square file, preferably filing them as shown in the illustration, which has purposely been enlarged in order to show the cutting edges clearly. If thus made, the reamer, while cutting, will tend to push the chips ahead ; this feature contributes to the smoothness of the hole reamed by it, since there is little danger then of the flutes becoming clogged. After giving clearance to the cutting edges, harden at the very end and temper. A very smooth hole can be obtained if the outer corner of each cutting edge is slightly rounded over with an oilstone. CHUCKING REAMERS FOR ROUGHING. 36. While rose reamers are commonly used in screw machines, chucking machines, and^ lathes for roughing out cored holes, they are really better adapted to finish reaming. Other forms of reamers are better adapted to roughing out, as they will cut much faster and be more economical in maintenance. One of the best reamers for roughing out cored holes in chucking work is a reamer that may be called a multiple-lipped twist drill, made with three or four cutting edges. They are usually made as shell reamers in the larger sizes, and as solid reamers in the smaller sizes. The flutes are cut on a right-handed helix of such pitch as to give the cutting edges an angle of about 15° with a plane passing through the axis. An end view of a four-lipped twist drill is shown in Fig. 15. Milling cutters suitable for making this form of groove can be obtained of the Brown & Sharpe Manufacturing Company, Providence, Rhode Island, on regular order for 28 TOOLMAKING. § 26 sizes up to 3 inches. These drills are sharpened, like twist drills, by grinding on the ends. They are made like rose reamers with no relief given to the lands between the grooves, the lands serving to guide the reamer straight. The helical grooves give keen cutting edges and insure that the reamer clears itself of chips. If made as a shell reamer, the hole must be ground to size after hardening and temper- ing. The outside may then be ground to size, with a taper of about .001 inch to the inch, being smallest at the back end, to prevent roughing up or binding in the hole, while the reamer is mounted on its own arbor. As reamers of this kind are intended for roughing out, it is unnecessary to grind them to correct size within a fractional part of a thousandth of an inch. This applies to other roughing reamers as well. For a four-lipped twist drill, the width of the lands may be about one-tenth the diameter of the drill. The hole, if the reamer is made as a shell reamer, should in general not be larger than one-half the outside diameter. The grooves may be spaced slightly irregular, preferably so that opposite cutting edges are on the same diameter. For small work, three grooves will work fairly satisfactorily. ADJUSTABLE REAMERS. 37. Reamers are made adjustable within narrow limits for two different purposes. In the first place, reamers are made adjustable for the purpose of readily taking up the wear and allowing several sharpenings without losing the standard size. Such reamers are purposely so made that the size to which they are set cannot be varied without machine work, the idea being to keep the user from tamper- ing with the size. On the other hand, reamers may be made adjustable for the purpose of allowing the diameter of the hole reamed by them to be slightly varied either way from the standard size. They are then made to be adjusted by the user, while the former is adjusted by the toolmaker. To distinguish between the two designs, many toolmakers con- fine the term adjustable reamer to reamers that cannot be TOOLMAKING. 29 §26 adjusted without machine work, and call a reamer intended for varying the diameter of the hole an expanding reamer. 38. There is an infinite number of designs possible for making a reamer adjustable. Some of these are shown; these designs are not offered as finality, but as suggestions. In general, the smaller sizes of adjustable and expanding reamers can be bought of the manufacturers more cheaply than they can be made, and it is only in the larger sizes or in special reamers that there is any economy in making them in the tool room. 39. The design of reamer shown in Fig. 16 is an adjust- able reamer. It consists of a body containing a number of dovetailed grooves cut at an inclination to the axis. Blades that form the cutting edges are carefully fitted to these slots. These blades butt against the shoulder of the collar a at the back end and are firmly held against it by the lock- nut b. In order to show the blades clearly, the locknut has Fig. 16. been omitted in the end view. When the reamer has worn sufficiently below size to make it unserviceable, the nut b is loosened, the blades are partially driven out, and the shoulder of the collar a is faced off sufficiently to make the reamer slightly over size when the blades are driven home again. The blades are then reground and stoned to- standard size. The design shown can readily be converted into an expand- ing reamer by placing a nut in the place occupied by the collar a. By varying the position of the two locknuts, the blades can then be expanded or contracted slightly. In 30 TOOLMAKING. §26 designing such a reamer, it is-well to bear in mind that the range of expansion for a given longitudinal movement can be increased by making the inclination of the slots with the axis greater. The slots are usually planed in on the planer or shaper. This, in general, is cheaper than milling them. 40 . The design shown in Fig. 16 is suitable for holes that pass clear through the work. If the hole is blind, how- ever, it cannot be reamed to the bottom, since the locknut projects beyond the end of the blades. The design shown in Fig. 17 may then be adopted. In this, the slots are Fig. 17. inclined the opposite way from that shown in Fig. 16. Instead of a locknut, a flat-headed screw is used at the front end, which bears against a shoulder on the under side of the blades. By means of this screw and the locknut at the back, the blades may be forced outwards or drawn inwards. The design illustrated is for an expanding reamer; it may readily be used for an adjustable reamer by making the locknut at the back end screw against a shoulder. In that case, to adjust it, the shoulder is turned down; the back nut is then screwed tight against it and the front screw hove up in order to lock the blades. 43 . An inserted-blade expanding reamer of somewhat different construction is shown in Fig. 18. In this design, the blades are flat and consequently easily fitted. The 31 § 26 TOOLMAKING. Section on//ne A B. Fig. 18. blades are beveled at the front and back; the slots that receive the blades are also beveled at the back end. A central tapered pin bears against the bottom of the blades; by screwing the pin in or out and screwing up the locknut, the blades are forced outwards or drawn inwards. The blades, after harden- ing and tempering, require to be ground flat and parallel on the sides; they must be a good fit in the slots. The inner face of the blades, which bears against the taper pin, should also be ground straight on a surface grinder. The taper pin may be hardened and drawn to a purple color; it should then be ground true. After assembling the reamer, adjust the pin and locknut so as to be midway between its two extreme positions and then grind the outside to standard size. Relieve and taper off the ends as in any other reamer. The locknut may preferably be hard- ened, but the body of the reamer should be left soft. The body should be made of tool steel in the smaller sizes, i. e., for sizes below 1^ inches. Above this size, it may be made of machinery steel. The design shown in Fig. 18 is suitable for reamers from f inch up. 42. The most common forms of expanding reamers are shown in Fig. 19. In both designs, the ream- er is made at first exactly as if it were a solid reamer; an axial hole is 32 TOOLMAKING. §26 then drilled and tapped for the adjusting screw, and, finally, the reamer is split. Referring to Fig. 19 (tf), the reamer is split at the end. Screwing the taper-headed screw inwards (b) Fig. 19. expands the reamer; it is then locked by the locknut shown. This reamer becomes large at the end. In the design shown in Fig. 19 ($), the end is left solid, but the reamer is split by sinking in a narrow milling cutter right back of the end. The slots may commence at a dis- tance from the end. equal to about one and one-half times the diameter of the reamer. The length of the slots should be about four times the diameter of the reamer. The num- ber of parts into which the reamer is split varies with the diameter. Reamers up to -J inch may be split into two parts; up to § inch, into three parts; and above that size, into four parts. Split expanding reamers are the cheapest expanding ream- ers to construct ; they are open to the objection, however, that expanding does not change their diameter uniformly throughout their length. Whether this objection is serious enough to prohibit their employment for a particular case must be decided upon the merits of the case. The diameter of split expanding reamers depends on the service expected of them. If they are made expanding simply §26 TOOLMAKING. 33 in order to be able to ream holes to a standard size, they should originally be ground and stoned to the standard diameter. If they are intended to ream holes at will slightly above or below standard size, they must be made slightly under the Standard size. FORMED REAMERS. 43 . When holes that are neither straight nor conical (tapering) are to be finished by reaming, so-called formed reamers must be used. Some shapes of formed reamers can be readily ground in the ordinary grinding machine; others, again, require special apparatus for their production. Formed reamers in general are avoided as much as possible, as they are very expensive in first cost and exceedingly diffi- cult to duplicate if a great degree of accuracy is required. There are some jobs, however, that simply cannot be done without them; in that case, the toolmaker must use his ingenuity as to the best way of grinding them to correct size and shape. FOUR-SQUARE REAMERS. 44 . If a long hole is to be finished very true and very smooth, as, for instance, the bore of a rifle barrel, a type of reamer differing entirely from any shown heretofore must be used. This type, which is shown in Fig. 20, is very little known outside of armories, where it is used practically to the exclusion of all other reamers for the purpose of finish- reaming the bore of gun barrels. It is well adapted to similar machine-shop work. The reamer is made of square tool steel. The four sides are hollowed out, as shown in the end view. If the reamer is large, this may be done in the milling machine, shaper, or planer; for small reamers, it may be done by filing. The reamer is then hardened and tempered and ground on the surface grinder, grinding the corners only, until it is per- fectly straight and parallel. Its diameter across corners is 34 TOOLMAKING. 26 made 10 0 6 inch smaller than the diameter of the hole to be reamed. It is then stoned carefully to give very smooth edges, using the finest grade of Arkansas oil- stone. The extreme ends are slightly tapered off by stoning. In use, a slip of hard wood, as b , which extends the whole length of the reamer, is inserted between one side of the reamer and the walls of the hole. This causes the edges a , a to cut. After passing through the hole, a strip of tissue paper is placed between the reamer and the slip of wood; this causes the reamer to take another cut. This is repeated until the hole is the cor- rect size. Copious lubrication is essen- tial to good work. The slip of hard wood may be confined longitudinally by two pins, as shown. A reamer of this kind is suited only for removing minute amounts of metal. But, on the other hand, it will produce a degree of finish that cannot be excelled by any other kind of reamer. It requires pulling through the hole in order to work best. A four-square reamer may be made with- out hollowing out the sides; it is then, however, more difficult to sharpen when worn. The length of a four-square ream- er may be about eight times its diam- eter. fig. 20 . FRONT CHAMFER. 45. Straight reamers intended to cut at their ends only, like rose reamers and chucking reamers, are to be made with a very slight taper for clearance. 26 TOOLMAKING. 35 This taper is so slight that the part back of the cutting edges still serves as a guide. Straight reamers that have their cutting edges formed on their circumference require the front end to be slightly chamfered off in order that they may enter the hole easily. COUNTERBORES. 46. The design of a counterbore depends on several conditions, which are: the nature of the metal it is to be used for, the range in the size of holes to be counterbored, the number of holes to be counterbored, and the distribution of metal around the hole. SOL-ID COUNTERBORE. 47. When, a counterbore is to be used for a relatively small number of holes and is to be thrown away after serving its purpose, it is advisable to adopt a cheap construction in order to reduce first cost to the lowest limit. Probably the cheapest counterbore that can be made is the two-lipped flat counterbore with a solid teat, which is shown in Fig. 21. This can be forged very near to shape, and needs but little machine work and filing to make it serviceable. After forging, center at both ends; turn the shank to the required size; then reverse and turn up the teat, finishing it with a fine file. Turn the counterbore to correct size and 36 TOOLMAKING. §26 face the cutting edges. Finish by filing the sides smooth and give clearance to the cutting edges. If the counterbore is to be used for wrought iron or steel, a keen cutting edge may be given by filing as shown at a in dotted lines. For cast iron and brass, it is better to leave the cutting edges without any front rake. A slight relief may be given to the faces b , b to prevent them from binding in case the counter- sinking is to be carried to an appreciable depth. If the counterbore is intended only for squaring up the face around a hole, no relief need be given to b } b. Only the cutting edges need be hardened; they may -be drawn to a straw color. The process of hardening leaves the teat hard ; some toolmakers draw the end of the teat to a blue color by inserting it into red-hot lead for the purpose of preventing i's breaking off. Since the teat is most liable to break off close to the cutting edges, however, and since it cannot be drawn to a spring temper clear up to the edges without par- tially softening them, many toolmakers believe that it is a waste of time to draw the teat to a higher color than the cutting edges. 48. When a hole is drilled close to a projection, and when it is required that the counterbore should cut part of the projection away, it is better to use a counterbore with four cutting edges. This may be turned down from bar tool steel and have its cutting edges formed by cutting grooves with a 60° cutter in the milling machine. The grooves may be cut on a right-handed helix, making an angle of about 15° with a plane passing through the axis of the counterbore if it is intended for wrought iron and steel. For brass and cast iron, the grooves may be straight. The cutting edges are to be given clearance by filing; it is advisable to give clearance to the lands also. The counter- bore will then have much less tendency to spring from the projection while cutting part of it away. 49. Solid counterbores, while cheap in first cost, are open to two serious objections. In the first place, they are difficult to sharpen; in the second place, they are limited in 26 TOOLMAKING. 37 their range to holes as large as the teat or larger. They can be adapted to holes larger than the teat by forcing a bushing over it. As it is rather difficult to remove the bushing, this method of making a counterbore adapted to several sizes of holes can only be considered as a makeshift, especially as the difficulty of properly sharpening it is retained. Two-lipped and four-lipped solid counterbores are sharpened by grinding — on the sides, in case of a two- lipped counterbore, and on the flat side of the grooves in case of a four-lipped counterbore. BUILT-UP COUNTERBORES. 50. Inserted-Teat Counterbore. — The counterbore shown in section in Fig. 22 overcomes the objections raised against the solid counterbore. It is slightly more expensive to make, but will serve for a greater variation in size of hole than any other. In addition, it can be sharpened very easily. As shown in the figure, it has a central hole bored to receive the shank of the teat, which is held in place by the setscrew. After turning the outside, the central hole Fig. 22. may be bored true and reamed, running the large end of the counterbore in the steady rest. The grooves may then be cut between centers in the milling machine, or the counterbore may be held in a chuck, as is most convenient. A 60° milling cutter should be used if four cutting edges are given. For wrought iron and steel, the grooves may be cut along a right-handed helix; for brass and cast iron, they may be straight. After hardening and tempering, the hole should be lapped out; teats of the desired sizes may- then be turned and fitted to the counterbore. These teats 38 TOOLMAKING. § M may be hardened at the end and drawn to a straw color. Unless the counterbore is used for exceptionally fine work, there is little need of grinding the teats to run true. As they are to be hardened at the extreme end only, there is little likelihood of their springing sufficiently to interfere with the working. The shank of the teat should be a good sliding fit, so that it may be easily removed when the set- screw is loosened. The counterbore can readily be sharp- ened by grinding on the end after the teat is removed. 51. Inserted-Cutter Counterbores. — When but very few holes of a special size are to be counterbored, and there is little likelihood of the counterbore ever being wanted again, the simple form shown in Fig. 23 may be adopted. Its chief recommendation is its cheapness. The objection- able feature is that it can take but a relatively light cut, which requires careful feeding to prevent breakage of the cutter. It consists of a bar that fits the hole to be counter- bored, and a cutter driven into a circular hole drilled clear through the bar. For small counterbores, the cutter may be made of drill rod. Referring to Fig. 23, after the bar is turned to a fit, the hole for the cutter is drilled and reamed Fig. 23. and a blank piece of drill rod of sufficient length driven in. This is then turned to the correct diameter and faced on the front side. It is next driven out of the bar and filed to a cutting edge, as shown, giving front rake for wrought iron or steel. The cutter is now hardened all over and driven home again. 52. For large work, a counterbore may be made as shown in Fig. 24. The bar is slotted and a flat cutter is closely fitted to it; the cutter is confined by a key, as shown. A moderate range of variation in the diameter of §2G TOOLMAKING. 39 the counterbored hole is obtained by setting the cutter out of center. The cutter is readily sharpened. Whether to harden the end of the bar or not must be decided upon the merits of the case. Many toolmakers believe that it is the best plan to leave the end of the bar soft and to turn it down sufficiently to receive a hardened bushing that is a good snug fit and kept from turning by a pin. HOLLOW MILLS. SOLID HOLLOW MILLS. 53. Hollow mills are chiefly used for screw-machine and turret-lathe work for roughing down and finishing stock fig. 25 . preparatory to threading. When intended for finishing, they are usually made adjustable. For roughing out, solid mills are preferred, since, in general, they are not as C. 5. IIJ .— 33 40 TOOL MAKING. 26 springy as adjustable mills. Hollow mills may be made in a great variety of forms. For small work, the most common form is the solid mill shown in Fig. 25. This is commonly made with four cutting edges formed by milling with a side milling cutter of about double the outside diameter of the mill. In order that the mill may work easily, it must be relieved inside by filing it as shown. The rear of the mill is to be bored larger in diameter than the cutting end. This allows it to clear on long cuts, and, at the same time, makes it easier to file the clearance. In making the mill, it is advisable to mill out the cutting edges before giving the clearance inside; if this is done, the clear- ance can be filed more rapidly, since there is then but a relatively small quantity of metal to be removed. The milling cutter is to be set by trial until it makes a about one-sixth the inside diameter and b about eight-tenths of the inside diameter. The back of the mill may be bored about one and one-fifth times the diameter at the front end. The faces on which the cutting edges are located are usually spaced equidistant and lie in planes passing through the axis. The mill is hardened as far back as the end of the milling and drawn to a straw color from the back, set- ting it on a red-hot piece of iron. All sharpening is done by grinding on the end. 54 . An adjustable hollow mill may be constructed in the same manner as the adjustable spring die shown in Fig. 3, using a clamp collar to adjust it. INSERTED-BLADE HOLLOW MILLS. 55 . For large work, hollow mills may be made with in- serted blades, constructing them if desired non-adjustable in the same manner as the solid die shown in Fig. 2. If desired adjustable, a design similar to that shown in Fig. 4 may be adopted. 56 . A very good .design of a hollow mill with removable blades and adjustable for sizes within narrow limits, is shown §26 TOOLMAKING. 41 in Figs. 26 and 27. Fig. 26 shows the mill taken apart; Fig. 27 shows it assembled. The mill consists essentially of a body a in which a number of slots, as b , are cut at an inclination to the axis. These slots receive the cutters c , c , which are a loose fit in them. Fig. 26 . The cutters are rectangular in cross-section; their rear end butts against the adjusting nut d. They are held in place by a tapering collar e, which surrounds them and is pushed home by a locknut located at the front end. The inside of the collar e is bored out sufficiently large to clear the body a and to fit the outside of the cutters, which extend slightly above the tapered surface of a. Clearance spaces Fig. 27. for the reception of the chips are cut between the slots, as shown at f t f. These clearance spaces communicate with the outside by an opening cut through the body and a corre- sponding opening in the collar. To set-the mill to a smaller size, the locknut g is loosened in order to loosen the cutters. 42 TOOLMAKING. §26 These are then pushed forwards, and, consequently, closed in by turning the adjusting nut d forwards. Tightening the locknut forces the taper collar over the cutters and thus locks them. In order to set the mill to a larger diameter, the cutters are loosened by unscrewing the locknut; the nut d is then turned back and the cutters pushed against it by hand. They are locked again by screwing the locknut home. A hollow mill constructed in accordance with this design is rather expensive as far as first cost is concerned. It is very economical in its maintenance, however, since new cutters can be made for it at a very slight cost. By making the cutters of suitable shape, the mill can be adapted to a limited range of sizes. 57. When making the mill, it is advisable to cut the bottom of the slots at the same distance from the axis, in order that the cutters may all be alike. After the first set of cutters has been made, a filing jig may be constructed, in which spare cutters can be filed exactly alike in height, length, and shape of cutting edge. A simple filing jig for this purpose is shown in Fig. 28. It consists of two parts doweled together. One of the cutters out of the first set made serves as a model; it is placed between the two parts of the jig, butting its rear end against the stop a . The jig is then worked down to the height of the cutter and is §26 TOOLMAKING. 43 beveled to suit it; as the cutter is hardened, this can be done readily. The jig is now hardened and used to duplicate the cutters. It is made in two parts doweled together in order to cheapen its construction; the act of clamping it in the vise clamps the soft cutter placed in it at the same time, thus obviating the necessity of any clamping device. The filing jig must be made of tool steel. Before the jig can be used, the cutters must be cut down to the correct width for the slots in the mill body, which should be exactly alike to allow the cutters to interchange. HOLLOW MILL FOR ANNULAR MILLING. 58. Hollow mills can be used with advantage on some classes of work for milling the outside of a cylindrical pro- jection central with a hole passing through it, provided great accuracy is not required. The mill is then made with a central guide pin, as shown in Fig. 29. This pin is to be Fig. 29. hardened at the end and drawn to a spring temper. It is recommended to hold the pin by means of a setscrew to allow ready removal when the mill is to be ground. In order to facilitate the filing of the inside clearance, it is advisable to bore out the rear end of the mill somewhat larger than its inside diameter. TOOLMAKING. (PART 3.) CUTTING TOOLS AND APPLIANCES. MILLING CUTTERS. SOLID MILLING CUTTERS. 1. Number of Cutting Edges for Solid Cutters. — iMilling cutters up to 6 inches in diameter are usually TABLE OF CUTTING EDGES FOR MILLING CUTTERS. Diameter of Cutter. Cutting Edges. i 6 i 8 l 12 n 14 H 16 2 18 H 21 3 24 31 26 4 28 5 30 6 32 §27 For notice of copyright, see page immediately following the title page. 2 TOOLMAKING. §27 made solid, and above that size they are made with inserted teeth. The number of cutting edges for solid milling cut- ters intended for general work may be as given in the pre- ceding table, which is believed to conform very closely to average practice. The cutting edges are generally made with a radial face, as indicated by the dotted lines in Fig. 1 ; the spaces on the circumference may be cut with a cutter that will produce an angle of about 50° between the face and the back of the tooth. This angle gives an ample depth to the clearance spaces, and, at the same time, gives well-supported cutting edges. The milling cutter used for forming the teeth is run in deep enough to leave the lands from .02 to .04 inch in width, according to the size of the cutter that is being made. If teeth are cut on the sides of the cutter, as shown in Fig. 1, the spaces may be cut with a milling cutter that will produce an angle from 60° to 70° between the face and the back of the tooth. When milling the teeth on the sides, §27 TOOLMAKING. 3 the index head cannot be left at the 90° mark or at the 0° mark, but must be inclined a little, in order that the cut- ter may make the lands of equal width. The amount that the index head is to be inclined depends on such variable conditions that computation of it is a difficult problem; in practice, it is most rapidly found by an actual trial. After cutting the teeth, remove all burrs by filing, and harden. The tempering is done to advantage by inserting a red-hot piece of iron in the hole, thus making the cutter softest at the inside. Draw to a good straw color. Since the diame- ter of the hole is very likely to change in hardening, it is considered good practice to make it slightly smaller, say .004 inch per inch diameter of the hole, and finish by grind- ing. To reduce the time required for grinding the hole, it may be recessed, as shown in the sectional view of Fig. 1. It is recommended that the sides of the boss be also ground straight and true with the hole. 2. Grinding Milling Cutters. — The teeth are sharp- ened on a cutter grinder, using the finger of the grinder as a means for obtaining the proper cutting clearance. The teeth maybe given a clearance of about 3°; that is, the angle between the face of the teeth and the top of the teeth may be about 87°. If this degree of clearance is given, the teeth will cut freely and the cutter will last well. If more clearance is given, the cutting edges will dull quite rapidly. For grinding the teeth on the side of a milling cutter, a small emery wheel must be used in order to get proper cut- ting clearance without touching the adjoining cutting edge. The method of grinding milling cutters does not differ essen- tially from that employed in grinding reamers; the only difference is that the cutting edges, as a general rule, are finished entirely by grinding, no oilstoning whatsoever being done on them. In order to get the best work out of a milling cutter, it is essential that a cutter grinder be used for sharpening it. It is impossible to grind a cutter by hand so that it will be round. Milling cutters that cut only on their ends when 4 TOOLMAKING. §27 used for grooving may advantageously be ground so as to be slightly smaller at the rear, say about .01 inch per inch of length. When grinding cutters, it is well to bear in mind that only very fine cuts must be taken, since, otherwise, the temper will be drawn from the extreme cutting edges, which spoils the cutter. The grinding of a cutter is a job that cannot be hurried without inviting disaster to the cutting edges. 3. Helical Cutting Edges. — When making a helical milling cutter, more commonly known as a spiral mill- ing cutter, choose a helix that will give the cutting edges an angle of about 20° with a plane passing through the axis of the cutter. It does not make any particular difference whether the helix is right-handed or left-handed when the cutter is intended for a machine in which the cutter arbor is supported at the end. However, when used for a machine in which the end of the arbor is free, the helix should be such that the end thrust due to the action of the spiral cut- ting edges will tend to force the arbor home; that is, if the cutter is right-handed, the helix should be left-handed; if the cutter is left-handed, the helix should be right-handed. In order that there may be no misunderstanding about the terms “right-handed” and “left-handed” when applied to milling cutters, they are here defined as follows: Standing in front of a milling machine with a horizontal spindle, and looking toward the spindle, if the milling cutter revolves in the direction of the hands of a watch, it is a left-handed cut- ter ; if it revolves in a direction opposite to that of the hands of a watch, it is a right-handed cutter. A right-handed helix, however, is one that, in advancing, turns in the direc- tion of the hands of a watch. A left-handed helix turns in a direction opposite to that of the hands of a watch. 4. Nicked Teetli. — For heavy milling, spiral milling cutters with nicked teetli are an advantage, since they break up the chips, which enables a heavier cut to be taken than is possible with an ordinary cutter. A satisfactory way of nicking them is as follows: Gear an engine lathe to 2 1 TOOLMAKING. 5 cut a thread having a pitch about equal to the distance between two teeth of the cutter, and with a round-nosed tool cut a half-round thread having a width equal to about one-fourth the pitch of the thread. This is preferably done before the clearance spaces are milled in the cutter. In- serted-teeth cutters with either straight or helical cutting edges, and solid wide cutters with straight cutting edges may advantageously be nicked by cutting a helical groove. MILLING CUTTERS WITH INSERTED TEETH. 5. Designs. — When milling cutters exceed 0 inches in diameter, the cost of making them of one piece of tool steel Fig. 2. becomes rather high; in general, it is cheaper to make them with small teeth that are inserted in a body of cheap ma- terial, as cast iron or machinery steel. There is a great variety of designs that will make a satisfactory cutter. The 6 TOOLMAKING. §27 simplest design is that in which the cutters are fitted to dove- tail slots and driven home after hardening. In order to make a good job, the cutters must be very carefully fitted, which makes renewal rather expensive. Again, as the slots must necessarily be dovetailed, they are expensive ones to make. These considerations have led to designs that do not require such close and expensive work, although they are not quite as simple. Two standard designs are shown in Fig. 2. In both, the cutters are rectangular in cross-section. Owing to this shape, the slots can be milled very cheaply, and cutters to fit them can be made at an expense slight in comparison to that involved in making dovetailed cutters. The design shown at (a) is one that has been adopted by the Morse Twist Drill and Machine Company, New Bed- ford, Massachusetts. Rectangular slots receive the cut- ters a , a\ the body is milled out between every second pair of slots to receive the wedge-shaped piece of steel b, which is drawn home by means of the fillister-headed screw shown, and thus locks the cutters. A space is left between the bot- tom of the piece b and the body; this space allows a slight variation in the thickness of the cutters. In the design shown at ( b ), the metal between every sec- ond pair of slots is slotted with a narrow slot, as c , c. Before cutting the narrow slots, a hole is drilled clear through and reamed “ taper ” to receive the taper pins . When the required angle is greater than 90°, instead of laying off that angle, its supplement is laid off. Subtract the required angle from The correctness with which an angle can thus be pro- duced naturally depends on the skill of the workman in working to the scribed lines and on the accuracy with which they have been located. As a general rule, it may be stated that a much greater degree of accuracy can be obtained by this method than is possible by laying off angles with the ordinary bevel protractor made for machine-shop work. All other factors remaining as before, the accuracy attainable will be greater as the base line, as be, Figs. 14 and 15, or a e, Fig. 16, is made longer. TAPER GAUGES. 27. Different Definitions of Taper. — When an angular gauge is ordered to represent a certain taper per foot, the toolmaker should find out by inquiry, first of all, what the person ordering the gauge understands by the term “taper.” Unfortunately, the term has no definite GAUGES AND GAUGE MAKING. 23 § 28 meaning, being used in different senses in different locali- ties. Referring to Fig. .17 (tf), the taper is defined by some as the difference in diameters (d—d') per foot of length, the taper in all cases being expressed in inches and fractional parts of an inch. The measurements for diameter are made on lines perpendicular to the axis, which is also the line bisecting the angle made by the sides a b and e foi the taper- ing piece. In Fig. 17 (b) the difference in the radii (r—r 1 ) per foot of length is considered as the taper. In this case, the measurements for the taper are made on lines perpen- dicular to the axis, or line bisecting the angle included between a b and e f t but only to one side of the axis. Evi- dently, if the taper is expressed in accordance with Fig. 17 (b), it will be only one-half that of Fig. 17 ( a ), but yet the angle included between a b and ef will be the same in either case. When the taper of flat work, as keys or wedges, is meas- ured, probably the most common way is to take one side, as e Fig. 17 (c), as a base line and measure the taper by the difference (Ji — h') in height of perpendiculars, as e a and fb, erected at the ends of the base line. Many persons will measure the taper of flat work in the manner shown in 24 GAUGES AND GAUGE MAKING.* §28 Fig. 17 (d). Here the difference in height is measured to both sides of a line bisecting the angle included between the sides a b and e /and on lines perpendicular to the bisecting line. This method is the same as that shown in Fig. 17 (a). Now, on first thought it would seem, wheir comparing two pieces of the same nominal taper, of which one has been measured according to Fig. 17 {c) and the other according to Fig. 17 (d), as if there were no difference in the angles included between a b and e f. There is a decided difference, however, as can be seen by referring to Fig. 18. In this figure, the triangle a f g represents a taper of 8 inches per foot measured in accordance with Fig. 17 (c) ; the tri- angle abc also represents a taper of 8 inches per foot, but measured in accordance with Fig. 17 (d). An inspection shows that there is a decided difference in the angles e and h. 28. Laying; Out a Taper Gauge. — If a taper gauge is to be laid out on sheet steel, the method of laying it out naturally depends on the method by which the taper is measured. Suppose a taper gauge is to be made for a flat wedge that is three inches long on one side and 1 inch high at the thick end. The taper is to be 1 inch per foot, GAUGES AND GAUGE MAKING. 25 § 28 and the person ordering the gauge wants the taper to be measured by taking the measurements perpendicular to one side, that is, as shown in Fig. 17 (c). Then, before the lines can be scribed on a sheet-steel gauge, the height at the thin end of the wedge must be calculated. If the taper is meas- ured as shown in Fig. 17 («), (c), or ( d ), the difference in height, or in diameter in case of round work, may be found by the following rule : Rule. — Divide the given length by 12 and multiply by the taper. When applying this rule to a taper measured as in Fig. 17 ( d ), it is to be observed that it gives the difference in height of lines the given distance apart and perpendicular to the line bisecting the angle, on which line the given dis- tance is measured. If the taper has been measured as shown in Fig. 17 ( b ), the result given by the rule must be doubled to obtain the difference in diameters. Applying the rule given, we get, for the case under con- 3x1 sideration, \ inch as the difference between the large and small ends. Then, the small end is evidently 1 — \ == J inch high. The laying out of the gauge is now a simple matter. Draw a straight line 3 inches long ; erect perpen- diculars at the ends f inch and 1 inch high, and join the ends of the perpendiculars by a straight line. Then cut out the metal and file to the lines. When the taper has been measured in accordance with Fig. 17 (a) or (d), scribe a straight line of the required length and at its ends erect perpendiculars. Lay off half the heights (or diameters) on each side of the line first scribed and join the ends of the perpendiculars by straight lines. When making a sheet-metal taper gauge or angular gauge, it is not advisable to cut out the metal with a chisel, since this may spring it considerably out of true. It is better to saw out the metal with a hack saw, or drill a row of holes close together and then cut through the metal remaining between the holes with a saw or file. 26 GAUGES AND GAUGE MAKING. §28 29. Originating Tapers and Angles. — The most accurate way of originating a taper or an angle (except a 60°, 90°, and 180° angle) is shown in Fig. 19. The same O' d 0 ] principle that is involved in originating a taper or angle allows the same method to be used to measure accurately a taper or angle whose exact measure is not known. In Fig. 19, a and b are two straightedges that are ground and lapped as nearly true as possible. They are so mounted in a suitable frame that they can readily be shifted and then locked rigidly. Steel disks c and d ground and lapped truly cylindrical and of any convenient diameter are placed between the straightedges and in contact with them. Then, the diameters of the disks and their center-to-center dis- tance, all of which dimensions can be accurately measured, definitely determine the taper included between the straight- edges, or the angle, and these data can then be calculated by the following rules: 30. If the taper is measured in accordance with the method shown in Fig. 17 (a) and ( d ), the taper included between the straightedges is calculated as follows: Rule. — Divide the difference in the diameters of the disks by twice their distance from center to center . From a table GAUGES AND GAUGE MAKING. 27 § *8 of natural sines , take the angle corresponding to the quo- tient. Then, in a table of natural tangents , find the tan- gent corresponding to this angle. Multiply the tangent by 2f If the taper is measured in accordance with Fig. 17 (b), divide by 2 the result obtained by the rule just given. Example. — The disks being 2 inches and 4 inches in diameter, and their center- to-center distance being 4.5 inches, (a) what is the taper in inches per foot if measured in accordance with Fig. 17 ( a ) or (d)7 {{?) What is the taper if measured as in Fig. 17 (6) ? 4 — 2 'Solution. — ( a ) Applying the rule given, we get Q ^ ^ ^ = .22222 as the sine. The nearest angle is 12° 50'. The tangent corresponding to this angle is .22781. Then, the taper is .22781 X 24 = 5.4674 in. per ft. Ans. (b) Dividing answer in {a) by 2, we get 5.4674 -f- 2 = 2.7387 in. per ft. Ans. 31 . If the taper is measured according to Fig. 17 (< c ), use the following rule: Rule. — Divide the difference in the diameters of the disks by twice their distance from center to center. Find the corresponding angle in a table of sines ; double the angle thus found and find its tangent. Multiply the tangent by 12. Example. — Taking the same values as in the previous example, what will be the taper per foot if measured in accordance with Fig. 17 (c) ? 4 — 2 Solution. — Applying the rule just given, we get Q ^ — - = .22222 as the sine. The nearest angle is 12° 50'. Doubling this angle, we get 25° 40'. The corresponding tangent is .48055. Then, the taper is .48055 X 12 = 5.7666 in. per ft. Ans. 32 . When the taper in inches per foot is given, to find the diameters of the disks and their center-to-center distance : Rule. — Assume the diameters of the disks as dictated by judgment. Divide the taper by 2k, if the taper is measured in accordance with Fig. 17 (a) or (d). If measured in accordance with Fig. 17 (b), divide the taper by 12. From a table of natural tangents , find the angle correspondmg to the quotient. Then , from a table of natural sines , take 28 GAUGES AND GAUGE MAKING. §28 the sine corresponding to the angle. Finally, divide the difference in the diameters of the disks by twice the sine. Example. — If a taper of 2 inches per foot is to be originated, what must be the center-to-center distance of the disks, assuming them to be 2 inches and 3.5 inches in diameter, {a) if the taper is measured according to Fig. 17 (a) and (d) ? (b) if the taper is measured accord- ing to Fig. 17 (b) ? Solution. — (a) By the rule just given, 2 24 — .08333. The nearest angle corresponding to this tangent is 4° 46'. The sine of this angle is .0831. Then, = 9.0253 in. Ans. .Uool X " (b) 2 -r- 12 = .16666. The nearest angle corresponding to this g <5 2 tangent is 9° 28'. The sine of this angle is .16447. Then, ^447 = 4.560 in. Ans. 33. When the taper is given in accordance with Fig. 1 7 (c), assume the diameters of the disks as dictated by judgment. Then, to find their center-to-center distance : Rule. — Divide the taper by 12. From a table of natural tangents, find the corresponding angle. Find the sine of half the angle thus found, and divide the difference in the diameters of the disks by double the sine. Example. — If the disks are 2 inches and. 3.5 inches in diameter, what must be their center-to-center distance to produce a taper of 2 inches per foot measured in accordance with Fig. 17 (c) ? Solution.— Applying the rule just given, 2 12 = .16666. The nearest angle corresponding to this tangent is 9° 28'. Half of this g g 2 angle is 4° 44'. The sine corresponding is .08252. Then, ■ ■ ■ ‘ ■ . 082o2 X 2 = 9.0887 in. Ans. 34. It occasionally happens that it is desired to find the angle included between the lines ab and ef, Fig. 17, when the taper is given. Then, if the taper is measured as in Fig. 17 (a) and (d) : Rule. — Divide the taper by 21/.. Look up this value in a table of natural tangents and double the corresponding angle. Example. — What angle corresponds to a taper of 3 inches per foot, if the taper is measured as in Fig. 17 (a) and ( d ) ? 28 GAUGES AND GAUGE MAKING. 29 Solution. — By the rule just given, 3 -4- 24 = .125. The nearest angle is 7° 8' and twice this angle is 14° 16'. Ans. 35 . If the taper is measured as in Fig. 17 (b ) : Rule. — Divide the taper by 12. Find the corresponding angle in a table of natural tangents and double it. Example. — A taper of 3 inches per foot is given in accordance with Fig. 17 ( b ). What is the angle ? Solution. — 3-5-12 = .25. The nearest angle is 14° 2'. Then, the required angle is 14° 2' X .2 = 28° 4'. Ans. 36 . If the measurement for taper is made according to Fig. 17 (c): Rule. — Divide the taper by 12. From a table of natural tangents , find the angle corresponding to the quotient. Example. — What angle corresponds to a taper of 3 inches per foot measured as in Fig. 17 (c) ? Solution. — 3 12 = .25. The nearest angle = 14° 2'. Ans. 37 . When the straightedges of Fig. 19 are to be set to a .given angle by means of the disks, their center-to-center distance may be found as follows: Rule. — Take the sine of half the angle from a table of natural sines. Divide the difference in the diameters of the disks by double the sine. ' Example. — If an angle of 20° is to be originated, and the disks are 2 inches and 4 inches in diameter, what must be their center-to-center distance ? Solution.— 20° A- 2 = 10°. The sine of 10° = .17365. Then, 2 - = 5.7587 in. Ans. . 1736o X 2 38 . In case it is desired to measure the angle included between the straightedges: Rule. — Divide the difference in the diameters of the disks by twice their center-to-center distance. From a table of natural sines y take the angle corresponding to the quotient and double it. GAUGES AND GAUGE MAKING. 30 § 28 Example. — The disks being 2 inches and 5 inches in diameter, and 5 inches from center to center, what is the angle included between the straightedges ? pj 2 Solution. — 1 = — .3. The nearest angle is 17° 27'. Then, "X 5 17° 27' X 2 = 34° 54'. Ans. 39 . If the center-to-center distance calculated by any of the rules previously given is less than half the sum of the diameters of the disk, either one of the disks must be made smaller or the other one larger, and the calculation repeated until the distance becomes larger than half the sum of the diameters. The center-to-center distance can be measured in two ways: Measure the distance between the disks and add half the sum of the diameters; or measure the distance over the outside of the disks and subtract half the sum of the diameters. In order to originate an accurate taper gauge for flat work, the device shown in Fig. 19 is set to the given taper. An inside gauge is then fitted to it, continuing the fitting until no daylight can be seen, when the gauge is placed between the straightedges. The outside gauge is then care- fully fitted to the inside gauge just made; it thus becomes a duplicate of the taper (or angle) included between the straightedges. If necessary, either one of the pair of gauges is kept as a reference gauge to show wear of the other. Taper gauges for round work (conical work) are made both as inside, or plug, and as outside gauges. The device is first set to the angle (or taper) required; the plug gauge is then ground until no daylight can be seen, when it is placed between the straightedges. The outside, or ring, gauge is next ground until it exactly fits the plug gauge, using the finest grade of Prussian blue as a marker to show the fit. 40. Originating a 60° Angle. — A 60° angle can be originated most readily by the method first used by Pratt 6 Whitney for originating a standard with which thread GAUGES AND GAUGE MAKING. 31 § 28 gauges could be compared. The principle made use of is that in an equilateral triangle each interior angle is equal to 60°. Then, if three bars are made, as a , b, and c, Fig. 20, each of them exactly equal to the other, and with the holes the same distance apart and in the same relative positions in regard to the sides, the center lines of these bars when connected by pins passing through the holes will form an equilateral triangle; and, as the inside and outside surfaces of the bars are parallel to the center line, all angles included between the inside or outside of the bars will be 60° angles. TRY SQUARES. 41. Making a Try Square. — A 90° angle may be originated in several ways. The first method here given will produce two try squares, both of which, if skilfully made, will be about as correct as it is possible to produce them. There is one appliance necessary, however, on the truth of which the correctness of the try squares will depend. This appliance may be either a straightedge or a surface plate; eithe'r one of them may be used, but it must be as true as skill and ingenuity can make it. When making try squares, it is easiest, as a general rule, to do all truing on 32 GAUGES AND GAUGE MAKING. § 28 the blade, since the amount of metal to be removed is usu- ally quite small. To make the try squares, finish the stocks by grinding their top and bottom surfaces parallel and as nearly plane as possible. A surface-grinding machine is invaluable for this work. If it must be done by hand, great care is required to make as good a job of it as can be done by the surface- grinding machine. The two stocks having been finished, fig. 21 . insert and fasten the blades, which have been previously ground true and parallel. Select the square that seems to be the most accurate, using judgment in the selection. Fit the other square to it until they fit either way, when stock is placed against stock and blade against blade, as shown in Fig. 21 (a). The two squares are now duplicates of each other, but it is not known as yet whether the angle between stock and blade is correct, or if not, which, way the squares are out. To test this, place both squares blade to blade on a surface plate or straightedge, as shown in Fig. 21 (b), and with tbe stocks resting on the surface plate or straightedge, observe if the blades are in contact with each other throughout their length. If they touch so that no daylight can be seen between them, both squares are correct. Suppose, however, that there is an opening at the top, as shown in Fig. 21 (b). Then, this shows that the angle between stock and blade is smaller than 90° ; conversely, if the opening is at the bottom, 28 GAUGES AND GAUGE MAKING. 33 the angle is larger than 90°. Next, take one of the squares and shift its blade one-half the amount indicated. If the shifting must be done by grinding the blade, grind off the probable amount on one side and then make the other side absolutely parallel to it. Now, fit the second square to the first square just corrected; place them blade to blade again on the surface plate or straightedge, and repeat the cycle of operations until the squares will fit when placed stock to stock and blade to blade. Both squares will then be correct. 42 . Testing Try Squares. — If a try square is to be tested for correctness, the most obvious way is to compare it with a test, or reference, try square. If there is none at hand and circumstances permit, an ex- cellent substitute for a test square may be made as shown in Fig. 22. Take a piece of good machinery steel or well-annealed tool steel having a length not less than the length of the blade of the try square, and a diameter of not more than the inside length of the stock. Recess one end about y 1 ^ inch deep, making the diameter of the recess about ^ inch less than the outside diameter. Turn the outside true and straight; slightly bevel the edge at the recessed end and then finish by grinding and lapping between dead centers, and finally, without previous removal from the grinding machine, accurately face the annular ring at the cupped end. Obviously, if the cylinder is finished true and straight, the angle between the plane of the ring and the cylindrical surface is a right angle. Since there should not be any difficulty in lapping the device straight within a variation of .00002 inch, and since the ring can be ground to be in a plane perpendicular to the axis within an insensible amount of variation, it is Fig. 22. 34 GAUGES- AND GAUGE MAKING. 28 believed that this is the most accurate method of originating a 90° angle that has been devised. This device may be used for testing the truth of the inside and outside angles of a try square. To test the inside angle, the try square is applied directly to the device, as shown in Fig. 22. To test the outside angle, the device and try square are both placed on a surface plate and brought in contact with each other. Practical considerations will fix a limit within which this device can be used. These considerations are the weight allowable and the facilities for grinding and lapping; from these, the toolmaker can readily determine the limits within which the method just given is applicable. A simple method of testing try squares intended for com- paratively rough work is shown in Fig. 23. One edge of a Fig. 23. wooden or metal plate that forms a fair approximation to a plane surface is trued up to a straightedge. The stock of the square is then placed against this edge and a faint line is scribed along the blade. The square is now reversed, as shown by the dotted lines; if the blade coincides with the scribed line, the square is true. If the blade is farther away from the line at the top than it is near the stock, it shows that the angle is less than 90° ; conversely, if it is far- ther away near the stock than at the end of the blade, the 28 GAUGES AND GAUGE MAKING. 35 angle is larger than 90°. This method shows double the error. 43. Making a Test Block for a Square. — A refined method of making a test block for testing try squares was made public in 1896 by Mr. G. A. Bates, an expert tool- maker of Brooklyn, New York. The construction of the test block is shown in Fig. 24. It consists of a rectangular cast-iron frame a, which has a groove of rectangular cross- section all around its circumference. The sides of the groove are finished straight and parallel by planing or milling. Four separate blades, as l?, I?, are closely fitted to the groove in the frame; they are connected to the frame by well-fitted fulcrum pins c , c located near one end of the blades. The end of the blades opposite the pins is connected to the frame by small bolts, as d, which fit tapped holes in the blades and pass through a clearance hole in setscrews, as e\ these setscrews are fitted to holes tapped in the frame. 36 GAUGES AND GAUGE MAKING. § 28 Evidently, by moving the setscrews and setting up the locking bolts, each blade can be rotated slightly around its fulcrum and then locked in position. While the blades are shown as having a T shape, they may be made rectangular as well, or, if considered desirable, the edges projecting from the frame may be thinned down by beveling. The measuring surfaces of the blades are filed and scraped so as to make true plane surfaces, scraping them either to a true surface plate or to a true straightedge. It should be remembered that the value of the test block depends, to a large extent, on the straightness of the measuring edges; hence, these must be made as perfect as skill and ingenuity can make them. The setscrews e and locking bolts d should have a rather fine pitch of thread, say 40 threads per inch, or even finer, as a sensitive adjustment can then be readily obtained. The screws e must be a good snug fit, since any looseness will destroy the value of the testing block. 44 . I n order to set the test block so that any two adjacent blades are at a right angle to each other, a tem- porary try square is made out of sheet iron or sheet steel. A very convenient form of such a try square is shown in Fig. 25. In- stead of finishing the* inside of the blades throughout their length, they are cut away in order to leave the small projec- tions shown. When any change is required, it is easier to dress down the projections than to Fig. 25. refinish the blade throughout its length The try square having been finished until it is believed to be fairly accurate, it is applied to two adjacent blades of the test block. One of these blades is then adjusted until both blades fit the temporary try square. Suppose the try square has been used on the top and right-hand blade of the test block and that the top blade has been adjusted. Then, it is 28 GAUGES AND GAUGE MAKING. 37 next applied to the top and left-hand blade ; the latter is now adjusted to fit the try square. The bottom blade is finally adjusted from the left-hand blade and to the try square; on applying the try square to the bottom and right-hand blade, any error of the try square will be shown multiplied four times. The try square is now corrected and the blades of the test block readjusted. These operations are repeated until the try square fits exactly all around the test block; when this is the case, any two adjacent blades of the test block are at a right angle to each other, and the try square is also truly square. STRAIGHTEDGES. 45 . Originating a Straightedge. — A correct straightedge can be produced either by fitting it to an absolutely correct surface plate, or it can be originated in accordance with the following axiom : Three straightedges cannot fit one another unless all three are straight. The C. S. Ill— 38 38 GAUGES AND GAUGE MAKING. 28 facilities at command of the toolmaker will determine which method is to be used. Three straightedges having been finished all over, select one of these as a trial straightedge ; perferably select the one that is believed to be nearest correct. Mark this i, and mark the two others 2 and 3, respectively. Carefully fit straightedges 2 and 3 to i, as shown in Fig. 26, until no daylight can be seen between 1 and 2 and 1 and 3 when holding them up against a strong light. This done, place 2 and 3 together, as shown in the illustration. Any deviation from a straight line will now show double. Take one of these two equal straightedges, say 2 , and reduce its error. Use this as a trial straightedge and fit 1 and 3 to it. Place 1 and 3 together, observe the error, and reduce it on number 3. Use 3 as a trial straightedge and fit 1 and 2 to it. Place 1 and 2 together, reduce the error of 1 and use it as a trial straightedge once more, fitting "2 and 3 to it. Repeat these operations until all three straightedges fit one another ; all three will then be straight. It is not possible to use fewer than three straightedges, since two straightedges can be perfectly fitted to each other, and be a perfect fit on each other in any position in which they are placed, without being anywhere near true. 46. Forms of Straightedges. — Straightedges are made in various forms. Most generally they are made rect- angular in cross-section, and of uniform width throughout their length. They must then be made wide and thick enough to give stiffness sufficient to prevent any sensible deflection with reasonable care in their use. If their width is made equal to .12 times the length increased by .6 inch, and their thickness equal to .005 times the length increased by .05 inch, a satisfactory degree of stiffness can usually be obtained, provided the length of the straightedge does not exceed 40 inches. Since toolmakers are by no means agreed upon what deflection is permissible, the proportions here given are to be considered as those that we think will give satisfactory results. §28 GAUGES AND GAUGE MAKING. 39 Straightedges become more sensitive, that is, they will more readily show a minute deviation, as their measur- ing edge is made narrower. They are most sensitive when made so that they touch the work merely along a line; i. e., when they are in line contact with it instead of in surface contact. Then, carrying out this idea, a straightedge may be given sufficient thickness and width in order to give stiffness, and it may be beveled at its measuring edge in order to give sensitiveness. Beveled straightedges are usu- ally beveled sufficient to leave the measuring edge y 1 -^ inch wide. When beveled off more than that, the cross-section bears a close resemblance to that of a knife blade, and the straightedge is then called a knife-edge straightedge. A very satisfactory cross-section of a knife-edge straight- edge is that adopted by Pratt & Whitney and shown in Fig. 27 («). This form combines stiffness, lightness, and convenience of handling. The more common form is shown in Fig. 27 (b ) ; it is simply beveled on both sides to give a narrow edge. In both forms of knife-edge straightedges, the actual testing edge a has a semicircular cross-section; in other words, the testing edge, instead of forming a plane surface, forms part of a cylin- drical surface. When thus made, they can be held at a slight angle to the work, without in any way interfering with the correct- ness of the measurement. Hence, they are more easily used than straightedges in which the testing edge forms a plane surface; these must be held so that the testing surface is in contact all over with the surface to be tested, for if canted over so that one edge of the testing surface is in contact with the work, a wrong indication will be given if that edge should be out of true. As a general rule, in making straightedges with a plane-surface testing edge, little attention is paid to making the bounding edges of the testing 40 GAUGES AND GAUGE MAKING. 28 surface absolutely straight; this would add considerably to the cost without gaining any particular advantage. Besides, the sharp edges would rapidly wear out of true. Knife-edge straightedges cannot be very readily originated by making three fit one another. The reason is that it is practically impossible to hold two of them together so as to be in contact all along. On account of this difficulty, knife- edge straightedges are usually fitted to a straightedge hav- ing a plane-surface testing edge, or to an accurate surface plate. 47. Hardening Straightedges. — Straightedges in- tended for work in the shop are usually hardened on the testing edge, and occasionally all over. The object of hardening is to reduce the liability of wear. Since the hardening process sets up severe internal stresses, which are gradually released by the aging of the steel, hardened straightedges will occasionally become crooked and require refitting. If the edge alone is hardened and the back is left soft, this change of shape will, as a general rule, be small enough to be negligible. Straightedges intended for refer- ence only, i. e., for testing working straightedges, may be left soft; large straightedges must usually be left soft on account of the difficulty of hardening. To harden a straightedge on the edge only, place it between iron bars clamped to it, leaving the edge exposed. Heat evenly all over and then quench. The iron bars pre- vent the water from coming in contact with the back and sides, which are consequently left soft. 48. Finishing the Testing Edge of a Straight- edge.— To make a straightedge with a plane-surface test- ing edge, it should be ground as nearly straight as possible on a surface grinder, if hardened, and then finished by stoning and lapping. If left soft, it is finished by filing, scraping, and lapping. The straightedge having been finished very nearly true by filing with a dead smooth file, §craping i s begun, A neat device for scraping, and one that GAUGES AND GAUGE MAKING. 41 § 28 has proved very useful in this connection, is shown in Fig. 28. For want of a better name, and from its resemblance to the carpenter’s plane, it may be called a scraping plane. As shown in the figure, it consists of a body, one side of which, as b, is finished by planing to suit the shape of the straightedge that it is intended for. The scraping tool is set so that its cutting edge is at an angle of about G0° with the line of motion of 'the plane; it will then take a shaving cut. The edge of the scraping tool slightly projects beyond the surface a , say about .0005 inch. It is stoned to a very keen edge, as nearly straight as possible; if made with a triangular cross-section of cutting edge, as shown, it will cut both ways, and make a very good job if supplied with plenty of lard oil and kept sharp. Suppose now that the plane is held with its surface b against the side of the straight- edge, and, with the scraper resting on the testing edge, is moved back and forth. Then, it follows that, the scraper being prevented from canting over to one side or the other, the angle between the side of the straightedge and its meas- uring edge will be constant throughout the length. In the illustration, the scraping tool is shown as being held in place by friction; if well fitted to the sides of the slot, this will be sufficient. If considered necessary, it may 42 GAUGES AND GAUGE MAKING. 28 be held in place by a key, or by screws; adjusting screws for setting it out may also be provided. For the final finishing by lapping, a small L-shaped piece of cast iron may be provided. If the lapping is then done with one leg of the lap resting against the side of the straightedge, the lap cannot be canted to one side or the other, and, consequently, a good job can be done more rapidly than could be done otherwise. Knife-edge straightedges, while the most sensitive straight- edges that have been devised, are, at the same time, the most difficult ones to make. After grinding them as nearly straight and true as circumstances permit, they must be finished by oilstoning with a very fine Arkansas oilstone, frequently comparing them with a plane-surface straight- edge. No special directions that could be given will make their production an easy matter ; it is a matter of patiently stoning down the high spots until the knife edge fits the reference straightedge all along at any angle within range at which it may be held. Very large straightedges, say, above 40 inches long, are rarely made as knife-edge straightedges ; the usual plan is to make them in the form of a narrow surface plate and of cast iron. They may have a T shape, with a rib of ample depth and thickness to prevent deflection. Straightedges of this form are originated in the same manner as surface plates ; one being kept as a reference straightedge, others may be made from it by comparison. SPECIAL GAUGES. 49. Where a large number of pieces are to be made interchangeable, this quality can only be preserved by limit gauges so constructed as to caliper the piece in all essential directions. In some cases, one set of limit gauges will be sufficient; in others again, two or more sets may be required owing to the difficulty, if not impossibility, of gauging the work all over in one operation. Owing to the 28 GAUGES AND GAUGE MAKING. 43 infinite number of shapes possible, no definite rules can be given as to the construction of special gauges ; each case must be treated on its own merits, and the toolmaker must exercise his ingenuity as to the best way of designing and constructing the gauges. The only general directions that can be given are to make the gauges as simple, durable, and capable of exact duplication as circumstances will permit. Furthermore, always provide means of getting the work out of the gauge, or the gauge away from the work without ruining the gauge, in case the work should stick. A few special cases of gauge making are given below ; the gauges shown and the remarks made in regard to them are intended only as suggestions of how a gauge may be made for the pieces of work shown. It is not to be inferred that the way the gauges are made is, in each instance, the best method of construction possible and the only one applicable. Circumstances alter cases; while a gauge designed as shown may be eminently suitable for one set of conditions, it may be either too refined or not refined enough for other condi- tions and requirements. 50 . In Fig. 29 (a) is shown a rather simple piece of work, which is finished on the edges in a profiling machine, (a) and has a hole through one end. The sides are to be par- allel and of a given thickness. It is required to gauge the shape in relation to the hole; it is also essential that the hole and the thickness be correct. To gauge the hole, a cylin- drical limit gauge may be employed ; for the thickness, a 44 GAUGES AND GAUGE MAKING. 28 limit snap gauge is best adapted ; for gauging the shape, a gauge may be made as shown v in Fig. 29 ( b ). The gauge consists essentially of a flat plate a pierced by a hole of the same shape and size as the work. This plate is mounted on a block b, which carries the pin c, and the latter serves to locate the work properly in the gauge. The pin is made the minimum size allowable for the hole in the work. Then, if the work is placed over the pin and if it drops into the hole pierced through it is known that the shape of the piece is not over the size. The degree of accuracy with which the work fits into the gauge is determined by ocular inspection. While the gauge shown determines whether the piece of work will go into place or not when the machine or device that it is intended for is assembled, it does not determine whether it is too small to satisfactorily perform its allotted function. But, if another gauge is made similar to that shown in Fig. 29 (b), preferably on the same block, and if this second gauge is made slightly below the minimum size permissible, a limit gauge would be thus obtained. In that case, if the work enters the smaller gauge, it is proved to be too small ; if it refuses to enter the larger gauge, it is shown to be too large; but if it enters the large. gauge and does not enter the small one, it is correct in size within the amount of variation existing between the large and the small gauge. In order that the work may readily be removed from the gauge, a large hole may be drilled through the block b , as shown in the illustration. The work is then pushed out of the gauge either with the fingers or with a small wooden or metallic rod. 51 . A somewhat different case of gauging is shown in Fig. 30. In this instance, the object of gauging is to deter- mine whether the center-to-center distance a of the holes is correct within the predetermined limit of variation. The simplest kind of gauge for this work is a plate with two fixed gauge pins of correct diameter placed the required distance apart. Such a gauge is open to one objection, however. If §28 GAUGES AND GAUGE MAKING. 45 the pins happen to fit the holes in the work rather closely, it is quite difficult to remove the work from the pins after it has been forced on, since it is not an easy job to draw the Fig. 30. work off squarely. This objection can be overcome by ma- king one of the pins, as b , movable; it is then to be made a good sliding fit in the body of the gauge. The other pin, as c, is rigidly fixed. Withdrawing the movable pin allows the work to be readily drawn off the fixed gauge pin. 52. A pin gauge of the construction shown in Fig. 30 apparently forms at the same time a limit gauge. Referring to Fig. 31, let b and c be the gauge pins. Let them be placed 1.18 inches from center to center. Assume that the holes in the work, by pre- vious gauging, have been proved to be larger than .449 and smaller than .451 inch. Then, obvi- ously, the gauge pins must be made small enough to enter the holes when their size is the smallest permissible, i. e., .449 inch. Now, assuming that the holes are larger, say .451 inch, the work will go over the gauge when the side of the holes 46 GAUGES AND GAUGE MAKING. §28 touches the inside of the gauge pins, as in Fig. 31 (#), or the outside of the gauge pins, as in Fig. 31 (b), and also when the center-to-center distance, for the size of . hole assumed, varies between these two extreme positions. In the first extreme position, the center-to-center distance will be 1.182 inches; in the other, it will be 1.178 inches. We thus obtain as the extreme limit of variation 1.182 inches — 1.178 inches — .004 inch, or, as the limit of variation in the size of the holes is .451 inph — .449 inch = .002 inch, a vari- ation double that which is permitted in the size of the holes. Now, suppose that the holes in the work happen to be the same size as the gauge pins. Then, the work will not enter at all unless the center-to-center distance of the holes coin- cides with that of the guide pins. If it varies but .001 inch from it, the gauge will not go into the holes; the work may thus appear worthless when in reality the holes may be located quite within the permissible limit of variation. Now, suppose that the gauge pins are made smaller than the smallest size of hole permissible, say .002 inch, thus making their diameter .447 inch. Then, if they are placed 1.18 inches from center to center, the work will go over the pins if the center-to-center distance of the holes varies between 1.178 and 1.182 inches, if the holes are the smallest permissible size. If, however, they are the largest size allowable, as .451 inch, the work will go over the gauge pins if the center-to-center distance varies between 1.176 and 1.184 inches. 53 . Having seen that reducing the diameter of the gauge pins results in an increase of the range of variation within which the work will pass over the gauge pins, we will now investigate how this range can be reduced. The most obvious way is to reduce the limit of variation in the size of the holes. Suppose that the holes being nom- inally .45 inch in diameter, we place their limiting sizes at .4495 and .4505 inch. If the holes are small, say below 1 inch, there is not much difficulty in reaming them within this limit. Then, if the gauge pins are made .0005 inch GAUGES AND GAUGE MAKING. 47 § as below the smallest permissible size of hole, or .4495 — .0005 = .449 inch, the work will go over the pins if the center-to- center distance of the holes in the work varies between the limits of 1.1785 and 1.1815 inches; that is, if it varies .0015 inch either way from the nominal center-to-center distance. The limit of variation in the center-to-center distance of the holes that can be detected by a pin gauge can be further reduced by constructing one of the pins, preferably the fixed pin, in such a manner that it can be centrally expanded to fit the hole in the work. If this is done, the limit of varia- tion in the center-to-center distance within which the work will go on the gauge will be reduced to one-half of that obtained otherwise. A satisfactory way that may be suggested for gauging the center-to-center distance of holes is to make both pins adjust- able to the size of the hole; one pin is then rigidly fixed and the other is mounted on a slide provided with a vernier that reads to zero when the center-to-center distance is correct. If the work is placed over the pins and both pins are then expanded to fit the holes, the amount that their center-to- center distance differs from the nominal distance is then read off directly by the aid of the vernier. Such a gauge is rather expensive; the circumstances of each case must deter- mine if the investment is advisable. 54 . In Fig. 32 is shown a suggestion for a gauge intended to gauge the center-to-center distance a of holes at a right 48 GAUGES AND GAUGE MAKING. § 28 angle to each other. At the same time, it is intended to gauge the distances b and ^ between the faces indicated and the axes, or center lines, of the holes. A gauge pin d may be made to fit closely in the hole in the left-hand boss; this pin is inserted at a right angle to the surface e. The mov- able gauge pin f fits the hole in the right-hand boss; it is placed with its center line parallel to the surface e and the distance b from it. Then, if the work is placed over the gauge pin d and then held or clamped with the clamping bolt shown against the surface e , while the upper surface of the right-hand boss is against the stop g, it will be seen that the gauge pin /cannot enter and pass through the hole of the right-hand boss unless the distances a, b y and c are correct. DIES AND DIE MAKING. (PART 1.) DIES AND PUNCHES. GENERAL FEATURES. DEFINITIONS AND EXPLANATIONS. 1. Meaning of the Term Die. — Dies are devices for cutting, forming, or otherwise manipulating metals and other substances. They are ordinarily grouped in pairs and act together, being moved toward one another, usually under heavy pressure. One die alone could not do the work ; there must be something to press the material into it, and that something is the other die, its mate. Such a pair of tools is sometimes called a die , but this term lacks definite-* ness and mistakes might occur when designating one or the other tools in question. Although somewhat awkward, the term a pair of dies seems to be the better name, notwith- standing that in some instances three separate members, or possibly four, may be necessary, as in the case of double- action and triple-action dies. Where one die is smaller than, and enters, the other, as in punching, cutting, and sometimes in forming, the entering part is usually called the punch, and the part into which it enters the die. Very often the name plunger is applied to the punch, while the die is not uncommonly called the matrix. Where either has some peculiar shape or some § 29 For notice of copyright, see page immediately following the title page. 2 DIES AND DIE MAKING. §29 (h) Fig. h (i) §29 DIES AND DIE MAKING. 3 special function to perform, the workmen operating it may- give it a special name, but the names given are now in almost universal use. 2. The Ram and Bed. — Before classifying dies into special kinds, it will be well to consider some features that are common to almost any kind, such, for instance, as the various methods of fastening the punch to the ram, and the die to the bed , of the press in which they are to be operated. The bed is the solid, or anvil, part of the machine, on which the die is fastened, while the ram is the moving member usually descending from above, to which the punch is attached. Occasionally, however, the ram works from below and may be so enlarged at the top as to form a moving bed, while the stationary part of the press holds the upper die and is in such case termed the head. 3. Methods of Fastening Dies. — In Fig. 1 is shown a group of dies that may be of any of the various kinds, as far as the method of attachment is concerned. At (a) is shown a punch a with a cylindrical shank b, to be held by a setscrew or clamp in the ram, and a die c , adjustably held in a chuck d by setscrews e, e , the chuck having a flange f that may be gripped with clamps on the bed, or bolster, of the press. A bolster, in general, is a flat plate lying loose upon the bed, so that it may be adjusted laterally and clamped down in any desired position. Its purpose is to partly fill any space where the dies happen to be thin, and also to act as a bridge over any hole in a press bed, especially when small dies are to be attached. At ( b ) is shown a punch a with a conical shank b , to be held by a setscrew in the countersink c. The die d is cylin- drical and is held in the chuck 'e by the setscrew f, which fits into a countersink similar to that shown at c , in the punch. The chuck has holes in its flange, through which tap-bolts may be screwed into the bolster. At ( c ) is shown a punch a with a screw thread b that is to be screwed into the ram, and a die c screwed into the chuck d. The flange of the chuck is held by clamps to the 4 DIES AND DIE MAKING. §29 bolster. Both the punch and die have holes e for a span- ner, with which they are to be turned. A wedge fastening is shown at (d), where both the punch a and the die b are of a dovetail section, the punch to be held in the ram and the die in the chuck by wedges. At ( e ) is shown a punch a , to be held to the ram by tap bolts through the flange b, and a die c held direct to the bolster, or bed, by tap bolts running through the holes d , d and screwing into the bolster. A pair of cutting dies, as shown at (f), may be held in a similar manner. No flange, however, is used on the punch a , but tap bolts from above screw into the body of the punch. A pair of triple-action dies is shown at (g) with the shank a of the punch so made as to be loosely held in the press plun- ger by a special latch, while the blank holder b is held to the flange of the ram by tap bolts. The die c is clamped to the top of the bolster, and the matrix below is held in the lower plate of this special bolster by a dovetail and wedge. At (//) is shown a pair of double-action dies with punch a , blank holder b , and die c , all made to screw into place. A pair of coining dies are shown at (i) with their collar a. They are of conical shape and are both held by adjustable setscrews in a manner similar to that for holding the chuck shown at ( a ). The collar is inserted in the bolster of the press and held by a clamping ring. 4. Comparison of Fastenings for Dies. — Obviously, various other devices may be used, the object being merely to fasten rigidly one of the dies so that it cannot shift while at work, the other being adjusted exactly under it by trying them together, and then both being securely fastened to the press. The old-fashioned way was to have the adjustment with the setscrews, as shown at Fig. 1 {a). The pressure of these setscrews is apt to spring or twist the die out of shape, especially if it happens to be in the form of a somewhat thin ring. The most modern system of clamping a die down on a flat surface, after it is located in the proper position, is shown at (c) and (e). DIES AND DIE MAKING. 5 §29 It must not be understood that the various methods of fastening the punch and die are necessarily arranged in pairs in the order given, as any of the upper fastenings may be combined with any of the lower ones. Neither are lower dies always held in chucks, but they are often complete in themselves with their flanges. There is an economy in the use of chucks where the dies are small and where there are many nearly of a size. In some cases upper chucks are used, secured to the ram by any one of various methods. Small dies or punches may then be fastened in the chucks. 5. Forms of Dies. — In order to gain a general idea of the nature and almost infinite variety of the forms con- structed by the use of dies, one should study the following illustrations, together with the pressed-metal forms that he may see every day. Thinking of and studying the forms, with the question of how they can best be produced con- tinually before him, will be of great value. Some of the (7. S. HI.— $9 6 DIES AND DIE MAKING. §29 common varieties of these tools are shown in Fig. 2. A shearing punch and die are shown at {a), which is well adapted for cutting off bar metal or making short, straight cuts. The pair of dies shown at (b) is for the purpose of making fruit-can tops, while the combination square dies shown at (c) would make very good sardine cans. At (d) is shown a die chuck for the purpose of holding the die in place. The range of useful articles that are made by dies is very great, and their value is often much greater than the cost of their production. Fig. 3 shows some of these shapes. A piece of ornamental ironwork for buildings is shown at (a). The bicycle pedal shown at (b) is made up of several stamped pieces, while the dish shown at ( c ) is made of a single piece of metal. At ( d ) is shown the ordinary reaper seat, which is now used so extensively instead of those that have been cast. It is made from a single piece of metal CLASSIFICATION. 6. Names of tlie Classes. — Dies may be roughly clas- sified according to the operations that are sometimes per- formed upon a single piece of metal, as cutting , forming, DIES AND DIE MAKING. 7 §29 curling , drawing , and coining. This classification is wholly functional, and a variety of subclasses may be derived from them, the names of which are also functional. Thus, in the cutting class, there are chiseling, shearing, and punching dies, the latter being really shearing tools with the edge extending all the way around, instead of part way, as with shear blades. There are also repunching or drifting dies, which are really more in the nature of the paring tools of the machinist, the process being somewhat analogous to planing or slotting. In the forming class, besides forming dies proper, there are bending, embossing, and seaming dies. The seaming dies are often in the form of horn dies, where the work is placed upon a cylindrical or prismatic horn, and has its seam at the jointed side tightly mashed. The curling class is generally used in a preliminary operation, or with other dies in a series, and is for the pur- pose of turning over or curling edges and rims of various articles. In the drawing class are the single-action and double- action processes, also various forms of redrawing, with diam- eters decreasing from the original operation. There are also analogous operations, such as wire drawing and spinning, which, not being performed by presses, need hardly be fur- ther considered here. In the coining class are the analogous operations of drop forging and squirting. The latter process is the one by which are made the soft-metal collapsible tubes that are so largely used for holding artists’ paints and other semi- liquid substances. Both this and coining, as well as some others, are notable instances of the flow of solids. Additional complication in the names of. these tools are caused by the use of combination dies, which are usually known by this name, although sometimes called compound dies. In general, they combine the functions of cutting and forming, cutting and drawing, or cutting and emboss- ing, as used largely in the making of shallow or deep tops and lids for fruit cans, blacking boxes, kitchen utensils, etc, 8 DIES AND DIE MAKING. § 29 The term compound will be used in this Section for dies com- bining similar processes, as several cutting, or several form- ing operations. A still further ambiguity in the naming of these tools occurs with the various kinds of gang dies. The adjective gang alone does not mean anything very definite, but is generally applied to a group of punches and dies fastened in common into their respective plates. Sometimes these are all alike, as in gang-cutting dies, where a large number of similar pieces are to be punched at the same time. In other cases the pieces may be different, or some of the dies in the gang may be cutting dies, and some forming or embossing dies. Certain forms of gang dies are known as progressive dies. These are generally used for cutting, but sometimes for cutting and forming, at successive operations, on the same piece of material, as in cutting washers, cutting and emboss- ing tobacco tags, etc. For cutting an ordinary washer, for instance, a hole is punched at the end of a strip of iron, which is then passed to a second position, where a pilot pin, projecting from the bottom of a larger punch, enters the hole previously made and centers it. Meanwhile, the punch descends into its die and cuts the exterior periphery of the washer around the hole in question ; at the same time the punch which made that hole is descending into its die and punching a new hole farther along the strip. This in its turn becomes the nucleus, so to speak, for the next washer, and thus a complete article is produced at each stroke of the press after the first one, until the strip of metal is exhausted. In general, care must be taken not to make the names of dies too positive without specifying what they are to do. QUALITY AND DESIGN OF DIES. 7. Temper Required. — The popular idea of a die is that it must be of the best quality of steel, hardened to the greatest degree that it will stand .without crumbling. This is true for cutting dies for thick and hard metals, for many §29 DIES AND DIE MAKING. 9 kinds of embossing dies for doing fine work, and for coining dies; for cutting soft metals, say, under inch thick, and even tin plate, sheet iron, and annealed low-carbon steel, one of the dies may be left moderately soft, with an air temper only. When the edges of a soft die get dull it may be hammered cold and upset to bring the cutting edge to place again. After this has been done, the other die, which meanwhile has been ground upon the face to make it sharp, is forced through or over its mate, shaving the two dies to a perfect fit. In various forming dies, especially where the work does not have vertical edges, the working parts may be of untempered steel, usually of high carbon, to get greater hardness and durability. In still other cases the working surface of forming, and especially of drawing, dies are made of a good quality of cast iron. This is especially true where the cup-like shapes, such as household utensils, to be formed or drawn, are of an approximately spherical or conical form, and where the exact diameter does not need to be main- tained. In other cases, wrought iron or mild steel is good enough for working surfaces, sometimes being case-hard- ened. There is economy in not heating any part of a die after it is once brought to shape, either for hardening or case-hardening, for in every hardening operation there is a risk of temper cracking, and every heating distorts the metal. Hence, in cutting dies where they must be hardened and the fit must be good for thin metals, some grinding should be done after the hardening. This is easily done with round and elliptical shapes, where the grinding can be done in the lathe, but with irregular shapes it is often quite difficult. S- Degree of Accuracy Required in Dies. — There are many degrees of accuracy in tools of this class, accord- ing to the quality of work needed. In deciding the material, hardness, and general quality of a pair of dies, the amount of probable production must be ascertained. If but a small number of articles are to be made, the cheapest possible dies 10 DIES AND DIE MAKING §29 that will make them properly should be selected. If, on the other hand, large quantities are to be produced, and especially if they must be very uniform in dimensions, it is good economy to spend any amount of time and money necessary upon the dies in order to make them as perfect as possible in every detail ; furthermore, careful study should be given to make them of composite design, so that the parts most liable to wear can be cheaply replaced, and thus avoid making entirely new dies. Sometimes, to lessen the risk of cracking and to allow straightening the dies, so-called com- posite steel bars3.ro, used;. these are soft iron for two-thirds of their thickness, while the other one-third is steel, which is welded on. Another point to be decided in the case of cutting dies is how closely they shall fit each other. For thin metals, the punch should enter the die with a good sliding fit. For punching bar and plate iron, it is customary to make the punch loose in the die to an amount equal to at least one- sixteenth the thickness of the metal. Dies made in this way are more durable and require considerably less pressure than when fitting each other closely. Indeed, it has been found by the well-known Seller’s experiments that the least resistance in punching occurs when the punch is smaller than the die by one-fifth of the thickness of the metal. This, however, usually leaves the holes with too much taper. In punching boiler iron and various forms of bar metal for ships, bridges, buildings, etc., the amount of taper allowed in the holes is usually from inch to T6 inch, which does no harm with holes that are in any case loose upon their bolts or rivets. 9. Attachments Used on Dies. — Many of the ordi- nary attachments to dies, which may or may not be applied, and which are oftener needed for cutting dies than any others, are various forms of gauges for locating the work, and strippers for preventing it from rising. In shearing, a device termed a hold-down is often used. This is simply an arm extending out loosely over the top of the bar or 29 DIES AND DIE MAKING. 11 plate to be sheared to keep it from tipping, especially when the shear blades are worn and have dull edges. lO. Die Making in General. — There can be no fixed and definite rules for die making, as is the case with some of the other products of the toolmaker. While in some cases each die is simply a piece of steel of the proper shape, in other cases much careful designing is needed to get the best results in economy and durability. The choice of widely differing methods is often open to the die maker, even in the production of a single article. CUTTING DIES. PLAIN DIES. 11. The plain die shown in Fig. 4 is made up of four distinct essential parts, which are: the hardened and tem- pered block a , which does the cutting ; the stripper plate b y fig. 4. which strips the stock from the punch; the guide strip c , which guides the stock; and the gauge pin d , which gauges the location of the holes punched in the stock. By stock is here meant the material to be punched, which in DIES AND DIE MAKING. 12 §29 • most cases comes in long parallel strips, and is generally fed by hand or automatically. The punch consists of not less than three essential parts, which are: the punch proper e, which does the cutting; the collar f t which takes the thrust; and the shank^, by means of which the punch is attached to the ram of the press. These three parts may be one piece, as shown, or they may be separate pieces united by suitable means to form the punch. Dies like the foregoing may be intended to pierce a hole of a given shape through the material, in which the punching or wad is the waste material, or scrap, as it is commonly termed, or it may be that the punching is the article desired, in which case the remainder of the stock is the scrap. 12. Self-Centering Punch. — Dies intended chiefly for producing holes do not always need a gauge pin ; in many cases, the material in which the holes are to be punched is cen- ter-punched at the point at which the hole is to be located ; the punch may then be provided with a small coni- cal point a, Fig. 5, which enters the center-punch mark and thus centers the work. When holes are to be punched equidistant, a gauge pin will in many cases be found of great advantage, inasmuch as by it the laying out of the holes on the work can be avoided. The conditions that exist in each case will readily deter- mine whether a gauge pin can advan- tageously be used or not. fig. 5. 13. Spiral Punch. — Fig. 6 shows a punch the cutting edge a of which is made in two or more spiral curves, instead of being in a single plane, as in the one shown in Fig. 5. This DIES AND DIE MAKING. 13 § 29 is supposed to make it cut more easily, but with a small hole in thick metal the effect cannot be very great. The dip or shear given to large punches working in thin sheets enables the cut- ting to be performed pro- gressively ; that is, one end is cut clear through before the Other end commences to cut. This punch is very cheaply mounted by the shank b and coupling c , which can also be used to hold any number of other punches. It is of a shape that is cheaply made and has in it the least possible material. In Fig. 6 the work is shown at d and the stripper plate at e. A piece already punched may have other punching done within the space enclosed by its bounding edges by means of a second die, thus accomplishing the required result in two separate operations. 14. Gauge Die. — The dies for the second operation may be arranged as shown in Fig. 7. The punching, or blank, as it is often termed, turned out by the first opera- tion is shown at (a ) ; this is to be pierced by the holes a and a\ see (b). The die is pierced with properly located holes of correct diameter and the punch plate is provided with two punches, as b and b' . The sectional view of the die is taken on the line A B. The guide strip and the gauge pin of the first operation die are here replaced by a gauge plate c attached to the die. This is fastened in such a position that it will properly locate the blank in rela- tion to the holes in the die. The gauge plate has an opening of the same shape as the blank, but sufficiently larger to allow it to be freely Fig. 6. 14 DIES AND DIE. MAKING. §29 inserted. If a stripper is attached to the die, it will not only be difficult to insert the blank in the gauge plate, but it will also be difficult to remove it. It is also difficult to keep clean the opening in the gauge plate. To overcome these objections, the stripper d may be fitted to the punch, being Fig. 7. attached by means of two heavy screws ) (C) Fig. 16. separate operations must be performed, namely, cutting and drawing. When a large number of pieces are to be drawn, § 30 DIES AND DIE MAKING. 17 operation. The depth relatively to the diameter depends much on the thickness, as well as the quality, of the material. 20. Combination Cutting-Drawing Dies on Plain Work. — It is obvious that for making a cup as shown, two Fig. 17. 18 DIES AND DIE MAKING. 30 however, dies may be designed that will cut the blank and form the cup in one operation, thus greatly reducing the time cost per piece. Such dies will be about twice as expen- sive as two single pairs of dies. A variety of combination spring drawing dies is shown in Fig. 17, which is intended to draw the same piece that was shown in Fig. 1 ( b ). Referring to Fig. 17, a is a lower chuck holding the die which is bored to the diameter of the blank, with its upper edge sharp. The blank is cut out by the punch c, the outer edge of which is also sharpened to form a cutting edge. The punch is bored centrally to the outside diameter of the cup, and the inner edge is nicely rounded. An ejector d, actuated by the helical spring shown, serves to push the cup from the upper die in case it should stick there. This is free to move in the direction of its axis, and is confined as to its lowest position by a shoulder in the cutting punch and an abutting flange of its own. The blank holder e is placed within the lower die; it sur- rounds the forming punch f, which is stationary in this case. The blank holder also serves to strip the finished cup from the punch. The pressure on the blank holder is obtained from a helical spring placed below the chuck; this spring operates on a movable sleeve g with a large flange in which pins i, i are carried. These pins pass freely through holes in the chuck and the flange of the punch; they abut against the lower surface of the blank holder, which is thus actuated by the spring. The lower die must be provided with a suitable guide strip, gauge pin, and stripper for the stock, arranged in the same manner as for any ordinary cutting die. These appurtenances have been omitted in the draw- ing for the sake of clearness. 21 . The Operation of Cutting-Drawing Dies. — The operation of these dies is as follows: The descending upper die cuts the blank from the stock; it is immediately gripped by the blank holder and confined between its upper surface and the lower surface of the cutting punch, the spring below the bolster giving the pressure necessary to DIES AND DIE MAKING. 19 30 prevent wrinkling during the drawing. As the upper die keeps on descending, the blank and blank holder are car- ried down until they strike the upper surface of the forming punch f ; the outer zone of the blank is then gradually pulled out and the cup is formed around the punch. The appearance of the work in successive stages is the same as was shown in Fig. 16, except that the work will be bottom side up. In order that the blank holder may be inserted, the lower die and forming punch must be made separate. They may then be connected together in any convenient way that will insure proper centering, as, for instance, by providing the punch with a threaded flange screwed into a threaded recess of the die, as shown. All spring-drawing dies are intended to be used in single-action presses , although they are double- action dies. 22. When a double-action press is available, a very much simpler design of drawing dies is possible. Such a press is provided with two rams working within each other, and independently adjustable. The outer ram, conveniently termed simply the rani , is so actuated that for a certain period of the revolution of the press shaft it will be at rest. The inner ram may properly be termed the plunger. It continues its downward motion, giving a certain excess travel, by which is measured the attainable depth of work. Fig. 18 shows a design of drawing dies for a double-action press, intended to form the cup shown in Fig. 1 ( b ). Refer- ring to the illustration, a is a chuck bored to receive the drawing die b, and threaded to receive the cutting die c. To insure correct location of the two dies with reference to each other, the one may be recessed to fit a central project- ing shoulder of the other, as shown. The two dies may be rigidly held together by any convenient means ; for instance, the outside of the cutting die may be threaded, and suitable holes may be provided to receive a wrench, as shown in the illustration. The upper die d , which is the blank holder and at the same time the cutting punch for the blank, is fitted to the C. S. III .— 42 20 DIES AND DIE MAKING. § 30 ram, and the inner part, or drawing punch e , is fitted to the plunger. The ram is so adjusted that when d has descended and is at rest, it is close enough to hug the blank confined between its lower surface and the upper surface of the die, and thus furnish the pressure necessary to prevent wrinkling. The drawing punch is to be so timed that it will not strike the blank until it has been confined by the blank Fig. 18 . holder. The cup is then drawn by the punch. The finished cup is stripped off by the sharp lower edge of the drawing die. This kind of a die is comparatively inexpensive ; the price should not exceed 50 per cent, more than plain drawing dies that do not cut; it should be considerably less than that of cutting-drawing dies for a single-action press, where spring action must be provided. DIES AND DIE MAKING. 21 § 30 23. Drawing Work With Tapering or Curved Walls. — So far, only the drawing of cups with walls at a right angle to a flat surface has been considered. It is pos- sible to draw work with tapering or curved walls, however, as, for instance, the work shown in cross-section between the upper and lower dies of Fig. 19. In this case, a flange is left on the open end of the work, which is done by not drawing the metal entirely from between the blank holder b and the upper surface of the drawing die a. The die shown is a combined cutting and drawing die; the cutting edge of the lower die is formed on a removable ring c , and hence is easily renewable in case of wear or accident. To eject the 22 DIES AND DIE MAKING. § 30 drawn work from the lower die, an ejector d may be fitted. This may be spring-actuated, as shown, or it may be posi- tively operated by some moving part of the press. Whether or not an ejector, often known as a knock-out , is to be fitted depends on the shape of the work. In many cases this is such that it can easily be lifted out of the lower die; in that ease, the ejector may be omitted. Drawing dies for work as shown need not always be made of tool steel. In many cases they may be made advantageously of close-grained cast-iron. The particular design of dies shown in Fig. 19 is intended for a double-action press. It is also possible to design com- bination dies for the same work to use in a single-action press.' Such may be constructed on the same principles as the die shown in Fig. 17. In order to prevent wrinkles from forming in the walls of work having a cross-section similar to that shown in Fig. 19, the pressure of the blank holder on the confined outer zone of the blank must be quite heavy. If wrinkles cannot be prevented from forming in the body, they can afterwards be removed by roller-spinning the work in a suitable lathe. 24. Combined Cutting, Drawing, and Emboss- ing Die. — For work like that shown in Fig. 20 ( a ), dies may be designed that will cut the blank, draw the rim, and emboss the flat top in one operation, thus enormously redu- cing the time cost per piece below what it would be in case these three operations were performed in separate dies. The design of die to be used for this class of work depends on the type of press that’ is available. For a single-action press, the design shown in Fig. 20 ( b ) is a satisfactory one. As a matter of course, this may be modified in various ways to suit conditions. In the illustra- tion, the dies are shown hard together, with the work between them; when the dies are apart, the upper ejector a projects beyond the face of the embossing punch b. The combined blank holder and ejector c in the lower die is then DIES AND DIE MAKING. 23 § 30 in its uppermost position. The pressure necessary for suc- cessful drawing is supplied by a number of heavy helical springs that may extend into recesses bored into the blank holder in order to effect a saving in the height of the die. For the same reason, the springs for the upper ejector may (bj Fig. 20. be placed within recesses bored into it, if circumstances per- mit. The lower cutting die may be solid, as shown, or a small tool-steel ring may be attached to a cast-iron body. The point to be observed in making any kind of a combina- tion die is to design it so that it is cheap in first cost, and that all wearing parts can be easily and cheaply renewed. 24 DIES AND DIE MAKING. §30 When a double-action press is available, these dies may be designed as shown in Fig. 21. Evidently no stripper will be needed for the upper die, as the embossing and drawing punch a will automatically strip the finished work from the upper die. The lower embossing die b may act as an ejec- tor by making it movable. It is then actuated by the spring shown. If it is stationary, then an ejector may rise inside DIES AND DIE MAKING. 25 § 30 of it. Comparing Figs. 20 and 21, it is seen that there is far less work required to make the dies for a double-action press. The design shown may be modified in various ways, as deemed advisable by the toolmaker. Referring again to Figs. 20 and 21, the lower die should be fitted with a suitable guide strip, gauge pin, and stripper for the stock. These have been omitted in the drawing for the sake of clearness. 25 . Triple-Action Drawing Dies. — Both of the designs just shown will discharge the finished work on top of the lower die. In many cases this is objectionable; the Fig. 22 . design may then be modified, as shown in Fig. 22, if circum- stances permit. In this case, the lower embossing die a is entirely separate from the drawing die b, and is placed some distance below it. The blank holder c cuts the blank and holds it; the drawing and embossing punch d first draws the 26 DIES AND DIE MAKING. §30 rim of the work and finally embosses the bottom. As the punch ascends, the sharp lower edge of the drawing die strips the work off from it. The work then falls and is removed through the opening e in the lower die. It will rarely be necessary to fit an ejector to the embossing die. Evidently, this design of die can be adopted only for the work that can be pushed laterally clear through the drawing die. These dies are of the general class known as triple- action, because originally the lower embossing die was operated from below by a separate special ram, thus making three motions to the press instead of two. The present practice, however, is usually as shown. Obviously, the stroke of the press plunger must, relatively to the ram stroke, be longer than usual. 26. Discharge of Work From Dies. — The lateral ejection of the work, through the doorway e e, Fig. 22, at the back of the die, is sometimes performed by a sliding pusher rod worked by the press. More often, however, the press is set in an inclined position of some 40° from the ver- tical, so that work done in these dies, and also in such as are shown in Figs. 3, 4, 17, 19, 20, 21, and 22, may slide out by the action of gravity. SIZE OF BLANKS FOR DRAWING AND FORMING. 27. Obtaining the Size of the Blank by Trial. The only sure method of getting the correct size or shape of a very irregular blank that is to be subjected to a drawing or forming operation is a tentative one. Naturally, it is likely to prove expensive. A blank is cut as near to the correct size as judgment dictates; it is then drawn or formed and the results are observed. A new blank is then prepared, modified from the first one in accordance with the results obtained in the first trial. This is then drawn or formed, and the cycle of operations repeated until the correct size and shape of blank are obtained. The cutting parts of combination dies are often left unfinished while the drawing §30 DIES AND DIE MAKING. 27 parts are used to ascertain the cut in the manner just explained. 28. Rules for Size of Blank. — The following for- mula for the diameter of the blank in cylindrical work will give quite a close approximation to its correct size: Let d — diameter of cylindrical cup in inches; h = height of cup in inches; r — radius of corner in inches; x — diameter of circular blank in inches. Then, for a sharp-cornered cup, as shown in Fig. 23 ( a ), x = \/d* + 4d h. (1.) Example. — Find a v trial diameter of blank for a cup to be drawn 1 inch deep and 2 inches in diameter. Solution. — Applying formula 1, and sub- stituting values, we get x = j/2* + 4x2x1 = 3.464 in. Ans. 29. For a round-cornered cup, as shown in cross-section in Fig. 23 ($), x = 4 / (b) FIG. 33. JIGS AND JIG MAKING. JIGS. CLASSES AND USE OF JIGS. DEFINITIONS. 1. In the manufacture of duplicate parts, special devices or fixtures are largely used for guiding the cutting tools in such a manner that the work produced by them becomes alike in all essential features, independent of the skill of the operator. Such devices or fixtures are commonly called jigs; they are used chiefly for the production of holes of circular cross-section by drilling or reaming operations or by both in conjunction, and are also used occasionally for guiding taps, files, or other tools. 2. Jigs are called drill jigs, reaming jigs, tapping jigs, or filing jigs, or, in case of several operations of dif- ferent kinds, combination jigs; the name given implies the operation in the performance of which the jig is intended to aid. The design of jigs for any of these operations does not differ in any essential particular; hence, whenever the word “jig” is used hereafter, it will be understood to be applied in the general sense. § 31 For notice of copyright, see page immediately following the title page. 2 JIGS AND JIG MAKING. § 31 ESSENTIAL PARTS. 3. All jigs consist of certain essential parts, which are the guides for the cutting tools; the body, which supports the guides and the work; the stops, or gauges, which locate the work correctly in reference to the guides and to one or more points or surfaces of the work; the clamping arrangement, which serves to hold the work to the body; and the supporting surface or surfaces, which rest on the table of the drill press and insure parallelism of the axes of the guides with the axis of the spindle that carries the cut- ting tool. 4* The clamping arrangement and the supporting sur- face do not necessarily form an integral part of the jig, but may be separate therefrom. Thus, in some cases, the jig and the work may be held together by C clamps or machin- ists’ clamps; likewise, the supporting surface may be some suitable part of the work itself. In all cases, however, these two features must exist in some form, and the plane of the supporting surface must be perpendicular to the axis of the guide. TYPES OF JIGS. 5. Clamp Jigs and Box Jigs. — There are two general types of jigs in common use, each of which has its own sphere of usefulness. The one type is intended for work where the axes of all holes that are cut by the aid of the jig are parallel. The holes need not necessarily be loca- ted in the same plane, nor must they be drilled from the same side of the jig. Since jigs of this type frequently re- semble some form of a clamp, they are by common consent termed clamp jigs, although in some cases the resemblance between the jig and a clamp is very faint, or has entirely disappeared. The other type of jig is intended for work that requires the holes that are to be cut through it, or into it, to be at various angles to one another. Since jigs of this type most frequently resemble some form of a box, the name of box jig is commonly applied to any jig intended for holes at angles to one another. 31 JIGS AND JIG MAKING. 3 GENERAL REQUIREMENTS. G. There are a number of general requirements, some or all of which must be partially or entirely fulfilled in the design and construction of any jig. The extent to which any or all of the requirements must be taken into considera- tion depends on circumstances; each particular case must be decided on its own merits with special reference to the com- mercial feature. Thus, it may be considered as the height of folly to make a jig worth $50 to do a job worth $20 and which, furthermore, will never be duplicated. 7 . One of the most important requirements is the ease of inserting work into a jig and removing it from the jig. Evidently, the easier this necessary operation is performed, the more work can be turned out by an operator when all other conditions remain the same. Ease of insertion and removal under proper management means reduction of the time cost per piece. 8. A jig should be so constructed that it can easily be cleaned, especially those parts of it that act as stops and locate the work properly. Chips getting between the work and the stops will throw the work out of true, and, conse- quently, will result in an improper location of the holes. While the amount may not be very large, in many cases it will be sufficient to spoil the work. Now, since it is gener- ally agreed that the most stringent orders will fail to make an operator clean the stops of a jig properly before inserting a new piece of work when a large output is demanded, it is considered best to make the stops self-cleaning, ,as far as can be done, or to design the jig so that it can be cleaned with a minimum effort and preferably without any special appli- ances. 9. Interchangeability of the work depends, in a great measure, on proper location of the stops, which should be so arranged as to give an invariable location of the work in relation to the guides of the jig. When work that is liable to vary slightly in its dimensions is to be operated upon in 4 JIGS AND JIG MAKING. § 31 a jig, the stops may occasionally have to be made adjustable in order to accommodate any slight variation in size or shape. 10. Ease of clamping the work to the jig, or vice versa, is a feature that may profitably be studied carefully if a large number of pieces are required to be made in the jig. A rapid clamping arrangement that needs little muscular effort is conducive to a reduction of the time cost per piece. 11. Clamping arrangements require to be so designed that the act of clamping the work to the jig, or vice versa, will not spring the work or the jig. If either is sprung out of true by the act of clamping, inaccurate work will natu- rally result. 12 . Durability of a jig is a requirement that depends on the number of pieces the jig is to be used for as to the extent to which it is to be fulfilled. In general, only such dura- bility should be provided as will serve the extent of service without any serious loss of accuracy. 13. Adaptability to conversion into a combination jig that may be used for either drilling, reaming, or tapping any or all the holes can readily be secured by removable guides of sufficient size, so arranged as to always center themselves during insertion. Since the guides almost invariably take the form of hardened concentric steel bushing, this is, as a general rule, a very easy matter. 1 4. Capability of accurate duplication is of prime im- portance not only when the jig is in constant demand, but also when a number of like jigs are required. In the first case, the natural wear and the unnatural abuse a jig is liable to receive will sooner or later call for its duplication ; both in the first and in the second case, an accurate duplication can, in almost all instances, be readily provided for by making the jig or jigs either from a master jig preserved for this purpose, or from templets of suitable form made from the first jig and preserved. JIGS AND JIG MAKING. 5 § 31 15. Sufficient extent of supporting surface will prevent any canting of the jig under the downward pressure of drill- ing and reaming, and will thus result in a reduction of the breakage of cutting tools. The supporting surface need not necessarily be an unbroken plane; in many cases, three legs, which, of course, will give a steady support in spite of any slight inequalities of the drill-press table, are greatly pref- erable to an unbroken surface. In other cases, four, and even more, legs whose ends lie in the same plane may prove of advantage, especially when the distance that three legs must be apart in order to prevent canting is beyond the range of the drill press available. In order that the jig may not tip over under the pressure of cutting operations, all guides for the cutting tools must lie well within the polygon that is formed by connecting all adjacent points of support by straight lines. 16. Stiffness is not only desirable for most jigs, but also becomes essential when exact duplication of the work is re- quired. The act of clamping the work to the jig, or the jig to the work, with many designs subjects the jig to bending stresses that tend to deform it. Since these bending stresses cannot be expected to be alike each time the jig is used, it follows that the amount of deformation will vary; conse- quently, the work done with the aid of the jig will also vary. Stiffness may best be obtained by properly distributing the metal to resist such bending stresses as the jig may be sub- jected to; the proper arrangement of supports and clamping arrangements will in a measure contribute toward stiffness. 17. Absence of sharp corners means ease of handling; any feature that makes a tool agreeable to the touch may confidently be expected to reduce the time cost per piece. 18. Accuracy of the jig itself, while mentioned last, is the most important requirement. It should always be remembered that any inaccuracy of the jig will be dupli- cated in the work ; and if the cutting tools are loosely guided, the errors may enlarge. While accuracy is essential, there 6 JIGS AND JIG MAKING. 31 is such a thing as carrying it to an extreme. The toolmaker should always aim to obtain the accuracy that is essential; any further reduction means a large outlay of money that is generally not warranted by the conditions of the case. JIG DETAILS. GUIDE BUSHINGS. 19. Permanent Bustlings. — The guides for the cut- ting tools, which are usually drills, reamers, or taps, most frequently take the form of hardened steel bushings set into the jig body. The hole in the bushing is made to fit the drill, reamer, or tap shank closely ; the outside of the bushing is exactly concentric with the inside. 20. The bushings may be made in various forms to suit different purposes. Common forms of plain bushings, in- tended to be driven into suitable holes in the jig body, are shown in Figs. 1 and 2. Refer- ring to Fig. 1, the bushing is seen to be straight inside and outside, except that the end where the drill enters is rounded out to allow it to enter easily. This plain bushing is the cheapest bushing to make, and, if well fitted to the hole that receives it, is thoroughly satisfactory. The only objectionable feature is that when a drill too large for the hole is forced down on the bushing, it is liable to push the bushing through its seat. This is very liable to happen when the jig is used on a multiple-spindle drill press. 21 . In order to prevent the bushing from being pushed through its seat, it may be made tapering on the outside, or it may be allowed to project from the seat. The projecting part is then enlarged to form a shoulder. While tapering the outside of the bushing will accomplish the object to be attained, it is an expensive form of bushing to produce. JIGS AND JIG MAKING. 7 § 31 Likewise, it is expensive to bore the seat for it, especially if great accuracy in the location of its axis is required. On the other hand, a tapered bushing is easily removed. 22 . The most common form of a straight bushing with an enlarged head is shown in Fig. 2 ( a ). The shoulder Fig. 2. under the head is made square. This is objectionable, how- ever, for two reasons. In the first place, in hardening the bushing, a crack is liable to form in the sharp corner; in the second place, while forcing the bushing home into its seat, the head is rather liable to be broken off. The end that receives the drill is rounded off inside and out, usually semi- circular, as shown. 23 . A better form of a straight bushing is shown in Fig. 2 ( b ). Here a liberal sized fillet is left under the head, which obviates the liability of cracking in hardening, and reduces the liability of breaking the head off while forcing the bushing home. In the bushing shown, the end is rounded out considerably more on the inside than on the outside; this makes it easier for the drill to find the hole and hence is preferable to the semicircular rounding off shown in Fig. 2 ( a ). When the bushing is to be ground on the outside after hardening, it is advisable to very slightly neck it down under the shoulder with a round-nosed tool; when grinding the outside, the emery wheel can then pass clear over the part being ground. The necking down is clearly shown in Fig. 2 (c). 24 . In many cases, it is necessary for the bushing to project some distance beyond the lower part of its seat, in JIGS AND JIG MAKING. §31 order that the point of the drill or end of the reamer may be supported close to the work. In that case, the bushing may take the form shown in Fig. 2 ( d ). As. shown in the illustration, it is counterbored part way down, in order to reduce the friction of the drill or reamer against the inner surface of the bushing. The part that serves to guide the cutting tool does not, in general, need to be any longer than twice its diameter. The bushings so far shown are not intended to be removed except for the purpose of renewal when worn. 25. Removable Bushings. — Any ordinary jig can readily be converted into a combination jig by fitting it with two or more sets of bushings. One set may then be made to fit the drills; the second set may be made to guide the reamers; and the third set may suit the tap shanks. Obviously, the bushing must be easily removable. There are quite a number of ways in which this may be done. 2G. The simplest way is to make a straight bushing a sliding fit in its seat and then confine it by a setscrew. While this can be done advantageously in many cases, in others the location of the bushing prevents the use of a setscrew. If that happens to be the case, some toolmakers will fit a tapered bushing to a tapered seat, relying on the friction to hold the bushing in place during the cutting operations. 27. Some forms of a tapered removable bushing are shown in Fig. 3. The simplest form is shown in Fig. 3 (a ) ; the bushing is removed by driving it out with a drift and a hammer. A better form is shown in Fig. 3 (b). Here the (a) Fig. 3. JIGS AND JIG MAKING. 0 31 bashing is made long enough to project beyond its seat; its projecting part is made hexagonal to receive a wrench, by means of which it may be loosened. In order that the time required for the handling of the wrench may be saved, the projecting part may have a handle permanently attached to it, 'as shown in Fig. 3 (< c ). The objection to this last form is that, in many cases, the handle may interfere with easy handling of the jig. 28. Tapered removable bushings are not only open to the objection that they are expensive to produce, but also are liable to be thrown out of their true location by any foreign matter, such as chips or waste, getting between the outside of the bushing and its seat. In this respect, a straight removable bushing will have the advantage, since it will push all foreign matter out of its hole during inser- tion. On the other hand, in the case of the tapered bushing, wear of the seat will not affect the accurate loca- tion of the bushings to an appreciable extent. 29. Removable bushings may be threaded on the outside, and may be provided with a hexagonal head, as shown in Fig. 4 (a). The seat for the bushing is then (b) Fig. 4. chased or tapped to suit. Since the bushing is very liable to change its shape and diameter in hardening, a bushing that is threaded should be finished entirely before chasing the thread in the seat. Obviously, after hardening, it is difficult to grind the thread truly concentric with the hole; for this reason, the use of a bushing of the form shown in Fig. 3 (a) is not to be recommended for work that requires very accurate location of the holes. Furthermore, the 10 JIGS AND JIG MAKING. § 31 unevenness of the thread induced by the hardening process will cause a rapid wear of the thread in the seat, thus destroying the accurate location. 30 . A better form of a threaded bushing is shown in Fig. 4 ( b ) and (*;). Here the thread is not relied on to center the bushing properly, but serves merely as a con- venient means of attaching and detaching it. The bushing is centered by a cylindrical part that closely fits a corre- sponding part of the seat; the thread is made a fairly good fit in the seat. The cylindrical part of the bushing may be either below or above the threaded part; if it is above, the thread in the seat can be tapped clear through, which allows the use of a plug tap. This design of a threaded bushing is preferable for accurate work, since the cylindrical part, after hardening, can be ground true with the hole. While the bushings shown in Fig. 4 all have a hexagonal head, they may be, and occasionally are, made with a large nurled head, and also with a handle similar to that shown in Fig. 3 (c). 31 . Clamp Bushings. — A jig bushing may serve a double purpose; that is, it may be used for guiding the cutting tool and, at the same time, for clamping the work to the jig body. This is done by making the threaded part of the bushing long enough to allow the end to be screwed down on the work. There are many cases where the adop- tion of one or more clamp bushings will allow a very simple design of a jig. Fig. 5. 31 JIGS AND JIG MAKING. 11 32. In some cases where the work has cylindrical pro- jections or a recess, a jig bushing may be made to act as a stop for centering the work properly and clamping it at the same time. Thus, if the work has a cylindrical or conical recess, the lower end of the bushing may be turned conical, as shown in Fig. 5 ( a ). If the work is to be centered by a cylindrical or tapering projection, the lower end of the bush- ing may be recessed conical, as shown in Fig. 5 (5). 33. Size of Guide Hole. — The size of the hole in the bushing has a very important influence on the accuracy with which the holes are drilled into the work. In all cases, the drill or reamer must be loose enough in the bushing so as not to bind and seize. This looseness does not need to be much; if the hole is .001 inch larger than the cutting tool, there is little danger of sticking. How much the hole should be made larger than the drill would be easily determined if it were not for the fact that the commercial sizes of the drills do not, as a general rule, agree very closely with their nominal size. While the variation between different drills of the same nominal size is not very large, and not sufficient to be appreciable for ordinary work, this variation becomes quite appreciable when accurate work is to be done by jig drilling. If a number of drills of the same nominal size are meas- ured, some will be found over size, some under size, and, per- haps, a few correct size. The toolmaker now has the choice of several methods of procedure. He may make the guide hole sufficiently large to fit the largest drill in the lot, which involves a consequent serious looseness of fit of the under- size drills; or he may make the guide hole standard size and stone down all drills that are over size; or, further, he may make the bushing to suit the smallest under-size drill, and stone all other drills down to suit this size. 34. Which of these methods is to be adopted is purely a question of the accuracy with which the holes are to be located, and the accuracy with which the drilled holes are to represent their nominal size. When accuracy of location 12 JIGS AND JIG MAKING. §31 is the most essential factor, the third method is preferable; if keeping the holes to the standard size is deemed most im- portant, the second method may be adopted; and for a com- paratively rough job, the first method may be chosen. In choosing a method, it is to be observed that great accuracy, in regard to keeping all holes drilled with the aid of the jig to the same size, must not be expected by drilling; as well known, a drill can drill a hole considerably larger than itself if it is ground so that its point is out of center. 35. Material for Bushings. — The material to- be chosen for making the bushings depends on the resistance to wear that is deemed essential. Hardened tool-steel bush- ings left as hard as fire and water can make them will resist wear better than machinery-steel bushings that have been case-hardened with cyanide or prussiate of potassium. Machinery steel will answer very well for bushings that are intended for temporary jigs; if the jig is in constant use, however, it is usually advisable to choose tool steel and harden the bushings. 36. Grinding Bushings. — Since the hardening proc- ess not only changes the size but also the shape of the bushings, they should be ground both inside and outside after hardening, if great accuracy in the central location of the guide holes in reference to the seat is deemed essential. In many cases, however, dependence can be placed on the fact that forcing the bushing home will partially correct any deviation from roundness induced by hardening, especially if the walls of the bushings are thin. In that case, the bushings may be lapped to size after they have been forced home. CLAMPING DEVICES. 37. Jigs are supplied with clamping devices of vari- ous forms for one or both of two different purposes: to clamp the work to the jig body or to clamp some part of the jig made movable to provide for inserting and removing work. §31 JIGS AND JIG MAKING. 13 38. Clamps intended for the purpose first mentioned may be designed in various ways to suit different conditions. For some work the hook bolt shown in Fig. 6 is very well adapted, being cheap in construction and easily ap- plied. The bolt proper passes through a hole in the jig, which it fits closely. It is made long enough to have the head hook over some projecting part of the work, and may be supplied with a wing nut as shown, or have an ordinary hexagonal nut. In some cases, a large nurled nut may be of advantage. The greatest clamping pressure can be obtained with a hexagonal nut and a wrench; a mod- erate pressure can be obtained with the wing nut or the nurled nut. However, the wing nut or nurled nut allows the hook bolt to be applied more rapidly. It will be under- stood that in order to allow the work to be inserted or removed, the loosened hook bolt is turned so that its head is away from the work; when the work has been inserted, the head is turned toward the work and hooks over it. The clamping is then done by screwing up the nut. 39. In jigs that partially or entirely surround the work, it is most commonly held in place by setscrews, which may be designed in several ways. When drop-forged thumbscrews are avail- able, they are generally used, since comparatively little work is required to finish them. When these cannot be obtained, the setscrews may be made as shown in Fig. 7 by driving a cylindrical pin into a hole drilled through the head of the screw. In many cases, the ordinary setscrews that can be bought in the market may be used. These, however, require a wrench for tightening, and hence are not so readily used as thumbscrews, or the screw illustrated in Fig. 7. Fig. 14 JIGS AND JIG MAKING. 31 40 . Fig. 8 shows a common clamping arrangement for locking two parts of a jig together. The thumbscrew shown Fig. 8. is screwed into a tapped hole in the jig body, as a. The shank passes through a slot b' in the movable part b of the jig. This slot is wide and long enough to allow the head to clear it when the screw has been given a quarter-turn from the position shown. Evidently, this is a very rapid clamp- ing arrangement. The only objection is that, as the threads and the bearing surfaces wear, the head will finally come in line with the slot in the movable part. 41 . Fig. 9 shows a hinged bolt, which is hinged to the stationary part a of the jig by means of the pin shown. The bolt passes through a slot in the movable part b , open on one end, and is provided with a nut and washer. The nut may JIGS AND JIG MAKING. 15 § 31 be a wing nut, as shown, or a hexagonal or nurled nut. Wear of the bearing surface or of the pin joint does not affect the clamping. As the nut must be unscrewed some distance to allow the bolt to be swung clear of the slot, this arrangement is not quite so rapid as that shown in Fig. 8. 42. Fig. 10 shows a hinged cam-lever pivoted to the sta- tionary part a of the jig. Its shank passes into a slot in the movable part b\ the bearing surfaces of the head engage inclined surfaces of the movable part. Where extreme ra- pidity of clamping is desired, this design can be recommended. STOP-PINS. 43. I n order to prevent any shifting of the work in the jig during the cutting operations, one or more stop-pins may be provided. These are usually made cylindrical, and are closely fitted to the guide bushing. They should be provided with a suitable handle to facilitate withdrawal. To prevent shifting of the work, a stop-pin is pushed through the bushing into the hole in the work as soon as the hole has been drilled. Since the work must be confined at least in two places to surely prevent any liability of shifting, two stop-pins are often provided. It is a good idea always to select the holes that are the farthest apart for the stop-pins. C. S .. 111.— 43a 16 JIGS AND JIG MAKING. §31 JIG MAKING. EXAMPLES OF JIG DESIGN. 44 . Owing to the innumerable shapes that the work a jig is intended for may have, no specific directions can 'be given as to the design of a jig. The general requirements previously given should in each case be fulfilled to the extent that the circumstances render advisable. The designs given here will serve as suggestions to the toolmaker, but they must be modified to suit conditions and requirements. 45 . The simplest form of a jig is shown in Fig. 11. The jig simply consists of a flat plate made of suitable ma- terial. The outline of the jig is the same as that of the work; holes are drilled in the jig to serve as guides. The jig is intended to be laid on the work and is then clamped to it by any suit* able and convenient means o NS 45 Drill. G N2 45 Drill. o N? 50 Drill. Fig. ii. so that its outline coincides with that of the work. 46 . Such a jig is cheap, and will serve well for flat work where extreme accuracy in the location of the holes is not essential. For small work it will last quite well if made of sheet tool steel and hardened all over. When it is to be used for a small number of pieces, it may be made of machinery steel and the holes case-hardened. When the holes wear, either a new jig must be made or the holes counterbored to receive hardened steel bushings. 47 . In the latter case, the jig takes the form shown in Fig. 12, which may be considered as the second step in the development of a jig. Since the bushings can be replaced easily when worn, the center-to-center distance of their axes can be accurately preserved. Beyond this fact, the design §31 JIGS AND JIG MAKING. 17 shown is not particularly more advantageous than the one shown in Fig. 11, ex- cept that it may be used for sizes that would prevent heating and hardening the en- tire jig. 48. Fig. 13 illus- trates a more advanced form, in which stops have been added for the purpose of alining the jig on the work. In this particular instance, the stops are formed by flanges a, a and pins b , so placed as to suit the outline of the work. If the different pieces of work are quite uniform, as, for instance, if the outline has been fin- ished by profiling, punching, or milling, quite accurate work fig. 13. can be done in a jig of this design. In many instances, it is not even necessary to clamp the work to the jig, as the stops will often be sufficient to prevent shifting of the jig. 49. A further development of a jig is shown in Fig. 14, where a clamping attachment has been added. The jig is here made in two parts, hinged together at one end. The 18 JIGS AND JIG MAKING. § 31 pressure of the hand of the operator is intended to clamp Fig. 14. the work to the jig; stop-pins placed to suit the outline of the work insure an unvarying location of the holes in refer- ence to the outline. A jig of this kind is well adapted for drilling holes through small flat work of uniform thickness. JIGS AND JIG MAKING. 19 g 31 50. Fig. 15 shows a jig design well adapted for drilling holes through flanges. The jig body is recessed to go over the flange, and the jig is attached and clamped by means of the hook bolts shown. Attention is called to the position of the hook bolts in reference to the bushings. They should always be so located that neither the head of the hook bolt nor the nut can ever come in the way of the drill, reamer, or tap that is intended to be guided by the bushing. Jigs of this design are readily modified to be alined to a bored or cored hole in the work by providing the lower surface with a projection of suitable shape instead of the recess shown. 51. With the exception of the jig illustrated in Fig. 14, all the designs thus far shown depend on the work itself for furnishing a supporting surface to sustain the downward thrust of the cutting operations. Fig. 16 shows a jig in which the work is placed within the jig, and where, conse- quently, the thrust is taken by a suitable surface of the jig. Referring to the illustration, it is seen that the jig is made of two parts for the sake of convenience in machining it. The cover a is fastened by the screws shown; an invariable location of the bushings in reference to the stops is insured 20 JIGS AND JIG MAKING. § 31 by dowel pins b, b. This precaution is necessary when the stops are contained in a part of the jig that is separate from that which carries the bushings. The work is pushed against the stops by the setscrews c and c ' ; it is held down by the setscrew d. In this case, the surface e of the jig has been selected as a suitable stop to gauge the location of the work sidewise; its longitudinal location is gauged by the stop-pin f. It will be observed that the setscrew c is placed at an angle with c' . Owing to the way in which it bears against the work, the tightening up of the setscrew will not only push the work against both stops, but will also prevent any longitudinal movement, thus doing away with the necessity of placing another setscrew at the right-hand end of the jig. The design shown possesses several disadvantages. In the first place, it is rather difficult to clean it properly; in the second place, it is easy to spring the work out of true with the setscrew d. b b Fig. 17. 52. Fig. 17 shows how a jig may be made for the same piece that the design shown in Fig. 1G was intended for, in §31 JIGS AND JIG MAKING. 21 order to overcome the objectionable features of that design. The jig body a is composed of one piece in this instance, which is open in front to allow easy insertion and removal of the work, and to make the jig accessible for cleaning. In order to do away with clamping screws and stops, the bush- ings b, b themselves are made to act as such. This makes a very simple and cheaply made jig, well adapted for work like that shown clamped in the jig. Fig. 18. 53. Ease of insertion and removal and accessibility for cleaning may often be secured by making some part of the jig movable. Thus, in Fig. 18, the top part a of the jig is 22 JIGS AND JIG MAKING. § 31 Fig. 19. JIGS AND JIG MAKING. 23 § 31 hinged to the body b; the two parts are clamped together by the hinged bolt c. In order to show the slot in a clearly, the wing nut and washer of this bolt are shown removed in the plan view. The work is supported against the thrust of the cutting operation by clamping bushings d, d ’, the ends of which are chamfered in order to act as stops at the same time. The guide bushings e % e in this case have a shoulder on their lower end for the purpose of preventing the upward pressure of the- clamping bushings from moving them. Three legs/", /"are fastened to the jig body; these legs rest on the drill-press table while the jig is in use. They must be made long enough to insure that the lower end of the clamping bushings will always come clear of the table. The design is shown applied to work in which the holes do not lie in the same horizontal plane; it may be applied to other work, however. Every part of the jig is accessible ; the work is automatically centered and the disadvantages of threaded guide bushings are avoided. The liability of springing the jig in the clamping operation is greatly re- duced by providing the clamping bushings with nurled heads on which the fingers of the operator will slip before he can tighten them sufficiently to spring the jig out of true. 54. Fig. 19 shows a form of jig that is largely used for drilling holes in the flanges of work that has a cross-section similar to that shown in the illustration, where a represents the work. Since three legs would, in this case, make the jig rather complicated, four are used. The jig body b is simply a flat plate into which four legs are screwed. Two opposite legs are slotted to receive the yoke c , which is hinged at one end, and secured in position at the other end by a removable pin d. This yoke carries the setscrew e , by means of which the work is clamped to the jig. When the work has a hole in line with the setscrew, the latter may terminate in a circular plate, as e ' . To insert or remove the work, the jig is turned upside down; the pin d is then removed and the yoke swung out of the way. When the 24 JIGS AND JIG MAKING. 31 Fig. 20. JIGS AND JIG MAKING. 25 § 31 jig is used for castings, which, as well known, are bound to vary slightly in size, the jig may be provided with a self- centering arrangement. Referring to the figure, f is a plate that can be rotated by means of the handle g. This plate carries three pins z, i that enter slots formed in the jaws /z, h . These jaws are pivoted to the jig body by screws, as k , k , and their axes are placed nearer .the axis of rotation of the plate f than the pins z, z. In consequence of this, a right-handed rotation of the plate will cause the jaws to swing around their ful- crum screws until they come against the work, which is thus centered. The design of centering arrangement is not given as the best one that could be devised, but simply shows one way of accomplishing the object to be attained. 55. All the jigs so far shown are intended for drill- ing work ip which the axes of all holes are parallel. Fig. 20 shows a jig designed for drilling holes in three different direc- tions in one chucking. Referring to Fig. 20, the work a , which is shown in perspective in Fig. 20 ( a ), is to be pierced by the holes c, d< and