MACHINE SHOP TOOLS AND SHOP PRACTICE A BOOK OF PRACTICAL INSTRUCTION Describing in Every Detail the Construction, Operation and Manipulation of Both Hand and Machine Tools INCLUDING CHAPTERS On Filing, Fitting and Scraping Surfaces ; On Drills, Reamers, Taps and Dies ; -The Lathe and Its Tools ; Planers, Shapers and Their Tools ; Milling Machines and Cutters ; Gear Cutters and Gear Cutting ; Drilling Machirtes and Drill Work ; Grinding Machines and Their Work ; Hardening and Tempering, Gearing, Belt- ing and Transmission Machinery ; Useful Data and Tables. BY WILLIAM H. VAN DERVOORT, M. E. SIXTH EDITION Illustrated by 673 Engravings of the Latest Tools and Methods, all of which are fully described NEW YORK : THE NORMAN W. HENLEY PUBLISHING COMPANY 132 NASSAU STREET 1911 - T^s """ If OF THE \ I UNIVERSITY A OF JJ I tr*F ' " ' ' '--:ii rs"<(: iii i> i uK COPYRIGHTED BY W. H. VAN DERVOORT 1903 Composition, Printing, and Electrotyping By MACGOWAN & SLII-I-I-.K 30 Brekman Street, New York, U. S. A. PREFACE. This book is the outgrowth of a series of articles prepared by the author for the students in machine shop practice at the Uni- versity of Illinois; some of these articles having recently been published in "Machinery." An effort has been made to treat the subject in a clear and comprehensive manner, carefully avoiding all unnecessary matter and presenting to the apprentice and mechanic many points pertaining to the tools with which they come in daily contact, and about which they are often unable to obtain all the information necessary, in order that they may use these tools correctly and efficiently. In treating on the various classes of small and machine tools, the author has endeavored to bring out much pertaining to the construction and care of these tools, as well as upon their uses. The importance of the machinist having at least *a limited amount of information on the subjects of Fastenings, Gearing, and Belting and Transmission Machinery has prompted the addi- tion of chapters upon these subjects. The author wishes to acknowledge his indebtedness to the publishers, the Industrial Press, and the tool manufacturers, who have so kindly assisted him in getting together many of the illus- trations and tables used in this work. March, 1903. W. H. VAN DERVOORT. INTRODUCTION. The correct manipulation of metal working tools comes per- fectly natural to many of our young mechanics, and they easily become expert in their use. It seems to be born in them, and they make good workmen no matter how poor the tools with which they work and how bad the instruction they receive ; but where one such man is found there will be a dozen others who can acquire the necessary skill to be called good machinists, only after careful study and close application of the most thorough instruction. The time required to accomplish this will depend entirely on the .man and the conditions under which he works. Under favorable circumstances two to six years will be requirea. The more the apprentice reads and thinks the more quickly will he master his trade. Every apprentice should be a regular sub- scriber to at least one good paper treating on the subject and should READ it. He should never fail to look over the advertising pages of each issue, as these pages constitute a perfect index of progress along the line of his chosen occupation. The reading will create thought, will broaden the ideas and put the young man in a better position to appreciate what he sees and hears. The young machinist must keep constantly before him the two requisites of a good mechanic accuracy and rapidity. The first he must acquire, and if he would succeed in these days of close competition, he must couple with it the ability to produce such work quickly. He should, above all things, train his judgment, having it continually with him, and should learn as quickly as possible the strength of the materials with which he is to deal. This will come more by experience than by calculation and let good judgment and common sense aid in making the experience bill low. "Observation is a great teacher." Therefore he should learn to observe, noting carefully the ways in which the skilled me- chanic performs his work. His thoughts must be kept contin- ually on the work in hand, studying better and quicker ways to do it. He can gain the confidence of his employer in no better way 12 INTRODUCTION. than by strict attention to his work, careful observance of all regulations pertaining to the management of the plant, and a sincere disposition to do at all times his very best. He should be perfectly free to ask questions ; sensible ones, as the other kind will injure his cause. He must be cautious about making sugges- tions as they are usually not thankfully received. When the foreman gives precise instructions as to how to perform a piece of work, the instructions must be followed to the letter, even though he thinks he can do it in a better way. He is probably wrong, but if not the opportunity to do it his way will come soon, and in such a way as to please rather than provoke, by proving the better method. He must learn to take a hint, as the foreman may at times suggest rather than tell him that it would be best to do the other way ; and above all things he must not have to be told a second time. It is bad to duplicate accidents to tools or mistakes on work, and especially so when previously cautioned on these points. He cannot be too neat and orderly, not only with his tools and work, but in his personal appearance. The young mechanic should never lose an opportunity to visit other shops, as he will be sure to get some good ideas from them. More can often be learned in some poorly equipped, ill-man- aged concern than in a shop running under the most perfect sys- tem, as we are often more forcibly impressed with the how not to do it, than with the how. A careful perusal of the trade cata- logues issued by all the leading machine and small tool builders cannot fail to be of value, as in those catalogues will be found many excellent cuts, with description of tools, and often valuable hints on their manufacture and uses. Mechanics who learned their trade before the introduction of modern tools and methods frequently fail to appreciate the im- portance of their making an effort to familiarize themselves with the nicer points of detail of the later small and machine tools. The successful working and tempering of high grade steels and the methods of grinding now employed have been the principal factors in the successful manufacture of the many excellent small tools now in use. Better tools, better methods, better workmen and the best of mechanical ability have evolved from the ill- designed and inefficient tools of but a few years ago the excellent ones of to-day. INTRODUCTION. 13 Many mechanics, both old and young, fail to appreciate the finer points in a good tool ; they fail to realize that every line, curve and angle in its construction represents the most careful study, and in most cases have been arrived at only after years of experimentation. In taking up the subjects pertaining to machine shop tools, their construction and uses, two general subdivisions may be made, small tools and machine tools. Under the head of small tools may be placed all hand tools, measuring tools, cutting tools used in machine tools and jigs. The subdivision of the work com- monly performed on metal-worKing machine tools may be briefly outlined as follows : First Turning and Boring ; as performed in the lathe, screw- machine, turret-machine, vertical boring mill, etc., in which the work is usually made to rotate to a cutting tool or tools which, aside from feeds, are stationary. This operation usually pro- duces curved or circular surfaces, both internal and external, but may, as in facing, produce a plane surface. Second Planing Operations ; as performed on the planer, shaper, slotting machine or key-way cutter, where the work is given a straight line motion to a stationary tool, or, as in the three latter types of machines, the tool is given a straight line motion over stationary work. In the former case the feeds are given to the tool while in the latter the work usually receives one or both of the feeds. In the case of the traverse head shaper, however, the tool is given both feeds over perfectly stationary work. Third Milling Operations ; as performed on the various types of milling machines where a rotating cutter produces plane, curved or formed surfaces on the work, the latter usually receiv- ing the feeds. Fourth Drilling; the forming of circular holes in solid stock by means of a revolving tool at one operation, the tool usually receiving the feed. Drilling differs from boring in that the latter term applies to the enlarging and truing of a hole already formed. Fifth Grinding ; these operations involve the removal of metal and finishing of the surface by an abrasive process, the material being ground rather than cut away. The universal and surface grinding machines correspond with the lathe and planer, a -rotat- ing wheel of emery or corundum taking the place of the cutting tool in the latter machines. Grinding operations, although neces- I4 INTRODUCTION. sarily slow, make possible the accurate finishing of the hardest metals. The scope of this v/ork will not permit going too much into the details of machine tool construction. It is, however, hoped that the principal points of construction and methods of operation may be brought out clearly and in such a way as to aid the young mechanic in quickly becoming master of the several classes of machine tool operations above enumerated, and suggest some thought for the older mechanic. CONTENTS. CHAPTER I. The Hammer and Cold Chisel , 17 to . ai CHAPTER II. The File and Filing 22 to 47 CHAPTER III. Scrapers and Scraped Surfaces 48 to 54 CHAPTER IV. Standards of Measure , 55 to 63 CHAPTER V. Calipers 64 to 81 CHAPTER VI. Gauges and Indicators 82 to 92 CHAPTER VII. Rules, Squares and Other Small Tools 93 to 102 CHAPTER VIII. Drills 103 to 1 13 CHAPTER IX. Reamers 114 to 124 CHAPTER X. Taps and Dies 125 to 141 CHAPTER XL Drill and Tap Holders 142 to 153* CHAPTER XII. Mandrels 154 to 162 CHAPTER XIII. The Lathe 163 to 181 CHAPTER XIV. The Lathe in Modified Forms 182 to 196 CHAPTER XV. Lathe Tools 197 to 209 CHAPTER XVI. Chucks and Drivers for Lathe Work 210 to 219 ,6 CONTENTS. CHAPTER XVII. Lathe Work, Between Centers 220 to 247 CHAPTER XVIII. Lathe Work on Face Plate, Chuck and Carriage 248 to 263 CHAPTER XIX. Boring and Turning Mills 264 to 272 CHAPTER XX. Planing and Shaping Machines, Their Tools and Attachments 273 to 298 CHAPTER XXI. Planer and Shaper Work . 299 to 305 CHAPTER XXII. The Slotting Machine and Key Seater 306 to 311 CHAPTER XXIII. Milling Machines 312 to 335 CHAPTER XXIV. Milling Machine Cutters 336 to 349 CHAPTER XXV. Milling Machine Work 350 tp 378 CHAPTER XXVI. Gear Cutters and Gear Cutting 379 to 396 CHAPTER XXVII. Drilling Machines and Drilling Work 397 to 422 CHAPTER XXVIII. Grinding Machines and Grinding 423 to 439 CHAPTER XXIX. Hardening and Tempering 440 to 449 CHAPTER XXX. "ings ; 450 to 462 CHAPTER XXXI. Gearing 463 to 489 CHAPTER XXXII. Belting and Transmission Machinery 49010516 CHAPTER XXXI 1 1. Miscellaneous Shop Equipment and Conveniences 517 to 527 CHAPTER XXXIV. Useful Tables and Data 528 to 544 CHAPTER I. THE HAMMER AND COLD CHISEL. The hammer and cold chisel are a noisy pair with which the apprentice becomes acquainted early in his shop experience, and his aching" arms and battered knuckles tell of the introduction. The machinist hammer, as generally used, weighs from three- fourths to one and one-half pounds, exclusive of handle. It FIG. r. is made of high-grade steel, carefully tempered on head and pene and usually of the form shown in Fig. i. The eye is left soft as it will, in that condition, better resist the shock without danger of cracking. The head is usually made cylindrical with FIG. 2. a slightly crowning face. For the ball pene is often substituted the straight pene, Fig. 2, and the cross pene, Fig. 3. The pene is used almost entirely for riveting purposes. The eye should j8 MODERN MACHINE SHOP TOOLS. be enlarged slightly at each end; the handle can then be fitted in from one side and wedged to fill the enlargement of the eye on the other side. Hard, smooth wedges are not suitable for this purpose, as they jar loose too easily. Soft wood or roughed metal wedges serve the purpose well. The handle should be of straight-grained, dry, second-growth hickory, twelve to sixteen inches long ; depending on the weight of the hammer. The handle should not be too stiff in the shank, as too rigid a connection between hammer and hand causes undue shock, and consequent tiring of the hand. It should be so set in the eye that its length is at right angles to the axis of hammer head, and its long cross section parallel with this axis. The face of the hammer should be kept true and smooth, by careful grinding and polishing. Should the edges become chipped FIG. 3. a good smith can dress and retemper the head, making it as good as new. In its use the hammer should be grasped near the end of the handle, giving it a free arm swing and carrying the head through a nearly vertical plane. If the plane of the swing approaches a horizontal the weight of the hammer will produce a twisting effort on the fore arm which will be very wearing. The handle should be grasped with only sufficient force to safely control the blow. Machinists' cold chisels, for ordinary shop uses, are generally made from seven-eighths or three-fourths inch octagonal steel, and when new should be about eight inches long. The flat sur- facing chisel, as shown in Fig. 4, should be dressed about three inches back from the cutting edge. The flats A A should be plane surfaces symmetrical with the sides of the octagon. The THE HAMMER AND COLD CHISEL. 9 thickness of the bit at C should not exceed three-sixteenths inch for ordinary work and can usually be made somewhat thinner. Care must be exercised in the grinding of the facets c c. The angle of their faces with each other will depend on the hardness of the metal to be cut. For the softer metals, as copper, babbitt and lead, 25 degrees to 30 degrees will work well ; for brass and FIG. 4 cast iron, 40 degrees to 55 degrees; and for steel, 60 degrees to 70 degrees. The smaller this angle the more nearly will the center line of the chisel approach the plane of the work and the greater will be the cutting resultant of the blow. It is therefore advisable to make this angle as small as the nature of the work will permit. These facets should be ground straight in their width, as shown at A, Fig. 5 ; not rounded as shown at B, as in that case the facet would not form a guide and it would be found difficult to FIG. 6. FIG. 7. make a smooth, straight cut. The facets should also be ground at a uniform angle with the flats, thus bringing the cutting edge parallel with the flats, as shown in end view at A, Fig. 6, and not as -shown at B. The cutting-edge formed by the intersection of these facets should be at right angles to the length of the chisel. For smooth chipping the cutting-edge should be slightly rounded in its length, as shown in Fig. 7. When ground straight the cor- ners, e e, are likely, to dig into the work and are more apt to break away than when ground rounding. 20 MODERN MACHINE SHOP TOOLS. In forging, the cutting-edge should always be made wider than the diameter of the body of the chisel. When the tool is to be used on wrought iron or steel this width should exceed the diameter from one-thirty-second to one-sixteenth of an inch, Fig. 4; but when for use on the softer metals the excess may be as much as one-half of the diameter of the body, as shown in Fig. 12. The flat chisel can be modified in form to suit special con- ditions, as for example, the cutting of the flat sides of a mortise requires a chisel the axis of which will follow a line nearly par- allel to the work surface. Such a chisel is shown in Fig. 8, in FIG. 8. which one flat is parallel with the length of chisel having at the end a wide facet at a slight angle with the length, this in order to be able to guide and control the cutting-edge of the tool. The cape chisel is used as a parting tool, for grooving and key waving. It is of the general form shown in Fig. 9. In this PIG. 9. chisel the thickness at A must be less than the length of the cutting-edge in order that the tool can be given a small amount of side-motion in the groove it cuts, otherwise it would be difficult to guide the cutting-edge. This chisel, when made as shown in Fig. 10, forms the tool usually used for grooving straight oil ways FIG. 10. THE HAMMER AND COLD CHISEL. 21 in loose pulleys and shaft-bearings. For cutting spiral grooves in half boxes this chisel should be forged with a curved instead of a straight bottom face. The diamond-pointed chisel is shown in Fig. n. This tool is FIG. II. usually used for squaring corners, and is generally made as shown in figure. The head of all chisels should be dressed round and somewhat reduced in diameter, as shown in figures. When the head be- comes battered redress it, as small pieces of steel are apt to fly from a bushed chisel head, embedding themselves deeply in the hand holding the chisel. In using the cold chisel grasp it near the head with the full hand, knuckles up. Do not hold it too tightly but with sufficient force only to guide and hold it to the work. When the surface of the work is difficult to get at the workman is justified in hold- ing the chisel between thumb and fingers, or with palm of hand up. The eye should follow the cutting-edge, not the head of the chisel, when delivering the blow, and light taps with the hammer should not be used before each heavy blow. It will require FIG. 12. some practice before the beginner can accomplish this without disastrous results to his knuckles. In tempering the chisel for general machine shop work it should be drawn nearly to a blue which gives a tough temper that will stand well on all, except chilled iron and hard steel work. CHAPTER II. THE FILE AND FILING. A piece of high-grade crucible steel, forged to shape, ground, cut and carefully tempered, forms that tool so indispensable to the mechanic the file. The file maker is no longer compelled to forge his blanks from stock of unsuitable proportion, but receives from the steel manu- facturers stock of the required cross-section to make all standard shapes. This reduces the forging to a minimum, it being only necessary to cut the stock to the required lengths, to draw down the point and form the tang, the latter operations being very rapidly performed under power hammers. The National Association of File Manufacturers prescribe to 12 13. 16" the steel makers the forms of cross-sections they require. Con- sequently, all makers of file steel can furnish any section correct to gauge. In Fig. 13 are shown the correct cross-sections of steel for flat files, even inch lengths, from 4 to 16 inches. In Fig. 14 are shown the cross-sections of file steel for all the shapes in general use. Each section is for an 8-inch file, full scale. The names of the files made from steel of these sections are, referring to the numbers of the figure: I, "Hand"; 2, "Flat"; 3, "Mill"; 4, "Pillar"; 5, "Warding"; 6, "Square"; 7, "Round"; 8, "Half- round"; 9, "Three-square"; 10, "Knife"; u, "Pit-saw"; 12, "Crossing"; 13, "Tumbler"; 14, "Cross-cut"; 15, "Feather-edge"; 16, "Cant-saw"; 17, "Cant-file"; 18, "Cabinet"; 19, "Shoe-rasp"; 20, "Rasp." THE FILE AND FILING. 23 It will be noticed that many of these files are named from the form of their cross-section, 'and that those so named are the ones most used for general work; while the others receive their names from the special character of the work they are expected to be used upon. It will also be noted that the stock for files of rec- tangular cross-section may be classified as to thickness as fol- lows : "Square," the thickest; "Pillar," "Hand," "Flat," "Rasp" and "Warding." As to width, "Hand" is the widest; "Flat," "Rasp," "Mill" and "Warding" are the same width; "Pillar" materially narrower, and "Square" the narrowest. The "Half-round" is not a full semicircle, the arc being about 19 80 one-third of the full circte. On the other hand, the "Pit-saw" is a full half circle in .section. The "Three-square," "Cant-saw" and "Cant-file" differ in sec- tion in their angles, the former having equal angles, 60 degrees, and equal sides, the next 3535 and no-degree angles, and the latter 30 30 and i2O-degree angles. The length of the file is measured from point to heel, and does not include the tang. The tang is usually made spike shaped to receive a plain ferrule handle. Some makers modify the form of tang to fit patented handles. As forged, the blank for a "Hand" file, Fig. 15, is parallel in 24 MODERN MACHINE SHOP TOOLS. thickness from heel. to middle and tapered from middle to point, making the point about one-half the thickness of the stock. edges of the blank are usually left parallel. They are, however, sometimes drawn in slightly at the point. The "Flat" file blank, Fig. 16, is parallel in both of its longi- tudinal sections from heel to middle and tapered in both sections from middle to point, the thickness of point being about two- thirds, and width about one-half that of the stock. For the "Mill" file the blank is parallel in thickness from heel to point, and usually tapered to about three-fourths the width FIG. 15. FIG. l6. of the stock. The "Mill" file is often made blunt that is, of equal width and thickness throughout its length. The blank for the "Warding" file is tapered in width from heel to point and is of uniform thickness. Aside from width, the "Pillar" file is similar to the "Hand" file. The "Pillar' file is also made in narrow and extra narrow patterns, the extra narrow approximating a square in section. The "Three-square," "Square" and "Round" are also made in slim and blunt forms. The "Slim" is a file of regular length, but smaller cross-section, and the "Blunt" of equal cross-section from heel to point, being either "slim" or regular. After forging, the blanks are thoroughly annealed in annealing THE FILE AND FILING. 25 furnaces, the operation taking from twenty-four to thirty-six hours. When the blank comes from the furnace, it is twisted and scaly, and must be subjected to a straightening process, after which the scale is removed by grinding on very heavy grind-stones. The blanks are next draw-filed to make them perfectly smooth and even, after which they are ready for the cutting. Files are classified under three heads "Single-cut," "Double- cut" and "Rasp." The "Single-cut" file or "Float,". as its coarser cuts are sometimes called has surfaces covered with teeth made by single rows of parallel chisel cuts extending across the faces at an angle of from 65 to 85 degrees with the length of the file. The size of this angle depends on the form of the file and the nature of the work it is to perform. The "Double-cut" file has two rows of chisel cuts crossing each other. The first row is, for general work, at an angle with r-r ^-^7- FIG. 17. the length of the file of from 40 to 45 degrees, and the second row from 70 to 80 degrees. In the "Double-cut" finishing files the angle of the first cut is about 30 degrees, and the second from 80 to 87 degrees with the axis of the file. The "Double-cut" gives a broken tooth, the surface of the file being made up of a large number of small, oval-pointed teeth inclined toward the point, and resembling in shape the cutting end of a diamond pointed cold chisel. In the rasp the teeth are entirely disconnected from each other. They are round on top, and are formed by raising, with a punch, small portions of stock from the surface of the blank. The ma- chinist seldom has use for a rasp, as they are intended for filing the softer materials, as wood and leather. The regular grades of cut upon which the coarseness of a file depends are "Rough," ".Coarse," "Bastard," "Second-cut," "Smooth" and "Dead-smooth." The "Rough" file is usually 26 MODERN MACHINE SHOP TOOLS. single cut and the "Dead-smooth" double cut. The other grades are made in both double and single cut. These grades of coarse- ness are, however, only comparable when files of the same length are considered, as the longer the file in any cut, the fewer the teeth per inch of length. This is shown in Fig. 17, where a 4- inch and 1 2-inch "Bastard" file are placed side by side for com- parison. The relative degrees of coarseness for the different cuts are COARSE. BASTARD. SECOND CUT. SMOOTH. FIG. l8, shown, for the "Single-cut" in Fig, 18, and the "Double-cut" in Fig. 19, a portion of an 8-inch file being taken in each case. The value of a file depends entirely upon three things quality of stock from which it is made., the form of its teeth and the temper. The stock should be of the very best, as tool steel is seldom put to any use where its lasting qualities are more severely taxed. As to the forming of the teeth : It is only within the past few years that machine-cut files have come prominently upon the market, it being generally believed that a file to be first class must be hand cut. In Fig. 20 are shown portions of two 1 4-inch flat "Bastard" files; of these one is hand and one machine cut. The difference between these cuts is so slight that only an expert, THE FILE AND FILING. 27 with the files rather than their pictures before him, could tell, with any degree of certainty, which was the hand and which the machine cut. Up to the time of the perfecting of the increment cut file, the great trouble with machine-cut files was in the perfect uniformity of the teeth. In a hand-cut file the width and spacing of the teeth depend entirely upon the skill of the workman ; and no matter how carefully . he does the cutting, irregularities of a thousandth of an inch, more or less, will occur in the spacing and in the angle at which he holds the broad chisel that forms the teeth. These slight variations will cause the teeth to be of uneven height and irregular outline. These irregularities are now very faithfully reproduced in the increment, machine-cut file. It is difficult to make a file having teeth of uniform height and FIG. 20. outline, as in the case of the ordinary machine-cut file, take hold of the work. The reason for this is that so many teeth present themselves to the work surface that the workman must exert great pressure on the file to make them bite. With the file having teeth of irregular height, fewer will come in contact with the work, and the pressure required to make them take hold will be correspondingly light. As these long teeth wear down, the shorter ones will begin to do work ; but the file will, of course, not cut so freely as when new. Again, hr using the file with teeth of uniform height, it will, when pushed to the work, pro- duce, at the start, grooves which will grow deeper as the file is moved forward, and, due to the broad cut, will be quite certain to vibrate and "chatter." On the other hand, the uneven teeth of the hand and increment cut files, will so adapt themselves to the 28 MODERN MACHINE SHOP TOOLS. surface of the work that only a few teeth at any particular point in the length of the file will cut. The metal left between these teeth will be removed by the teeth following, perhaps a dozen or more rows of teeth being required to finish the cut started by one. This is shown, for a "Single-cut" file, in Fig. 21, where the several irregular lines represent as many tooth outlines drawn on an exagger- ated scale. These teeth come successively to the work, and if all their high points were brought together they would form a straight line, as shown, which would be the outline of the resulting cut. The cutting of an increment cut file con- sists in the forming of the teeth by a chisel operated in a machine, and so controlled that the spacing between teeth may be increased or decreased, the same being subject to a small amount of irregularity, as well as a slight variation in the angle of the teeth with each other. As manufactured by one company, the spacing of the teeth from point to middle is increased, and from middle to heel decreased. Another leading manufacturer increases the pitch from point to heel. It will be understood that the increment of space is very small. In a 12-inch "Bastard" file, having teeth spaced progres- sively wider from point to heel, the pitch of teeth at heel is about .01 of an inch greater than at the point, which makes the average increase per tooth about .00003 f an mcn - In machine-made files the cutting is very rapidly performed, the chisel receiving from 500 to 3,500 blows per minute, de- pending on the weight of the file being cut. The blank is cut from point to heel, and when turned over is placed on lead strips to protect the teeth already formed. After cutting, the files are inspected and assorted as to quality. They are then tempered, any material change in shape due to hardening being rectified at the time of tempering, after which they are ready for final inspection. This consists of trying each file on a piece of hard steel and making sure that it is free from temper cracks. They are next coated with oil and wrapped in oiled paper, to prevent rusting, after which they are packed in boxes, ready for the market. The teeth of a file remove metal by a shearing cut. This is most apparent in the "Single-cut" files, where the teeth have THE FILE AND FILING. 29 lateral length; but is equally true of the pointed tooth of the "Double-cut" file. A file bites freer on work having a narrow surface than a wide, because fewer teeth come in contact, at any point in the stroke, with the work surface, and consequently less pressure is required to make the file bite. On very thin work the teeth of a "Double- cut" file bite so freely that the danger of breaking them is great. For work of this character the long tooth of the "Single-cut" is best adapted, as its form gives it greater strength, and the shear of the cut is smoother, one tooth coming into cut as another leaves. On the broad surfaces, however, the teeth of the "Double- cut" have the advantage. A file is "tapered" when it is thinner at the point than at the middle, and is "full tapered" when thinner at point and heel than at the middle. The reasons for thus tapering a file are, first to FIG. 22. reduce the number of teeth that come in contact with the work, and, second, to enable the operator to file a straight or plane surface. The first reason is evident ; the second is shown in Fig. 22. If the file is perfectly straight, as shown in I, the motion in order to produce a plane surface on the work must be abso- lutely parallel to this surface. This the most expert mechanic can scarcely be expected to do, and the result will be work rounded at the edges A and B. If the file is tapered, its surface will be slightly convex, as shown in 2, and if moved entirely across the surface, straight work will result. The workman will experience little difficulty in accomplishing this, as he can allow the' ^notion of the file to deviate slightly from a straight line, and stnr not cut away the edges A and B. If the file is not moved clear across the work, a concave surface will of course result. 3e as smooth as possible, and very close to the exact finish diam- eter. The danger of filing work out of round increases as the speed of rotation decreases. That is, if the work is of small diameter and makes a number of revolutions per stroke of the file, the surface will be nearer round than when only a few turns are made per stroke. When the work diameter is large, making the rotation slow, it is practically impossible to file equal amounts from all parts of the surface, inasmuch as parts of the surface of the' work are quite certain to come under the action of the file more frequently than others. It is best in filing this class of work to give the file a comparatively slow stroke, and as long a one as possible. It must be remembered that, ordinarily, the motion of the file to the work in cross, or draw filing, is comparatively slow say forty strokes per minute of perhaps eight inches each. As the file is cutting only about one-half of the time, the actual velocity of cut in such a case would be not far from fifty feet per minute. The intermittent motion of the cut prevents the teeth from be- coming extremely hot. In filing revolving work, the number of strokes per minute will not be so great, but the length of the stroke will be some- what increased. This will give practically the same cutting speed, due to the motion of the file, as in cross filing. To this must be added the velocity of the work surface under the file, which will vary from fifty to one hundred feet per minute. In cross filing stationary work, only a short length of the file's sur- face is cutting throughout the stroke, which concentrates the work on relatively few teeth. In the filing of rotating work, however, nearly all of the file's length is brought into action at each stroke, which offsets largely the disastrous effect on the teeth, due to too high a cutting velocity. The file must not be held stationary, allowing the work to revolve to it, as in that case a few teeth do all the cutting, and a grooved surface is quite certain to result. The file should be held as for cross filing, Fig. 23, and should, as it is moved forward over the surface of the work, be given a small amount of lateral motion. If a large amount of metal is to be removed the file should be pushed diagonally over the work, as shown in Fig. 45, the direction of the stroke being frequently changed, THE FILE AND FILING. 43 thus causing the file marks to cross each other, which, as pre- viously explained, causes the file to cut more rapidly and pro- duce a truer surface than when continually moved in one direction. When, however, a nice finish is required, the stroke should be at r \ FIG. 45- right angles to the axis of the work, as shown in Fig. 46, and should, as indicated by dotted lines, be kept parallel to this posi- tion, in its sweep from left to right. In filing rotating work, as in the draw filing of cylindrical surfaces, the number of teeth in contact with the work surface at any instant is relatively small, consequently less pressure is re- quired to make the file bite, other things being equal, than in the filing of plane surfaces. This feature also enables the use of files on rotating work, which, due to their concave surfaces, could 44 MODERN MACHINE SHOP TOOLS. not be used on plane work. This affords an excellent oppor- tunity for using up those files, or parts of files, which, owing to their warped condition, are unfit for careful work on plane surfaces. In filing the face of a rotating disk the same care in the selec- tion of the file must be used as for work on a stationary plane surface,, only the high spots being available for this purpose. This, unlike the work on the cylindrical surface, concentrates the work on a small portion of the file's surface, and consequently the velocity of the work should be lower. For this class of filing the file must be held firmly, to overcome its tendency to move in and out on a radial line. In the filing of all rotating work, and especially work having projections or irregularities, care must be exercised to prevent the file from catching in the work. For this purpose a file without a handle should not be used, as in the case of its catching it is very apt to drive back, forcing the tang into the operator's hand or wrist. Frequently, when the character of the work necessitates filing up close to the face plate, chuck, or driver, it will be found convenient to run the lathe backward, the operator standing at the back of the machine. A file to do its work fast and well should be kept free from its cuttings. If the metal is of a- non-fibrous nature, as with cast iron or brass, the cuttings pack solid between the teeth, thus holding the teeth out of the work and preventing the file from biting freely. A sharp blow of the file's edge against the vise back after every few strokes will remove most of these cuttings ; if, however, too many strokes are taken before cleaning they lodge so finely that a file brush, as shown in Fig. 47, must be used FIG. 47- to remove them. These brushes are usually made of fine wire mounted in leather, and tacked to a light wooden back. A stiff bristle brush serves this purpose well, and for very fine-cut files is preferable to the wire. In filing steel and wrought iron, the character of the ma- THE FILE AND FILING. 45 terial reduces the disposition of the cuttings to pack between the teeth; but, under most conditions, a more serious trouble, that of "pinning" occurs. Cuttings "pin" when they lodge so firmly that they cannot be removed with the brush. Unlike the particles of cast iron,, which crowd down below the cutting edges of the teeth, and do not injure the work, but simply re- tard the cutting of the tool, the pin usually stands well above the teeth and scores the work surface at every stroke. The "pin" can usually be removed by drawing the wire file brush firmly across the surface ; those that resist this treatment being removed by the scorer. The scorer is simply a piece of soft wire flattened thin at the point, and carried broadside, rather than edgewise across the file surface. After a few strokes it becomes serrated and constitutes a short tooth comb, which picks out the pins quite easily. Pinning may be somewhat reduced by chalking the surface of the file, which has also the effect of reducing its bite. A lit- tle oil on the file will frequently reduce the tendency to pin. It should be used, however, only on the fibrous metals, as it glazes 'the surface of the non-fibrous metals, making them harder to cut. Chalk is usually applied to a file when a smooth, fine work surface is desired. The effect of the chalk is to prevent the teeth from cutting as freely as when it is not used, and thereby pro- duces about the same result as would occur if a finer cut file had been used. It becomes necessary to rechalk the file after each cleaning, an operation requiring some time, and which can, by using the fine file, usually be avoided. When oil has been used on a file it can readily be removed by thoroughly chalking and brushing two or three times, as the chalk soaks up the oil and leaves a dry surface. In fine filing operations, where it is quite important to know the exact spot on the work surface where the file is cutting, the surface can be dimmed after every few strokes by passing the palm of the hand over it. The dry, soiled hand will deaden the surface enough to clearly show where the file cuts on its next few strokes, and will in no way injure the cutting of the tool. Files are frequently injured by improper care while not in use. When boxed at the factory they are brushed over with oil and wrapped in oiled paper, which prevents them from rusting. When this oil has disappeared they will, if exposed to moisture,^ rust 46 MODERN MACHINE SHOP TOOLS. readily. As there is a large exposed tooth surface the deterioration due to rust is rapid. Files should never be thrown together in a drawer, or even allowed to come into contact with each other, or with other tools, as the delicate edges of the teeth are most easily broken down, and the value of the file seriously impaired. They should be kept in a drawer, separated from each other by low partitions, and arranged according to length, section, cut and condition, thus facilitating the selection of any desired file. Any form of file rack, in which the file hangs from its handle, is satisfactory. The tendency is for files to accumulate, a large number that are nearly worn out littering up the file drawer or rack, injuring the good ones and doubling the time required in selecting a file for any piece of work. A number of these partially worn files are quite necessary in the file drawer of the mechanic who is engaged on work of a gen- eral character, as he will very carefully avoid putting the new or better ones on the hard scale of castings or forgings. The machinist should at all times exercise good judgment in the selection of the proper file for any piece of work as he cannot otherwise expect to get economical results from the files he uses. Except in cases where his work is all of one character he will ex- perience little difficulty in so selecting that he will always be able to use his partially worn files to good advantage on much of his work, thus saving the new ones for the best work. The broad surfaces of cast metals require the sharpness of the new file to properly cut them, while the narrow surfaces are readily cut by the somewhat dulled teeth of the file that has seen a moderate amount of service. Steel and wrought work will reduce the file to a condition where its further use is un- economical except as it may serve to protect the better ones by being used for cutting thin, hard materials and removing fins and scale from castings and forgings. Thin castings, and especially the fins on them, are quite apt to be chilled, making them harder than the file, a condition not conducive to the health of that tool. The sand must be thor- oughly removed from castings before applying even the poorest file, as otherwise, the grindstone action will soon render the file absolutely useless. The sand can be largely removed by brushing, but the scale only by a chemical treatment which softens rather than removes . THE FILE AND FILING. 47 it. This process, commonly known as pickling, consists in the washing or soaking of the castings in a blue vitriol solution, or dilute sulphuric acid. The length of time the casting should re- main in contact with the pickling solution depends on the strength of the solution and the degree of softness required. They should be thoroughly washed off with water when taken from the bath and after drying the scale can be brushed with a wire scratch- brush or rattled off. When the castings so pickled are to be finished on any of their surfaces by painting, it is important that they are thoroughly cleaned, as otherwise the scale will eventually flake off, taking the finish with it. In such cases the castings when removed from the acid bath should be thoroughly soaked in a neutralizing bath of strong, hot soda or potash water. They can then be rinsed in hot water and dried. Pickling operations should be performed in a well-ventilated room, or preferably in the open air, as the fumes are poisonous, and in the case of sulphuric acid, explosive when mixed with the proper proportions of air. The pickling vats if of iron must be lined with sheet lead. Vats of wood are frequently used, care being taken to protect the hoops or other iron fastenings from coming in contact with the solution. A wooden vat lined with sheet lead makes a very satisfactory combination. Vessels of glazed or vitrified earthenware are suitable when the work is suspended and not thrown into the solution. For cleaning brass castings a solution of nitric and sulphuric acids with water is usually used. The common proportions are i part nitric acid, 2 parts sulphuric acid, and 2 parts water. The castings are left in the solution but a short time and then thor- oughly rinsed first in cold, and then hot water, after which they are dried in sawdust. CHAPTER III. SCRAPERS AND SURFACE PLATES. The scraper is a tool used by machinists for producing truer surfaces than can be produced by the ordinary planing and filing processes. It is strictly a tool to be used on stationary work, al- though the distinction between it and the hand turning tool used by the brass worker is not clearly drawn. The flat hand scraper, as usually formed, is shown in Fig. 48. FIG. 48. It is forged from a piece of flat steel of from ^ to i>4 mcn m width by l /% to 3-16 of an inch in thickness. The point is drawn down so that the end is about 1-16 of an inch thick, as shown in Fig. 49. The flats should be ground well back from the FIG. 49. FIG. 51 point and the end at right angles to the length of the tool, as shown at A, Fig. 49, thus making the angle of the cutting edges but slightly more than 90 degrees, as shown at B, same figure. The end should be ground slightly rounding in its length to prevent the corners from digging into the work and the tools taking too bro~d a cut, which tends to produce a waved or chat- tered surface. SCRAPERS AND SURFACE PLATES. 49 If the end is ground so as to give one side a keener cutting edge, as shown in Fig. 50, this edge will cut faster, but the surface produced will ordinarily not be so smooth as in the former case, it being difficult to prevent the tools chattering. The scraper.* including handle, should be from 10 to 12 inches long, depending on the size of stock and the character of the work on which it is to be used. If too long it will be springy and will not do good work. As the angle forming the cutting edge must be kept very sharp, a high temper is necessary, and the end faces after being ground must be oil-stoned often in order to make the tool cut properly. The double ended scraper shown in Pig. 51 is a form fre- quently used. This scraper should be made somewhat longer than the one shown in Fig. 48, from 14 to 16 inches being about right. The central portion, which serves as a handle, should be enlarged and knurled, or twisted in the forging, so as to enable the hand to grip it firmly. * A form of scraper shown in Fig. 52 is sometimes employed- on fine work. The disadvantages of this form arise from its hid- den cutting edge while at work, and its having but one cutting edge, thus necessitating more frequent grindings than with the .straight tool. The scrapers shown above are suitable for use on plane or convex surfaces. If a concave surface is to be worked upon, a scraper of semicircular cross section, as shown in Fig. 53, will be used. Frequently in scraping circular surfaces, and more especially in the softer metals, as brass or babbitt, a three-cornered scraper can be used to advantage. Such a tool is shown in Fig. 54. FIG 54. 5 m h + 1-32 inch. Set to the 5 and add the sum of the decimal equivalents for 1-16 inch (.0625 inch) and 1-32 inch (.0312 inch ) = .0937 inch, which should be set back from the ^s in the ordinary manner. This does not interfere with reading the caliper decimally in the ordinary way. This caliper is made in twelve sizes, from i to 12 inches. The FIG. 83. i -inch to 6-inch sizes have yokes made from drop forgings of bar steel, and the larger sizes have yokes made of steel castings, all neatly finished and japanned. The face of the anvil is formed by a hardened steel plug of same diameter as {he end of the measuring point. The measuring range of each size is i inch, and for adjustment of all sizes other tl'*n the i-inch caliper, standard end measure test pieces are required. In calipers of this class the yoke is frequently lagged with wood or hard rubber to prevent the expansion and consequent inaccuracies that arise from handling with the warm hand. A form of yoke micrometer in which provisions are made for a wider range of measurements is shown in Fig. 83. It is made in four sizes having a range of from o to 12 inches. The anvil is mounted in the end of a spindle, which is provided with stops 76 MODERN MACHINE SHOP TOOLS. exactly I inch apart. A slight turn of the anvil spindle when either stop is to be used brings it firmly against its seat, in which position it is securely clamped. Beam micrometer calipers are illustrated in Figs. 84, 85 and 86. In each case the regular micrometer head of one inch capacity FIG. 84. FIG. 85. FIG. 86. is mounted upon a suitable slide which moves over the beam of the instrument. Three distinct methods, however, of making the several inch settings are employed. CALIPERS. 77 In Fig. 84 the inch settings are made to accurately graduated rulings on the beam. In Fig". 85 these settings are made by inserting the tapered steel pin in the holes in the sliding jaw and their corresponding holes in the> beam. A separate set of holes is used for each set- ting. The holes are bushed with hardened steel bushings ground and lapped to fit the tapering plug. In Fig. 86 is shown a beam micrometer of six inches capacity. The sliding jaw carries a regular micrometer screw head of one inch range and moves over a cylindrical barrel in which is an accurately bored hole to receive three end measure test pieces, one, two and three inches long. An arm on the head extends into the bore through a radial slot in the cylinder, and by means of the test pieces enables the setting of the head at fixed distances FIG. 87. one inch apart. A zero mark on the cap and barrel determines the proper pressure on the test pieces for each setting. The capacity of the beam micrometer for measuring flat work is limited only by the length of the beam. For round work the height of the jaws limits the diameter, usually to about 4 inches, since in order to keep the weight of the instrument within rea- sonable limits it is not advisable to make the jaws much greater than 2 inches high. In Fig. 87 is shown a bench micrometer for measuring all sizes, from zero to 2 inches. It has a twenty-thread screw with fifty divisions on the dividing head, thus giving direct readings to i-iooo of an inch. The zero adjustment is obtained by turn- ing the head on the screw, it being held in position by a lock nut. As a bench machine its simplicity and convenience rec- ommend it for general shop use. 78 MODERN MACHINE SHOP TOOLS. The Pratt & Whitney standard measuring machine shown in Fig. 88 is an instrument of precision for originating and dupli- cating standard dimensions. It is a beam micrometer of the greatest refinement as to design and construction. The bed is very heavy and rests upon three neutral points to overcome flexure and effects of changes of temperature. Resting on the side of the bed is a standard measurement bar in the surface of which are inserted hardened steel plugs at intervals of one inch. On the polished surface of each plug is a very fine ruling, the distance from ruling to ruling being one inch at 62 degrees Fahrenheit within a limit of error of 1-50,000 of an inch. To one end of the bed is secured a headstock which carries the t FIG. 88. fixed measuring point. This point is secured in a plunger backed up by a light helical spring. Secured to the plunger is an auxiliary jaw which holds between its face and the face of another jaw secured in the head a small cylindrical plug gauge by friction alone. The tension of the spring is sufficient to hold the small gauge at an angle from the vertical. The movable head carries the micrometer which consists of a 5o-thread screw and a dial having 400 divisions with an adjustable zero arm. The microscope with micrometer eyepiece is secured to the movable head in such a position as to cause its line of /i.^ht to pass over the rulings on the plugs when the head is moved from end to end of the bed. CALIPERS. 79> In obtaining the zero setting the micrometer screw is run all the way out and the zero on the dial made to coincide with the zero on the adjustable arm. The measuring points are next brought in contact, approximately by means of the fine adjusting screw shown at the rear of the movable head and exactly by a slight movement of the micrometer dial. When the pressure between the measuring points is just sufficient to allow the "sensitive piece" above referred to to drop to a vertical position but not to fall out, the zero on the adjustable arm is made to coincide with the zero on the dial and the hair line in microscope to coincide with the ruling on the first plug. In making a measurement the movable head is carried back and the microscope made to read on the ruling on the plug which corresponds to the whole number of inches to be measured ; the "sensitive piece" is inclined from the vertical ; the piece to be measured is placed upon the supports shown and the measuring points adjusted against it with just the amount of pressure re- quired to cause the "sensitive piece" to swing to the vertical posi- tion. The reading is then taken. The slightest excess of pressure will cause the "sensitive piece" to drop out. The direct reading on the dial is 1-20,000 of an inch, and one- half of this amount can be quite readily approximated to. In deal- ing with such minute variations in dimensions the utmost care must be observed in the manipulation and especially in the effects of changes in temperature. Fig. 9 shows the Sweet's measuring machine, which is made 8o MODERN MACHINE SHOP TOOLS in 4, 6 and 8 inch sizes, and may be classed under the head of bench micrometers. This instrument, which is intended for practical shop uses, reads as regularly furnished to i-iooo and 1-1280 of an inch. When required a vernier is used on the head, which gives readings of i -10,000 of an inch. The range of meas- uring screw is I inch, test pieces being furnished for setting the sliding anvil to the inch zero positions. Fig. 9oa shows a portion of the measuring head. A i-io inch pitch trapezoidal thread measuring screw is employed. This form of thread gives a square bearing on its work side, and the quick pitch facilitates rapid adjustment. The knurled thumb nut drives through a friction. The outer disc of the dial is divided to hun- A. B FIG. 90. dredths, thus giving for each division i-iooof i-io = i-iooo of an inch. The reading is made on the front edge of the index bar. For the fractional readings the left-hand disc is used. It is divided into 128 parts, and every eighth division numbered, as shown in Fig. 900. One revolution of the screw equals i-io of { an inch =128 divisions on the dial, whence one division = i-io 8 of 1-128 == 1-1280 of an inch. The upper edge of the index bar is graduated to sixteenths for convenience in getting the ap- ' proximate setting. All readings are, however, made on the front | edge of the bar. Referring to Fig. 90^ : Following the straight lines from o to I, 2, 3, etc., back to zero (16) five complete revolutions are made, 1 which carries the screw back y 2 inch. Then every five divisions | are 5-16 of i-io = 1-32 of an inch at the measuring point, and CALIPERS. <51 every 2 l / 2 divisions equals 1-64 of an inch; and since each division is divided into eight equal parts on the disc, 1-128, 1-256 and 1-1280 may be found by using 10, 5 and i of these small divi- sions, respectively. For example, in Fig. 90 the reading line is 6-32 inch beyond the 16-32 (.5) inch mark == 22-32, and the 6 on the disc should nearly coincide with the 22-32 division. Bring the 6 to read at the lower edge, and the measuring point will be 22-32 inch from the anvil. If 23-32 inch had been wanted, the 7 on the disc would have been brought around to the reading edge. If 47-64 inch was required, the 7 would be carried past the read- ing edge twenty divisions and in like manner ten more divisions would make it read 95-128 inch. Any error in the pitch of the measuring screw which would FIG. 91. j affect the number of turns per inch is corrected by setting the i index bar at an angle with the axis of the screw. Assume, for j example, that the ten turns of the screw advance the measur- j ing point i-iooo inch too far. The screw is too long, and less i than ten revolutions should be made by an amount equal to one :j of the divisions on the outer disc. The outer end of the index j finger will be raised this amount above the inner end gradua- i tion. This corrects the error proportionately from end to end of : the screw. An example of the inside micrometer caliper is shown in Fig. 91. It is used for making inside measurements and reads to thousandths through a y 2 -'mch range. The instrument shown, with its extension rods makes any measurement between 3 and 6 inches. The nut and check nut on the extension rods may be adjusted down to compensate for any wear of the points. CHAPTER VI. GAUGES AND INDICATORS. There is nothing more confusing to the young mechanic than the use of the several systems of gauges used in designating the sizes of wire, machine screws, drills and plate thicknesses. Unfortunately, most of these dimensions differ from each other for corresponding numbers by comparatively small amounts, yet an amount sufficient to cause error if the one is mistaken for the other. The following table gives for comparison values for only a few numbers under each of the several gauges in most common use : si + - o w O - ? _ t/5 V o *J B bfl o .^ fc^ tx QJ bjD ' ^ w> 35 "> .S cx 3 O p ^ fl * 68 3 *- 3 Q ! J I II ! r I ilfefcU 1 Uwlll ^WTHELS.STARRETT.CO. _ ATHOLMASS.US.A. "" A I-.U I I T IT I FIG. 107. ruling to use, as there is then no danger of inadvertently mis- taking a tenth for an eighth division, etc. For this reason, rules graduated in twelfths and fourteenths should not find their way into the machinist's tool box, as he will not have occasion to use these divisions, and their presence will call for greater care in selecting the proper division, with the loss of time incident to changing ends with and turning over the rule in order to get at the division required. The end graduation, as shown in Fig. 1 08, is frequently very convenient in taking measurements in re- cesses where the length of the scale would prevent the use of the regular graduation. Standard steel rules, as made by our leading makers, are re- markably accurate. To be sure, the length varies slightly with the changes in temperature, but these changes are not ordinarily great, and the material measured is usually affected about the 94 MODERN MACHINE SHOP TOOLS. same amount in the same direction ; so we may feel assured that any errors arising from this source are well within the limit of the personal error of the operator in making a measurement. The late refinements in the manufacture of steel rules have enabled the production of very accurate tempered ones on com- paratively thin steel. What we usually know as the standard rule, however, is graduated on thick steel, and is not tempered. The tempered rules possess the decided advantage of resistance to wear. An untempered rule is easily mutilated, and soon rounds its corners through wear, making its ends unfit for ref- erence. The tempered rules may be classed as heavy, tempered, semi-flexible and flexible. The heavy are about one-tenth ; the tempered, one-twentieth ; the semi-flexible,, one-fortieth, and the flexible one-eightieth of an inch thick. For general work the heavy or tempered will be found best suited. The flexible are I 1 1 1 1 1 1 1 1 I-E ==- \ 8 =r* to TnliTilih Mi III Illlllllin FIG. I08. FIG. 109. graduated on one side only, and are of value in measuring curved or irregular outlines. In this connection it will be well to call attention to the gear rule shown in Fig. 109. Its application is in the sizing of gear blanks and where, by rule of thumb, two diametrical pitches are added to the pitch diameter of the gear in obtaining the whole diameter. Thus, if the pitch is No. 7 diametrical and the num- ber of teeth 34, then the pitch diameter = 34-7 = 4 6-7 inches, and the blank or whole diameter = 4 6-7 -j- 2-7 = 51-7 inches, which can be taken directly from the scale. This rule is of great convenience where many blanks for varying pitches and num- bers of teeth are to be sized. In Fig. no is shown a neat kink which will be found of value in taking measurements similar to the ones shown in the figure, as well as for setting inside calipers. The hook may be quickly removed. It is hardened, and in connection with a tempered rule forms a reliable tool. In Fig. in is shown a standard steel square. This tool is RULES, SQUARES AND OTHER SMALL TOOLS. 95 made of cast steel, tempered and accurately finished. The two sides of the angle are called the blade and the beam, the length of the blade being measured from the inside of the beam. The form shown in Fig. 112 is preferable when the length of the blade exceeds eighteen inches, as it can be more readily repaired in case of accident. Either of the methods shown in Figs. 113 and 114 may be used by the machinist in testing the accuracy of a square, the latter being the more exact of the two. In Fig. 113 A is a plane plate THE.L.S.STARRETT.CO ATMOL,MASS:U.S,A, FIG. III. FIG. IIO. B.&5. Proy. R.I Pa-t Jan. 17, 1882. 3 I : D C L F J l G l FIG. TI2. FIG. 113. FIG. 114. of iron with one edge, B C, perfectly straight. The surface A should be smooth and true. The square is first applied as shown at F and a fine. line D E .scribed along its edge. It is then re- versed to position G, when, if the edge exactly lines with the ruling D E, the square is correct. If, however, the edge and line do not coincide, the square is inaccurate by one-half the varia- tion as shown. Since this method depends for its accuracy on the eye of the operator it cannot be called an exact one. The method shown in Fig. 114 reduces the amount of the personal error, since the eye detects readily the ray of light that passes through an exceedingly small opening. In the figure the cylin- 9 6 MODERN MACHINE SHOP TOOLS. der A, which has been ground accurately parallel and faced on the lower end slightly dishing, rests on a plane surface, a stand- ard surface plate being best suited to this purpose. As the sur- face of the cylinder is at right angles to the surface of the plate the square can be compared with this angle by placing it as shown in the figure. For most general work the thin steel squares shown in Fig. FIG. 115. 115 serve very well. They are cut from sheet steel, carefully made but not hardened, and are usually graduated, as shown, on both sides. The combination square shown in Fig. 116 is a satisfactory FIG. 1 1 6. tool, which, with careful use, retains its accuracy. The blade is readily adjusted to any required length, which is of special value in transferring measurements. The 45 degree angle is of fre- quent value, as is the centering head which is used on the blade RULES, SQUARES AND OTHER SMALL TOOLS. 97 as shown. The blade is a standard steel rule, splined to receive the key which draws the edge of the blade close to its seat in the beam. In Fig. 117 is shown a box square, or as it is more commonly known, a key seat rule. With this tool lines upon a cylindrical surface parallel with the axis may be drawn. While it is in- tended for use on external surfaces, as shown at A, Fig. 118, it will at times serve a good purpose on internal, as shown at B, FIG. 117. FIGS. Il8 AND 119. same figure. A form of box square, shown in section in Fig. IKJ, possesses the advantage of wider range than that of Fig. 117. In Fig. 1 20 is shown a pair of key rule blocks attached to a common steel rule thus making a very simple and efficient key seat rule. For a great deal of his work the machinist is satisfied with using the edge of a good steel rule to determine its straightness ; but when he wants to know to a certainty that the work is straight it is a source of great satisfaction to be able to refer to a standard straight edge Such a straight edge is shown in Fig. 121. It is a piece of steel of thickness depending on its length, nicely finished, with its two edges parallel with each other and MODERN MACHINE SHOP TOOLS. straight. They are regularly made up to six feet in length, such a tool being about three inches wide by three-eighths of an inch FIG. 1 2O. thick. Up to four feet in length they are frequently tempered .on the edges. A cast iron or surface straight edge is shown in Fig. 122. FIG. 121. These tools are designed for an entirely different class of work than the one shown in Fig. 121. The edge is wide and scraped to a true plane, with the body so formed as to best resist defiec- FIG. 122. tion from its own weight and distortion due to changes in tem- perature. These straight edges are used in the production of long plane surfaces like planer bed V's and lathe shears, pre- RULES, SQUARES AND OTHER SMALL TOOLS. 99 cisely as the surface plate is used in the production of broad plane surfaces, and they are generally much larger and heavier than the style shown in Fig. .121. Hack saws are used for severing purposes, both by hand and power, the comparatively recent introduction of the power hack saw machine having increased many times the possible use- fulness of the hack saw blade, a cut of which is shown in a hand frame in Fig. 123. The original Stubs' and German blades were soft enough to be sharpened by riling, were made of excellent material, and were high in price. Their expense and the trouble required to keep them properly sharpened limited their use to a narrow range. The bringing out of the modern hard blade, at a price sufficiently low to warrant throwing it away as soon as it became too dull to do satisfactory work, has practically super- FIGS. 123 AND 124. seded the old blade and made the hack saw one of the most important tools in the machinist's kit. Hack saw blades are made with fourteen teeth per inch for general work. When, however, they are to be used on tubing or thin metal a greater number of teeth is advisable, as they will not bite so freely, and the danger of stripping the teeth is much less. For this purpose blades having twenty-five teeth per inch may be had. As with a file, the fineness of the bite depends on the number of teeth in contact with the work. The judgment of the operator must, therefore, determine what pressure to apply on the saw for the varying conditions of cut. As with other cutting tools, the hack saw does more work and stands up to it better when the IOO MODERN MACHINE SHOP TOOLS. pressure is sufficient to make the teeth cut free, rather than scrape and glaze the surface, as is the result when the pressure is too light. The blade* must be strained in the frame to prevent its kinking. The strokes should be uniform, not exceeding forty per minute. Oil should not be used on the teeth, as it decreases their cutting efficiency. Blades are regularly made from six to eighteen inches long, those exceeding twelve inches being little used. For any work the blade should be as short as possible, as the cost of the blade and danger of breakage increases with its length. Blades longer than eight inches for hand and twelve inches for power frames are seldom required. The frame should be stiff. In this respect the non-adjustable, or solid one, shown in Fig. 124, is preferable. All hand frames should be so con- structed that the blade can be faced at right angles to the posi- tion shown in the figure, which is quite necessary when a deep cut is to be taken near the edge of the work. Everybody uses the screw driver, yet how seldom, even among mechanics, do we find it properly ground. In Fig. 125 is shown at A an edge view of the point of a screw driver, as usually ground; and at B a view showing how it should be ground. When the screw driver, A, is applied to the slot of the screw head it bears only at the center of the upper edges, C and D, of the slot, and the force required to turn the screw forces the driver out of the slot, which injures, if not completely ruins, the head of the screw. With B the case is different. The parallel sides of the bit take squarely a hold of the sides of the slot and the screw is driven without in- jury, and with much less exertion than in the former case. The screw driver should be made of good tool steel and given a tough temper. In Fig. 126 is shown that much used tool, the monkey wrench. This is a genuine wrench, and should only be used as 'such. It should never be used as a hammer ; neither should it be' expected to stand all the force a thoughtless workman can apply at the end of four feet of gas pipe slipped over the handle as an extension. It should, however, when properly closed on the flats of a nut, RULES, SQUARES AND OTHER SMALL TOOLS. IOI stand safely all the average man would care to exert with both hands on the handle. As the nut often starts more easily with a quick jar or shock than by the application of a steady force, it is permissible to strike the end of the handle in the direction shown by the arrow with a rawhide or wooden mallet, or the end of a soft block of wood. The operator's judgment must determine how heavy a blow he can safely use. The surfaces A B should be smooth, plane, and parallel with each other. These wrenches usually fail by bending at C. If the bend is slight, A can be most easily made parallel to B by filing, but when badly bent it should be carefully straightened. The jaws of the wrench and the nut or square upon which it F ~ B< \ r\ ^E m PV (J -/ FIGS. 126 AND 127. is being used will be least injured when the jaws are closed firmly on the work. This necessitates slackening them slightly and closing again every time the wrench is changed. By giving the hand a slight rolling motion around the handle, with the fore- finger against the knurled head of the wrench screw, a sufficient amount of motion can be given to the sliding jaw to close on and release from the work without loss of time. The sliding jaw, due to its long bearing on the shank, is much stronger than the fixed jaw, consequently the wrench should be operated in the direction of the arrow, Fig. 126. An examina- tion of Fig. 127 shows that when turned as above indicated the maximum pressure comes at B and C, which places the shorter 102 MODERN MACHINE SHOP TOOLS. leverage on the weaker jaw. If . turned in the opposite direc- tion the pressure comes at D and E, which increases the bending tendency at F, and also the pressure on the screw. The great variety of combination wrenches on the market pos- sess little merit. When we use a wrench we do not want to have a hammer, a screw driver, a nail puller, 'and a dozen other "useful tools" in our way at one time. When finished standard nuts are to be turned the solid wrench is preferable to the adjustable, as it can be made to fit closely to the nut with less danger of injuring it. In Fig. 128 is shown a, finished case-hardened, solid wrench. The angle of the open end is fifteen degrees with the length of the handle, which enables a hexagon nut to be turned when the wrench can be carried FIGS. 128 TO 132. through thirty degrees only. These wrenches may be had double ended. The box wrench has a closed opening, as shown in Fig. 129. This particular form is commonly called a tool post wrench. The socket wrench, shown in Fig. 130, is made for square and hexagon nuts and cap screws, which are to be operated upon in deep or inaccessible places. W T hen a great many small nuts are to be quickly set, the socket wrench, in Fig. 131, operated in a bit brace., does the work rapidly. It frequently happens that a nut must be turned which is in so inaccessible a place that the handle of the wrench can be car- ried through only a few degrees. In such cases, the ratchet wrench, shown in Fig. 132, serves its purpose well, the effect on the nut being much more satisfactory than when the set chisel and hammer are used. In the use of all solid wrenches they must fit the nut closely, as otherwise both nut and wrench will be injured, the nut rounding and the wrench spreading. CHAPTER VIII. DRILLS The twist drill which has come into such universal use, has superseded the old, flat, forged drill which, for so many years, held without rival the first position as a tool for producing cir- cular holes in metal. For the needs of its day, it served its purpose well. The advancements along mechanical lines demanded a better tool for this work, however, and the twist drill resulted, brought out in practically the same form as now used, the prin- cipal recent improvements being mostly in slight changes in form, and its more accurate production due to improved methods of manufacture. The flat drill, as used for metal work, is generally of the form .shown in Fig. 133. It is made from rotund stock, is forged thin at FIG. 133. the lips, and ground as shown in the figure, with three cutting edges A, B and C. This is a very accommodating sort of a tool, being capable of producing a number of holes of different diam- eters, yet, approximately equal to the width of the drill. The dis- advantage of this adjustability, however, lies in the fact "that the size of hole wanted cannot ordinarily be produced. The flat drill has no lands, as that part of the twist drill be- tween flutes is called, to steady and guide it in the work. Conse- quently, the hole drilled will usually not be round, and should the point of the drill strike the side of a small blow hole or soft spot in the metal being drilled, as frequently happens in working cast IO4 MODERN MACHINE SHOP TOOLS. metal, the point will drift toward this spot, thus making- a hole that is neither round nor straight. This is shown at A in Fig. 134. In order to drill holes approximately to size with the flat drill, it is necessary that the cutting lips be most carefully ground. The angle of the lips with the axis of the drill must be equal, other- wise one cutting edge will perform all the work, and will dull quickly, due to this double duty. The pressure on the cutting lip will crowd the point, causing it to revolve in a small circle about the center of revolution. This will cause the other flute to cut slightly at its outer end, thus producing a hole of larger diameter than the width of flat. This is shown at B, in Fig. 134. The cutting lips should be of equal length, with their intersec- tion in the axis of rotation of the drill. If one lip is longer than the other, the diameter of the hole drilled will depend on the FIG. 134. \ length of this long lip, as it will rotate about C, its central axis, as shown at A, in Fig. 135. In case the intersection of the lips does not fall on the axis of the drill, the one lip is thereby made longer than the other, and the hole drilled will again be large, as the tool will spring an amount sufficient to allow it to revolve about C instead of its true axis, and the length of the long flute again determines the diam- eter of the hole drilled, as shown at B, in Fig. 135. The first cost of the flat drill is small, and the results obtained by its use usually poor. Its only advantage lies in the fact that it can readily be forged and tempered to do work on extremely hard metals. The flat drill, ground thin and tempered hard, is a valuable tool for drilling hard steel or chilled iron, as it will in that form take hold of metal that the twist drill will not touch. It also makes a convenient extension drill, as it can be readily formed on the end of a long bar of steel. DRILLS. 105 The flat drill is not adapted to the drilling of deep holes, as it does not free itself of chips. It is largely used for roughing out cored holes, preparatory to boring, which work is very destruc- tive, due to scale and sand, to the land clearances of twist drills. When so used in a lathe, the drill is held against the dead center and fed forward by the tail screw, the work revolving. About 1860, twist drills, having milled flutes, were first placed an the market. Previous to this date, however, drills with flutes produced by filing and the twisting of the flat stock had been used to a limited extent. In Fig. 136 is shown a taper shank twist drill. A A are the flutes, B B the lands, C the metal between the flutes the web, D D the lips, E the shank and F the tang. The center or grinding line is the fine line running along the bottom of each flute, and FIG. 136. serves as a guide to the lips in grinding so their intersection will fall in the center of the drill. The three clearances in the twist drill are : first, the "body clearance" of one-half to one-thousandth of an inch per inch of length of the fluted portion ; second, the "land clearance" of about one-half of one circular degree as shown at A A in the end view, Fig. 137, and last, the "lip clearance" made by grinding back the~ ends G G of the lands, Fig. 137, to properly clear the cutting edges H H. There are three cutting edges, H, H and C ; of these C is the lo6 MODERN MACHINE SHOP TOOLS. least effective, as it is not a free cutting edge and grinds rather than cuts the metal. By reducing the thickness of the web at the point as shown in Fig. 138, thus making the cutting edge C short, the efficiency of the drill is materially improved. This is of greatest value with drills of large diameter where the webs are made thick to give the necessary strength. The points may be thus thinned by grinding on a small emery wheel. The flutes of twist drills as usually manufactured are cut by milling from stock of round cross section. Numerous attempts have been made to produce a satisfactory hot rolled drill, in which the flutes are formed by passing the stock which is rectangular in cross section and heated to a forging point, through spiral rolls. A hot forged drill has recently been placed on the market. In FIG. 138. FIG. 139. this tool the flutes and twist are produced by forging, and great strength and durability of cutting edges are the claims for it by the manufacturers. In order to give the drill greater strength toward the shank, the web is increased in thickness from the point to the end of the flute. This thickening of the web is accomplished by gradually withdrawing the milling cutter, from the blank as the cut ad- vances. This makes the flute shallower at its upper end, with a gradually decreasing area of cross section from the point to the shank. This contraction of the flute area prevents the free de- livery of the chips and consequent clogging of the drill. It is therefore necessary to make the flute area equal throughout its entire length. This is usually accomplished by making the pitch of the flute spiral uniformly greater from point to shank, and is DRILLS. 107 known as an "increase twist" drill. It is also produced by giying the flute a spiral of "constant angle," and increasing the width of flute toward the shank. This latter result is obtained by slightly changing the angle of the arbor carrying the flute cutting mill with the axis of the drill blank as the cut advances, and the mill is receded from the blank, in giving a web of in- creased thickness. This latter method makes the lands narrower at the shank end of the flute and thereby reduces somewhat the strength of the drill. On the other hand, it possesses the ad- vantage of giving a constant angle of rake to the cutting lips as the length of the drill decreases. This is shown in Fig. 139, where the angle of rake is 27^ degrees for either form of drill when the tool is new. When worn nearly to the shank, this angle in the "increased twist" drill is materially decreased, while for the "constant angle" drill, it remains the same. For the small drills, the blanks are usually made from steel FIG. 140. wire. They are first cut in lengths and then given a body clearance by filing. The flutes are each cut separately. With the drills of larger diameter, the blanks are turned in a lathe and finished to exact diameter by filing. In cutting, they are held upright in a vertical machine, both flutes being cut at the same time. The clearance of the lands is made by either milling or grinding, and with the large drills both lands are relieved at the same time. Drills are given a cutting temper the entire length of the flutes, and are carefully straightened after this process. Twist drills are sometimes made slightly over size, and after tempering are ground perfectly straight. This adds little to the value over the properly straightened drill and increases consider- ably the cost. Twist drills having more than two flutes are frequently used for enlarging drilled or cored holes. They are very efficient for this purpose, but as the lips do not intersect at the point, they cannot drill a hole from the solid stock. A three flute twist drill is shown in Fig. 140. They are regularly made in sizes from T /6 inch to 3 inches, varying by thirty-seconds. The straight flute io8 MODERN MACHINE SHOP TOOLS. drill is one having the flutes cut parallel to the axis of the drill, and is in other respects similar to the twist drill. A straight flute drill is shown in Fig. 141. In Fig. 142 is shown a hollow drill which may be used to advantage in the drilling of deep or long holes, the chips passing out through the hollow shank. Great care must be exercised in grinding the twist drill, as the FIG. 141. same troubles on a smaller scale as those shown in Figs. 134 and 135 for the flat drill will result from the improper grinding of the twist drill. The angle of lip clearance should be greater at the center than at the outer ends of the lips and must not be excessive, as in that case the drill bites too rank. If this angle is too small, however, the cut is not free and excessive heating re- FIG. 142. suits. The angle of the lip to the axis of the drill should be 59 degrees. This gives a straight cutting lip as shown in end view, Fig. 137. There are a number of drill grinders made that will grind drills satisfactorily. The experienced mechanic usually prefers to grind his drills by hand, depending upon his eye and judgment for the proper angles and clearance. It is in this way that all new drills are ground before leaving the factory. The standard shanks for drills are straight and taper. The taper shank is shown in Fig. 136. It is made in six sizes, and DRILLS. 109 known as the Morse taper, which is approximately fa inch per foot. The exact taper for the several sizes is given in the follow- ing table ; also the limiting sizes of drills on which each taper is generally used: TABLE OF MORSE TAPERS. No. of Taper. Taper per foot. Smallest Drill using^ each Taper. Largest Drill using each Taper. i 2 3 4 6 .605 .600 .605 .615 .625 .634 If ft * *& Special. 1 2 3 Special. In Fig. 143 is shown the shank of what is known as the grooved shank drill to be held in a special chuck. These grooves may also be applied to taper shanks. Drills are also made with square shanks to be held in ratchets and bit braces, also with shanks of various special forms. Taper shank drills are made and carried in stock by 1-64 inch sizes from fa of an inch to 2.y 2 inches, and by 1-16 inch sizes from 2^/2 inches to 3 inches. All sizes over 3 inches are special and made only to order. Straight shank drills are made by 1-64 inch sizes from 1-16 of an inch to 2^ inches. A regular straight shank drill is the same length over all as a taper shank. What are known, however, as jobbers' sets, running from 1-16 of an inch to }/ 2 inch by 64ths, are considerably shorter than the regular lengths. The wire gauge sizes run from No. 80 the smallest twist drill regularly made to No. i. The No. I wire gauge drill is .228 or about 15-64 of an inch in diameter, while the No. 80 is but .0135, or a little more than i-ioo of an inch in diameter, This latter drill is an exceedingly delicate little tool, having flutes quite perfectly formed. Drills are made in what are known as letter sizes, from A to Z, A being the smallest, .234 of an inch, and Z the largest, .413 of an inch. These drills are made with straight shanks. Millimeter sizes from 6 to 50 m.m. are made by most American makers. From 6 to 25 m.m. sizes increase by ^2 m.m. advances. The milli- meter drills are made in both straight and taper shanks. It has not been found practical to give drills smaller than No. 74 wire gauge, .0225 of an inch, land clearance, and many drills considerably larger than this are not so cleared. no MODERN MACHINE SHOP TOOLS. Practice is somewhat at variance as to the best speeds at which to run drills. The later tendencies are to reduce the feeds and increase the number of revolutions, that is for the smaller sizes. For the larger sizes, the number of revolutions varies little from TABLE OF DRILL SPEEDS. Diameter of Drills. Speed for Wrought Iron and Steel. Speed for Cast Iron. Speed for Brass. ^ inch. 1712 23S3 3544 X " 855 1191 1772 K. 397 5^5 855 H 265 375 570 % 183 267 412 % 147 214 330 % 112 168 265 % 9 6 144 227 i 7 6 H5 191 *X 68 102 170 *X 58 8 9 150 iH 53 81 136 i% 46 74 122 i% 40 66 H3 i% 37 61 105 i# 33 55 9 8 m 3i 5i 9 2 the old practice. The above table gives the speed of drills in revolutions per minute as recommended by a leading manufac- turer of drills. A rule that is easily remembered and gives approximately the correct speed is, dividing 80, no and 180 by the diameter of drill, will give the number of revolutions per minute for work on steel, cast iron and brass respectively. The results will be rather low for the smaller sizes and high for the larger sizes. The feeds for drills should vary with the diameter of the drill and the hardness of the metal being drilled, and will usually be I -200 to 1-50 of an inch per revolution of the drill. In drilling wrought iron or steel, the drill should be flooded with oil, or some suitable drilling compound, which lubricates the cutting edge and carries away the heat of friction. Cast iron and brass are drilled dry. A drill with cutting lips having no angle of rake will work best in brass. A straight flute drill or twist drill with lips ground as shown in Fig. 144, is well suited to this work. In drilling deep holes in steel, especially when the drill is held DRILLS. Ill in a horizontal position, it is difficult to properly lubricate the cutting edges of the drill. To overcome this, oil tube drills one of which is shown in Fig. 145 are being very successfully used. In this drill oil is forced to the cutting lips, thus thoroughly lubricating them, at the same time helping to force out the chips and keep down the temperature. The usual method of making this drill is to mill small grooves in the lands parallel to the flutes and se- cure, by solder, in these grooves small tubes which, at the shank end, are usually made to open into a hollow in the shank from which suit- able connection is made with the oil supply. One manufacturer uses the following unique method for producing these oil passages. Two small holes are drilled parallel to the axis in the stock from which the tool is to be made. The length of these holes is somewhat more than the length of the grooved portion of the finished* tool, so as to connect with the hollow shank. After these holes are finished the stock is heated to a low forging temperature and then twisted FIG. 145. an amount such as. to make the holes come parallel with the flutes when cut. A cut of this drill is shown in Fig. 146. Oil tube drills are necessarily expensive to manufacture ; their FIG. 146. use will, however, frequently more than double the output of the machine driving them. The drilling of holes that are to be tapped requires a drill equal in diameter to the root diameter of the tap, and is called a tap 112 MODERN MACHINE SHOP TOOLS. drill. The machinist soon fixes*in his mind the proper tap drills for the taps he most uses. When there is any uncertainty as to the proper diameter, consult a table of tap drill sizes or caliper the end of the taper tap, and select a drill that will just allow the point of tap to enter ; this will give a full thread. The following table gives the sizes of tap drills from l /4 of an inch to i l / 2 inches for the V and United States Standard threads. The United States Standard number of threads per inch are those taken. TAP DRILL TABLE. Drill for U S. S. Diameter of Tap. No. of Threads. Thiead Drill for V Thread. % 20 ,3^ U TS 18 % % 16 ~fy ft 14 ii tl % 13 if V?f 12 T 7 f % II % 1^ $4 10 $6 19. 7 A ? It ft o ? ? TIT ll A 7 TTT ft l /4 7 I 1 / I-gm i^ 6 i>! iK 6 4i Ul The location of a hole to be drilled is usually indicated by a center punch mark ; if the hole must be drilled exact to this center a circle of diameter equal to the diameter of the hole to be drilled should be described about the punch mark as a center, as shown at A in Fig. 147. A few light prick punch marks should be made, A A A A, on this circle. If the drill runs to one side as shown at B in Fig. 147, it 'can be drawn back by cutting away the wide edge with a cape chisel as shown at B ; this chisel cut should run DRILLS. to the center. The drill must be brought concentric with the circle A A A A in this manner before it begins to cut the full diameter, as it cannot then be readily shifted. When the surface upon which the holes are laid out is a machined one, it is often better to scribe a circle about the center mark slightly larger in diameter than the required hole and drill to the center of this circle. This leaves the laying out circle on the work and readily shows any inaccuracy in the drilling. The laying out and drilling of holes in this manner when ac- curate location is necessary, requires care and skill and is usually an expensive operation. When many similar pieces are to be so drilled, it is usual to provide a suitable jig or drilling template, which insures accuracy and requires very much less time. The subject of jig drilling is taken up in Chapter XXVII. On a large amount of drilling work the hole. in one part serves as a guide for drilling other holes in other parts of the work, and in many cases it is possible to use one piece of work, which has been care- fully laid out and drilled, as a template for drilling other similar pieces. When the point of the drill breaks through the work and the pressure is thereby greatly reduced, care must be exercised in the handling of the feeds to prevent the drill from worming or drawing through without cutting the full circle. In case this occurs, one of three things will certainly result: break the work, the drill,, or stall the machine. A straight flute drill or a twist drill with lips ground as shown in Fig. 144 will not worm through and are good tools to use for drilling thin or sheet metals. Keep the drill sharp by proper grinding. CHAPTER IX. REAMERS. In order to produce holes as round, straight, smooth and uni- form in diameter as is required in the construction of accurate machinery, a reamer must be used. As has been shown in a pre- ceding article, the drill cannot be relied upon to produce holes possessing the above qualities. A reamer is a sizing tool having two or more teeth either par- allel or at an angle with each other, the latter forming what is known as a taper reamer. These teeth may be either straight or spiral ; a spiral tooth producing a shearing cut, while a straight tooth gives a square cut. As to their construction, reamers for producing parallel holes may be divided under two general heads solid and adjustable. All taper reamers come under the solid class. A solid reamer is one having a shank and teeth made from a single piece of tool steel. The expansion reamer is a built-up tool, the usual form consisting of a shank and head, the head having suitable recesses in which are secured the cutting teeth. As adjustment to com- pensate for wear only is attempted, the amount of expansion is small. The number of teeth, their form and spacing are the important considerations in the construction of this tool. Reamers having fewer than five teeth are not to be used where accurate cylindrical truth is desired. A reamer having three teeth cannot be de- pended upon to produce round holes, inasmuch as any irregu- larity in the hole being reamed affects the cutting of the tool. This is shown in Fig. 148, where a depression A exists in the drilled hole. When the tooth B comes to this point it drops in, thus decreasing the cutting of C and D, and produces a hole not round. The same effect to a lesser degree is produced in a reamer having four teeth, Fig. 149. When the cut is relieved at A, the pressure of the cut at C will crowd the tool toward E. Since the pressure of cut at B and D balance each other, any decrease of cut at C causes an increase at D, and B and C will overbalance D, the body of the reamer moving an appreciable distance toward REAMERS. 115 E. With five or more teeth this effect practically disappears. The more cutting edges, the more smoothly will the reamer work. The construction of adjustable reamers does not admit of as many teeth as can be formed on a solid reamer, yet the advantage of adjustability to a certain extent offsets this. Reamers having an even number of teeth equally spaced do not produce as good results as those having an odd number of teeth. In the former, the teeth fall opposite each other, causing greater tendencies to vibration, and in the case of reaming irregular hole's, the greatest cut will be carried on two opposite teeth ; but with an odd number of teeth, the greatest cut must be carried on at least three teeth. Reamers having an even number of teeth but irregularly spaced are very extensively made. A cross-section of such a tool is FIG. 148. FIG. 149, FIG. 150. FIG. T5I, FIG shown in Fig. 150. The effect is practically the same as having an odd number of teeth. The form of tooth usually employed is shown in Fig. 151. The front face is on a radial line, the flute being well filleted at the root. If an angle of rake is given the tooth, as shown in Fig. 152, and specially so if the fillet at root is cut away, the tooth will spring out under the cut, producing an oversize hole. The grinding of the clearance on top of the tooth is an impor- tant point in the construction of a reamer. The clearance should be sufficient to properly relieve the cutting edge. If too great clearance is given, the tooth will be weak and chatter in the work. As frequently produced, the cleared surface is slightly concave, the amount depending on the diameter of the emery wheel used in grinding it. As a plain surface is desirable, a wheel of large diameter which gives approximately such a surface, should be employed, or better still the face of a cup emery wheel which gives a straight clearance. lib MODERN MACHINE SHOP TOOLS. The arrgle of clearance will depend on the distance the axis of the emery wheel is set back or the axis of the reamer, as shown in Fig. 153. In no case must the wheel come in contact with the front face of the tooth being ground or the one next behind, and the guiding finger which steadies the reamer must always bear against the front face of the tooth being ground. When the diameter of the reamer is large and the pitch of the teeth so small that the necessary clearance cannot be given except by using too small an emery wheel, the wheel can be mounted on an axis at a considerable angle with the axis of the reamer, as shown in Fig. 154. This produces a plane surface; but due to the wear of the emery wheel is not as satisfactory as the use of the cup wheel. The wheel must be so placed as to cut its entire width, other- FIG. 153. FIG. 154. wise it will be grooved and the cutting edges of the tooth round- ed off. A hand reamer is a tool for hand use ; while a chucking reamer is operated in a machine. Fig. 155 illustrates a standard solid FIG. 155. hand reamer. In its manufacture, the stock is first cut to length and then turned to a diameter about 1-64 inch over finish size. REAMERS. H7 The flutes and square on the end of shank are next cut by milling processes. Tempering is the next operation, from which it usually comes warped to a greater or less extent. After straightening, the centers are lapped out and the reamer ground in a grinding machine to diameter and cylindrically true. All standard reamers are made .0005 of an inch over size. This is because a new reamer, before being used, should have its cutting edges stoned slightly, which will just about bring it down to exact diameter. If this is not done, the edges will give down a little on the first few holes reamed ; so that if the reamer was made to exact diameter it would fall below size too quickly. The shank is usually ground about .001 of an inch smaller than the fluted portion, and in its use serves as a gauge to indicate when the reamer has fallen, through wear, below .001 of an inch under size. The shank should not be marred in any way, as in that case the purpose for which it was so carefully brought to size is lost, and in cases where the reamer is passed through the work, Damage to the hole is apt to result. The last operation previous to grinding the clearance and final inspection in the manufacture of a reamer is the buffing out of the flutes. This is done by passing- them under a small vulcan- ized emery wheel^ which has first been trued to the exact outline of the flute. The hand reamers are regularly made in two lengths ; what is known as the short reamer being considerably shorter both in the flute and shank than the regular or jobber's reamer. The diameter of the point is about 1-64 of an inch under size, the tool tapering to exact diameter at about one-fourth the length of the tooth from the point. The balance of the teeth are ground nearly parallel, the diameter at the shank end being from .0005 to .00075 of an inch small. This slight taper counteracts the tendency that all reamers have to ream a hole slightly over size at the top, which is due to the tool remaining longer in contact with the wall of the hole at the top than at the bottom. The limit of error allowed in their manufacture does not exceed .00025 of an inch. When, for the parallel shank of the hand reamer, a taper shank is'substituted, the reamer becomes adapted to use in a drill press or other machine. The form and length of flute is the same as for the regular hand reamer, except at the point, where the teeth instead of tapering for one-fourth of the length of the flute, run parallel to the point. This form is used because the reamer cuts MODERN MACHINE SHOP TOOLS. easier and faster, and as it is steadied by the spindle, no difficulty is experienced in starting it true. In Fig. 156 is shown a spiral fluted reamer. They are always tf!3. 156. cut with a left-hand spiral. They give a smooth shearing cut and are specially valuable for machine reaming on centers as they do not tend to draw into the work and off from the center. They are also made in shell and taper. Fig. 157 illustrates a fluted chucking reamer with taper shank. V 157- The total length of this tool is approximately the same as the length of a hand reamer. The teeth are short and slightly tapered at the point, which facilitates starting when used against the dead center of a lathe. It is also made with straight shank. The rose chucking reamer, Fig. 158, is of the same length and FIG. 158. provided with the same forms of shank as a fluted chucking reamer. The head is ground cylindrical with cutting teeth on the end. The circular flutes do not form cutting edges, their office being to carry the lubricants to the point of the tool, and, espe- cially when used in a horizontal position, to carry away the chips. It is therefore important that a flute be provided for each cutting lip. The head is given only a slight clearance in its length. The result is that holes produced with the rose reamer are usually round and straight, but not so smooth as those formed by longer REAMERS. cutting edges. The lack of clearance in this tool makes it unsuit- able for reaming deep holes, as a small amount of heat causes it to expand an amount sufficient to bind in the hole reamed. In Fig. 159 is shown a three-flute chucking reamer. These FIG. 159. reamers have the shanks and fluted portion ground cylindrically true and are specially 'adapted to the reaming of deep cored holes. The shell reamers, Figs. 160 and 161, are chucking or rose FIG. 1 60. FIG. 161. reamer heads, having round central tapered holes, the taper used being j/s of an inch per foot for the reception of the arbor shown in Fig. 162. A rectangular slot or key-way is milled across the FIG. 162. shank end to receive the cross key of the arbor; several sizes of reamers fitting each size of shank. The first cost of a set of shell reamers and arbors is but little less than that of a set of regular rose or fluted chucking reamers. I2O MODERN MACHINE SHOP TOOLS. In Fig. 163 is illustrated a taper hand reamer. The reamer shown is a standard taper pin reamer having a taper of l /4 inch per foot. The Morse taper reamers of approximately ^s inch per foot and the Brown & Sharpe standard taper reamers of y 2 inch per foot are in all respects similar to the taper pin reamer shown. When a solid reamer, through wear, falls below standard size an amount greater than the allowable limit of error, it can be brought up to standard size again only by drawing the temper, upsetting the teeth by driving against their front faces, retemper- ing and regrinding. This is an expensive and unsatisfactory operation. It will usually be found best to grind it to about .005 under size and use it for a sizing reamer. In some cases it is possible to grind them to the next thirty-second or even sixteenth size smaller. This makes the teeth wide on top ; but if the clear- ance is properly ground, the reamer will work well. In such cases, FIG. 163. care must be taken to obliterate the original size stamp, and re- place with a new one to avoid errors. It must not be inferred that a properly made solid reamer falls quickly below size when properly used. Its life as a standard tool depends upon the hardness of the metal reamed and the amount of cut it is required to take. It must be remembered that the standard reamer is a finishing tool, and must, as such, be capable of reaming a great many holes to practically the same diameter. To accomplish this the cut must be very light, never exceeding 1-64 of an inch, and preferably not more than .005 to .01 of an inch. When great uniformity is required, a sizing reamer .005 to .007 of an inch under size, usually operated by power, is first passed through the hole. This leaves a true hole and equal cut for the finishing hand reamer. There are numerous adjustable reamers on the market. Fig. 164 shows the Cleveland common-sense expansive reamer in which a screw in the point forces a tapered plug into the tapered .hole in the center of the tool which expands the teeth, the slots parallel to the teeth and extending through to the bore, allowing the necessary amount of spring. It is evident that the teeth ex- REAMERS. 121 pand most at the center, but as the amount of expansion necessary to preserve standard diameter is very small, this will have little effect on the working of the tool. The cylindrical portion of the point is called the "guide" or the "pilot" point, and is usually ground .005 to .007 of an inch under size, which of course limits the amount of stock Teft for finishing. This reamer is made from y% of an inch to 2J/2 inches in diameter, and is strictly an ex- pansive reamer. A form of Morse adjustable blade reamer is illustrated in Fig. 165. It consists of a suitable number of blades or chasers, fitting FIG. 164. FIG. 165. FIG. 1 66. milled slots and abutting against a ground tapered plug in the center of the head., the end of which is threaded into the shank. By screwing the plug in, the blades are forced out the required amount, and when adjusted, the dished-head nut engages the beveled ends of the blades, holding them firmly in position. These reamers have an adjustment of about 1-32 of an inch, and are regularly made in sizes from fy of an inch to 2 inches. Fig. 1 66 illustrates an adjustable reamer in which the blades, which -are unequally spaced, are fitted in radially tapered grooves. Cupped collars engage the beveled ends of the blades, holding them firmly in position. The adjustment is made by slacking the upper collar and forcing the blades toward the shank by the 122 MODERN MACHINE SHOP TOOLS. lower collar. A reamer of this class with steep taper to the bottom of the grooves and long threaded portions can be adjusted for several sizes. This, however, is not considered good practice, the adjustment being simply to maintain one size. This adjust- ment, however, is great enough to allow for several regrindings. Those classes of adjustable blade reamers in which each blade is set out independently should be reground after each ad- justment, as it is almost impossible to set the blades out equally. In using the reamer it should be turned continually forward, both on the advance and on the withdrawal. Turning it backward while in the work is quite apt to injure the tool, diie largely to small particles of cuttings lodging between the clearance sur- faces and the wall of the hole. In hand reaming the tool can usually be passed through the work. Oil should be used freely in reaming steel or wrought iron. Cast iron and brass are usually reamed dry. A small amount of oil will, however, frequently improve the quality of the work in these metals. The preparation of the holes for taper reaming is of great im- portance. As a reamer should not remove all the metal that would be left if a drill the size of the point of the reamer were passed through the work, several drills of different diameters may be used, producing a stepped hole, as shown in Fig. 167. If FIG. 167. the work is done in a lathe, the taper attachment or compound rest can be advantageously used, using a boring tool to- enlarge the drilled hole. If the lathe has neither of these attachments, the hole can be stepped out, as in Fig. 167, with the boring tool. A roughing reamer, Fig. 168, is well suited to the preparation of a hole to be taper reamed. FIG. 1 68. REAMERS. 123 A simple form of reamer shown in Fig, 169 will frequently obviate the expense of a special reamer when only a few holes are to be sized. The tool can be made at slight expense, and when carefully constructed will produce very good results. The taper pipe reamer, Fig. 170, is a roughing reamer of standard pipe tap taper for sizing a drilled or bored hole before tapping with pipe tap. The reamers used for reaming center bearings in work to be FIG. Ii machined between centers are shown in Fig. 171. A is the "old Hartford" reamer with one cutting edge. It cannot be relied upon to produce a true conical hole. A "new Hartford" center reamer is shown at B. It has three cutting edges, and will pro- duce a true hole. These reamers are intended to follow a small drilled center hole, and are made with 6o-degree, 72-degree and FIG. 170. 82-degree angles, 60 degrees being the standard. They are also made in several sizes from 14 to ^ of an inch, largest cutting diameters. A form of combination center reamer and drill, in which the drill and reamer blades are held in a suitable shank, is shown at C. At D is shown a combination, center drill and reamer that has come into general use. It is admirably adapted to its work, being efficient, simple and inexpensive. The drill steadies the reamer, which makes it cut smoother, and insures its coming central with the drilled hole. This is of special value 124 MODERN MACHINE SHOP TOOLS. when the surface of the work is uneven. The countersink is simi- lar to the center reamer, having, however, a greater number of teeth. When reaming either taper or parallel in a lathe, the work rotating and the reamer held against the dead center, true work "must not be expected, if the reamer is allowed to follow directly after the drill, as it is practically impossible to so start a drill that the drilled hole will be exactly concentric to the axis of the lathe spindle. This will cause the point of the reamer to move in a small circle around the center of the rotation, producing a tapered instead of a parallel hole. If true holes are required, the drill used should be enough smaller than the reamer to allow for the truing of the hole with the boring tool, which will bring it con- centric with the axis of rotation before the reamer finishes it to exact diameter. When the reamer is used in a drill press, correct results will be obtained only when the hole reamed is exactly concentric with the drill spindle, otherwise the reamer will be held against one side of the hole, making it elliptical in cross-section at the top. These difficulties in producing perfect reamed holes by machine-driven reamers, compel the extensive use of tlie hand reamer, the holes having been previously sized with an unclersize reamer. CHAPTER X. SCREW THREADS, TAPS AND DIES. As to their uses, screw threads may be divided into two classes ; first, those used for fastenings; and second, those used for com- municating motion. The term "fastenings" is applied to any device used to hold together two or more pieces, either holding them rigidly together or constraining any relative motion be- tween them. The important position that the screw thread holds under this head becomes forcibly apparent when we consider a machine, as a lathe, for example, and wonder how we would man- age to hold its numerous parts together without the use of this device. The lead and cross feed screws in a lathe are examples of screws used to communicate motion. In Fig. 172 are shown the three forms of threads used for fastening. In the V thread the angle of the sides with each other is 60 degrees, the top and root of the thread being sharp. The United States standard thread, or 'as it is often called, the Sellers or the Franklin Institute thread, is . the same as the V, with the top cut off and the root .filled in. The amount taken from the top and added to the root is one-eighth of the height of the Y thread, thus making the United States standard thread three-fourths the depth of the V thread. The United States stand- ard form of thread was recommended by the Franklin Institute in 1864. This system was devised by Mr. William Sellers, and has become the acknowledged standard thread in the United States. Its points of superiority come from the fact that it does not cut so deep into the stock as does the V thread, thus leaving a stronger root, while the small amount cut from the top and bottom of the V thread has little strength value. It is more cheaply produced, as threading tools with flattened points stand up under their work much better than those with sharp points, and the filled root does not form a distinct fracture line as does the sharp root of the V thread. This form of thread is well adapted for interchangeable work, being used by the leading builders, and its complete adoption should be urged by all. 126 MODERN MACHINE SHOP TOOLS. In the Whitworth* or English standard thread the tops of the threads are rounded off and the roots filleted in. The angle of the sides with each other is 55 degrees, and the amount taken from the top and added to the root is one-sixth of the height of the V thread, having 1 sides at a 55 degree angle with each other. Each of the threads shown in Fig. 172 is to scale for stand- ard one and one-quarter inch bolts, and the dimensions given will facilitate comparison. 172. SCREW THREADS, TAPS AND DIES. 127 In Fig. 173 are shown three forms of screw threads used for communicating motion. The pitch of the screw is the distance it advances in making one revolution ; thus, the pitch of a screw having eight threads per inch is one-eighth of an inch. It is usual to refer to the number of threads per inch, rather than to the pitch. For ex- ample, in Fig. 172 it is seven threads per inch, rather than .143 of an inch pitch. SQUARE THREAD 128 MODERN MACHINE SHOP TOOLS. All screw threads may be either right or left handed. Fig. 174 illustrates a left hand screw. The left hand screw enters its nut "by turning it counter clockwise. When a steep pitch is desired and the diameter of the stock would be too small to permit the use of a single thread, two or more parallel threads, dividing the pitch into two or more parts, may be used. Such are known as double, triple and quadruple threads. A triple thread is shown in Fig. 175, with single thread of same pitch shown dotted. The United States standard admits of no oversizes and specifies LEFT-HAND THREAD " 1 \ A/ V/ V V vxAiAlA YIYIYMV A[AJ/\!/Y\ FIG. 174. FIG. 175. the number of threads per inch for each size, as well as prescrib- ing the form of thread. For special work, however, it is fre- quently advisable to use a different number of threads per inch from that specified in this system, but such will, of course, not be standard, and must always be looked upon as special. The following table gives the principal diameters and corresponding numbers of threads, as determined in the United States standard system : TABLE OF SCREW THREADS. Diameter of Bolts. Number of Threads per Inch. Diameter of Bolts. Number of Threads per Inch. X 20 ^y% 7 JL 18 \]^ 7 3^ 16 I y^ 6 7*r 14 1/4 6 H 13 l^ 5 fm 12 2 4/1z ft II 2 K 4 X 10 3 , 3^ X 9 3* 3 1 A 1 8 4 3 The screw threads with which the machinist has to deal are SCREW THREADS, TAPS AND DIES. I2 9 produced by cutting processes, in winch the thread is formed from the solid stock. Cut threads are produced either by means of a single pointed cutting tool or a chaser used in a lathe, or by means of taps and dies. In the first case the pitch of the screw being cut is dependent on the lead screw oi the lathe, while in the latter case the pitch is dependent on the le~d of the tap or die. Screws used for communicating motion, or where accuracy is desired, are cut in the lathe, while those used for fastenings are usually cut by the other method. The tap is a tool used to produce internal threads, and the Taper. Bottoming. die is a tool used in cutting the external threads. Hand taps and dies are those intended to be used by hand, while machine tapi and dies are those operated by power in a machine. The hand tap is shown in Fig. 176. It should be made of a high grade steel, and of a temper specially suited to the severe work it is called upon to perform. It is provided with a round 130 MODERN MACHINE SHOP TOOLS. shank, with milled square to receive the tap wrench. This shank- is frequently turned to the exact diameter of the root of the thread, and used to gauge the final settings of the single pointed thread- ing tool, with which the thread of the tap is finished, it having been previously roughed down with a chaser. This work is done in a lathe having an accurate lead screw, the accuracy of the tap depending largely upon this screw. Hand taps are made in sets, three taps comprising what is known as a tap set. These are called the taper, plug and bottom- ing, as shown in Fig. 176. As manufactured by the Pratt & .Whitney Company, the only difference between these taps is in the form of the point. They all have the same thread parallel at the root, and if passed entirely through the work will produce similar threads. The taper tap is parallel on the point for a dis- tance equal to one-fourth the diameter of the tap. This point is made the diameter of the roots of the teeth, which is the correct size of the hole to be tapped in order to produce a full thread. The teeth at the shank end are parallel for a length equal to the diameter of the tap, and the balance of the teeth are tapered to the parallel portion at point. This gives a number of teeth be- tween which the cutting duty in forming a full thread is divided. The taper taps manufactured by some makers have teeth, in which the root diameter is small at the point, increasing on a uniform taper to the parallel portion near the shank end, and thus dividing the taper between the top and root of the teeth. In the plug tap the first three teeth are tapered off, as shown, while in the bottoming tap the teeth extend full to the point. The fractional teeth at the point, which would be very apt to break, are ground away. The taper tap is best suited to the starting of a thread, but unless the hole passes clear through, a complete thread will not be formed. The plug tap makes a full thread nearly to the bot- tom of a hole, which may be finished to the very bottom with the bottoming tap. The bottoming tap should be used, however, only to finish out the thread, as practically all the cutting is done by the four point teeth, which severely taxes their strength. When possible, it is best to drill the holes sufficiently deep to allow the plug tap to finish the required length of thread. The plug tap is best suited to general work, but requires greater care in starting it axially true with the hole than the taper tap. Machine taps are usually made of the plug pattern, but as they are SCREW THREADS, TAPS AND DIES. 13! held true to the work, no difficulty is experienced in starting them straight. Four grooves are ordinarily milled in the tap, thus forming four sets of cutting edges. The form of this groove varies some- what, but has little effect on the cutting qualities of the tap. It is usually so formed as to bring the cutting faces of the teeth on a radial line, as shown in Fig. 177, and should be only deep enough to allow room for chips and oil when tapping deep holes. If the groove area is made too large the strength of the tap is seriously impaired. It will be notic- ed in Fig. 177 that the teeth are comparatively short, less than one-third of the circumference having teeth. The shorter the teeth the less FIG. 177. will be the frictional resistance and the weaker will be the tooth. As tap teeth are shortened by grinding from the front face, the teeth must not be made too short when new. Hand taps and all others that are backed out of holes tapped are not given thread clearance. As standard taps do not admit of oversizes, a relieved thread tap would, if standard when new, fall below proper diameter when ground on the front faces in sharpen- ing. A tap having relieved teeth will, when backed out of the thread it is cutting, allow the cuttings to wedge between thread and teeth, seriously injuring both work and tap. The backing of such a tap while in the work will frequently shale off the front face of the teeth. Taps that pass through the work by driving continually for- ward, as with nut taps, are given relieved teeth ; they cut freer and there is less friction between tap and thread, but should not be turned backward in the thread. The relief on these teeth is produced with uniformity and rapidity on machines specially de- signed for this purpose. Standard taps are made from one to five one-thousandths of an inch oversize to allow for the wear on the top of the teeth. This means that a little less than the one-eighth is taken from the top of the teeth ; the root diameter and sides of the teeth being cor- rect, this does not affect the fit of the thread. In Fig. 178 is shown a pulley tap used largely for tapping the holes for set screws in pulley hubs, a hole being drilled in the rim sufficiently large to allow the tap and shank to pass through. It is a regular plug tap with a long shank ; the diameter of the shank MODERN MACHINE SHOP TOOLS. is the same as the diameter of the tap. It may.be had with any reasonable length of shank, and will be found a very convenient tool for tapping holes in inaccessible places. The stay-bolt tap, as shown in Fig. 179, is a combined reamer and tap, used by boiler makers for reaming and tapping the holes for stay-bolts. The taps are made long, as the plates are often widely separated, and must be tapped together, as otherwise the stay-bolts will not enter the second plate without springing the plates a fraction of the pitch. These taps are sometimes made as long as five feet. They run from three-quarters to one and one- half inches in diameter. A hob, or master tap, is one used for cutting the threads in dies. Fig. 180 shows a hob for cutting pipe dies. The pipe tap shown in Fig. 181 has full teeth to the point, the standard pipe taper being three-quarters of an inch per foot. The following table gives the number of threads per inch and tap drills for standard pipe taps : s uLiMu V. Fir,. 178. FIG. 179. FIG. I 80. FIG. l8l SCREW THREADS, TAPS AND DIES. 133 Diameter of Pipe. Number of Threads. Tap Drill. % 27 X 18 . H 18 / 14 %{ 14 i I- 'H .\ 1 M ' 1 2 i*H 3 2 8 3* 3/^ 8 3fff 4 8 4A In -case a pipe reamer is not used for sizing ahead of the tap the holes may be drilled 1-64 inch larger for the small sizes and 1-32 inch for the large sizes. Fig. 182 shows a machine or nut tap. It is provided with a long easy taper on the threaded portion and a long shank some- what smaller in diameter than the root of the thread. A combination drill and pipe tap, shown in Fig. 183, is in quite general use. It is a valuable tool for drilling and tapping gas and water pipes under pressure. A collapsing tap is one in which the teeth or chasers, after cut- ting the thread, are carried toward the center enough to allow them to clear the threads so that the tap can be removed without backing. This not only saves time, but the wear on the teeth incident to backing them out of the threaded hole. A form of col- lapsing tap manufactured by the Geometric Drill Company is shown in Fig. 184. The mechanism is such that when the two side stops come in contact with the work the lead or draw of the tap releases a clutch in the head which unlocks the mechanism and the chasers are in- stantly collapsed. The setting of the stops determines the depth of the threaded hole. The chasers are then expanded again and locked in position for the next operation by means of the handle shown on the body of the tap. A graduated adjustment provides for slight variations in the diameter of the tap. The advantages of the collapsing tap over the solid lies in the saving of time due to being able to allow the machine to run continuously forward, thus saving the time required with the solid tap to back out. The backing out not only injures the tap 134 MODERN MACHINE SHOP TOOLS. but is quite apt to injure the thread. Again, the possibility of changing slightly the diameter of the tap is frequently of value. A limited number of different sizes may be tapped with each size of head by substitut- ing different sets of chasers. Taps are tempered hard and are conse- quently brittle. They give no warning before they break, therefore care and judgment must be exercised in their use. In using hand taps, a wrench which fits closely the square on the shank, and having opposite handles of equal length, should be used. The pull on the handles should be uniform and equal. This produces a torsional strain in the tap, which, if working under proper conditions, it will safely resist. Any excess of pressure on one handle will produce a transverse strain which endangers the tap. FIG. 182 FIG. 183. FIG. 184. SCREW THREADS, TAPS AND DIES. 135 It frequently is necessary from the nature of the work to use a single handle. In such cases the operator must grasp the head of the tap and wrench with his left hand and balance the trans- verse moment of the pull at the end of the handle, allowing only the turning effort to be received by the tap. In tapping full threads in tool steel great care must be exer- cised, especially if the stock is not thoroughly annealed. If much of this work is to be done two taps should be used, the first one through removing only a part of the stock, and the second finish- ing. In tapping double threads, two, or even three taps, should be used. This becomes necessary from the fact that with a double thread twice the amount of stock must be removed per revolution of the tap as with a single thread of the same depth. Taps for square threads should also be used in pairs, unless made extra long with a long tapered portion. When a thread is to be tapped at right angles to the surface, FIG. 185. -A do not depend on the taps following the drilled hole, but in start- ing test the angle by squaring to the shank of the tap. A tap started crooked must be squared up while the first two or three threads are being cut ; an attempt to square it later may result dis- astrously to the tap, and will produce a threaded hole enlarged at the opening. Dies may be divided into two general classes ; the first should include all dies requiring to be passed over the work several limes in the production of a finished thread ; the second, those that pro- duce a finished thread at once over. The first class, example of which is shown in Fig. 185, con- sists of a stock in which cutting dies are held. These dies are capable of sufficient separation to enable them to be passed over the work upon which the thread is to be cut. By means of a set screw or threaded handle the dies may be closed an amount suf- ficient to make them cut a full thread. 136 MODERN MACHINE SHOP TOOLS. In the manufacture of these dies they are threaded with a hob tap, the diameter of which is twice the depth of the thread greater than the diameter of the work the die is to be used upon. This makes a die with teeth, the tops of which fit the work when the thread is started. This is shown in Fig. 186. It greatly facilitates the starting of a true thread. The conditions at the finishing of the thread are shown in Fig. 187, in which A A are the cutting edges. When the thread is started these edges have no clearance, FIG. 186. FIG. but as the. dies are forced toward the center an increasing clear- ance is formed. This is clearly shown in the figures. The dies are chamfered off on the advancing side for two or three teeth, so that these teeth do the most of the cutting, those following simply sizing. If desired to cut a full thread close up to a shoulder the die is turned over. Under the second class we consider first the screw plate, shown in Fig. 1 88. This is a thin plate of tempered steel, in which a FIG. 1 88. . 189. number of holes of varying diameters, threaded with different pitches and provided with opposite notches to form cutting edges, have been produced. It is a primitive tool, suited only for work of small diameter, where correct threads are not required. Dies of the second class are usually made adjustable to com- pensate for wear. In Fig. 189 is shown a form of die largely used SCREW THREADS,, TAPS AND DIES. 137 for small sizes, one-sixteenth to one-quarter of an inch. It is. given a spring temper at C, .and is held in a wrought ring, not shown in the figure. A small set screw passing through the ring and engaging the notch shown in the die edge, serves to spring the die together, when through wear it becomes over- size. Fig. 190 illustrates the Grant adjustable die, in which the four chasers are held in a cast-iron collet surrounded by a wrought ring. The chasers are beveled off on the outer ends, which en- gage with corresponding beveled grooves in the ring. By forc- ing the ring down, the chasers are moved toward the center. The FIG. 190. amount of adjustment in this die is one-thirty-second of an inch. The chasers are numbered, with corresponding numbers on the side of the grooves in which they belong. This prevents the possi- bility of putting together incorrectly when the chasers have been removed for grinding. This die is sharpened by grinding back the front face of the chasers. They should be ground only a short distance back of the tooth root, so as not to interfere with the bearing in the collet. In Fig. 191 is shown the lightning adjustable die. The stock is bored out to receive the two halves of the die. The taper head screws B B fix the size and the binding screws A A A A hold the 138 MODERN MACHINE SHOP TOOLS. parts firmly together. A separate stock is provided with each size of die. In Fig. 192 is shown a solid machine or bolt die. It is made of B FIG. 191. the same form as the solid pipe die and may be used in either a hand or power holder. The spring die shown in Fig. 193 is for use in a machine and where smooth, accurate threads are desired should be used in pairs, one for roughing and one for finishing. A clamp collar fitted over the end of the die prevents its spreading. This form of FIG. 192. die can be sharpened by passing a thin emery wheel through the grooves. Self-opening and adjustable dies are for machine threading very generally used. The advantages are the same as for the collapsing tap. Fig. 194 illustrates the Geometric Drill Com- SCREW THREADS, TAPS AND DIES. 139 pany's self-opening die. This tool is usually mounted in the turret of a chucking machine or screw machine. The chasers are set up for the cut by turning the head until the mechanism locks FIG. 193. them into position. Pulling forward on the chasers unlocks the head and a spring throws the dies out. In operation the die is moved forward over the work until the end of the thread is FIG. 194. reached, when by stopping the carriage the forward lead or draw of the die unlocks it and the chasers spring open. By means of the two screws and graduations shown on the I4O MODERN MACHINE SHOP TOOLS. side of the tool a micrometer adjustment, which controls all the chasers, is quickly made, thus making it possible to make a tight or loose fitting screw as desired. The die head shown is provided with a roughing and finishing attachment controlled by the small lever at the back. In using this attachment the chasers are held out for the first cut over about i-ioo of an inch, which is taken at the second cut. This is necessary only when extremely uniform and accurate threads are required. The chasers may be very quickly removed for sharpening or changing from one size to another. For pipe threading opening dies are very extensively used. The advancing edge of the die chasers in all forms that produce a finished thread at one cut, is chamfered off for two or three teeth, which divides the cutting duty and facilitates starting the thread. The die should not be run bottom side up on the work, as in that case the first tooth does nearly all the cutting duty. Only in unusual cases is a workman justified in this procedure. Oil should always be used liberally on the tap or die when cut- ting steel cr wrought iron; a little oil on the tap when cutting cast iron or brass makes it run easier and does no injury to the thread or the tool. Sperm or lard oil is best for this purpose. In threading steel or wrought iron by hand the tap or die should, after every two or three turns forward, be given a slight turn back. This facilitates the removing of the' cuttings and allows the oil to find its way to the points of the teeth. No matter how accurately a tap or die is cut the hardening process will distort it somewhat. If this distortion followed any fixed law, allowance could be made in the threading that would offset this variation, but as the distortion is variable, even when the conditions are the most uniform possible, it is difficult to make allowance for it. As a general thing the taps contract in length, thus decreasing the pitch, and expanding in diameter. A die of standard diameter must not be used to thread stock that is one-thirty-second of an inch oversize, as the strain on the die parts is too great. The practice of rolling iron one-thirty-second of an inch over- size is to be condemned as the cause of mistakes, lack of inter- changeability and general confusion, at the same time having no advantages. It is not practical to roll ordinary bolt stock to ex- act sizes, yet the variation need not be great and can be taken care of by the standard dies. SCREW THREADS, TAPS AND DIES. 14! The speed at which threads may be cut with taps and dies in power machines depends very largely upon the character of the work, quality of the thread required and the conditions under which the. work is performed. Cast iron and brass can be threaded at much higher speeds than steel. For equal diameters fine pitches may be cut at higher speeds than coarse pitches. Smooth, accurate threads require comparatively slow speeds. For rough work a speed of from 15 to 20 feet per minute is satis- factory when the work and cutters are flooded with good screw cutting oil. 'A speed of 10 feet per minute is quite fast enough when smooth, accurate threads must be had. When the work has been heated up by a preceding operation the speed for thread- ing cannot be as high as if the work was perfectly cold. This is usually the case on the screw machines where the threading fol- lows a heavy turning operation. As the threading requires but little time as compared with the turning it is common to sacrifice speed in threading for higher efficiency in turning, all of which tends toward truer and better threads. To determine the diameter of hole required to give a full thread, caliper the root diameter of the tap, the point of the taper tap, or consult a table of tap drills. The number of threads per inch is always plainly stamped on the tap or die. Remember that United States standard for five-eighths of an inch is n, not 10, and for half an inch is 13, not 12 threads per inch. Always keep die and tap threads sharp by grinding from the front faces of the teeth. When dull they jam rather than cut the stock and require excessive power to operate them. CHAPTER XL DRILL AND TAP HOLDERS. Drivers adapted to the proper holding of drills and taps while in use are quite essential to their long life. Very frequently the shank end of these tools gives out while the cutting end remains in good condition. This usually comes from not having the proper holders in which to drive them, but very frequently through the sheer carelessness of the operator. A mechanic is always annoyed when he finds the drill he wishes to use with the shank mutilated and the tang twisted. Workmen cannot be blamed for not using what their employers will not furnish, yet very frequently they will not use them, or rather use them properly when they are provided. A dog tight- ened onto the shank of a taper shank drill, with a bar of iron resting on the shank and under the tail of the dog, will hold the drill from rotating when held against the tail center of the lathe and operating on chucked work. At least it will hold it part of the time, the rest of the time it is slipping under the dog screw, which plows up the surface in fine shape. Of course, the operator who would use a taper shank drill in this manner has not the time to smooth up the shank when he finishes with the drill, but leaves it for the other fellow to do. The other fellow is also in a hurry, and jams the drill into the taper, tearing the drill press spindle, growls because it won't run true, and finally when he twists the tang off, declares that taper shank- drills are not fit to drill lead with, and all because the taper, due to its roughed condition, not fitting properly in the bearing in the spindle, threw the entire load on the tang, which should not be expected to carry it. Drills are usually held in sockets or chucks, depending on whether they have taper or straight shanks. As has already been explained in a preceding article, the shanks of taper shank drills are turned to standard tapers. While great refinement is not exercised in producing these tapers, they will be found to vary but little from the exact taper. This is of importance because the socket shown in Fig. 195 should drive the drill not by the tang alone, but largely by the friction between the surfaces of DRILL AND TAP HOLDERS. 143 the shank and bearing in the socket. For the larger drill sizes under each taper the tang is the weakest part of the drill. Thus the tang of the No. i taper on a one-fourth inch drill will break the drill before it will twist, but on a nine-sixteenths-inch drill, which has the same tang, the tang will twist rather than break the drill that is, assuming that the drills are driven by their tangs alone. In the socket the tapered bearing should not extend bevond FIG. 195. FIG. 196. FIG. 197. FIG. 198. the bottom of the shank or mortise through the shank, and the slot should be but slightly wider than the thickness of the tang. This gives the tang a good bearing well down toward its base. The slot must be sufficiently long to allow the taper drift or key, shown in Fig. 198, to be inserted over the end of the tang to force the drill out. If the shank or bearing in the socket is jammed, the former will not enter the bearing the proper depth, the tang will catch on the point, the frictional drive between shank and bearing surfaces will be decreased and a' twisted or 144 MODERN MACHINE SHOP TOOLS. broken tang will usually result. Frequently, in twisting, the tang will force the drill out of the socket an amount sufficient to allow it to turn in the bearing, the tang cutting out the sides of the slot at the bottom and thus ruining the socket. In Fig. 199 is shown the new Cleveland drill socket and a drift. The design of this socket is to prevent the battering and upsetting of the drill tangs, the drift seating squarely upon the end of the tang" as shown. \Yhen sockets are to be fitted to spindle or turret bearings having other than a Morse taper, they may be obtained with FIG. 199. rough shanks, which can be turned to the desired size or taper. Such a socket is shown in Fig. 196. When it is desired to bush the bearing in the drill spindle or socket to a smaller size, the bushing or sleeve shown in Fig. 197 is used. It is the same as the socket, except the shank is made to envelop the bearing, thus decreasing the length of the con- nection. Sleeves are not as convenient as sockets when the drill is to be frequently removed, as it is necessary to remove the sleeve before the drill can be forced out. In such cases it DRILL AND TAP HOLDERS. 145 is best to bush the spindle bearing to the size larger than the drill taper, and then use a socket for the last reduction. In Fig. 200 is shown a sectional view of the Cleveland grip FIG. 2OO. socket. The object of this socket is to provide a stronger drive for the drill, and thus avoid the twisting of the tang. A key-way is milled in the shank of the drill, into which the key A of the socket is forced by rotating the collar B through about one-fourth of a revolution. The collar is recessed as shown at C, the recess being eccentric to the socket. When the collar is turned so that the deep part of the recess is opposite the key, forcing the drill out crowds the key back out of way. When the key- way is properly milled, the key so fits it that the drive is entirely removed from the tang. This makes it possible to use drills which have had their tangs twisted off. This collar and key, when applied to the end of the drill press spindle, will hold the drill from worming into the work and pull- ing out of the spindle when the point of the drill strikes through. It will also prevent boring bars from pulling out of the bearing ivhen used for under-cutting, a feature appreciated by those who have much of this kind of work to do. When the taper shank drill is to be used in the lathe for work on chucked pieces, the holder shown in Fig. 201 is excellently FIG. 201 k adapted. It is virtually a sleeve having a long handle attached, which may be allowed to rest on the carriage of the lathe, the shank end of the drill being steadied on its own center against 146 MODERN MACHINE SHOP TOOLS. the tail center of the lathe. Another holder for this purpose, Fig. 202, is made in which a center in the holder is used rather than the drill center. In Fig. 203 is shown a sleeve holder in which the sleeve is kept from rotating by means of the two screws, which have points turned to fit the slot in the sleeve. Another form of lathe socket is shown in Fig. 204. By put- ting a bar through the round hole it may be used between centers and becomes similar to the holder shown in Fig. 202. It is, how- fever, usually used in the tail spindle bearing, the outside taper FIG. 202. being the same as on the dead center. When so used it is much safer than when used between centers, as the drill or reamer it holds cannot pull off center. The holder used for driving the Graham grooved shank drill is shown in Fig. 205. It is made in four sizes, holding from 2*/2-inch drills down to 3-32 : inch drills. By means of reducers, one of which is shown in the figure, small drills may be held in the large chucks. These holders are very compact, being but FIG. 203. little larger in diameter than the common socket. As the grooves in the drill are cut parallel with each other, taper shank drills may be grooved to fit correctly in these holders, which, as with the socket shown in Fig. 200, makes a good method for reclaiming drills that have lost their tangs. The above are all positive drive holders, which, in the case of DRILL AND TAP HOLDERS. 147 sudden stopping of the drill will break it if the machine does not stall. To overcome this, numerous friction drive holders have been devised, one of the best being shown in Fig. 206. In this holder the socket A is held by friction between the end of the FIG. 204. FIG. 205. FIG. 206. 148 MODERN MACHINE SHOP TOOLS. shank G and the collar B. F F are fiber washers between the sliding surfaces, which gives a smooth motion when slipping occurs, and enables the operator to more easily adjust the tool to the proper grip. The collar C forms a lock nut to preserve adjustment. The bushings E, which carry the drills, fit in A, being driven by two keys. In its use the collar B is adjusted up until the friction will just nicely drive the drill. This tool, which is made in two sizes, is provided with the necessary bushings for holding drills and taps up to i^ inches in diameter. Although bushings for holding the ordinary square shank taps may be had, the tap with special shank as shown in the figure is best adapted to use in this holder. In machine tapping, and especially where more than one size of drill is to be used, much time may be saved by the use of this holder. Take, for example, the drilling and tap- ping of engine boxes, where two drills are used, one the diameter of the stud through the cap, and the other the tapping size for the stud. Each drill is placed in a holder, E. The changes from stud drill or tap drill and to tap are made by slipping out the one holder and putting in another, all of which may be done with- out stopping the spindle. Another form of friction tap holder is shown in Fig. 207. In this holder the upper half of the clutch is keyed to the shank, the lower half turning free on the end of the shank. The jaws of the clutch are beveled on their edges, the spring, which is readily adjusted for tension, holding the halves in contact. When the drive on the tap becomes too heavy, the beveled edges force the clutch halves apart, thus allowing the machine spindle to rotate without turning the tap. .The frictional drive tap holders shown in Figs. 206 and 207 require a reversing spindle machine in which to operate them. In Fig. 208 is shown the "Star" tapping attachment which contains a reversing mechanism, thus adapting it to tapping work on ma- chines without reversible spindle. As with the others it is pro- vided with an adjustable friction drive which can be adjusted to the required tension to drive any size of tap the tool will operate. In its operation the body of the tool is held from rotating by securing the chain shown to some fixed part of the drilling ma- chine. In driving tire tap forward the upper spindle, which is independent of the lower, is engaged with the lower by allowing the weight of the body to engage the clutch, which is keyed to the upper spindle, to lock with the lower. The upper bevel gear DRILL AND TAP HOLDERS. 149 runs idle on the upper spindle. When the tap has passed through the work or bottomed as the case may be, raising the drill- ing spindle first disengages the clutch from the lower spindle, and then clutches it with the upper gear, thus driving the lower spindle through the bevel gears in the reverse direction at an in- creased velocity due to the increased ratio in the gearing. When a number of holes are to be tapped to the same depth the stop FIG. 207. FIG. 208. FIG. 209. shown is used. When this stop comes in contact with the surface of the work, the body of the tool stops and the tap and its spindle draws away from and disengages the clutch. A slight upward movement of the driving spindle engages the gears and the tap is backed out. The "Presto" drill chuck, Fig. 209, is a positive driven holder provided with an assortment of drill sleeves which may be se- I5O MODERN MACHINE SHOP TOOLS. cured in the holder without stopping the rotation of the machine spindle. The sleeves are driven by a tang and held in position by two pins in the body of the holder which engage the groove shown in the sleeve. The collar, which rotates upon the body of the holder, when down locks the pins into the groove and when held up allows the pins to throw back, releasing the sleeve. A marked saving in time is effected by the use of holders of this character on work requiring various sizes of drills especially when the drilling machine is provided with but one spindle. Straight shank drills must be held in drill chucks, of which there are a large variety on the market. In Figs. 210 and 211 are shown two well-known chucks for this purpose. They are exam- ples of the two general classes, Fig. 210 showing a chuck in which the jaws have a radial motion, and Fig. 211 one in which FIG. 210. the radial motion is due to another motion along the axis of the chuck. Chucks of the class shown in Fig. 210 are made in sizes to hold from o to 2 inches, while those of the class shown in Fig. 21 1 are not made beyond J^-inch capacity. The drill cjiuck shown in Fig. 212 is regularly made in two sizes holding drills to }/ 2 inch. It consists of a shank, sleeve nut and taper split bushings. The bushings are hardened and hold but one size of drill, separate bushings being required for each size. The compactness of this chuck makes it a very convenient tool for light work. By using a split steel sleeve parallel on the outside and tapered to fit the drill shank on the inside, taper shank drills may be satisfactorily held in the parallel jaws of the drill chuck. In the Pratt chuck, a bar through the chuck has a DRILL AND TAP HOLDERS. 15! rectangular hole, which receives the tang of the taper shank drill, thus making a positive drive. In using drill chucks, it would be well to bear in mind that the keys and spanners furnished with them will grip the jaws suffi- ciently tight upon the drill without the assistance of a 1 2-inch monkey wrench or two feet of gas pipe. Overstraining a chuck destroys its accuracy. Always remove a chuck from the spindle FIG. 211. the same as you would a drill or socket with the drift. Don't feel that because it has a large hub you are expected to knock it out with a hammer. Before inserting the shank of a drill, socket or chuck in its bearing', wipe both surfaces to free them of oil and dirt, thus making- them hold better and preventing injury to the surfaces. FIG. 212. In using the drift, a light upward blow on the underside of the outer end will usually start the drill easier than a heavier blow on the end in the direction of its- length. The solid tap wrench, an example of which is shown in Fig. 213, is provided with one or more square holes to fit the squares on the end of the taps. The principal objection to the solid tap wrench is that each hole will properly fit but one size of tap 152 MODERN MACHINE SHOP TOOLS. shank, thus requiring a number of wrenches to meet general re- quirements. When more than one hole is made in this wrench, the handles become of unequal length when using any but the central hole, which results in an unbalanced pressure on the opposite sides of the tap, producing a transverse strain, in the resistance of which the tap is weak. Good judgment on the part FIG. 213. of the operator will, however, enable him to balance these pres- sures. Again, the tendency is to use these wrenches on taps the squares of which are too small to properly fit in the holes, thus rounding and twisting the tap squares. In Fig. 214 is shown an adjustable tap wrench. These FIG. 214. wrenches adjust to fit a wide range of sizes. Of the particular wrench shown, five sizes take all taps from the smallest to i l /2 inch. The dies forming the squares are carefully hardened and fitted in the body of the wrench, thus preserving a true square, FIG. 215. which fits nicely the square on the tap to which they should be closely adjusted. The T-handled tap wrench, Fig. 215, is an excellent tool for holding small and medium-sized taps in the tapping of holes in inaccessible places. It is virtually a split chuck having four DRILL AND TAP HOLDERS. 15 J slots cut in the shank which engage the four corners of the square on the tap shank. It is an excellent wrench for driving pin reamers. Frequently the nature of the work prevents the use of a tap wrench having two handles. In such cases the single handled wrench is used. The handle is preferably attached to the shank through a ratchet, which enables the operator to take shorter strokes than would be necessary with the solid end wrench. Some- times a common monkey wrench is used for this purpose. It should be a good wrench, having square, true jaws, which should be carefully tightened onto the tap shank each time the wrench is put on. In using a single-handle tap wrench, the workman must steady the shank with the left hand, so as to offset the side pull on the tap. CHAPTER XII. MANDRELS. The term mandrel is applied to that class of tools upon which work that is to be machined between centers is usually held. It is frequently called an arbor, although the distinction between the two may be quite clearly defined. A mandrel is designed to carry work that is to be operated upon by a cutting tool, while on the other hand the arbor carries and drives a cutting tool, as with the milling machine and saw arbors. Mandrels may be classed under two heads, solid and expand- ing. The solid mandrel is made slightly tapering, in order that it may be forced to a tight fit in the bore of the work. The amount of this taper varies with the class of work the mandrel is to be used on, it being but slight at the most. A bar of common round iron or steel centered and turned to the required diameter constitutes the mandrel in its simplest form. Such a tool, as is usually found in the average jobbing shop, is shown in Fig. 216. It is hardly worthy the name man- FIG. 2 1 6. drel, and although a solid one might fairly come under the ex- panding, or rather shrinking class, as it is brought down by turning and filing to fit the bore of every new piece of work that comes along. It has one quality, however, that can always- be depended upon, and that is untruth. With mandrels of this class accurate results cannot be expected. Since a mandrel must be rigid, it should be as short as the nature of the work will permit, and made of as stiff a material as -possible. Its centers should be carefully formed, and the body finished cylindrically true upon them. The centers, at least, should be tempered or case hardened, to prevent their wear- in out of true. In Fig. 217. is shown the correct construction for the end of a .mandrel. The end for a length about equal to the MANDRELS. 155 diameter of the tool is reduced slightly in diameter and provided with a flat on one side, against which the screw of the dog or driver is set. As the dog is very apt to mutilate somewhat the ends, .this reduction in diameter is quite necessary. Since the accuracy of the mandrel depends so much on its centers, it is necessary to protect them as much as possible from injury while forcing the mandrel into the bore of the work. This is best FIG. 217. accomplished by recessing the ends around the center bearing as shown in the figure. The angle of the bearing should be 60 de- grees, with a small hole drilled at the bottom. The object of this drilled hole is to prevent strain being thrown onto the delicate point of the machine center, and to form a small oil reservoir to aid in lubricating the bearing. In Fig. 218 is shown a hardened and ground steel mandrel. These tools are made for general shop work, the length increas- ing with the diameter from 3*4 inches for a l /\ -inch mandrel to 17 inches for a 4-inch. These lengths are, of course, arbitrary FIG. 218. and may for special uses be materially increased or decreased. As manufactured by the several makers, these mandrels differ but little in length and details of design. They should be made of a good grade of tool steel, carefully hardened with the centers lapped true after the hardening, and the body ground cylin- drically true upon these centers, it being rotated upon stationary or dead centers for this last operation. When the greatest possible accuracy is required it is con- sidered best to make these mandrels of tough, unannealed tool steel, with the ends only hardened. This arises from the fact 156 MODERN MACHINE SHOP TOOLS. that the steel if hardened throughout changes somewhat in form and receives temper strains, which, although relieved in the grind- ing, does not allow the tool to immediately take its permanent set. For this reason a mandrel that has been hardened throughout should be first rough ground, leaving a small amount for final finishing. This finishing should not be done for some time after the rough grinding, thus allowing the tool to season and to acquire permanent set. The set will not be appreciably altered if only a very small amount is left for the final finish. Hardening makes the mandrel stiffer and less liable to surface injury than in the case of the unhardened one. It is not, how- ever, for the purpose of allowing careless workmen 'to run their cutting tools into its surface with the idea that it will not be injured thereby. Cutting tools are usually made of a higher grade steel than the mandrel, and often tempered harder, in which case the mandrel suffers if the tool comes in contact with it. These mandrels are usually tapered about one-hundredth of an inch to the foot, the diameter being exact at the center. The size is stamped on the flat at the larger end. They will fit holes reamed with standard reamers, although the taper prevents uni- form grip on the work at the two ends of the bore. In forcing these mandrels into the bore, good judgment must be exercised, as they constitute a wedge, which will produce- enormous pressure if forced too hard, resulting in bursting the work if hard and brittle, or if soft in permanently enlarging the bore and giving it a taper corresponding to that of the mandrel. The use of the hardened and ground mandrel dees much toward the preserving of uniformity in the size of holes, in the work of shops, where these tools are used. A hole only a few thou- sandths of an inch under or over size prevents, in the first case, the mandrel from entering, and in the latter allows it to fall through. Its slight taper makes it a good comparative gauge by means of which minute differences in diameter of bores may be compared by the relative distance to which the mandrel enters. Expansion mandrels, while possessing the decided advantage over the solid ones of a parallel grip in the bore of the work, have too often the disadvantage of complication of parts, which makes them unsuitable for the most accurate work, and especially sd after they have become somewhat worn. These objections, however, can hardly be said to exist in the case of the mandrel shown in Fig. 219. This mandrel consists of a cast-iron bushing, having- a MANDRELS. 157 tapered bore, which fits accurately the taper of the mandrel. The bushing 1 , which is ground externally, parallel and to exact diam- eter, is split partly through at two points, and entirely through at a third, thus allowing for a slight expansion when the mandrel is driven in. Three bushings varying by sixteenths for the smaller and eighths for the larger sizes may be used on each size of man- drel. The taper used is y 2 inch per foot, the bearing surfaces being accurately ground. It is evident that the allowable amount of expansion is small, yet sufficient to grip firmly in an accurately FIG. 219. sized hole. An attempt to expand this bushing in an oversized hole would result in cracking it ; a thing that would happen before the bushing, due to its expansion, would throw the mandrel ap- preciably out of true. The bushings are regularly listed from Y% inch to 3and tool, and tapered work results. As all engine lathes are provided with a set-over adjustment in the tail-stock, this method of turning tapers is always available. As the amount of side adjustment is limited to a small range, only slight tapers can be produced in this man- ner, and especially so in cases where the work is long. Thus, if the tail center can be set over one inch and the work is four feet long, then, as shown in Fig. 335, it will be turned two inches 335. smaller at the dead center end than at the live center end, which would give a taper of one-half inch per foot. If the work was one foot long, as shown by the dotted lines, it would have a taper of two inches per foot. The above indicate:, the method for determining the amount to set the tail center over to produce any taper per foot within the limits of the adjustment. Thus, if the work is eighteen inches long and a taper of five-eighths of an inch per foot is required, at one foot the offset would be one- half the required taper or five-sixteenths of an inch, and at one and one-half feet it would be 1^2X5-16, or 15.32 of an inch. This is, of course, only an approximate method for determin- ing the proper amount of set-over, as the exact amount must, m nearly every case, be found by trial. It will, however, serve bet- 230 MODERN MACHINE SHOP TOOLS. ter than a guess for the first trial. The principal objection to this method of taper turning is that the centers of the lathe no longer point toward each other, and the center bearings in the work do not, therefore, bear properly upon them. This fre- quently causes excessive wear on the bearings and sometimes throws the work out of true. The ends of the work must be faced off perfectly square, or otherwise the work will be sure to run somewhat out when held on offset centers. Since in this class of turning the work does not stand at right angles to the face-plate, it is necessary to al- low for some in-and-out motion for the arm of the dog or driver through the face plate. When the lathe is provided with taper attachment, as shown in Fig. 336, external tapers may be turned without offsetting the dead cen- ter. This leaves the true bear- ings on the centers and does not necessitate the difficulty of hav- ing to adjust the dead center for parallel turning each time after a taper job has been done. Taper attachments are given a much wider range than can be obtained by offsetting the center and are equally as useful in boring tap- ered holes as in turning external tapers. In all taper attachments the mechanism is such as to operate the tool rest direct from a guide set at any required angle, within its limits, with the shears of the lathe and independent of the cross-feed screw, yet at the same time retaining the in-and-out adjustment of the cross-feed screw. As several parts and con- sequent joints are required in such combinations, a considerable amount of back lash usually exists. The effect of this back lash is to let the tool start on a parallel cut until the back lash is taken up, when it starts off on the required taper. This can usually be overcome by carrying the tool enough beyond the end of the work to allow the slack to take up by the time the tool is brought up to the cut. It will be understood 'that it is not necessary to let the feed bring the tool up to the cut, as it can FIG. 336. LATHE WORK BETWEEN CENTERS. 23! be advanced quickly by hand, the only point being to carry it far enough tc take up the slack by the time the tool reaches the work. On work of small diameter, where the tool strikes the side of the center if moved beyond the end of the work, the back lash can generally be taken up by pulling out or pushing sharply in on the tool post, depending on the direction of taper the at- tachment is set to turn. Thus, if it is set to turn an increasing taper from the dead center toward the live, the angle of the guide will be such that its end nearest the head stock will be the closest to the shears and the inside face of the block will be forc- ing the tool back from the center of rotation. It would then be necessary, in taking up the back lash at the beginning of the cut, to push the tool toward the center. The maximum range usual- ly given the taper attachment is four inches per foot. It is seldom necessary to turn or bore steeper tapers than can be bored with the taper attachment. When, however, such are required, a lathe with a compound jest can be used. Examples of the compound rest are shown in Figs. 242 and 243. Its con- struction is such as to allow the upper slide which carries the tool to be set and secured at any angular position with the cross slide, thus enabling the turning or boring of any taper. Although the range is small, steep tapers are usually short, and it is conse- quently seldom that the tool must be reset in turning any ordi- nary taper. When a lathe is to be kept continually on taper work, a posi- tive taper-turning lathe is superior to one having a taper attach- ment. In lathes of this character the head and tail stocks are mounted upon an auxiliary bed or platen which is pivoted at the center and clamped at each end of the rrfain bed. The axial alignment of the head and tail spindles is maintained, thus allow- ing the work to bear squarely upon the centers. A suitable graduation at one end of the bed enables the operator to set the line of centers at any desired angle, within the range of the ma- chine, with the shears and line of travel of the tool. This ar- rangement not only possesses all the good features of the taper- turning attachment, but eliminates the troubles arising from back lash. In all taper turning it is necessary to set the point of the cutting tool at the height of the center in order to obtain the taper indicated by any setting. If the tool is set above or below center, the resulting taper will be less and slightly concave. 232 MODERN MACHINE SHOP TOOLS. In turning an external taper to fit a tapered bore the correct taper must be obtained before the work is brought down to exact size. In making the preliminary setting for the first cut too great rather than too small a taper should result, as the measure- ment will be taken at the small end, and if the taper is too small the work, while large enough at the small end, will be under size at the large end. In getting the exact taper the work should be tried in the bore after each cut. As long as the difference in taper is considerable the sense of feeling may be depended upon to determine which way to vary the taper in order that it may correspond with the taper of the bore. When too close to note the error by that means, draw three lines with chalk lengthwise on the surface and at approximately equal distances apart. Place the work in the bore and turn it Carefully through a complete revolution. Upon removing it, if the chalk marks have been H H } -1 L__] - FIG. 337. rubbed apparently equal their entire length, the taper is correct. If, however, the marks have rubbed at one end and not at the other, a further adjustment must be made and another cut taken. For very accurate work a marking of Prussian blue is used in- stead of chalk. It is applied with the finger and rubbed down until the coating is very thin. In testing, the work should be turned in the opposite direction to that in which it rotated in machining, as the feed of the tool leaves a thread-like surface which tends to worm the work tight into the tapered bore. After the correct taper has been obtained, the work can be turned down to exact size, calipering at the small end. What is commonly known as offset turning between centers is illustrated by the example shown in Fig. 337. In this case it is required to turn the pin of the crank shaft, the shaft proper having been turned or preferably roughed down nearly to size. LATHE WORK BETWEEN CENTERS. 233 The offsets are at a distance from the center of the shaft equal to one-half of the required throw of the crank. By means of a surface gauge and plane table upon which the crank rests, the centers of the shaft, the offset centers and the center of the crank pin are brought into the same plane. By now placing the shaft on the offset centers, the center of the crank pin falls in the center of rotation, and by means of a long tool that will reach the pin through the throat of the crank, it is readily turned. A sufficient counterweight should be placed on the face-plate opposite the shaft to balance it and thus make the lathe rotation smooth. As it is not possible to use a center rest on work of this kind, and as danger of springing the shaft is great, consider- able care must be exercised in turning the pin. In turning the shaft, a center rest can be used. It is usual to place a block firmly in the throat opposite the ends of the shaft to prevent springing the arms together. The finishing cut should be a light one taken with the block removed and the centers very lightly adjusted, thus insuring a true running shaft when com- pleted. . Eccentric turning comes under exactly the same head. The center of the eccentric, however, usually comes inside the bore and the offset centers can therefore be placed in the mandrel itself. When a number of crank pins are to be turned, a face-plate fixture and floating tail center offset, as shown in Fig. 338, proves a very efficient tool. The shafts are all turned to the same diam- eter, which should be enough over size to allow for a finishing cut after the pins are finished. As the shaft is firmly held in the long jaw, a much heavier cut can be taken over the pin than when held as shown in Fig. 337. The tail offset carries an eccentric or floating center which can be adjusted to the tail center and clamped in position. In screw cutting between centers the proper change gears are adjusted on the lathe to give the required pitch, as described in Chapter XIII. The cutting tool is firmly clamped in the tool post with its center line at right angles to the axis of the work. The center gauge, shown in Fig. 97, may be advantageously used for setting the tool. The height of the tool should be such that its top face lies in a radial line drawn from the center of the work. If set above or below this position the angle of the thread cut will not correspond with the angle of the tool, nor will the sides of the threads be straight. The nut is next closed onto the 234 MODERN MACHINE SHOP TOOLS. lead screw and the tool set in for the first cut. If the thread to be cut is right-handed, the lead screw is given right-hand rota- tion with the lathe spindle running forward, thus leading the carriage and tool from the tail spindle toward the head. When the thread is to be left-handed, the direction of rotation of the lead screw is reversed, the tool is set at the face-plate end of the work and the lead is from the live toward the dead center. For each succeeding cut the tool is advanced slightly until the full depth of the thread has been formed. The first cuts^should be as heavy as the nature of the work will permit. The last cuts FIG. 338. should be light, in order that the thread may be finished smooth and true. If the threads are being cut on steel or wrought-iron, a liberal supply of thread-cutting oil should be kept constantly at the cutting edges. The amount of tool advance for each cut is usually gauged by means of a graduated dial on the lathe cross-feed screw, or a threaded stop screw which can be turned back slightly for each cut, thus allowing the tool to be set in a corresponding amount. When thoroughly practised in thread-cutting work the oper- ator usually gauges the amount of each cut instinctively by the position of the cross-feed screw crank. LATHE WORK BETWEEN CENTERS. 235 After each cut over the work, it is necessary to draw the tool out from the cut before reversing the work for returning the tool to the point of starting. This is due to the back lash in the long train connecting the tool and spindle. The tool should be carried slightly beyond the point of starting in order that the back lash will be taken up by the time it enters the cut. If it become necessary for any reason to remove the tool from the tool post before the thread is completed, great care must be ex- ercised in resetting it. The lathe should be run forward one or two revolutions, which takes up the back lash and starts the carriage forward, after which the tool can be set to the groove already cut. After the thread is started, the driver should not be removed, and if the work is removed for testing, it is necessary to put it back on centers with the dog or driver engaging the same notch in the face-plate. For this reason it is preferable to use for threading a small single-notch face-plate. If the work is long and springy, the follow rest B^Fig. 331, should be used to support it. In cutting double threads it becomes necessary after the first thread has been completed to advance the cutting tool an amount equal to one half the pitch, as shown in Fig. 339. This may FIG. 339. FIG. 340. readily be accomplished as follows: In lathes where the ratio between stud and spindle is one, mark a tooth on the stud gear and the corresponding tooth-space on the intermediate gear. Drop the intermediate gear out of mesh and turn the spindle until one-half of the number of the teeth in the stud gear have passed the marked space on the intermediate gear. Throw the gears into mesh and proceed with the cutting. It is, of course, neces- sary that the stud gear have an even number of teeth in the above case. If the ratio between stud and spindle is other than one, 236 MODERN MACHINE SHOP TOOLS. the stud gear must be rotated an amount proportional to that ratio. The better and more convenient method, however, is to have milled notches in the face-plate accurately indexed. Re- move the work aid place the tail of the dog or driver in the notch diametricall) opposite the one in which it was while the first thread was being cut. For triple and quadruple threads the above methods are equally applicable. As the common thread-cutting tool cannot be given any top rake it is not free cutting. The strain upon it is consequently great, and it at once becomes a hard tool to keep sharp and in proper condition. When the lathe has a compound rest the tool shown in Fig. 340 may be used for cutting V threads. The com- pound rest is set at 60 degrees with the axis of the work as shown in Fig. 341, and the tool set with the thread gauge in the usual FIG. 341. manner. The tool is given top rake and cuts a clean chip from the end a, it being advanced to the work by the compound slide. For cutting square threads, the tool used resembles a cutting- off tool with the plane of the blade set at the angle of the pitch of the thread, as shown in the end view, Fig. 342. The amount of this angle varies for all pitches and diameters, but the side clearance is usually sufficient to allow some variation in diameters without changing the center angle. For all classes of work on center it is very important that the centers be kept true and smooth. They are turned in the head- spindle to the correct angle, tempered and ground. The tail or LATHE WORK BETWEEN CENTERS. 237 dead center is ground first and the live center is then ground in place, and preferably not removed from its bearing after grind- ing. The live center should be marked close up to the nose of the spindle with a corresponding mark on the .spindle, thus mak- ing it possible to always put it back in the same position. Before putting centers into their bearings, both surfaces should be carefully wiped clean and dry. In Fig. 343 is shown a form of lathe center that can be very easily kept in shape without excessive grinding. In most threading work on the lathe the nut is not opened from the lead screw after the thread is once started ; the lathe after each cut being reversed and the tool run back to the be- FIG. 342. FIG. 343. ginning of the thread. When the thread is a long one much time is lost by following this method, and the nut should be disengaged and the tool moved quickly back to the beginning of the thread. In all cases where the number of threads per inch being cut is a multiple of the number of threads per inch on the lead screw, they may be cut simply by engaging the nut at any position on the screw ; thus, if the lead screw has six threads per inch, 6, 12, 1 8, 24, 30, etc., threads per inch may be cut by catching. the thread at any point, it being impossible to catch the tool in any position other than the right one." The reason for this is- evident from the following consideration. Assume the carriage and tool in the correct position and the nut engaged, the lead screw having say six threads per inch ; if now we open the nut and move the carriage in either direction, the nut cannot catch until the car- 238 MODERN MACHINE SHOP TOOLS. riage has moved a distance equal to the pitch of the lead screw or a sixth of an inch. For six threads this of course catches the next thread; for twelve threads it misses one and catches the second; for eighteen it misses two and catches the third, etc. For threads of which the number on the lead screw is a mul- tiple, as i, 2 and 3 with a six-pitch lead screw, the nut can readily be caught by inspection. Thus, if cutting one thread per inch the nut will catch exactly right on every sixth thread ; in cutting two threads it catches on every third thread,. and in cutting three on every second thread. Inspection must determine whether it has caught the right thread before setting the tool into the cut. Other threads, as 8 or 10, may be caught by inspection ; thus on the six-thread lead screw, moving the nut three threads moves 344. the point of the tool y* inch, which just catches the fourth thread on the eight-thread work, or the fifth thread on the ten-thread work. For any pitch other than those for which the above is ap- plicable set the tool for the cut slightly beyond the end of the work and mark the position of the carriage in .any convenient way. A stop clamped to the bed against which the carriage may be brought is very convenient. Next mark the face-plate and note the positio'n of this mark with reference to some fixed point on the lathe. After each cut open the nut, move the carriage to the stop and bring the face-plate to the mark, when the nut can be engaged with the lead screw, all parts being in the same posi- tion as when the thread was started. It is frequently desirable to run a rough or cored hole on the dead center. This would quickly cut the center and ruin it for accurate work until reground. The hole in work of that char- LATHE WORK BETWEEN CENTERS. 239 acter is usually too large to run on the regular center, if such were desirable, and either a large center must be provided to carry it or the hole plugged and a center bearing put in the plug. If the hole is concentric with the surface to be machined the large center is the cheapest and most convenient method. It is, of course, not adapted to the most accurate work, but for ordinary operations serves its purpose well. As it is necessary for the center to revolve with the work, to prevent its being cut, a special device is required. In Fig. 344 is shown such a center, common- ly known as a pipe center. The construction is evident ; the cone revolves on a stud and backs against a collar having a simple bear- ing surface to take the thrust. It is also provided with suitable channels for its proper lubrication. In Fig. 345 is shown an attachment secured to the carriage . FIG. 345- of an engine lathe for turning shafting. With this device the shaft is roughed down by two tools set opposite to each other, which serves to balance the pressure of the cut and reduce the spring to a minimum. After the roughing cuts, it passes through a suitable bushing held in the head and receives the final sizing and finishing cut from the tool shown at the back of the attach- ment. The device is simply a follow rest carrying three tools instead of one. In Fig. 346 is shown a device used on the lathe for the turn- ing of cross-head pins or other surfaces the nature of which pre- vents the possibility of complete rotation of the work. In this 240 MODERN MACHINE SHOP TOOLS. device a sleeve carrying two gears is secured on the nose of the lathe spindle. The gear next to the spindle bearing is keyed to the sleeve and rotates with the spindle. The second gear which carries the work driver rotates freely upon the sleeve. The first gear meshes with a larger one that is carried on a bracket .secured to the back of the. head stock. A wrist pin in the face of the large gear drives the rack which, as shown, gears with and drives the loose gear and thus causes the work to rotate independent of the spindle rotation. By properly proportioning the diameter of the gears and the stroke of the rack, the work can be made to oscillate back and forward through any desired part of the revolution, while the spindle has continuous forward FIG. 346. rotation. Thus in the turning of the cross-head pin shown, the cross-head moves through rather more than one-half of the full revolution, thus enabling the turning of a little more than one- half of the pin. The cross-head is then changed end for end on the centers and the other half turned. Frequently, with cross- heads to be used in single acting engines, where the pressure and wear are always on one side of the pin, a large flat can be ma- chined on the non-bearing side of the pin and sufficient rotation obtained to completely finish the pin without changing ends with the work. It is, of course, possible to turn a pin of this character without any special attachment, by either pulling the belt backward and forward and driving the work in the ordinary LATHE WORK BETWEEN CENTERS. 2 4 I manner or by allowing it to rotate free of the centers and oscil- lating it by means of a wrench or lever. These latter methods are slow and require an extra workman. An ingenious lathe attachment for backing off the teeth of milling cutters is shown in Fig. 347. In a device of this character either the tool or the work must be given a slight in-and-out mo- tion for each tooth on the cutter being relieved. In the case shown, the tool is held in the tool post and advanced to its cut in the ordinary manner. The mandrel A of the attachment has its centers slightly eccentric, the amount of the eccentricity being FIG. 347. enough to produce the desired amount of relief on one tooth of the cutter if mounted directly on the mandrel. The arm L is secured to the mandrel and driven from the face-plate by the carrier D. The sleeve B, which carries the cutter being operated upon, revolves freely upon the mandrel. The gear b is secured to the sleeve and the gear a is loose on the sleeve, and is held from rotating by the arm d which is secured to it and rests upon the top of the tool ; c is a pinion carried loose on the stud D and gears with a and b. Gear b has a smaller number of teeth than a, and as a does not rotate, the rotation of the pinion c around a advances b and the sleeve and cutter a certain fixed amount at 242 MODERN MACHINE SHOP TOOLS. each revolution of the mandrel. The geared ratio is such for any given number of teeth in the cutter that the advance per revolution is exactly equal to the circular pitch of the teeth in the cutter. The turning is such as to bring a tooth to the tool when the center of the mandrel is farthest from the tool, thus giving the relief as the tooth advances to the tool. It is evident from the above that the space between the teeth must be at least equal to the length of the, tooth. As this division of space and tooth in relieved milling cutters is not usual, it is necessary to allow the cutter blank to stand still while the mandrel is moving through a part of its revolution. This is accomplished by making the circular pitch of the teeth on about one-half the circumference of b equal to that of the teeth on a and the teeth on the balance of b of somewhat greater circular pitch. For that portion where the teeth are the same on a and b, the pinion simply turns around both and the sleeve remains stationary. During the balance of the revolution, however, the sleeve will advance an amount equal to the circular pitch of the cutter's tooth. With the regular tools and feeds on the engine lathe, plane, cylindrical and conical surfaces are readily machined. If the sur- face is spherical or of irregular outline, a forming tool or some special attachment must be used on the lathe to produce the re- quired outline. If the work is of circular section, the forming tool can usually be used to excellent advantage, as illustrated in Fig. 348. In this case the tail-stock cap shown in the figure is first chucked, bored at A, faced at B and threaded at D. It is then placed on a threaded mandrel and driven on the centers, The forming tool E, which is secured in the ordinary tool-post,, forms the bead and is set in until the proper diameter at F is ob- tained. The tool G, held in like manner, forms the hub and rounded end of the cap, the tool being set in until the diameter at H is equal to that at F. A common tool is then used to pro- duce the cylindrical surface I. If the length I is short it would be possible to combine the two forming tools into one. As the cutting edge is a long one it is, in any event, desirable to rough off the scale and true up the casting before applying the forming tools. This can be done by operating the regular feeds by hand. If the work does not run true when the forming tool is set to the cut, it will be difficult to produce satisfactory results, as the spring of tool and work will vary at different points in the revo- lution. The length of cutting edge that can be employed de- LATHE WORK BETWEEN CENTERS. 243 pends in any case upon the stiffness of the work and the rigidity of the lathe in which the work is to be done. Another illustra- tion of this system of forming is shown in Fig. 349. Here the rim of a hand wheel rounded by the forming tool is shown. If the section of the rim is a full circle, as at A, two settings of the tool are required, one of which is illustrated in the figure. It is here even more important than in the example shown in Fig. 348 to first rough the stock until it runs true, as the heavy cut of the forming tool will otherwise spring the work so that it will not run true when finished. For roughing out the rim a side- cutting tool can be used to good advantage, setting it at different angles to produce a section similar to that shown in the figure at B. If the tools are carefully made and kept in good condition, . -T 1 1 LLI i D : E FIG. 348. FIG. 349- very satisfactory results can be obtained upon a wide range of work, similar to the above examples. The tools should be so made that they can be sharpened by grinding from the top surface. If the tool is carefully made and the scale removed from the stock, it will do a larger amount of work before dulling materially. Forming tools of this char- acter are not expensive to make, and, when any considerable amount of similar work is to be produced, will pay for themselves very quickly. The tool shown in Fig. 349 may be used for turning balls from stock held between centers or in a chuck, as shown in Fig. 350. 244 MODERN MACHINE SHOP TOOLS. If the stock is held in the chuck, the ball will not be disfigured with the center bearing. A small tip will, however, remain where cut from the body of the stock. In forming balls in this manner it is necessary to caliper the diameter carefully, advancing the tool only far enough to produce a true sphere. This method will be found very convenient in the forming of balls on the ends of handles, the ball in such cases not being cut from the body of the stock, and perfect spheres not being necessary. In Fig. 351 is shown a simple ball-turning device. The shank of the cutter holder is round and fits in a suitable bearing which is clamped to the tool block. On the outer end of the shank is secured a long lever or preferably a worm and gear mechanism for rotating FIG. 350. FIG. 351 the cutter head and tool to the work. Although a truer sphere can be obtained with this device than by the use of the forming cutter shown in Fig. 350, the surface will not be as smooth as with the latter. The more elaborate device shown in Fig. 352 is better adapted to the turning of larger balls than either of the methods above referred to. While this attachment can be pro- vided with a shank and held in the tool-post, it is much more rigid when secured directly to the tool-block or in the place of the compound rest. The construction of the device is clearly shown in the figure. In order to produce a true sphere the cen- ter of rotation of the cutter-carrying disk must be exactly under the center of rotation of the work, and the distance of the point of the tool from the center of rotation then determines the radius of the ball. By setting the tool with its point past the center of LATHE WORK BETWEEN CENTERS. 245 the disk and bringing the center of the disk back from the center of rotation of the work a concave section can be produced in the work, the character of the section depending upon the relative position of centers and tool point. With work held in the chuck and the center of the disk under the center of rotation of the work, it is possible to produce on the end of the work either <: convex or concave surface depending en whether the point of the tool is back or ahead of the center of .rotation of the disk. A convex or concave surface can readily be turned with a tool held in the common compound rest, 'the only difficulty being in the control of the feed. When the cuts are light, however, satis- FIG. 352. FIG. 353- factory results can be obtained by moving the rest by hand, hav- ing its clamp bolts tightened just enough to steady the motion. In cases where the outline is irregular and too long to be conveniently produced with the forming tool, a common tool may be made to do the work, its motion being controlled by a guide having the same outline as the one desired and controlling the tool on the taper-attachment principle. The general arrange- ment is shown in the top view of a lathe carriage, Fig. 353. In this case the slide is disconnected from the cross-screw. B B is the guide which is secured to the bed of the lathe and independ- ent from the carriage. The finger A is secured to the slide and bears against the guide B B. A cord C is attached to the slide, 246 MODERN MACHINE SHOP TOOLS. passes over the pulley D and carries the weight W which serves to hold the finger A to the guide at all times. The point of the cutting tool must travel with the finger A, and, tracing the outline of B B, produce the same outline on the work. In this arrangement the tool is usually set to the work by adjusting it through the tool-post. A threaded adjustment in the finger A makes a good adjustment for the finer tool settings. This method is applicable only when the cross-section of the work is round. If an irregular cross-section is required, a different arrangement involving the use of a pattern or dummy is generally employed. The dummy is a pattern of the same cross-section as that re- quired on the work, and is mounted either on the same axis as that of the work rotation, or on a separate axis so geared as to make the same number of revolutions as the work, When the FIG. 354. work is short and both it and the pattern can be mounted on the same axis, the former method is, owing to its simplicity, prefer- able. In Fig. 354 is illustrated the former method. As in Fig. 353, the cross-feed screw is disconnected from the cross-slide and a weight provided for holding the finger against the pattern B, which rotates with the work. A second tool-post, back of the one carrying the finger, holds the tool that operates on the work. It is evident that the motion of tool point and finger is the same and that the outline of the work will be the same as that of the pattern. If the two tool-posts cannot be set sufficiently far apart to allow for the required length of cut, the finger can be carried on a suitable bracket secured to the side of the tool-block. It is quite possible by careful adjustment to start the cut with the use LATHE WORK BETWEEN CENTERS. 247 of the pattern, and allow the finger to lead from the pattern on to the work, thus enabling a long cut to be made with a short pat- tern. A careful readjustment of the finger is required for each cut in this case. It is not necessary that the pattern be of the same size as the work section, as it is frequently desirable to make it of a different size. It is quite possible to adapt the method of Fig. 354 to internal work. In Fig. 355 the work is secured on the tool-block and the pattern on the boring bar. In this case the work moves with the pattern instead of the tool. The example shown illustrates the FIG- 355- FIG. 356. method of boring an elliptical hole. By using a movable heaJ boring bar a thin pattern is all that is required. As a wide range of patterns can be used many forms of cams can be produced by the above method. The same method shown in Fig. 353 is applicable to face work on stock held against the face-plate or in the chuck. In this case the weight is placed at the end of the bed, the guide is secured to the cross-slide and the finger to the tail-stock, all as shown in Fig. 356. Many outlines can readily be produced in this manner. The tool is operated by the regular cross-feed mechanism. CHAPTER XVIII. LATHE WORK ON FACE-PLATE, CHUCK AND CARRIAGE. A large portion of the work done in the lathe may be classed as boring work as it comes under the following classifications : center rest, carriage, face plate and chuck work. An example of a boring operation under the first class was shown in Fig. 333. As work of this kind is usually performed on solid stock, a hole must first be drilled sufficiently large to allow the boring tool to enter. The drilling of this hole can be done to good advantage in the lathe by using a twist drill held on the tail center. The taper shank drill with holder, shown in Fig. 357, is best suited to this work as it clears itself readily of the cuttings and the holder prevents injury to the shank. In no case should the taper shank drill be held by a dog secured on the shank, as it is quite certain to slip and injure the tool. If a dog is to be used at all for this purpose, it should be in connection with a straight shank drill provided with a flat spot on the shank for the set-screw of the dog to seat upon. When considerable drilling of this kind is to be done in a lathe, it is advisable to have a set of drill sockets fitted to the bearing in the tail spindle. This not only makes a more satisfactory method for holding the drill, but overcomes the danger of the drill drawing off the tail center and being bent or broken by the cramp it would receive due to the single-handled holder. When holes of a considerable depth are to be drilled in this manner in steel, it is difficult to properly lubricate the cutting edges of the drill, and often the work and tool begin to heat and the cuttings to fill up the flutes. The drill must, therefore, be fre- quently removed for oil and cleaning. These difficulties are al- most wholly overcome by using the oil tube drill in places of this kind, as it provides for a constant and liberal supply of oil at the point, which not only improves the cutting and clear- ing of the chips, but carries away the heat of friction and thus enables the crowding of the drill to its full cutting capacity. As in this class of drilling the drill does not rotate, a common socket can be used in connection with the oil tube drill, it being simply necessary to tap for a small gas pipe connection in the side LATHE WORK ON FACE-PLATE, ETC. 249 of the socket over the supply hole in the shank of the drill. In an operation of this kind the important point is to get the drill started true. If the work has been centered for other operations previous to the drilling, this center forms a seat for steadying the point of the drill in starting. Even though this center runs perfectly true, it cannot be relied upon for starting the drill true. It is, therefore, necessary to steady the end of trie drill in a dif- ferent manner. In Fig. 358 is shown a common method. The steadying tool, which is held in the tool post, is made to bear against the front side of the drill, as close to the point as pos- sible. The drill should be held so that one lip is on the back side of the work surface or opposite the steadying tool. As the cut is started, the drill is crowded slightly back of the center, making the one lip do all the cutting. This makes it virtually a rigid boring tool that cannot sway and produces a surface con- centric with the axis of rotation. Just before the drill begins to cut a full diameter hole, the steady .tool should be backed away and the point of the drill left free to follow the center of rotation. If this work is carefully performed, it is possible to start a drill almost exactly true. When the surface into which the drill is to enter is plane, the centering tool with flat drill point shown in Fig- 359, and held in the tool post, is used. It forms a good seat for the drill to start in. For uniformly true and central holes the drill cannot be relied upon, and its use in the lathe is confined almost entirely to the opening up of the work previous to using a boring tool. For example, if a i-inch hole is required in a piece of work held on a face plate or in a chuck, a i-inch drill could not be depended upon for anything like a satisfactory result and a 63-64-inch drill fol- lowed by a i-inch reamer would be almost as bad. The only correct way in such a case would be to first use, say, a 15-1 6-inch drill which would remove most of the stock and allow a boring tool to enter. It can then be bored with the boring tool to the proper diameter or, if it is to be finished with a reamer, it should be bored to within about i-ioo of an inch of the exact size, which trues the hole perfectly previous to the reaming. The reamer should be held on the tail center, which latter must be exactly central. If the tail center is offset, a tapered hole will necessarily result: The size of drill to use for opening up previous to boring de- pends upon the nature of the work. If the finished hole is to 250 MODERN MACHINE SHOP TOOLS. be small in diameter and deep, a drill as large as possible should be used, since the boring tool will be a long and springy one necessitating light cuts which will remove the metal more slowly than would the drill. If, on the other hand, the hole is to be of large diameter and not deep, a drill should be used that is only large enough to enable a short, stiff boring tool to readily enter, as the boring tool will remove the stock faster than the drill would. In using the boring tool, it is generally well to feed both ways through the work as this tends to equalize the effect of the wear on the cutting edge. In cases where accurate bores are required, it is quite necessary not to change the depth of cut after the cut has started, as the effect of the spring of the tool will be quite marked. A boring tool tends to make the mouth somewhat larger than the balance of the hole it is boring, 359. n $ ft | Fia. 36D. Fig. '358. PIGS. 357 TO 360. because the tool does not take its full spring until the cutting edge passes the end of the bore. In the boring of parallel holes, the height of the cutting edge does not affect the parallelism of the bore. With tapered bore^ however, it is necessary that the tool set at the height of the center, as a different taper than the one required will result if the cutting edge is above or below the center. The amount of taper in either case would be somewhat smaller than when the. cutting edge is at the center. When the bores are long and of large diameter, the boring tool is no longer well suited to the work and what is known as a boring bar is used. These bars are of two kinds, those having a cutting tool fixed in its position on the bar, and those in which a cutting tool is secured in a mov- able head which traverses over the bar. The former are the least LATHE WORK ON FACE-PLATE, ETC. 251 desirable, inasmuch as they must be somewhat more than twice the length of the bore, while, with the latter, a length but slightly greater than the bore is all that is required. In Fig. 360 is shown a plain boring bar of the former type. The cutting tool may be of flat steel secured in a mortise through the bar by suitable wedges, or it may be, as shown in the figure, of round steel, fitting nicely the hole through the bar and secured in position by a set-screw which seats on a flat spot filed on e: ~A FIGS. 361 AND 362. the tool. The set-screw should have a smooth, flat point so that, when moderately tightened, the tool can be driven under it in adjusting the cut. This class of boring bar is suitable only on work secured to the carriage, as the work must be given the feed over the cutting tool. In Fig. 361 is shown a traverse head boring bar. A tool-carrying head fits nicely upon this bar. It is splined to receive the key which is secured in the head. The feed or traverse of the head is accomplished by means of a screw usually driven by a star feed from one end. By substituting for 252 MODERN MACHINE SHOP TOOLS. the star a spur gear on the screw and gearing this with a pinion, keyed on the lathe center, a smooth, steady screw feed results. When the bar is of large diameter as compared with the head, the screw can be dropped into a suitable spline, thus getting it out of the way and protecting it from injury. Boring bars of mod- erate size are preferably made of a medium grade of tool steel, as this is much stiffer than mild steel. For large bars, mild steel or cast iron is suitable. When cast iron is used, the ends should be plugged with steel to receive the centers, as the cast iron wears too rapidly to retain an accurate center bearing. Movable head boring bars, in which the head is traversed by means of the regu- lar carriage feed, can be used to good advantage in cases where the bar remains stationary and the work rotates. In Fig. 362 is shown a movable head bar of this class operating upon a cylinder secured to the face plate. The bar carries a long sleeve, one end of which terminates in the cutter. A dog or wrench secured to the outer end of the sleeve prevents it from turning and the tool post bearing against the arm of the dog transmits the regu- lar carriage feed to the tool. By off-setting the tail center as shown by the dotted line, a tapereti hole results which will be larger at the inner end of the bore, with the tool set as in the figure, but if the cutting tool is set at 180 degrees from the posi- tion shown, the bore will be larger at the outer end, as indicated by the dotted lines. Unless the character of the work is such as to enable its outer end to be run in the center rest when the bore is long, rotating the work is not satisfactory, as its outer end is too far from the lathe spindle to be sufficiently rigid. When the work is clamped to the carriage, it is always preferable to feed the cutting tool rather than the work as the carriage can then be clamped rigidly to the bed. This insures a more accurate bore'as the carriage, unless very closely gibbed, will lift on the up cut of the tool. In Fig. 363 is shown a movable head bar operating upon a cylinder clamped to the lathe carriage. In this case, off-setting the tail center as the bar rotates will not enable the boring of a tapered hole. The tapered hole, however, can be obtained by off- setting one end of the boring bar as shown dotted in the figure. If desired, the offset can be put on the bar itself, in which case it can, as shown in Fig. 364, be offset at the tail center end. By making the center bearing adjustable, as shown in the figure, any desired taper within the limits of its adjustment may be obtained. LATHE WORK ON FACE-PLATE, ETC. 253 In boring work, it is very important to see that the work is prop- erly secured on the carriage, face plate or in the chuck. It must be held sufficiently rigid to prevent its working loose and, at the same time, must not be sprung out of shape as, in such cases, when finished and removed from the lathe, it will be found out of true. In straight cylinder boring, more than one cutting FIGS. 363 AND 364. ' tool is usually employed as a single cutter springs the bar, thus requiring very light finishing cuts to produce satisfactory results. Three cutters steady the bar nicely, especially if care is exer- cised in setting the cuts about equal. A tool for finishing should not follow a roughing cutter, inasmuch as all the springing of the roughing cutter, due to its unequal work at different points of the bore, will be transmitted directly to the finishing cutter and 254 MODERN MACHINE SHOP TOOLS. thus produce an untrue cylinder. To insure true work, the fin- ishing cuts should always be light ones. The chucking of most work requires thought and judgment. Fixed rules cannot be laid down, as each case must be considered from its own peculiarities. The surface to be machined, the character of the finish, the possible chances for gripping it in the chuck jaws, and the likelihood of the work's springing are all questions that arise with each case. Frequently the form of the work is such that it cannot be held in the chuck. In such cases it is usually possible to clamp FIG. 365. the work to the face-plate or to an angle-plate secured on the face-plate. Setting up work in this manner requires care and time. If there are many similar pieces to be operated upon, it usually pays to get up a special chuck for holding them. Take for example the cylinder head shown in Fig. 365. This head must be bored on the inside and faced on the bottom. The post on the top of the head is so high that the regular chuck jaws will not reach the body of the casting. If but a single head was to bo finished, it would be secured to a knee-plate on the face-plate, as shown in Fig. 366. As large numbers are to be machined, how- ever, the special chuck shown in Fig. 365 is employed. In a case LATHE WORK ON FACE-PLATE, ETC. 255 of this kind a set of special jaws could be used in the -standard chuck. They would not be as convenient, however, as the special chuck. It is usually best to chuck work from the outside rather than from the inside, as the danger of breaking is less. When the work is light, and it must for the roughing cuts be chucked firmly, it is certain to be somewhat distorted. In such cases the chuck jaws should be eased off slightly before taking the finishing cut. Small pulleys, gear blanks, etc., should when possible bo FIG. 366. chucked on the hub. When so held and properly bored and turned, the finished work will run true. If the rim of the blank or pulley is heavy, as is the case with balance wheels, it should be chucked out upon the inside of the rim, setting the chuck jaws as close to the ends of the arms as possible. This allows the tool to be brought to operate upon the entire rim surface as well as upon the bore. Upon pulleys having light rims, and too large iti diameter to chuck by the hub, carriers, as shown in Fig. 367, secured to the face-plate and clamped on the pulley arms near the rim,, form excellent drivers. 256 MODERN MACHINE SHOP TOOLS. When the work has a reamed bore upon which it can be finished, a split chuck can be used to excellent advantage. Such a chuck for smaller diameters is shown in Fig. 368. The taper shank fits the center bearing in the head spindle. The nose is drilled, tapped and split, as shown. A tapering screw fits the threaded bore, and when screwed in, expands the chuck enough FIG. 367. to grip in a close-fitting bore. These chucks should be tempered and ground perfectly true. Their advantage over a hardened mandrel on this class of work lies largely in the convenience in putting on and removing the work and in the ease with which the cutting tool may be brought to the edge of the bore without fear of running into the mandrel. Nearly all turret machine operations are upon chucked work. FIG. 368. In the case of work upon bar stock some form of universal chuck is always used. The stock is of comparatively small diameter and the tools that operate upon it are brought successively into action, either by hand or automatically. A pointing box tool bevels the end ; a roughing box tool passes over, taking the bulk of the stock ; the finishing box tool reduces to exact diameter ; the die LATHE WORK ON FACE-PLATE, ETC. 257 threads it, and the cut of slide with an inverted tool in the back holder chamfers the head, after which the tool in the front head cuts it off. For this class of work on steel a copious supply of thread-cutting oil must be constantly applied to the tool. For bar work a comparatively small assortment of tools may be made to do a very wide range of work, but with turret ma- chines operating upon cast work, this is not usually the case, as each particular job usually requires its own special tools. Boring in the turret lathe is usually performed with a bar having a pilot point and carrying suitable cutters, as shown in Fig. 369. A suitable bushing in the nose of the spindle steadies the pilot end of the bar. A roughing cutter is used to remove the heavy stock, and this is followed by a sizing cutter in a second bar, or if the distance from the inner end of the bore to the nose of the FIG. 369. spindle is sufficient, a sizing cutter may be used in the first bar. .It should be so located that it does not start its cut until after the roughing cutter clears the work, as otherwise the spring of the roughing cut will affect the truth of the finishing cut. It is usual to finish the hole to exact size with a reamer, carried also in the turret. The above is a job for a plain turret lathe. If face surfaces are to be machined, and the number of pieces required will war- rant making the tools, a facing cutter may be used as shown in Fig- 370. The hole having been reamed to size in the work, the pilot bar P steadies the work while it is operated upon by the face cutter C, which is secured in a heavy cast head H, which in turn is bolted to one of the flat faces of the hexagon turret. Heavy spindle power is required to drive cuts of this character. 258 MODERN MACHINE SHOP TOOLS. When the cuts are long it is advisable to use two cutters, the first with serrated cutting edge to break up the scale before putting the finishing cutter into the work. The pilot bars should be hard- FIG 370. ened and ground to correct size, as there is danger with soft bars of their seizing the surface of the bore. With the turret lathes, Figs. 263 and 269, where an indepen- dent carriage is provided, operations on the face and circumference FIG. 371. of the work can be carried on at the same time the turret tools are operating on the bore. In Fig. 371 is shown a Gisholt lathe operating upon a stepped pulley. The bore having been finished, the long pilot bar is passed through it and entered into the bush- LATHE WORK ON FACE-PLATE, ETC. 259 ing in the nose of the spindle, thus forming a substantial support for the work. The heavy cast head secured to the carriage is provided with a cutting tool for each step of the cone, thus finish- ing all the steps in the time of the feed across one. In Fig. 372 is shown -a method of finishing cones and similar work in heavy plain turret lathes. The yoke YY is bolted to a flat on the turret. A stationary mandrel XX carries the work. A short hollow mandrel W is secured to the face-plate, exactly true with the spindle, and having a neat bearing in the yoke YY. XX fits the hole in W, and a suitable driver on the end of W engages the arms of the work, causing it to rotate upon a stationary spindle. Feeding the turret forward advances the cutters across the FIG. 372. steps of the cone. These methods are, of course, applicable to a very wide range of work. If it is required to bore a hole in a piece of work parallel to another hole that has been bored in the lathe, it is necessary to offset the work until the required bore is concentric with the axis of rotation. This involves very accurate chucking, and if the work is large, the swing of the lathe will frequently not permit sufficient offset. When enough work of this character is to be done to warrant its construction the attachment shown in Fig. 373 will be found very satisfactory. Its construction is simple, con- sisting of a suitable bearing that can be secured to the tool block and carrying a spindle or boring bar. A pulley for driving the bar can be attached directly to its outer end, or if the amount of use the attachment is to be put to will warrant it, it can be con- structed as shown in the figure. The spindle in this case is pro- vided with a taper bearing at F to receive a taper shank drill, an 260 MODERN MACHINE SHOP TOOLS. end milling cutter or a short boring bar. The outer end of the spindle carries the gear B ; gear C meshes with B and is carried on a radially adjustable stud. Gears B and C should be made to interchange or even be replaced by others, and thus provide for changes of speed -on the spindle. .The driving pulley E is carried loose on a suitable stud D, which clamps over the nose of the tail spindle. A pair of universal couplings with a telescop- ing shaft connects E and C and transmits the power. In the operation of this attachment belted power is transmitted to E and to the regular lathe feeds used for advancing the cutter to the work. The face plate must be blocked to prevent the work from turning. In Fig. 374 is shown a satisfactory method of blocking the face plate and, at the same time, of providing an adjustment for accurately locating the position of the bore. An attachment of this kind will frequently be found quite valuable -'!G. 373 FIG. 374. as, for example, in the boring of a crank disc for shaft and crank pin, the attachment boring the hole for the pin with rea- sonable certainty of getting it parallel with the bore for the crank shaft. Fig. 375 serves to illustrate a class of attachments that can be advantageously used for performing milling operations on the lathe. The attachment shown is secured to the tool block in the place of the tool post. The construction is such as to provide for suitable vertical adjustment, and the milling cutter to be used i> carried on an arbor held between the lathe centers. The attach- ment shown is suitable only for light milling operations, as it is not sufficiently rigid for heavy work. An attachment constructed along the same lines and attached to the carriage in place of the cross-slide can be made sufficiently rigid to enable heavy work LATHE WORK ON FACE-PLATE. ETC. 26l to be done upon it and will, in the absence of a milling machine, be found a most useful device. The boring of spherical sockets can readily be accomplished by means of the special attachment shown in Fig. 376. The small gear is mounted on the flattened end of a stub center which FIG. 375. FIG. 376. is fitted to the tail spindle bearing. The cutting tool is secured in the face of this gear and the gear caused to rotate by means of the rack which is carried in the tool-post and actuated by the regular cross-feed on the lathe. The cutting edge of the tool must be set at the height of the center. 262 MODERN MACHINE SHOP TOOLS. When a piece of work is to be externally turned to fit a certain hole or bore the character of the fit must be specified as a working fit, which may be close or easy ; a driving or forced, or a shrink fit. The working fit .indicates that the one moves over the other, either by sliding or by rotation, and the niceness of the fit will depend on the accuracy required and the means of producing perfectly cylindrical surfaces. In all working fits the difference in. diameter of cylindrical surfaces must be enough to allow a thin film of oil to cover the surfaces. When very accurately formed the difference in diameter can be extremely small and a perfect working fit maintained. If, however, the surfaces are not per- fectly true and smooth more allowance must be made, as other- wise the motion of the one upon the other produces heat, which usually causes unequal expansion and consequent locking of the two parts, the lubricant being forced from the surface. If slid- ing or rotation is forced under these conditions, the surfaces will seize and abrasion occurs. The larger the diameter the more allowance must be made for proper working fits. For small spindles accurately surfaced .00025 to .001 inch is sufficient, while with larger sizes from .005 to .01 inch must be given. Driving and press fits are those in which the shaft or plug is finished slightly larger than the bore and forced into the bore by driving or by pressure. On small work the operator usually depends upon his judgment as to the proper allowance. A differ- ence for each inch of diameter of the work of from .001 to .003 usually covers the range from medium to heavy forced fits. Shrink fits may be conveniently made on work of small or large diameter, as they involve only a means for heating up the ring or bore an amount sufficient to enlarge it, by expansion, enough to allow the shaft or center to enter easily. Driving fits are adaptable only to comparatively small diameters, as a hammer or sledge is usually employed to drive the parts together, while the forced fits involve some form of powerful press. Forced fits also are adaptable to comparatively small diameters ; thus, the driving axle of a locomotive is forced into the hub of the driving wheel, but the tire of the wheel is always shrunk onto its center. Ir< making forced fits the surfaces are coated with oil, which is of course not done in shrink fits. In making a forced fit there is a tendency to swage the metal, while with the shrink fit the bore closes squarely down upon the LATHE WORK ON FACE-PLATE, ETC. 263 center. The strains produced in either case are enormous. With a press fit it is very important that the parts come together squarely. With a shrink fit the bore usually expands enough to allow the shaft to enter freely. The correct placing of the parts together must be quickly done, as otherwise they will lock. Should the spindle fail to enter readily or stick before it is in the proper position, it must be instantly driven out. This may result from having allowed too much for the fit or from not heating the ring a sufficient amount. Forced fits being made with oil on the surfaces, which lubri- cates and preserves these surfaces, make it possible to remove by pressure the spindle when desired. With shrink fits this is not always possible, the surfaces are not lubricated and frequently the bore is heated an amount sufficient to cause a scale of oxide to form, which so roughens the surface that it clings firmly. If the bore is small the shaft can usually be moved by heating the ring and forcing under a powerful press. The shaft should be kept as cool as possible while the ring is being heated by appli- cation of cold water as close to the ring as possible. Care and judgment must be exercised, and even then the surfaces are quite certain to be injured by abrasion. When the work is of large diameter and the center can readily be kept cool as with the locomotive driving wheel the ring can be heated until it drops off from its own weight. From the above it will be noted that for work of large and medium diameter the shrink fit is most applicable and for work of smaller diameter the forced fit is best. In fact on small diameters where there is any likelihood of ever wishing, to separate the parts the shrink fit should not be used. CHAPTER XIX. BORING AND TURNING MILLS. Boring and turning mills constitute a special line of machine tools made necessary by modern methods of manufacture where large numbers of similar parts are to be handled and machined in an economical manner. In Fig. 377 is shown a 3O-inch boring FIG. 377. and turning mill of the vertical pattern. This represents the smallest size machine of this class regularly built. A comparison of this machine with an engine lathe reveals the same characteristic elements in both. It is virtually a face plate lathe standing on end; the bed and upright corresponding to the head stock and bed of the lathe. The spindle, face plate and driving mechanism bear a close resemblance in both machines and the cross rail, frame and slider on the boring mill correspond BORING AND TURNING MILLS. 265 with the carriage and compound rest on the lathe. For heavy work the structural advantages of the boring mill are much su- perior to those of the lathe. The form of the machine gives greater rigidity and as the work rests upon a horizontal table more liberal bearings can be provided than is the case with the lathe, at the same time overcoming the heavy overhanging parts. The ease with which work can be set up and adjusted on the horizontal table is a great point of advantage. In Fig. 378 is shown a sectional view of the spindle and table bearing on the mill, shown in Fig. 377. This large angular bear- ing has a self-centering tendency which tends to preserve align- ment. This form of table bearing as well as the flat and V bear- ings employed on other machines of this class provides a very lib- eral bearing surface; the ordinary weight load due to table and work seldom exceeding 25 to 30 pounds per square inch of bear- ing surface. Where a flat bearing of large diameter is employed, some builders provide a means of raising the table, for fast run- ning, from this bearing and running it in its spindle bearings, using the end of the spindle for a step bearing. The small sized machines are usually provided with turret heads, either plain or swivel. Automatic feed in all directions with feed knock off is usually provided. In Fig. 379 is shown a vertical boring mill of the larger class. The tool shown swings fourteen feet in diameter. It is also made to swing twenty feet by using an extended base upon which .266 MODERN MACHINE SHOP TOOLS. the housings are so mounted that they may be moved back from the center of the table. In the extended machines a radial arm mounted upon the cross rail, carries a boring bar which is used FIG. 379. for the hub work while the other heads are operating on the out- side portions of the work. In Fig. 380 is shown a standard horizontal boring and drilling machine. The range of adaptability of these tools is large, mak- ing them excellent tools for general work. The work to be oper- FIG. 380. BORING AND TURNING MILLS. 267 ated upon is secured to the table which is adjustable in three dir>-c- tions, thus making it possible to bring any part of the work sur- face into position to be operated upon by a tool held in the boring bar. Graduated dials on all of the table operating screws make exact spacings for holes in the work possible, a most valuable feature on many classes of work. For through work; as in the boring of cylinders, the bar is sufficiently long to extend through the outer support, a suitable cutter head being secured on the bar to carry the cutting tools. In the case of bores too small to allow the main boring bar to pass through, smaller bars fitted to the tapered bearing in the end of the main bar and fitting bush- ings in the outer support are used. The facing head shown at- FIG. 381. tached to the nose of the spindle may also be secured to the bar at any point, thus making it possible to face either end of work that the bar passes through. These machines may be advantage- ously used for heavy plain milling work. Another form of horizontal boring and drilling machine is shown in Fig. 381. Here the work table is mounted upon the bed and the vertical adjustment is obtained by moving the spindle vertically over a substantial upright. The outer bearing is geared with the head, thus causing it to move with the spindle. Automatic table feed adds much to the convenience of this tool for general work. 268 MODERN MACHINE SHOP TOOLS. For very heavy work it is frequently better to secure the work to a solid bed and give all adjustments to the spindle. Such a tool, commonly known as a floor boring, drilling and milling ma- FIG. 382. FIG. 383. BORING AND TURNING MILLS. 269 chine is shown in Fig. 382. The construction of the machine is evident from the figure. Automatic cross and vertical feeds are provided for milling. In Fig. 383 is shown an example of a floor boring mill at work on a machine frame. In the floor boring and drilling machine of Fig. 384 a uni- versal tilting table is provided. When fitted with a revolving table, operations can be performed on all sides and at any angle on a piece of work, the bottom excepted, without changing its setting. Cylinders may be bored in the lathe in the vertical, horizontal FIG. 384. or floor boring machines, but when a large amount of that class of work is to be done, a special cylinder boring machine, an ex- ample of which is shown in Fig. 385, is generally employed. In this machine only those features of the horizontal mill necessary for the required work are retained. A heavy boring bar, rigid outer support, double facing head and no vertical adjustment are the usual characteristics of these tools. The work is usually held in a suitable jig which permits of rapid setting. In securing work to the table of the vertical boring mill, the same care and methods are employed as with the lathe. When 270 MODERN MACHINE SHOP TOOLS. possible the work is held in chuck jaws or in special drivers, as shown in Fig. 367. The latter method has the advantage of not tending to spring and affect the circular truth of the work and leaves, as in balance wheel turning, both edges of the rim free to operate upon. The turning and boring tools used in machines of FIG. 385. this class are quite similar to those employed in engine lathe work, the grinding of the cutting edges being the same for similar work. The same boring bars, reamers and formed facing tools used in turret lathes may be used in the vertical mill. For cylinder boring work in the horizontal mill, the cutters arc FIG. 386. usually carried in a special head which fits over the main boring bar and may be keyed and clamped at any position in its length. A head of this description is shown in Fig. 386. The cutting tools, usually two or four in number are clamped in position ar.d BORING AND TURNING MILLS. 271 should be supported as far out as possible. These tools are preferably of self hardening steel ground to proper form from the bar stock without forging. In Fig. 387 is shown the method of boring and facing a gas engine cylinder in the horizontal boring mill. The yoke jigs or frames holding the work are securely bolted to the table and the work held by two set screws in each yoke. By means of these screws, and the table adjusting screws, the work can be trued FIG. 387. concentrically with the bar. The head shown in Fig. 386 is passed through the bore on a moderately fine feed and removes the most of the stock, the cut being divided between two or more cutters. A sizing cut is then taken back through the bore leaving only a small amount for the finishing cut. As the scale and sand has been removed by the first or roughing cut, a somewhat quicker speed can usually be employed on the sizing cut. As this cut is intended as a truing or sizing cut, the feed should not be too coarse. The finishing tool is next placed in the head and passed 272 MODERN MACHINE SHOP TOOLS. through on a coarse feed. This tool should have a broad cutting edge, very slightly rounded in its length; should be ground with very little clearance and stoned true and smooth. Its cut should be a light one and the cutting speed well within the safe limit for the steel employed. The object of the coarse feed is to dis- tribute the cut over a greater length of tool edge and to perform the work with the fewest number of revolutions possible, thus re- ducing the wear on the cutting edge to a minimum and produc- ing a parallel bore. Where a number of bores are to be finished to approximately the same diameter, it is advisable to have the fin- ishing tool set in an independent head which can be substituted for the regular head. This virtually corresponds to a reamer and makes possible very close duplication of bores. The end of the cylinder is next faced with the facing head shown, and if desired the holes for the cylinder head studs may be drilled and tapped by operating the cross and vertical table adjustments and using a drill and tap in the main bar. Where a number of cylinders are to be bored it is usually found more economical to do the drilling and tapping in a smaller machine. CHAPTER XX. PLANING AND SHAPING MACHINES. Their Tools and Attachments. The planer and shaper, with their modifications the slotting machine and key-seater, constitute a distinct class of machine tools, the office of which is to machine plane and irregular sur- faces that can be most readily machined by a straight-line cut. Although a considerable amount of work that, until a few years ago, was classed as planer and shaper work has been turned over to the milling machine, there still remains a very wide range of work that must continue as planer and shaper work. . These tools. bear_tp_ the machining of plane surfaces practically the same re- lationship that the lathe does to the machining of round work. The cutting tools used on the planer and shaper are practically the same as those used on the lathe, and the general principles in- volved in the operating of the machines are quite similar. The planer and shaper, although used on the same class of work, differ materially in design. In the planer the work moves to the tool, while with the shaper the tool moves over the work. In the planer the vertical and lateral feeds are given to the tool, while on the shaper the lateral feed is usually given to the work, the vertical feed, however, being given to the tool. In what is known as the traverse head shaper, both feeds are given to the tool and the work is held perfectly stationary. In Fig. 388 is shown a standard modern planer. The bed is deep and heavy with the work table moving in inverted vees. The housings or uprights are secured firmly to the bed and cross- tied at the top. The cross rail is gibbed to the front of the hous- ings and carries the tool head. The cross rail is adjustable verti- cally, being operated by the two elevating screws, by hand on the smaller machines, and by power on the larger ones. On the large machines, two heads are frequently used on the cross rail and one on the face of each housing, thus enabling several cuts to be taken on the work at the same time. The important features of the planer are its table driving mech- anism including reversing gear and the mechanism for operating 274 MODERN MACHINE SHOP TOOLS. the feeds. In some of the earlier planers the table was driven by a quick-pitch screw with suitable gears and pulleys at the end of the bed. This method has been entirely replaced by the rack and FIG. 388. gear drive and the Sellers or spiral gear drive. In Fig. 389 is shown the gear arrangement as commonly used in the rack and FIG. 389. PLANING AND SHAPING MACHINES. 275 gear drive. The rack A is secured to the bottom of the table. The gear B meshes with the rack and is driven from the pulley C through the gear reductions E F and B H. D and I are loose pulleys carrying belts that run in opposite directions. When the belt running in the direction of the arrow is on the pulley C the table and work move toward the tool, and when the reverse belt * is thrown upon C the table moves the work away from the tool, The backing belt is usually driven at about four times the velocity of the forward belt, thus giving the table what is termed a quick- return motion. The object of this is to get the table and work back and ready for another cut with the least possible loss of time. As applied to the planers by different makers, this mech- anism differs somewhat in its arrangement, but in all cases is a simple geared reduction. The reversing mechanism differs materially on the various machines. That used by the Gray Company on the planer shown in Fig. 388 illustrates one of the simpler methods. As quite clearly shown, the belt-shifting rings are attached to a pair of arms controlled by cams. The dogs, which clamp to the side of the table at any point in its length, engage the shipper lever on forward and return strokes, through the connecting rod, and move the cam plate and belt arms. The motion is such as to cause the belt driving to be shifted from the tight pulley before the other belt is shifted on, thus preventing both belts from get- ting on to the tight pulley at the same time. As these belts must be shifted very quickly and, when the table is making short strokes, very often, it is quite necessary that the belts be narrow and run at a high velocity. These belts will not shift properly if run too tight, and should always be of the best grade of double leather belting in order to stand the wear and pressure on the edges. As it is frequently necessary to run the work out from under the tool to take measurements, and it is not desirable to change the position of the dogs, the shipper lever is provided with a trip stop which can be raised, to allow the dog to pass over without changing its position. The planer cannot be depended upon to stop its table at exactly the same place each stroke. This variation may arise from changes in the pressure of the cut, but more frequently from changes in the speed of the belts, thus vary- ing the time in which the inertia of the rotating parts is over- come each time the belt is shifted. In Fig. 390 is illustrated a planer with a spiral geared or 276 MODERN MACHINE SHOP TOOLS. Sellers drive, and the planer shown in Fig. 394 also has a drive of this description. As shown in Fig. 391 the mechanism for driving the table is simple. A spiral pinion, usually having a quadruple thread, en- gages a rack, the teeth of which are at right angles to the length of the table. This throws the axis of rotation of the pinion away from the line of motion of the table an amount equal to the spiral angle of the teeth in the pinion and carries the pinion shaft at this angle through the side of the bed. This gives a broad bearing between the teeth of the pinion and rack and causes the line of pressure to come directly in the line of the table's motion,. Suit- FIG. 3)0. able bevel gearing and tight and loose pulleys on the outer end of the shaft complete the driving mechanism: This drive is noted for its smoothness of action, and freeness from the vibration fre- quently found in spur gear drives. The mechanism for operating the feed is comparatively sim- ple on most planers, the same mechanism usually operating both vertical and cross feeds on the cross rail head, or heads when more than one are used. As the amount of feed adjustment per stroke must be constant and as the length of the stroke varies, it is necessary that the feed-operating device give the full amount of feed adjustment during a relatively small amount of the table's stroke. In fact, the shortest stroke it is possible to have the table PLANING AND SHAPING MACHINES. 277 make, should give the full feed adjustment for each stroke. In Fig. 388 the arrangement shown is simple and effective and in modified forms is largely used by the different builders. The head which operates the feed is driven by the extended Rack FIG. 391. pinion shaft, the arrangement of parts being as shown in Fig. 392. The disc A is secured to the shaft and consequently ro- tates with the pinion, right or left handed rotation depending upon the direction in which the table is moving. The disc car- ries a casing B and cover C, the cover being held to B with the three studs D D D and against the friction washers E and F with a uniform pressure by the spiral springs under the nuts on the studs. If the casing is relieved, it and the cover C, together with the wrist pin G, rotate until the casing is again held. In the back of the casing is a slot H into which the. stationary pin I extends. 2 7 8 MODERN MACHINE SHOP TOOLS. The length of this slot is determined by the amount of casing rotation required. In action, the table starts on its stroke; B and G rotate until I strikes the end of the slot H and the rack has been moved up or down, depending upon which side of the center the pin G is. As the table continues its stroke, the disc A slips between the washers E and F, and G remains stationary. When the table starts on its return stroke, A rotates in the oppo- site direction, carrying with it B and G until the pin strikes the other end of the slot, the rack having received motion in the op- posite direction to that given on the forward stroke. Thus the rack is moved up and down once each time the table moves for- ward and back, and the amount of the rack motion depends upon the distance B is from the center and is independent of the length of the table stroke. A pinion X gears with the rack and through a shaft carries the gear A, Fig. 393. Gear B rotates free on the shaft, gears with C, and on its face carries the double pawl D. If the lower foot of this pawl, as it stands in the cut, is thrown in, it slips on the up stroke of the rack, but -drives the gear B in the direction of the arrow on the down stroke. If the upper foot is thrown in it slips on the down stroke and carries gear B in the opposite direction, the direction of feed being reversed. It is evident that with the wrist pin G, Fig. 392, on the same side of the center, the feed occurs at the beginning of the forward stroke when the feed is in one direction, and reversal of the feed makes it occur at the beginning of the return stroke. The wear on the feed mechanism is least when the feed occurs at the be- ginning of the return stroke, as it is not then necessary to move the tool while cutting. On the other hand, feeding on the return stroke makes the wear on the tool in dragging back somewhat greater. When the heads are attached to the face of the hous- ings, they are given a vertical feed on the housing in a manner similar to that already described. By removing the gear C from the cross screw and putting it on the feed rod, the vertical feed is operated in a manner similar to that for the horizontal feed. FIG. 393. PLANING AND SHAPING MACHINES. 279 The size of a planer is determined by the length of its table, the distance between housings and the maximum distance be- tween table and bottom of cross rail. The extension side planer is so constructed that the housing on the side opposite the driv- ing and feed mechanisms can be extended out over the widened bed. In this tool, the capacity is increased by spreading the hous- FIG. 394. ings, an extra long cross rail, of course, being required. This class of planer is of value in shops where only a small per cent of the work done requires a wide planer. Another modification known as the open-side planer is shown in Fig. 394. In this tool one housing is dispensed with entirely. The cross rail being heavy, strongly braced and carried on heavy housings on the one side removes the width limit on the work to be machined. 280 MODERN MACHINE SHOP TOOLS. When the work is very wide and overhangs the table by an ex- cessive amount it is necessary to provide some form of out-board support for the outer portion of the work to rest upon. On all planers the cross rail is elevated by two square-thread screws set in the face of the housings and geared together at the top. These screws are preferably right and left handed and must fo? very accurately cut, as otherwise the cross rail will not remain parallel to the table in its width at all positions. On the larger O o FIG. 395. FIG. 396. sizes where the cross rails usually carry two heads and are very heavy the elevating screws are operated by power belted from the countershaft. The form of bed shown in Fig. 388 is the one known as the deep box bed and is now quite generally used. It is strongly ribbed and its form is such as to make it very strong and rigid. The form of table guide quite exclusively used on planers is known as the inverted "V." In any planer it is very important that these guides be most carefully fitted and suitable means pro- PLANING AND SHAPING MACHINES. 2tSl vided for their lubrication. The bearing surfaces are usually grooved to retain and distribute the oil with suitable wipers pro- vided to carry the lubricant to these surfaces. In Fig. 395 is shown a common and very efficient method. .An oil well or pocket is cored in the bed near the center of the table's motion, and a pair of conical rollers carried in a suitable frame and held against the surface by a spring carries the oil from the well to the surface to be lubricated. The principal difficulty with this arrangement comes when the table is worked on short stroke for a considerable length of time, as in that case the portion over the rollers only is properly lubricated. On long strokes, however, the action is perfect. The planer table is always provided with a large number of holes for stops and for bolting the work to the table, also with suitable T-slots. These holes should be drilled and reamed and the T-slots planed or milled in order that the bolt heads may move freely in them. Fig. 396 shows a side view of a planer head. This same gen- eral form is used by all builders on both the planer and shaper. It is nothing more than the compound rest on the lathe, having in addition the tool box and apron. The cross rail corresponds to the carriage on the lathe. It is a rigid girder that contains the cross-feed screw and the vertical feed rod, and upon which the saddle travels, it being securely gibbed to the cross rail. The swing frame pivots at the center of the saddle's face and may be clamped at any desired angle, either side from the vertical, the amount of the angle being determined by graduations either on the edge of the frame or face of the saddle. The slider is gibbed to the swing frame and operated by the feed screw shown in the figure, either automatically or by hand. The automatic feed is accomplished in the same manner as for the compound rest, a section of which is illustrated in Fig. 243. The mechanism, of course, varies somewhat with the different builders. The tool box is pivoted to the slider and has a limited amount of adjust- ment each side from the center, being clamped rigidly in any de- sired position by the lock bolts shown. The apron, which fits neatly in the tocl box, is pivoted to the box at the upper forward corner, thus allowing it to swing outward on the return stroke and prevent the tool from dragging heavily over the work surface. The tool post is secured to the apron. The office of the tool box is to allow the tool to swing out from the work on the return 282 MODERN MACHINE SHOP TOOLS. stroke when machining side surfaces. It is evident that if the tool post was secured to an apron pivoted directly to the slider, the tool would swing straight out on the return stroke, which would be all right when machining top surfaces. If, however, side surfaces were machined, the tool, in swinging straight out, would drag up over the surface planed, injuring the tool and marring the surface. When, however, the apron pivots to a tool box that can be inclined somewhat away from the work sur- face, it is evident that the point of the tool will, upon the return stroke, swing out from the work ; but if the top of the tool box be inclined toward the side of the work, the tool will swing into the work surface, causing trouble. It is therefore necessary to swing the box in the opposite direction when changing from one side of 397- the work to the other. The tool clamping device may be an ordinary tool post as used on the lathe, but it is more commonly a pair of clamps, as shown in Fig. 397. What is known as the standard shaper is of the column or pil- lar pattern, one design of which is shown in Fig. 398, with several shaper attachments (to be described later). In this machine the upright is called the column. The cross rail is gibbed to its front face and is adjustable vertically by a suitable elevating screw. The box or knee is secured to a saddle which moves over the cross rail. The ram carries the tool head which is in every way similar to the one described above, the swing frame being pivoted to the end of the ram. In the example shown, the swing frame is rotated by means of a worm gear and hand wheel, which enables its operation while the -machine is in motion, a most con- venient method of shaping out concave surfaces. PLANING AND SHAPING MACHINES. 283 In all shapers the ram is actuated by one of two methods. The geared method provides for a rack and gear drive similar to that used in operating the table in the planer. It is simply a geared reduction, the quick return to the ram being accomplished by either the use of a smaller backing pulley or higher belt velo- city for the return stroke. This drive is illustrated in Fig. 389. In Fig. 399 is shown a standard pattern shaper having a rack and gear drive. This drive, although little used on small ma- chines, is always applied on the larger shapers. Machines of the pattern shown in Fig. 399 are regularly made in sizes from i6--inch stroke up to 48-inch stroke. The other method is known as the crank drive, in which a ' FIG. 398. crank or its equivalent, operated by a suitable system of gears, transmits the motion to the ram. The use of the simple crank drive has been superseded by crank drives which involve a quick- return motion. With the simple crank motion, not only is tfie time occupied on the return stroke of the ram equal to that on the forward stroke, but the relative velocity of the ram varies greatly between the beginning and the end of the stroke, being much more rapid at the middle than at the ends. With the quick- return motion, however, it is intended to reduce the time during which the ram is on its return stroke and thus give more time for 28 4 MODERN MACHINE SHOP TOOLS. the forward or cutting stroke, and also to average up as much as possible the relative velocity of the ram at the different por- tions of its forward stroke. In all cases the power is communi- cated to a shaft, usually by a belt running on a stepped cone,: causing it to rotate at a uniform rate of speed. Crank shapers as regularly made run in sizes from 1 4-inch to 3O-inch stroke. In Fig. 400 is shown the mechanism commonly known as the slotted or vibrating link. P is a pinion receiving motion from FIG. 399. the belted cone at a uniform rate of rotation, and gearing with the gear G. The link M M pivots at the point L and carries at its up'per end the rod R which connects with the ram at H. A block B is fitted nicely in a slot S in the link and is carried on the pin I which projects from the face of the gear G. The path of the pin is a a, the block B moving up and down in the slot and causing the link to. vibrate about L through the limits y y, carrying with it the rod R and the ram. If G rotates in the PLANING AND SHAPING MACHINES. 285 direction shown by the arrow and the tool end of the ram is at K, then the forward part of the stroke occupies that portion of G's rotation indicated by the angle x and the return portion by the angle y. It is, therefore, evident that the return stroke occupies FIG. 399 A. FIG. 3996. much less than one-half of the revolution of G. An analysis of the mechanism shows the motion of the ram to be much more uniform than with the simple crank, the velocity being faster at the beginning and end of the stroke and slower through the 286 MODERN MACHINE SHOP TOOLS. middle portions. As more of the time of each revolution is oc- cupied by the cutting stroke with the quick return than with the simple crank motion, the velocity of the cut will be lower and more uniform, thus enabling a greater number of strokes per minute to be taken than would be permissible with the simple crank motion. By carrying the pin I toward its center of rota- tion, the length of the stroke may be shortened by any desired amount. The Whitworth quick return motion, as illustrated in Fig. 401 Rar FIG. 400. is very largely used for shaper drives. Referring to the figure, P is the pinion that transmits the power to the gear G, causing it to rotate at a constant rate of speed. G rotates upon a fixed stud B of large diameter. The crank A is fixed to the shaft C which has a bearing in B eccentric to its center. A pin D is fastened in the face of the gear G and engages in the slot I in the back of the crank, thus causing the crank to rotate with the gear. A pin X carries the end of the connecting rod R which transmits the motion to the ram at Z. The path of D's rotation is about the center of B, and the path of X is about the center PLANING AND SHAPING MACHINES. 7 288 MODERN MACHINE SHOP TOOLS. of C. When the crank is in the position shown, the lever arm D C is minimum, and since D rotates at a uniform rate of speed, the velocity of X will be greater at this point than at any other point in its rotation. When D reaches the position D', the lever arm D C becomes maximum and the pin X is moving at its slowest rate. While X is going from W to W, in the direc- tion of the arrow, the ram Z is making its return stroke and the pin D has rotated from V to V or through somewhat less than one-half of its revolution. The forward stroke is made while R 02. moves from W' to W and D from V to V. It is evident from the above that more time is occupied on the forward than on the return stroke. A form of shaper well adapted to the machining of long pieces of work is shown in Fig. 402. In this tool the bed, which is long, carries the knee on its front face and the arm which corre- sponds to the ram on the pillar shaper is given a motion length- wise of the bed, the tool head being fed automatically in or out on the arm. This machine differs from the open-side planer, as illustrated in Fig. 394, in that the tool moves over PLANING AND SHAPING MACHINES. 28 9 stationary work, whereas the work moves under the tool in the open side planer. On that which is known as the movable head shaper, illustrated in Fig. 403, the work remains stationary and the ram is mounted in a saddle gibbed to the top of the bed and fed over the work. Shapers of this class are most excellently J ! ! "*"*! adapted to the machining of widely separated surfaces on heavy pieces of work. In the classes of shapers above illustrated the cutting stroke is the outward or push stroke. In the Morton or draw stroke sliaper shown in Fig. 404 the reverse is the case, as the tool cuts on the inward or draw stroke. This tool has been very success- 290 MODERN MACHINE SHOP TOOLS. fully used on heavy work and long strokes, and has been widely modified by its builders to suit special conditions. The head alone, attached to a suitable knee plate and driven by flexible shaft* rope transmission or electricity, is quite extensively used as a portable shaper to be clamped to the work that is to be ma- chined. Many of the cutting tools used on the planer and shaper are FIG. 404. the same as those used on the lathe, as, for example, the side- cutting, diamond point an4 cutting-off tools. There are, how- ever, several forms specially adapted to planing operations. The extended nose tool shown in Fig. 405 is used for cutting key- ways or for any class of internal work. This tool, unless short and heavy, springs badly. It should be held as high in the tool holder as permissible, thus reducing the spring to the least amount possible. The shape of the cutting edge is suited to the character of the work and should be given as small an amount of bottom PLANING AND SHAPING MACHINES. 2QI clearance as will enable it to take hold of the cut, otherwise it will dig into the work badly. The Armstrong planer tool shown in Fig. 406 takes the place of several forms of ordinary planer tools, as top roughing, right and left side roughing and right and left under-cut, all as shown in the figure. It may also be used to hold cutting-off blades or formed cutters of any class. A tool of this kind for the planer possesses the many advantages of FIG. 405. FIG. 406. FIG. 407. similar tools for the lathe in which a small cutting tool of self- hardening steel, ground rather than forged to shape, is used. The gang tool shown in Fig. 407 is often used on the planer where the surface to be machined is large and comparatively regular in outline. It consists, as shown, of several tools set one back of another in a suitable head held in the tool clamps in the usual manner. The cutting points are so adjusted that each takes the regular cut desired so that a regular feed of, say, 1-16 inch on each cutter would, on a gang cutter tool, enable the head 292 MODERN MACHINE SHOP TOOLS. to be fed over the surface one-fourth of an inch at each stroke of the work. A tool of this class carrying a roughing and a fin- ishing cutter must not be depended upon to produce satisfactory work when good machined surfaces are required, as the spring of the roughing cutter due to the inequalities of the work surface is communicated to the finishing cutter, and this must as a result produce a finished surface having much of the irregularity of the original rough one. Single tools of this character with special formed cutting edges are much used on special work. Planer and shaper tools should, almost without exception, be ground with very little bottom clearance. The rake should be suited to the hardness of the metal being machined. It is ad- visable, when possible, to have the cutting edge well back under the head so that the spring of the tool and head will not cause FIG. 408. FIG. 409. the cutting edge to dip into the work surface; it also tends to prevent chattering. This point is illustrated in Fig. 408, where at A is shown a tool whose cutting edge is well ahead, and at B one with the cutting edge well back. The dotted lines show the path the cutting edge tends to follow in each case, due to the spring of the tool itself. The spring of the head tends in each case to let the point into the work, but not so badly in the case shown at B as at A. On all top and side cuts the tool swings out and away from the work surface on the return stroke. For under cuts, however, except those of comparatively slight angle from the vertical, where the head can be angled to meet the condition, the tool must be held from swinging out on the return stroke, as it would in that case cause trouble, lifting the work or breaking it, the tool, or the head. For under cuts the tool should have a long shank extending well above the clarnp and blocked out at the top as shown in Fig. 409. As the tool PLANING AND SHAPING MACHINES. 293 drags back heavily in such cases, the wear on it is excessive. A side head, due to its position, is well adapted to under-cut work. Where much under-cut work is to be done and a side head is not available, or owing to the position of the work sur- face, not adapted, a relieving tool similar to the one shown in Fig. 410 can be made at a small expense. In this tool a stud projecting from the side of the shank carries a small tool hold- ing collar, which can rotate on the stud until the stop A strikes the shank. A light spring S bears against the stop, al- lowing it and the tool to swing back from the work on the re- turn stroke and bringing it back again for the beginning of the forward stroke. For finishing cuts at coarse feeds the broad nose tool shown in Fig. 411 is used. The corners are slightly FIG. 410. FIG. 411. rounded, as shown at A, B, and the tool given only a slight amount of clearance, as shown. The planer and shaper, when equipped with suitable attach- ments, are capable of a very wide range of what might be termed special tooling operations. An emery-grinding head is secured to the cross rail with suitable belted connections to drive its wheel and the planer table at the proper speeds, and the planer is con- verted into a very creditable plane grinding machine. This transformation, however, is not to be advocated, as the bearing surfaces of the planer are not properly designed for the pro- tection necessary against the flying particles of emery. The ctr- version, however, into a plane milling machine is more com- mendable, as the planer when provided with suitable feeds for the table is fairly well adapted to milling work. In Fig. 412 is illustrated a device that can readily be attached to the cross nil of any planer, virtually converting it into a slab milling mach'iie. The head of this attachment is so constructed that the spindle 294 MODERN MACHINE SHOP TOOLS. can be swiveled from horizontal to vertical. As there are many operations that can be more advantageously performed by milling than by planing, an attachment of this kind will frequently be of value in cases where a slab milling machine is not available. In Fig. 413 is shown an attachment for planing concave or con- vex surfaces. It consists principally of a vise pivoted in suita- Me housings at the points O O. The arm S is a part of the vise FIG. 412. and carries within it a stud terminating in the guide R. The bar G G is secured at any desired angle with the table to the post P, which is fastened to the side of the planer bed. If G G is parallel to the work table the vise will have no motion relative to its housing. If the bar is set as shown in the figure the farther end of the vise elevates as the table advances to the cut and a concave surface results. By inclining the bar in the opposite direction, however, the end drops as the table advances to the cut and a convex surface results. The arc of the circle planed depends on the amount of the angle between G G and the table ; PLANING AND SHAPING MACHINES. 295 the greater the angle, the smaller the radius of the surface planed. With the bar G G removed the vise becomes an ordinary planer vise, possessing the additional advantage of being adjustable to FIG. 413. quite an angle with the work table, a point of value in the planing of wedges. Planer vises, are very necessary accessories to both the planer and shaper, as a considerable amount of planer, and more es- FIG. 414. pecially shaper work must be held in the vise. In Fig. 414 are shown two forms of planer vises. The vise shown at A has a plain base, to be clamped in any desired position on the planer table. The adjustment of the movable jaw is clearly shown in the 296 MODERN MACHINE SHOP TOOLS. figure. The vise shown at B is provided with a circular base usually fitted with two tongues to fit the wards or T slots in the planer table and thus insure its being put on at the same angular position with the line of the table's motion. The circular bottom of the vise is pivoted at the center of the base and provided with a graduated rim, thus making it possible to set the jaws at any desired angle with the table's length. In this vise blocking is used between the clamping screws and the movable jaw. It is quite necessary in any planer vise to have the movable jaw so secured that it can be clamped down closely to its seat, as other- wise the clamping of the work between the jaws, will cause it to lift. The shaper vise is considered a regular shaper attach- ment, and is always furnished with the machine. The sliding jaw is always operated by a screw and gibbed to the body of the vise. The attachment shown in Fig. 415 is a special tool for the FIG. 415. planing of circular surfaces, as, for example, locomotive driving boxes. Its range is comparatively small. The long shank is held in the regular tool clamps. The head of the attachment is pivoted at its center in the end of the arm and operated by a shaft carried in a recess in the back of the arm. A worm and worm gear at the upper end of the bar provides a suitable feed drive for rotating the tool. When a considerable amount of work is to be done with the attachment a suitable automatic feed can readily be applied to the worm. The milling machine has taken most of the center work away from the planer. A pair of planer centers, however, an example of which is shown in Fig. 416, is frequently of great value. They are usually tongued to fit the wards in the table, and the head spindle is so indexed that the circle can be divided into a large number of equal parts. PLANING AND SHAPING MACHINES. 297 In Fig. 398 is illustrated a number of shaper attachments. The one shown on the machine is for planing spirals. The spindle of the head is rotated back and forward with the strokes of the ram through a suitable geared mechanism operated by the up-and-down motion of the block over which the inclined guide (which is actuated by the stroke of the ram) slides. The work to be operated upon is held between centers, and as the upper section of the knee can be inclined, spirals can be shaped upon tapered work. The shaper vise is shown at the rear of the cut. Two small centers attached to the jaws, as shown, are fre- quently found very convenient. The vise wedges shown on the extended base of the shaper are pivoted at the center and are used against one of the jaws of the vise in holding tapered work. In the front and on the left of the cut is shown a convex shaping attachment. This may be secured to the front of the cross rail in the place of the knee, and the feed attached to the geared feed mechanism shown, which gives the circular table, and such work as may be clamped on it, a rotating feed motion. This device can also be FIG. 416. secured to the knee in a horizon- tal position for operating upon special work requiring the ma- chining of radial surfaces. The circular attachment shown in the center of the foreground is provided with an arbor carrying two cones. Work having any bore within the limits of the cones can be held on the at- tachment, an automatic feed giving the work feed rotation. The index centers shown on the right are in principle similar to those shown in Fig. 416. They are, however, self-contained, both head and tail stock being secured on a suitable base casting, which in turn may be secured to the knee of the shaper. In Fig. 399 A is shown the circular attachment as used on the "Cincinnati" shapers. The spindle is driven by a worm and gear, either by hand, or automatically by the power feed mechanism shown. In Fig. 399 B is shown the automatic head feed used on this shaper. It is a positive acting mechanism, having a variable feed adjustment. The action corresponds to that used on the planer head feed, the short side shaft corresponding to the feed shaft in 298 MODERN MACHINE SHOP TOOLS. the cross rail and the motion is transmitted to the nut by two pairs of miter gears. Spiral planing attachments similar to the one shown in Fig. 398 are frequently applied to planers for the grooving of spiral rolls and work of that class. Another attachment for the cutting of spirals on the planer consists of a rack secured to the side of the planer bed at about the height of the surface of the work table. A pinion carried on a shaft running in bearings secured to the surface of the table and at right angles to its length gears with the rack. This cross shaft through a pair of bevel gears transmits its motion to a spindle parallel with the table's length and to which the work to be spirally planed is attached. The motion of the table causes the shaft, spindle and work to rotate at a rate determined by the velocity ratio of the gears. A shaper is sometimes used for key seating bores. There is a vertical supporting knee attached to the table for holding the work, and a special head attached to the ram in place of the ordinary tool box. This head holds a cutter bar, which is in the form of a broach, and will cut the keyway at one stroke of the ram. CHAPTER XXI. PLANER AND SHAPER WORK. The proper jsecuring of work in the vise or on the shaper or planer table for planing operations is a most important step in the production of satisfactory work. As the variety of work as- signed to these machines is great, the operator continually finds himself against a new problem requiring good judgment arid care. In most cases much more skill is required in the setting up of the work than in the machining. ' When the work is com- pact and heavy, and the amount of metal to be removed is rela- tively small, the danger of springing it is not usually great. If, however, the work is large, of irregular shape or light, the danger of springing is great. The springing is due to two causes : First, by ununiform or severe clamping which distorts the work and throws the machined surfaces out when it is un- damped ; second, the removal of the outer surface of a casting or forging, which frequently relieves shrinkage and forging strains and throws the work out of true. The first of these troubles can be overcome only by using the utmost care in setting up the work, and the second by, so far as possible, first roughing off all surfaces before taking any finishing cuts, thus allowing the work, after the roughing, to assume its normal condition as to strains. The most important consideration in the clamping of work to the table is to locate the points of clamp pressure directly over the points of support. The supports should be firm and bear as equally as possible between the work and the table. When only a thin shim is required to level up the work, it should preferably be of metal, as cardboard, leather or any compressible material will allow the clamp to spring the work. Good blocks and parallel bars are indispensable in the planer outfit. For work where the points of support vary in height, leveling wedges and small jack screws are most excellent, as they can be quickly adjusted to any desired height. These leveling wedges, especially if a single wedge is used, should be made with only a slight taper. In Fig. 417 is shown a pair of these wedges. When carefully made they form a good support and may be used to make the fine adjust- 300 MODERN MACHINE SHOP TOOLS. ment for height either directly on the work table or on top of other blocking. The planer jacks shown in Fig. 418 are most excellent, a few of these frequently replacing a large number of FIG. 417. blocks of miscellaneous shapes and sizes. A good set of planer bolts should be found on each machine. Common machine bolts are not well suited to this purpose as the heads are too thick FIG. 418. and not large enough to properly fill the T-slot. Planer bolts are preferably made of mild steel with heads turned to required thickness and milled on the four sides to properly fit the T-slot. FIG. 419. The clamp is usually made from a bar of flat steel with one or more holes drilled in it for the bolt, as shown in Fig. 419, and tapered somewhat on the work end to more readily enable it to PLANER AND SHAPER WORK. 3 OI be placed in the corners of the work. The clamp shown in Fig.. 420 is made from square iron and forms a substantial and con- venient form of clamp. Clamps of this character should be ap- plied to the work in the manner shown in Fig. 421, as closely as n FIG. 420. possible; that is, the bolt should stand close to the edge of the work and the blocking for the outer end of the clamp as far away from the bolt as convenient, thus throwing most of the bolt pull upon the work and not upon the blocking, as would be the FIG. 421 FIG. 422. FIG. 423. case if the bolt was nearer the blocking than the work. The T-slots should be sufficiently deep to prevent any reasonable bolt pull from breaking them out. This danger is, however, lessened 302 MODERN .MACHINE SHOP TOOLS. by placing the work or its point of support as close up to the bolt as possible. If the entire surface of the work is to be machined, clamps as above described cannot conveniently be. used as it would necessitate changing their position during the cut, a most deli- cate operation with results usually unsatisfactory if a true surface is required. When the work has considerable thickness, small lugs or flanges can be cast on the edges for holding the clamp point and in some cases a drilled hole in the edge of the work can be made to receive the point of the clamp. In cases where these methods are not convenient, the work can be held in the manner shown in Fig. 422. Two forms of post are shown in this figure, the one a plain pin to fit neatly in the round holes in the table and the other with rectangular base and tongue to fit FIG. 424. the T-slots. A common set screw with cone point fits any of the tapped holes in the post, the height of these holes varying to suit the thickness of the work and length of finger used. The fingers are cupped to receive the point of the screw and the work end pointed to engage a prick-punch hole in the side of the work or preferably formed flat as shown in the figure. A suitable post to receive the end thrust of the tool must in all cases be set ahead of the work, and should be made of steel, preferably a low grade of tool steel, to insure stiffness, and turned to fit neatly the holes in the table. It should extend well into the hole, but should not reach high above the table, from two to four inches being ample. The shorter it is, the less liable it is to get bent. In Fig. 423 is shown such a post. The two holes drilled through it at right angles to each other facilitate turning or prying it up, when, from any cause, it may stick too tight in the hole to be pulled out with the fingers. PLANER AND SHAPER WORK. 303 Round work may be held as shown in Figs. 424 and 425. In Fig. 424 the bar rests on the edges of the T-slot. In this case the edges should be in good condition. It is suitable for bars of small diameter only, while with the method shown in Fig. 425 where a knee plate is used a bar of any diameter can easily be held. A pair of V-blocks can be used very advantageously for hold- FIG. 425. ing round work. These blocks as shown in Fig. 426, should be tongued to fit the wards in the table and the V-notches planed with the blocks in place. A good knee plate is frequently quite necessary in the securing FIG. 426. of work on the planer table. The regular knee, on the shaper, however, serves the purpose on that tool. On long work the twisting, and deflection due to the weight of the work itself, must, where accuracy is required, be taken carefully 304 MODERN MACHINE SHOP TOOLS. into consideration. For example, long lathe and planer beds must in the machining be handled with great care. Take a lathe bed that is to rest upon legs at each end. It should have the seats upon which the legs are bolted planed first, the points of sup- port being not at the extreme ends but at points about one-fourth the bed's length from each end, with wedges so adjusted as not to twist the bed in its length. After planing the leg seats the bed can be turned over and clamped directly on these seats, the bed assuming its natural deflection, in which position the shears are planed. In securing work in the vise, the pressure of the jaw against the work should be as uniform along the surface gripped as pos- sible. . If the surface is somewhat irregular a soft packing, as paper or leather, will equalize the pressure. If there is much irregularity, however, .it is preferable to cause the vise jaws to grip the work at points rather than throughout their entire length. For this purpose a wedge or solid block should be used between the work and jaw and located as near the ends of the jaws as possible. When a jaw is tightened onto the work its tendency is to lift, causing the work to lift on the movable jaw side. For this reason the movable jaw should be fitted nicely to its slide with bolts, as previously shown in Fig. 414, for clamping it firmly after gripping against the work. Planer vise jaws are usually made of cast iron, and a false facing of soft steel secured with bolts to these jaws is excellent when finished surfaces are to be gripped between them. It is important for nice work to keep the vise jaws in good condition. The leveling and squaring up of work on the planer table is important. If the work has been laid out or some of its surfaces previously machined, the surface gauge will be used in bringing these lines or surfaces parallel with the table. If a line on the work is to be set parallel with the line of motion of the table, the surface gauge needle point will be adjusted to the line at one end with the base of the gauge against the side of the slider. The table is then moved under the cross rail and the other end of the line brought to coincide with the point of the needle. Another method is to square up from lines that have previously been planed with a fine sharp-pointed tool in the top surface of the table, and with the caliper divider caliper from the blade of the square to each end of the line on the work ; or, if this line is not too far from the edge of the planer table, the calipering may be PLANER AND SHAPER WORK. 305 from the line to a straighf edge placed against the side of the work table. When the line on the work surface is to be set at right angles to the length of the bed, the work is brought close Tip to the cross rail and the line adjusted to the surface gauge needle point, with the base of the gauge resting against the face of the cross rail ; or, as in the other case, the caliper divider with a straight edge placed against the face of the cross rail can be :used. In the manipulation of the planer and shaper the beginner should keep a few points closely in mind. All planers and geared shapers do not have a fixed length of stroke, the depth of the cut .and the speed of the countershaft affecting slightly the points at which reversals take place. Some allowance must therefore be made for the overtravel of the tool. An excessive amount of over- travel, however, means a large loss of time.... Roughing cuts shouTcf be as heavy and at as coarse feeds as the machine will conveniently handle and the strength and character of the work will permit. Before planing side surfaces see that the top of the tool box is inclined from the work. This allows the tool to swing out and clear the work surface on the return stroke. If it is not inclined the point of the tool drags hard on the work surface, and should it be inclined to the wrong side the tool will swing into the work, doing much damage. Raising the tool clear of the work on the return stroke preserves the cutting edge. Means for automatically accomplishing this are frequently employed. Keep the cross rail clamped firmly to the housings when in use and parallel with the table. Before putting in the feed see that the feed gear is on the right spindle, as otherwise the tool may start up or down when it is intended to move across the work. As there are usually more ways than one to do every piece of work, study the way in which it can best be done. The manner in which the work is set up, the kind of tools used and the way in which they are ground, as well as the efficient handling of the machine, all have an important bearing on the quality and amount of the work turned out. CHAPTER XXII. THE SLOTTING MACHINE AND KEY SEATER. The slotting machine is illustrated in Fig. 427. It consists primarily of a substantial frame, a tool-carrying ram and a table for supporting the work. While the plane of the table is the FIG. 427. same as on the shaper, the ram moves in a vertical plane, thus adapting it to work in which surfaces at right angles to other surfaces are to be machined. The table which is provided with feed rotation is mounted upon a slider and this in turn upon 3 THE SLOTTING MACHINE AND KEY SEATER. 307 saddle gibbed to the knee of the machine, thus providing a work table that may be rotated or moved to any position in its plane relative to the cutting tool and within the capacity limits of the machine. The slotter is very largely used for the cutting of key ways in hubs and the machining of rectangular, circular or irregular outlines which cannot readily be done on shaper, lathe or mill- ing machine. In Fig. 428 is shown a piece of work well adapted to the slotting machine. The surfaces a, b, and c can be ma- chined on the slotter more advantageously than on the planer or FIG. 428. shaper, as the side rests solidly upon the table and the form of the slotting tool is adapted to the job. On planer or shaper a knee plate must be used to clamp the work to, and an extension tool employed. The half boxes used on locomotive driving axles as shown in Fig. 429 illustrate another slotter job. Here the cylindrical bear- ing surface is machined by placing the work concentric with the work table. The table is so placed with reference to the tool that the necessary amount of rotation can be obtained without interfering with the tool or head. After each downward or cut- ting stroke the table is automatically rotated the necessary amount of feed for the next cut. By using a fine feed and a properly 308 MODERN MACHINE SHOP TOOLS. formed cutting edge on the tool very smooth true surfaces result. Connecting-rod ends and crank eyes are advantageously ma- chined on the slotter. The tools for the slotter are either forged on the end of heavy square bars of steel or inserted in steel bars of either square or round section. When forged the tool is usually of the form shown in Fig. 430. The cutting angles are the reverse of those of lathe and planer tools. The end angle turns the chip and is the angle of rake with x as the angle of clearance. As with planer tools the angle of clearance should be small in order to prevent the tool from chattering and digging into the work. The FIG. 429 FIG. 430. angle of rake y should be as great as the hardness of the metal operated upon will permit. For squaring out corners a tool similar to the diamond point is usually used. By properly indexing the rotating table spur and internal gear may be cut on the slotter, using a cutter of the cor- rect tooth space outline. The key seater is an outgrowth from the slotting machine, and although designed for cutting key ways only, will, when provided with suitable attachments, perform various classes of slotting machine work. A standard key seater is shown in Fig. 431. A cutter bar is operated by a crank motion in the base of the machine, similar to the drive on a slotting machine. The THE SLOTTING MACHINE AND KEY SEATER. 309 upper end of the bar is supported by a suitable overhanging arm. The work table upon which the pulley or gear to be key-wayed is supported may be tilted the necessary amount to give the re- quired taper in the key way, and is also capable of a slight in and FIG. 431. out motion, independent of the feed which advances it to the cut- ter. This motion is necessary in order to clear the cutter from dragging on the return stroke. The form of cutter used on this machine is shown in Fig. 432 3io MODERN MACHINE SHOP TOOLS. and the bar in which it is held in Fig. 433. These cutters are ground from the bottom only and should be kept sharp. The work is centered to the bore by suitable bushings. The feed screw is graduated to thousands and provided with a stop nut, which * FIG. 434. FIG. 433- enables any number of bores of the same diameter to be key- wayed to the same depth. For a great deal of special work a cutter bar of rectangular section can be conveniently used. In such a case the width of the cutter should exceed the thickness of the bar which allows the THE SLOTTING MACHINE AND KEY SEATER. 3! I cutter to work out square corners. For the cutting of external key-ways in short shafts and spiders the key-seater is excellently .adapted. For the key-seating of very large, heavy work portable key- seaters are used. In Fig. 434 is shown a Morton portable ma- chine operating on a large pulley. These tools are made in four sizes, ranging from 24 to 72 inch stroke. They are virtually draw stroke shapers without columns. They are operated either by a rope transmission or electrically, a motor in the latter case being attached directly to the machine. CHAPTER XXIII. MILLING MACHINES. The milling machine and its great popularity are due to the peculiar adaptability of the rotating cutter to the machining of plane and irregular surfaces on such a wide variety of work. The variety of work that the milling machine is capable of per- forming is much greater than can ordinarily be accomplished on the planer or shaper. In thoroughly familiarizing himself with these machines the mechanic has much more to learn as to set- tings and manipulation in the milling machine than in the planer and shaper. With the latter machines, however, more skill is required in the manipulation for the production of accurate work than with the former. This arises from the fact that on the planer all measurements must be separately made, inasmuch as the cutting tool generates the profile of the work by a series of parallel cuts, all changes in plane of the profile requiring sepa- rate adjustments and measurements. With the milling machine, however, the cutter is so formed as to generate the full profile of the work surface as the cutter advances, setting measurements alone being necessary. With the planing machines the accuracy of the work depends very largely upon the personal skill of the operator, while with the milling machine the accuracy of the cutting tool has much to do with the quality of the work. With the milling cutter and the work once set, the accuracy with which a certain work-surface profile can be produced upon one or more pieces depends wholly upon the wear on the cutting* edges of the cutter. As the cutters are usually formed with a number of teeth, the work is divided up among these teeth, re- ducing the wear upon them. This is not only because each unit of length of each tooth performs only a small portion of the total work as compared with the cutting edge of the planer tool of unit's length, but because thai: particular portion of the tooth is performing work for only a small portion of each revolution, thus giving it an opportunity to cool and recover before each time it comes in contact with the work. The advantage of the milling machine over the planer lies very largely in its ability to produce, with reasonable accuracy, a large MILLING MACHINES. 313 number of duplicate surfaces, the formed cutter arid removal of the personal error in the making of measurements by the oper- ator being the factors that enable it to produce these results. For the producing of many plane surfaces, and especially on work that is not to be duplicated, the milling machine possesses no advantage over the planer and'shaper. Its advantages for certain classes of work, however, are great, as illustrated, for example, in Fig. 435. This shows a milling gang cutter made up of seven cutters and capable of producing at one traverse over the work a profile that, if produced in a planer, would require no less than eleven separate measurements, aside from the working out to line of the curved portion. It is only after the operator has become skilled in its use and thoroughly familiar with its every detail that he can appreciate the great capabilities of this class of ma- chine tools. When used as a manufacturing tool, producing large numbers FIG. 435. of duplicate parts, the results obtained from the use of the milling machine lies almost wholly in the intelligent selecting of proper cutters and fixtures for each special operation and when once set does not require highly skilled labor to operate it. When used as a jobbing machine, however, the operator should be quick and skillful to obtain good results. The plain and universal milling machines of the column pat- tern are most extensively used for general shop purposes. In Fig. 436 is shown a universal machine of this pattern. The col- umn and knee resemble somewhat the same parts in the shaper. The upper portion of the column carries the spindle and cone, the spindle on all other than the smallest sizes being back-geared in precisely the same manner as on the lathe. The outer end of the spindle is always supported by a suitable overhanging arm. The work table is adjustable in and out from the face of the column and vertically, these adjustments being made by screws 314 MODERN MACHINE SHOP TOOLS. with operating handles conveniently placed and moving over dials graduated to measure the amount of table movement in thousandths of an inch. The knee is gibbed to the face of the column and, in the universal machine, the work table is gibbed in a swing frame which pivots to a slider which in turn is gibbed to the upper face of the knee. Through the office of the swing- frame the table can be set at an angle from its right-angle posi- tion with the .cutter spindle. In some machines the table can be carried through a complete revolution, while with others the range is limited. The table is provided with a longitudinal feed automatically operated in either direction. An automatic FIG. 436. in-and-out and up-and-down feed may also be applied when de- sirecl. The feed mechanisms are so designed as to give a wide range of feeds. The universal head, to be described hereafter, may be geared with the longitudinal feed screw for the cutting of spirals. The plain milling machines of the column pattern are similar in design to the one shown in Fig. 437. In this type of machine the work table is gibbed directly to the slider and its line of travel restrained entirely to one at right angles to the spindle. The universal head and tailstock of the universal type are omitted, plain dividing centers usually being used on these MILLING MACHINES. 315 machines. The work table is somewhat larger on the plain than on like sizes of the universal machine. The plain machines are preferable for plain milling work, as they are somewhat more rigid and simpler in construction. For tool room work the universal column pattern machine stands at the front. As probably more than 95 per cent of the milling work outside of the tool room is plain milling, we find the plain machine much in favor for general work. Although the column pattern is generally conceded as the proper style of design for the universal machines, such is not always the case for plain FIG. 437. machines, inasmuch as a great part of the plain milling runs into larger and heavier work. We therefore find plain milling machines built along entirely Different lines, especially when used for the plainest and heavier classes of work. In Fig. 438 is shown a form of plain machine commonly known as the Lincoln pattern. It is an exceedingly simple form of machine, yet very efficient on certain classes of work. The outboard support, for the spindle, together with the form of the bed, makes a rigid ma- chine. The driving cone is mounted on the bask side of the main 3 i6 MODERN MACHINE SHOP TOOLS. FIG. 439- MILLING MACHINES. 317 upright, driving the spindle through a pinion and gear connec- tion. As the vertical adjustment is in the spindle itself instead of in the work table, a suitable tightener is employed for keeping the belt tensions correct for all positions of the spindle. The work table is given the usual automatic feed under the spindle and suitable lateral hand adjustment. In Fig. 439 is shown a form of plain milling machines somewhat similar in appearance to the one shown in Fig. 438. The design, however, provides for a FIG. 440. larger work table and the machine shown has two heads, making what is usually termed a duplex miller. Machines of this class are well suited not only to the use of plain or axial cutters, but to the radial or end cutter. Thus on the double-head machine of Fig. 439 two radial cutters may be used at the same time on oppo- site sides of work secured to the table ; or one axial cutter can ma- chine the upper surface while a radial is working on the side. Fig. 440 illustrates what is known as a slabbing milling ma- MODERN MACHINE SHOP TOOLS. chine. It resembles in appearance a planer, is a massive, power- ful machine, and in the form shown carries a large slabbing cutter for removing heavy cuts at coarse feeds from the work. These machines are also provided with horizontal spindles which can be operated with or independently of the vertical spindles. In this case the horizontal spindle bearings are carried on the front faces of the housings. The vertical spindles usually carry \ FIG. 441. radial mills. The advantage of the radial mill over the axial cutter lies in the fact that in forcing it to its cut the pressure is mostly in the direction of the line of the feed and not at right angles to the surface being machined, thus overcoming most of the springing in the work that occurs or tends to occur in the use of the axial cutter. The radial cutter, however, does not leave as smooth a surface as the axial, but this disadvantage is, on a great MILLING MACHINES. 319 deal of work, more than overbalanced by the greater accuracy obtained. In Fig. 441 is shown a well-known vertical milling machine intended for such general work as can be more advantageously performed by a cutter operated in a vertical spindle than by one on the horizontal spindle pattern machines. This machine in many respects resembles the regular column pattern machines with the column carried upward and out over the table an amount sufficient to bring the spindle into the vertical position. FIG. 442. The vertical spindle brings the cutter more directly under the sight and control of the operator than when cutters of the radial class are used in the horizontal spindle machines. This type of machine also has the advantage of a circular feed by which a circular table, upon which work is placed, may be given a rotary motion. Thus a class of work may be performed that would otherwise require the use of formed tools in the lathe, and it can be done more quickly than in the lathe. Another form of vertical spindle milling machine is shown in Fig. 442. This machine is designed for longer and heavier 32O MODERN MACHINE SHOP TOOLS. work than the one last mentioned. The spindles are carried on a. radial arm, thus providing a cross adjustment to the spindle rather than the table. In Fig. 443 is shown a pattern of vertical milling machine, more commonly known as a die sinking machine and used for FIG. 443. recessing of circular or irregular shapes, as dies for drop presses. The work to be operated upon is held in a vise, which may be moved in all directions by means of compound table slides. The knee is adjusted vertically by the screw and large hand wheel shown. Cutters of small diameter are used and the belted MILLING MACHINES. 321 spindle drive gives a smooth steady motion to the cutter. Where a number of similar pieces are to be operated upon a pattern is usually used for guiding the work to the cutter. For the milling of very light pieces, as sewing machine or gun parts, for example, a light lever feed machine is much more convenient than the heavier pattern tools. The speeds are bet- ter adapted for the small diameter of cutters used and the quick table movement makes it possible to turn work out very rapidly. A machine of this character is shown in Fig. 444. The feed mechanism differs quite widely on machines by different builders up to the point of the connection with the work table. At this point one of two systems is invariably used the screw or the rack feed. With only a few exceptions the screw feed is used on the plain and universal machines of the column pattern. On the heavy slabbing and duplex machines the rack feed is usually employ- ed. The rack feed furnishes the best form for a quick movement of the table, but possesses the - disadvantage of allowing the table and work to draw under the cutter in cases of accident or carelessness on the part of the operator. With the screw feed the table can be moved only by the rotating of the screw. A FJG. 444. quick-geared return to the table as usually applied to the screw-feed machines. The work table is provided with T-slots for holding the clamping bolts and fixtures. The table is gibbed to the bed to prevent lifting and usually moves in flat or angular guides. The overhanging arm is usually made of the style shown in Fig. 436, which enables it to be used to receive and support the several special attachments made to be used in connection with ma- chines of the column pattern. Suitable ties are now furnished with most makes of milling machines connecting the outer end of the overhanging arm with the knee, which adds much to the rigidity of the table and spindle when heavy cuts are being taken. A comparatively wide range of feeds to the table of the milling machine is considered quite important and especially 322 MODERN MACHINE SHOP TOOLS. so on the back-geared machines where the variation of the size and speed of cutters is considerable. This range of feed is usually accomplished by means of stepped pulleys, gearing, or a combination of the two. Thus a pair of four-step pulleys will give four changes of speed and if these pulleys are of different sizes, by transposing them on their spindles four more changes may be obtained. The power of the feed mechanism must be sufficient to pull the feeds under all conditions, and convenient in changing from one rate of feed to another. The importance of being able to make quick changes may be illustrated in the case of large dia- meter end or radial milling cutters operating upon wide work. The rate of feed on entering and leaving the work can be ma- terially greater than when the cut is operating on the full width of the work. If the cuts are comparatively short the time saved by entering and leaving the work on quicker feed is of material importance. On machines other than the smaller sizes, automatic in and out and vertical power feeds are usually provided. The all-gear feed mechanism used on the Cincinnati milling- machines is shown in detail in Figs. 445 A and B and 446 A and B. By means of the sliding gear in the upper gear box, two changes of speed are given to the vertical shaft for each speed of the spindle. The vertical shaft through the pair of lower bevel gears drives the two feed gears which in turn drive the two feed cones which run loose and independent of each other on their shaft. The large feed gear meshes with the small gear on one cone and the small gear meshes with the large gear on the other cone. The intermediate gear by means of a suitable mechanism may be made to gear with any one of the cone gears, thus giv- ing a wide range of feed changes. In changing feeds the upper lever, 446 A, is placed in the extreme left-hand position. This throws the intermediate gear, Fig. 446 B, back an amount suf- ficient to clear the cone gears. By placing the lower lever in position indicated for the desired feed, the intermediate gear will be placed opposite the proper gear on the cone. Moving the upper lever to the right engages the gears. The variations in the rate of feed obtained give nearly a uniform progression. The dividing or universal head is the part of the universal MILLING MACHINES. 323 machine with which the beginner usually has the most trouble in familiarizing himself. A dividing or indexing head in its simple form, and as usually used on the plain milling machine, is shown in Fig. 447. With the tailstock shown it comprises what is commonly known as a pair of index centers. Suitable lugs on the bottom fit neatly in the neck of the T slots in the work table, thus preserving the alignment of head and tail spin- dles. The head spindle is capable of rotation only. It carries FIG. 445A. Spindle of Machine FIG. 445B. 324 MODERN MACHINE SHOP TOOLS. a worm gear which is operated by the worm and crank shown. The ratio between worm and gear is, on all indexing heads, one to forty. In the one illustrated there are 80 teeth in the gear and a double thread on the worm. It is therefore neces- sary to make 40 turns of the crank and worm to make one turn FIG. 446A. FIG. 4468. MILLING MACHINES. 325 of the gear and spindle. The crank moves over a carefully- divided dial which is secured to the head. A small pin, ad- justable radially in the crank, may be s'et to engage in the holes of any of the circles. As it is not desirable to have the index plates too large in diameter or the holes too small, several plates are necessary in order to get the range of divisions us- ually required. With the one shown three plates are finished, making all divisions up to 50, all even divisions to 100, with many of the uneven divisions between 50 and 100, and many even and uneven divisions above 100. The sector serves to assist in counting the number of spaces between the holes and can be adjusted to include any desired number of spaces between its two radial arms. As much of the miscellaneous dividing work done on an FIG. 447. index head is for 2, 3, 4, 6, 8, 12 and 24 parts, a more rapid means of obtaining these divisions than by turning the worm is frequently applied. In the centers shown, there are 24 holes, equally spaced, in the face of the worm gear, with a substantial pin arranged to engage in them. When dividing by these holes the worm is dropped out of mesh with the gear. The universal head is a more complicated piece of mechan- ism. In Fig. 448 are shown side and end sectional views of the Brown & Sharpe universal dividing head. A side view is shown in Fig. 449. The worm gear B is attached to the spindle, and a side shaft carries the worm A. The spindle head is mounted in a suitable housing and can be elevated through an angle of 90 degrees and firmly clamped in any position. The spindle may also be depressed through a few degrees. The universal head, as made by some builders is capable of spindle settings at any angle within o and 180 degrees. When used for plain indexing the worm can be disengaged 326 MODERN MACHINE SHOP TOOLS. from the spindle gear and the required division obtained by means of the index plate C, which is locked in position by the pin D. As only a limited number of divisions can conveniently FIG. 448. FIG. 449. be obtained in this way, the usual method is by means of the regular index plate I. The crank J is secured to the worm shaft, and the sector S is MILLING MACHINES. 327 held by a spring between the dividing plate and the crank witft. just enough friction to keep it in position when set. The sleeve to which the index plate I is secured, carries a gear on its inner end which meshes with another gear on the axis R and about which the head rotates in setting to different angles. This latter gear meshes with a third gear on the same axis and secured to the upper of a pair of spiral gears, which transmit the motion from the train of gears leading from the table feed screw. A post may be drawn out from the head and caused to engage in a suitable notch in the back of the plate, or, in cases where the holes are drilled through the plate, in one of FIG. 451, FIG. 452. the holes. This secures the dividing plate from rotation and divi- sions on the spindle are obtained in the same manner as described above. When it is required to rotate the spindle while the work is being operated upon by the cutter, 'as is the case in the cutting of spirals, a geared combination between the worm spindle and the table feed mechanism becomes necessary. The milling machine is capable of receiving a large variety of attachments for performing special operations, or regular opera- tions with greater facility than can be had with the machine in its standard form. The vise is a regular attachment on all universal machines 328 MODERN MACHINE SHOP TOOLS. and plain machines of the column pattern. It is of two standard forms ; plain, as shown in Fig. 450, and swivel as shown in Fig- 451. The plain vise is provided with tongues to fit the wards in the work table and can be readily set with the jaws parallel with or at right angles to the spindle. It cannot, however, be con- veniently set at any other angle. The swivel vise has a gradu- ated base resting on a plate which is tongued and bolted to the wards in the table. The swivel vise is very convenient for angu- lar milling. A special tilting vise shown in Fig. 452 is, with its tilting jaws and swivel base, well adapted to the milling of a large variety" of angular surfaces. In all milling machine vises the movable jaw is accurately fitted and gibbed to the body, and the jaw faces, which are usually made of soft steel, are secured to the jaws by means of screws. The surface of the jaw faces should be kept true and smooth, as they will then hold finished work surfaces true for the cut and without injury to the work. Extra jaw faces hardened and with roughed surfaces may be used for holding forgings, castings and rough work. For the holding of special and irregular work special formed jaw faces may be substituted for the regular ones. As the universal dividing head is a part of the universal milling machine, it is not considered as an attachment. The plain index head already described under Fig. 447, however, is strictly a milling machine attachment. A first-class, three- jawed universal chuck fitted to the spindle of the index head is a very necessary accessory to the machine, as much of the work to be operated upon can or must be held in the chuck. The vertical spindle milling head shown in Fig. 453, when ap- plied to the plain or universal machines, converts them into verti- cal spindle machines. These heads are supported on the overhang- ing arm, and the nose of the spindle bearing. The vertical spindle is driven from the main spindle by bevel gears. A graduated index enables it to be set at any desired angle from the vertical, thus making it possible to mill many angular sur- faces with a plain end or shank milling cutter. These attach- ments are very convenient for the cutting of T-slots, key seating and profiling, as well as angular work. Another attachment, termed a universal milling attachment, is shown in Fig. 454. This has in addition to the vertical spindle an auxiliary one at right angles to it and driven from it by means of spiral gears. With this auxiliary spindle set parallel with the surface of the MILLING MACHINES. 329 FIG. 453. FIG. 454. 33O MODERN MACHINE SHOP TOOLS. work table and its line of travel, it makes a convenient rack cut- ting attachment. In connection with the spiral head on the uni- versal machines, it can be used to advantage in cutting spirals of large spiral angle, as the axis of the cutter can be set to the spiral angle instead of the work table. The auxiliary spindle can readily be removed when not in use, leaving a simple vertical milling attachment. Attachments of this class become of special value in shops when the amount of work that can be advantage- ously done by vertical milling does not warrant putting in a verti- cal milling machine. In Fig. 455 is shown a circular milling attachment. It con- sists of a circular plate gibbed to a round base and provided with a worm gear into which the feed worm meshes. The base clamps to the table of the milling machine and the work is secured to FIG. 455- the top of the circular table, suitable T-slots being provided for the clamp bolts. This attachment is of special value on the verti- cal milling machines and in connection with the vertical milling attachments on the column pattern plain and universal machines. It may be provided with an automatic feed, which increases materially its usefulness where a considerable amount of work is to be done on it. This attachment can, when the table is suit- ably gibbed to the base, be clamped to a substantial right angle knee plate and the faces and periphery of work, as gear blanks, pulleys, etc., successfully milled with cutters on the main spindle of the machine. For this class of work an attachment similar to the one shown in Fig. 456 is best adapted. The construction of this attachment is evident. As shown, it is arranged to .carry two blanks to be operated upon at the same time, the rims being com- pletely finished at one rotation of the work. MILLING MACHINES. 331 It is frequently desirable to use cutters of small diameter and requiring high rotative speed in the larger sizes of milling ma- chines. As the spindle speeds are altogether too slow for this FIG. 45 d. FIG. 457- purpose, high speed milling attachments, one of which is shown in Fig. 457, are provided. The attachment consists of a frame which fits the front face of the column and carries a light spindle for receiving the small -cutters used. On the inner end of this spindle is a small pinion 332 MODERN MACHINE SHOP TOOLS. which meshes with an internal gear screwed on the nose of the main spindle. A rack-cutting attachment is shown in Fig. 458. A device similar to this is necessary when racks of any considerable length are to be cut on a milling machine, as the motion of the table in line with the spindle is not great, and the distance the cutter can be set from the nose of the spindle is also small. With the at- tachment shown, the length of the rack section that can be cut at one setting is Jimited by the longitudinal travel of the table. In the device shown, the frame is securely attached to the front face of the column, and the cutter spindle driven by a suitable chain of gears. The rack blank is clamped in the special vise FIG. 458. shown, and the depth and settings for each cut are obtained by means of the graduated dials on elevating and longitudinal screws. The feed is in and out by hand, or automatically, if the machine is provided with automatic lateral feeds. The spiral cutting attachment shown in Fig. 459 is adapted, in connection with the plain milling machine, to the cutting of spirals. It frequently happens that the amount of spiral milling to be done in a shop would . not warrant putting in a universal machine, and in such cases the attachment shown serves its pur- pose admirably. It consists of a circular base, carrying a suitable frame in which a work table is gibbed. The frame is preferably detachable from the base, graduated and capable of being clamped at any desired angle with the spindle of the machine. The work table carries a head and tail stock for supporting the work. The MILLING MACHINES. 333 head stock spindle carries at its outer end a bevel gear which revolves upon it. The rear face of the bevel gear is provided with circles of drilled holes, similar to an index plate. A radial arm keyed to the spindle carries a pin which engages in the holes of the plate and through which the drive is carried from the FIG. 459. gears to the spindle. Tlte balance of the gear combination is a suitable system of change gears substantially as described in con- nection with the universal dividing head. A worm .feed operated by hand is usually provided on attachments of this class. An attachment for the cutting of cams is shown in Fig. MILLING MACHINE SPINDLE FIG. 460. 460. It consists .of a base plate A, which can be bolted to the work table of the milling machine, and a head stock which is mounted on the slide C. C is gibbed to slide in the base plate. The head stock carries a spindle with a worm gear G on its outer end. The worm S engages the gear and the spin- dle is given a slow feed rotation by the pulley P or a crank which 334 MODERN MACHINE SHOP TOOLS. can be substituted in its place when power feed is not available. R is a small roller mounted on a suitable support which extends upward from the base plate. The master cam F, which is of the same contour as the required cam, is mounted on the spindle, as is also the work. The work table of the milling machine is ad- justed vertically and laterally so as to bring the center of the roller R and the milling cutter in the same axial line. A weight W connected by a rope, over a sheave at the end of the table, with the slide C, holds the master cam constantly in contact with the roller as the spindle and work are rotated. The master cam is usually of the exact size of the required cam, and in that case, the roller R should be of the same diameter as the milling cut- ter. If the master cam is larger or smaller than the required FIG. 461. cam, the diameter of the roller, for the same diameter of the cutter, must be decreased or increased as the case may be, in order that the sum of the master cam and the roller radii will at all points equal the sum of the required cam and the cutter radii. For the cutting of cylindrical cams the spindle must stand at right angles with the cutter spindle. The attachment is so constructed that the spindle head can readily be secured in such a position on the slide plate C. An oil pump for supplying a lubricant to the cutter and work when milling steel can properly come under the head of attach- ments. In Fig. 461 is shown such a pump. It is attached to a suitable reservoir and driven from an independent countershaft. In Fig. 462 is shown a slotting attachment for the milling machine. The guide casting is secured to the overhanging arm MILLING MACHINES. 335 at its upper end, and at the lower end is clamped to a yoke casting which is secured to the front face of the column. The guide may be set at any angle between o and 10 degrees either side of the center line. Motion is given the slide by a crank screwed on the nose of the spindle. The stroke of the slide can be adjusted to any required length between o and 2 inches. The tools, which FIG. 462. are provided with y 2 -mc\\ round shanks, are firmly clamped in position. In the use of the attachment both the longitudinal and transverse table feeds are available and by means of the gradu- ated dials very accurate readings can be made. This attachment is specially valuable in the forming of special tools, jigs, dies and templates. CHAPTER XXIV. MILLING MACHINE CUTTERS. The milling of metallic surfaces requires a rotating cutter pro- vided with one or more teeth having an edge and temper suited to the nature of the material operated upon. As to construction, milling cutters may be divided into the two classes solid and inserted tooth. All small and most of the medium-sized cutters may be brought under the first class, as they are made from a single piece of tool steel ; but when the dimensions become large the cost of the steel is an important point, which, together with the risks incident to the proper, hardening of such large masses of tool steel, warrants the greater expenditure of labor usually necessary in the making of inserted tooth cutters. The inserted tooth cutter has only teeth of tool steel, the core or body being of cast iron or mild steel. As to classification, milling cutters naturally fall under four heads, as determined by the four distinct varieties of work per- formed, as follows : Axial those cutters used for milling plain surfaces which are parallel to the axis of rotation of the cutter; Radial those which will mill plane surfaces at right angles to the axis ; Angular those used in milling plane surfaces at any angle other than 90 degrees with the axis; and Form cutters, used for machining all curved or irregular surfaces. In Fig. 463 A is shown an axial or plain milling cutter, as it is usually called. It has teeth on the cylindrical surface only, which, when the cutter exceeds about one-half inch in thickness, are cut spirally, as shown in the figure. When these cutters are less than three-sixteenths of an inch in thickness, they are called metal slitting saws, and the sides are ground slightly dishing, which serves to. give the teeth clearance in the grooves they cut. This is of much importance when the cut is deep, as is frequently the case when using the metal slitting saw. The spiral teeth on these cutters are necessary for the follow- ing reasons. If the teeth are straight, each tooth as it comes into action would strike square against the work, producing a- shock and consequent springing of work and cutter arbor; and as each tooth leaves the work the sudden release of pressure MILLING MACHINE CUTTERS. 337 causes reverse spring. If the cut is not deep, and only one or two teeth cutting at a time this effect will be more marked than when a greater number of teeth are in action, and the effect of the spring will be clearly shown by the waved and uneven condi- tion of the surface produced. If, on the other hand, the teeth are arranged spirally they will come into and leave the work gradu- ally, thus avoiding shock and, what is very important, give a shearing cut. Plain milling cutters with nicked teeth, an example of which G. 463A. FIG. 4636. is shown in Fig. 463 B, are especially adapted for heavy milling. The breaking up of the chip by the nicked tooth makes possible a very much heavier cut than can be taken with the ordinary form of continuous tooth. When provided with teeth on their faces, these cutters become what are called radial, face, side or straddle mills. When the FIG. 464. FIG. 465. teeth are on but one face and the cutters used for straddle work, they must be cut right and left, as otherwise one cutter would run backward. The cutter shown in Fig. 464 can be run in either direction, as it has teeth on both faces, and constitutes the form usually used. These cutters, when worked in pairs, and espe- cially for shoulder work, as shown in Fig. 465, should be care- fully ground to the same diameter. 338 MODERN MACHINE SHOP TOOLS. The end or shank milling cutter shown in Fig. 466 is virtual- ly a radial mill of small diameter provided with its own inde- pendent shank. These cutters are seldom made larger than i l /2 inches in diameter. Their form permits the small diameters, which are so necessary in much of the fine milling work. These cutters are made right and left handed, and frequently the teeth on the circumference are cut spirally, as shown, straight teeth, however, being most used. The advantage of the spiral tooth for the end mill when used as an axial cutter arises from the de- FIG. 466. creased Shock and vibration due to the steady shearing cut, which reduces the tendency of the tool to jar loose in the spin- dle or collet bearing. The direction of the spiral must be such that the end thrust of the cutting pressure tends to force the shank into, rather than draw it out, of its bearing. In a right- hand mill the angle of the spiral would be left-handed. If it is desired to mill a slot with the end of the shank cutter, shown in Fig. 466, which does not start at the edge of the work, a hole must be drilled into the work of a diameter at least equal FIG. 467. to the diameter of the space without teeth in the end of the cutter, as otherwise the cutter could be made to enter only a depth equal to the depth of this space, and could not then be moved along the work. A form of cutter shown in Fig. 467 overcomes this difficulty, as the inner ends of the radial teeth are provided with cutting edges, which enables them to cut their way out when moved along the work. The length of these cutting edges limits, however, the depth to which the cutter may be made to enter the work at any one setting. In this form of cutter a smaller number of teeth must be used. The end mill may be placed MILLING MACHINE CUTTERS. 339 under either of the two first classes, as it may be used for ma- chining surfaces which are either parallel with or at right angles to the axis of rotation. The standard T-slot cutter is shown in Fig. 468. This tool is used in cutting the slots, a section of which is shown in Fig. 469, the central portion of the slot having been previously removed. In the cutter shown, alternate teeth cut on the inner and outer edges. These face teeth, however, have little work to do, and are FIG. 468. on some cutters omitted, the faces being ground slightly dishing, to provide the necessary clearance. T-slot cutters are made 1-32 of an inch over size in diameter, to allow for grinding. They are usually made left-hand, as shown in the figure. In Fig. 470 is shown an angular cutter. These cutters are us- ually provided with face teeth, as shown in the figure. For straight work the face teeth may be omitted, the face being ground slightly concave. When the character of the work re- FIG. 469. FIG. 470. FIG. 471. quires the cutter to be used as an end mill, a threaded hole is substituted for the plain one and the cutter held on the end of a suitable screw arbor. These cutters are regularly made with 40, 45, 50, 60, 70 or 80 degree angles, either right or left-handed. In all of the cutters above referred to, the teeth are sharpened by grinding from their top edges, and since the surfaces milled are either planes or warped planes, the contour of the surface milled is not changed by so grinding the cutter. In form mill- 340 MODERN MACHINE SHOP TOOLS. ing, however, the teeth, if so ground, would lose their outline and would therefore not produce correct work after being sharp- ened. This difficulty is overcome by the use of the formed cut- ter, an example of which is shown in Fig. 471. This cutter is sharpened by grinding from the front face, A, of each tooth. The cross-section of each tooth is the same from front to back faces. The back face, B, being somewhat nearer the center of the cutter than face A, provides the necessary tooth clearance. The sharpening of this cutter simply reduces slightly its diam- eter, which has no effect on the contour of the machined surface, the cutter being adjusted for depth after each grinding. The original application of this method of forming the teeth was on gear cutters, but it has since been adapted to nearly all FIG. 472. classes of irregular outline cutters used for form milling. Fig. 472 shows at A a new gear cutter and at B a similar cutter, which has finished complete, at one cut in cast iron, gear teeth aggre- gating a total length of 7,472 feet, the necessary grinding to keep the cutter in proper working condition having reduced the teeth to the shape shown in the figure. The last tooth cut was, how- ever, quite as accurate in form as the first. In Fig. 473 is shown a group of formed milling cutters. The names of these cutters, as given below, refer to the special class of work each is designed to perform. A is a sprocket wheel cutter ; B, cutter for fluting reamers ; C, for grooving taps ; D, for cutting twist drills ; E, circular cornering cutter ; F, concave cut- ter, and G, a convex cutter. The hob cutter, Fig. 474, used for cutting the teeth of worm gears, has formed teeth. Angular cut- ters with formed teeth, Fig. 475, are now quite extensively used. MILLING MACHINE CUTTERS. 341 They are the only cutters regularly made with formed teeth that are used on work not classed under the head of formed work. The method by which the relieved teeth are produced is brief- ly outlined in the following. The cutter which is to form the teeth is an exact negative in outline to the outline of the required tooth. The form of the space required is very carefully laid out with a fine scriber on a piece of smoked sheet zinc. The zinc FIG. 474 FIG. 475 is then cut away, forming a template, to which the cutter is care- fully fitted ; the final fitting of the cutter to the template being made by oil-stoning after it is tempered. This work requires the best of skill, and when a cutter is once perfectly formed, other 342 MODERN MACHINE SHOP TOOLS. cutters may be made from the first milling cutter it produces. These cutters are made on the end of a, bar of steel and are as thin at the cutting end as strength will permit their being made. Take, for example, the gear cutter A, Fig. 472. It is first blanked to nearly the exact dimensions, the spaces which separ- ate the teeth cut and the blank secured on a rigid arbor, which is driven in a special machine at a slow rate of rotation. In front of the blank is mounted the outlining cutter in such a man- ner that it is given a small in-and-out motion once per revolu- tion for every tooth to be cut. When the cutter begins to cut at the face A, it is farthest from the center of the blank, and as the tooth advances to the face B, the cutter moves toward the center, thus cutting the tooth deeper at B than at A. While the blank is turning through the space to the next tooth the cutter FIG. 476. backs quickly to its outer position and repeats its motion for each tooth, until all are properly formed. Relieved tooth cutters are made from solid stock as large as seven inches in diameter and six inches in length. It is usual to make these large cutters in sections, as shown in Fig. 476. Such combinations of cutters are termed gang mills, and may frequently be made up largely of standard cutters. In the one shown, only the middle section is a formed cutter, the balance being regular stock cutters. What is known as the fly cutter is the simplest of the formed mills, and makes a cutter well adapted to small jobs of special work, where the expense of a regular form cutter would not be warranted. The fly cutter consists of a single tooth mounted in an arbor. In making the cutting tooth the stock is set slightly back from the center, and is then turned in a lathe to the desired outline, tempered and reset in the arbor, this time with a liner behind it, which throws it forward until the front face comes radial, and Hves the tooth the desired clearance. MILLING MACHINE CUTTERS. 343 As already indicated, the inserted tooth is virtually the only practical method of making very large milling cutters. The prin- cipal difference in cutters of this class lies in the form of tooth and the method of securing it in the head. Inserted tooth cut- ters necessarily have fewer teeth per inch of circumference than solid cutters. This, however, is considered by many as an ad- vantage. It certainly is on some classes of work, as when too many are used the cut per tooth is too fine, the metal being scraped rather than cut away, which produces excessive friction with a tendency to glaze the surface and rapidly dull- the cutter. In Fig. 477 is shown a form of axial milling cutter, which is used for heavy slabbing work. It is made in any required size and constitutes a very efficient tool for heavy work. The teeth are round pieces of tempered steel driven firmly into the soft PIG. 477- core, and then ground in place. It is found that cutters of this class do smoother and better work when the teeth are irregu- larly spaced. A radial mill constructed along these same lines is shown in Fig. 478. Here the teeth are held in position by set screws, and may be adjusted out when much worn. A plain disk may be substituted for the armed head, the set screws put in the back and more cutters used if desired. The cutting edges of the teeth should project beyond the circumference as well as the face of the disk. Cutters of this character are frequently made of very large diameter. Fig. 479 illustrates an inserted tooth plain mill, in which the teeth are nicked. The teeth are arranged spirally, and. the method of securing them in the head is apparent. The makers of this cutter also make plain solid milling cutters with the divided tooth. Fig. 480 shows a pair of mills, quite similar in construction, in 344 MODERN MACHINE SHOP TOOLS. which the tapered pins spread the stock an amount sufficient to grip firmly the teeth. In the cutter shown in Fig. 481 the teeth are pinched in their seats by drawing down with the screws the FIG. 480. FIG. 481. FIG. 482. FIG. 483. tapered bushings. This cutter is a form of large end mill to be carried on a special arbor. In Fig. 482 is shown a shell end mill- ing cutter. End mills larger than i l /2 inches diameter are made in this form with either straight or spiral teeth. The hole is MILLING MACHINE CUTTERS. 345 parallel, the drive coming on a key which engages the keyway cut across the butt of the mill. The inserted tooth is well adapted for use in cutters that must be kept up to fixed dimensions, as the teeth when dull can be set out and reground to the exact required dimensions. When in radial cutters of the class shown in Fig. 464 a fixed thickness must be maintained, they are made as shown in Fig. 483 and known as interlocking cutters. After each grinding it is necessary to put thin washers between the sections to make up for the reduction in thickness, due to the grinding. With large built-up cutters, interlocking sections are generally used where fixed widths must be maintained. The diameter of a milling cutter should be as small as the work will permit. The small cutter requires less power to drive it, cuts smoother, keeps sharp longer, makes its cut on a shorter length of feed than a large cutter, and is lower in first cost. Plain or axial cutters can usually be of small diameter as the cut is seldom deep, and the surface machined requires length rather than diameter of cutter. This is, however, reversed in the face or radial mill, where the diameter of cutter depends entirely on the width of the surface to be milled. Milling cutters are usually made with the front faces of the teeth radial, thus giving no angle of rake. The angle of clear- ance should be about 3 degrees ; the width of the top of the tooth being, before the first grinding, from .02 to .04 of an inch wide. Too much stress cannot be laid on the importance of. keeping milling cutters sharp, and especially the formed cutters. When a cutter starts to dull it begins to crush and remove by abrasion rather than cut the stock. This produces excessive friction be- tween the teeth and work, and unless the cutter is ground promptly, its edges will be entirely lost. In the case of a formed cutter, when dull, a few revolutions will often so badly snub the teeth that a fourth or even more of each tooth will be ground away before their perfect section is reached. This is a tedious process, and unless great care is exercised is very apt to result in destroying the temper on one or more of the teeth. The grinding of formed cutters requires an emery wheel of thin, dished section with a straight face at the edge. The tendency is to grind too much from the outer part of the tooth face, thus making a negative rake angle and poor cutting teeth. For grinding the ordinary form of tooth, a thin wheel of quite large 346 MODERN MACHINE SHOP TOOLS. diameter should be used. If the diameter is small the top of the tooth will be ground concave to such an extent that the cutting edge will be materially weakened. By so mounting the wheel that its axis is not parallel with that of the cutter it will grind the top of the tooth flat. This is not ordinarily done, however. The emery wheel used for this purpose should be a free cutting one, and not too fine, as a fine wheel glazes and burns the delicate edge of the tooth. Its grinding face should be thin, and the emery about No. 80. Milling cutters are driven from the machine spindle in three ways. Large cutters are frequently threaded directly to the nose of the spindle. This constitutes a most rigid and very satis- factory drive. They may also be carried on stub arbors, which FIG. 484. are either a part of or separate from the cutter, and lastly, upon through arbors, which may be supported on the outer end. The small cutters of the end mill class are usually provided with a taper shank and a tang for driving, as shown, for example, in Fig. 468. The Brown & Sharpe taper of ^ inch per foot is the taper usually given the shanks. These shanks fit either di- rectly in the spindle bearing of the machine or in the collets which serve as reducers. In Fig. 484 are shown two examples of milling machine col- lets. The one drives from a tang, the other from a flatted collar, which engages in a slot cut across the nose of the spindle. These collets are quite similar to drill sleeves. Examples of stub arbors are shown in Fig. 485. The shell end mill arbor shown at A is used to carry cutters of the class shown in Fig. 482 with parallel holes. The arbor shown at B has a tapered nose and drives the cutter by the key shown. The cutter is driven tightly on the nose of the arbor and the flat head MILLING MACHINE CUTTERS. 347 screw in the end prevents it from working loose. The nut shown runs over a fine pitch thread and is used for forcing the cutter off. Cutters of the class shown in Fig. 481 are usually carried on an arbor of this character. In the case of milling cutters with threaded holes, a screw arbor must be used. If the cutter is of small diameter and the work it performs light, a plain threaded nose which allows the cutter to screw up squarely against a FIG. 485. shoulder is satisfactory. If, however, the cutter is large and its work heavy, it will tighten so hard that difficulty is experienced in starting it loose. In cases of this kind an arbor similar to the one shown in Fig. 486 is well suited. The cutter screws onto the nose of the arbor at A. B is a clutch collar which slides on the arbor and over a feather key D, which prevents it from rotat- ing. E E is a nut which threads over the collar of the arbor. FIG. 486. In applying the cutter the nut E E is screwed close 'up to the shoulder and the clutch collar slid back as far as possible. The cutter is screwed on until its face touches the keys C C, which are a part of the collar B. The key seats in the back face of the cutter are placed opposite the keys C C, and the clutch collar moved forward engaging the keys. The nut E E is backed up against the clutch, holding all parts firmly. In removing the cutter it is simply necessary to slack the nut and draw back the 348 MODERN MACHINE SHOP TOOLS. clutch, thus leaving the cutter free to turn off. Threaded cut- ters, when left-handed should have left-hand threaded holes and when right-handed should have right-hand threads in the hole, FIG. 487. as otherwise the pressure of the cut will tend to loosen the cutter from its arbor. In Fig. 487 is shown a spring chuck collet used on the mill- FIG. 488. ing machine for holding small cutters having parallel shanks ; an example of such a cutter being shown in Fig. 488. Milling machine cutter arbors, an example of which is shown in Fig. 489, are fitted to the spindle bearings and driven in the FIG. 489 same manner as the collets. The extended portion of the arbor is ground cylindrically true and provided with a nut at or near its outer end for clamping the cutter between the washers. The arbor washers are of assorted lengths in order to accommodate MILLING MACHINE CUTTERS. 349 cutters of different thickness. When the overhanging arm sup- ports the bar at the end, a suitable bearing is provided on the end of the arbor. For supporting the bar midway in its length, a collar somewhat larger in diameter than the 'others fits a suit- able bushing in the overhanging arm. Arbor nuts should be right or left-handed, depending upon the direction of rotation, as a slipping cutter should tend to tighten rather than loosen the nut. Cutters of small diameter can usually be driven by the friction between washers and cutters alone. Larger sizes, how- ever, should be keyed to the arbor and for this purpose a spline is cut the full length of the arbor. In putting collets and arbors in their bearings in the spindle, both surfaces should be wiped clean and dry and driven snugly together. A soft hammer or block of hard wood should always be used to drive with. CHAPTER XXV. MILLING MACHINE WORK. Dividing a circle into equal parts by means of the plain or universal spiral head on the milling machine is known as "index- ing." When the index plate is secured to the spindle as at C, Fig. 448, and the divisions obtained by rotating the plate and spindle together, it is known as direct indexing. When the spindle is rotated by means of suitable geared connections and the index plate remains normally stationary the term indirect index- ing is usually applied. The indirect method can be classified under three heads, simple, compound and differential. Since, as shown in Fig. 448, forty turns of the crank J and worm A are required to make one turn of the spindle the follow- ing rule for simple indirect indexing may be given. Take 40 as the numerator and the required number of divisions as the denominator, and reduce. Thus, it is required to cut 32 teeth in a gear. 40-32, or i 8-32 of one revolution of the crank will make one division on the blank. The sector should be set to include 8 spaces (9 holes) on the 32 circle, or 4 spaces on the 16 circle could be used. If 108 teeth were required, then 40-108 = 20-54= 10-27, or 10 spaces on the 27 circle would give the required division. This ratio is not affected by multiplying or dividing both numerator and de- nominator by the same number. Therefore after reducing as low as possible, if that denominator does not correspond to the number of holes in any circle available, we can multiply or divide it by any number that would give us the proper number, also treating the numerator in the same manner. For example, 25 divisions require 40-25 = I 3-5 turns. We can use any circle divisible by 5, as 20, or 4 times the denominator. Multiplying the numerator by 4 also, gives 12 holes in the 20 circle. It frequently becomes necessary to divide a circle into a num- ber of parts which can not be obtained in the regular manner because a circle of the required number of holes is not on the index plate. If a circle for making one-half the required di- visions is on the plate, every other tooth can be cut; the work can then be rotated through one-half of one space and the bal- MILLING MACHINE WORK. 351 ance of the teeth cut. Thus if 96 teeth are required and no circle available, set for cutting 48 teeth, which gives 10 spaces in the 12 circle or 15 spaces in the 18 circle. After cutting once around, move the pin through 7^/2 spaces, and being careful that it is not moved, cut partly through on the tooth; stop the ma- chine without throwing out the feed and carefully adjust the driver to make up for the y 2 space, which brings the pin into another hole, and proceed with the cutting as for the first half. With care in the adjustment, the error in making the ^ setting will be slight. A method of compound indexing can be used to excellent ad- vantage for obtaining with the regular plates many divisions that may not be had in the regular manner. The application of this method requires plates with the holes drilled through, and the back pin R, Fig. 448, radially adjustable. The method con- sists in indexing forward on the front side of the plate in the regu- lar manner and adding to or subtracting from this movement an- other movement indexed from the back side of the plate. From tables calculated by W. Gribbons and given complete in ''Con- struction and Use of Milling Machines," a treatise published by the Brown & Sharpe Mfg. Co. To .divide into 91 parts, index forward, on the front of the plate, six spaces on the 39 circle; then index forward on the back of the plate, 14 spaces on the 6 14 2 14 98 + 182 280 40 49 circle. This gives 1 = 1 = - 39 49 13 49 637 637 91 or the equivalent of 40 holes in a 91 circle. If 99 spaces are required, index forward 15 spaces on the 27 circle and backward '5555 5 spaces on the 33 circle. This gives - 27 33 9 33 165 45 120 40 = = , or the equivalent of 40 holes in a 99 297 297 99 circle. For the two cases above given the method is exact. For a large number of the divisions practically possible the method is approximate. For example, to divide into 212 parts. 34~47 turns forward plus 6-49 of a turn forward gives 211.9995 teeth, a division sufficiently accurate for all practical purposes. In this case the teeth are not successively cut, 17 turns of the work- being required in which to catch all of the divisions. 352 MODERN MACHINE SHOP TOOLS. The above method is unique and will frequently be found of great value. Care must be exercised in making the moves, as the chances for mistakes are great, especially so as the back plate moves necessitates counting the holes each time, a sector not being provided. The new method of differential indexing, as applied by the Brown & Sharpe Mfg. Co. to all their universal spiral heads, is an exact method which not only overcomes the chances of error in the compound method, but is much more convenient. The spiral head is shown in Fig. 490, also in sectional views in Fig. 448. Referring to these figures, an extended shaft from the spindle carries a gear E, which through the idler D and the FIG. 490. gear C communicates the motion of the spindle to the gear train Fig. 449, connected with the index plate I. When pin P, Fig. 448, engages a hole in the plate the whole becomes a locked mechanism. Withdrawing P unlocks the mechanism and the rotation of the crank J, worm A and spindle causes index plate I to rotate either right or left handed, depending on whether one idler, D, or two are used, and the amount of motion relative to the crank is governed by the gears used. If gears E and C are of the same diameter, one turn of the spindle will make one turn of the index plate. This will require 40 turns of the crank J and as the rotation, due to using one idler, is in the same direction, the pin P has passed a given point on the index, but 39 times, thus giving 39 as the spacing number. MILLING MACHINE WORK. 353 Had two idlers been used the rotation would have been in oppo- site directions and 41 would have been the spacing number inas- much as the plate has gained a crank rotation. The manufacturers furnish a complete table of change gears for dividing all numbers up to 360. Take for example the division 317 referring to the table gear 64 should be used on the worm C, and gear 24 on the spindle E, with one idler. The ratio of worm to spindle rotation is f f = ft and as the plate and crank ro- tate in the same direction, the spindle loses ft of one revolution for every 40 revolutions o'f the crank, or 3 full revolutions in 320 turns of the crank giving 317 as the number of divisions. Set the sector to give J/s turn of the crank, or 3 spaces on the 24 circle. When the required ratio would give gears too large or too small in diameters they are compounded, thus keeping diameters within reasonable limits. Spirals cannot be. cut when the head is geared for differential indexing. For correct indexing there should be no slack or back lash in any of the parts. It is advisable, however, not to carry the crank and its pin past the hole, but to bring it up to the hole without the necessity of carrying it back, which would serve to let any slack affect the accuracy of the division. It is advisable, in order to prevent confusion, for the operator always to rotate the crank in the same direction, unless there is some special rea- son for doing otherwise. The radial arms of the sector are held in position, with refer- ence to each other, by friction. In rotating them over the face of Jhe plate, always take hold of the arm that strikes the pin, as there will then be no danger of changing their relative position through striking the pin with considerable force. In Fig. 491 is shown an end view of the dividing head, de- scribed in Fig. 448, secured on the end of the work table. The spindle S carries a spiral gear at its farther end, meshing with the upper spiral gear shown in Fig. 449. The gear marked "screw" is keyed to the feed screw and through the compound idlers transmits its motion to the gear on worm and through the spirals and spur gear connection to the worm and worm gear. When the spindle is so geared the post R is disengaged from the plate and the worm shaft is driven from the dividing plate through the pin P and the crank J. It is obvious that when the feed screw is at rest, the plate I is held without the pin R and the re- 354 MODERN MACHINE SHOP TOOLS. quired divisions obtained by carrying the crank over the plate in the usual manner. With all universal machines a table of change gears is pro- vided for determining the proper gears to use for producing a large number of spirals of different pitch. Any desired pitch of spiral can be obtained by making special gears, and a good many pitches not given in the table may be produced by other combi- nations of the regular gears than those given. The proper gear FIG. 491 for a required spiral pitch may be readily determined from the following considerations. The table lead or feed screws usually have four threads per inch. Assuming that number, if the gear of the screw had the same number of teeth as the one on the spindle S and was geared directly with it (that is, simple, not compound geared), then 40 turns of the screw would make 40 turns of the worm and one of the spindle; and as four turns of the screw are required per inch of the table motion, the pitch of the spiral would be 10 inches. If a spiral pitch of 6 inches was required, 6x4= .24, MILLING MACHINE WORK. 355 the number of revolutions the screw must make while the work rotates through one revolution. Then the ratio 24 teeth in driven gear 40 teeth in driving gear Put gear with 40 teeth on the screw and gear with 24 teeth on the spindle S. It is best when possible to use the simple gearing. If, however, the ratio is such that one of the gears would be extremely large or small, then the gearing should be compounded. For example, required pitch of spiral 32^ inches; 32^ X 4 == 130, or the revolutions of the screw per revolution of the work 130 No. teeth in driven .gear 40 No. teeth in driving gear As 130 would be a rather large gear and probably not furnished with the machine we could reduce the ratio to||, but this would also give numbers of teeth not usually furnished. It would then be necessary to compound. Resolve the ratio ^f^- into fac- tors ^-x-^ 3 . As these numbers are too low we can multiply both numerator and denominator by the same number, and we would have, for example, ^ x f = tt and V x i = if and as |-0 x || the ratio ^ we may use gears 40 and 52 as the driven gears. Either 20 or 32 can be placed on the screw and the other will be the inside gear on the stud. Either the 40 or 52 can be put on the worm shaft S and the other will be the outside gear on the stud. If any of the gears called for were not found in the regular set, the numbers could be changed by treating both numerator and denominator without changing the ratio. Thus in the last problem, if the last set did not contain a gear of 20 teeth, we could divide both numerator and denomi- nator by a common factor and multiply the results by a number that would give numbers corresponding to available gears. Thus in the ratio || divide both by 5 = = ' and multiply both by 6. This would give ||, which alters the numbers but does not change the ratio. In this manner it is usually possible to so manipulate the ratios that the exact or a very close approximation to the re- quired pitch can be obtained with the regular gears. The arrangement shown in Fig. 449 gives the proper rotation for cutting a right-hand spiral. If a left-hand spiral is required a reverse gear must be put into the series. This gear is carried on a suitable arm, and the gear marked 40 drives 72 through this 356 MODERN MACHINE SHOP TOOLS. gear, thus changing the direction of rotation of the worm shaft and spindle. In the cutting of all spirals the work table must be .set at an angle with the cutter's axis, an amount equal to the spiral angle of the work. For equal pitch of spiral this angle varies with the diameter of the work ; the larger the diameter the greater the angle. In the cutting- of any spiral the pitch of the spiral, the spiral angle, the number of teeth and the form of the .cutter must be known. Having this data, the work is placed between centers and the cutter brought over its center. The proper change gears for giving the required pitch are adjusted and the table swung toward the column the amount of the spiral angle. The rota- tion of the spindle must be left-handed for left-handed spirals, and right-handed for right-handed spirals, this change in di- rection of rotating being obtained by putting in or taking out an idle gear in the change gear mechanism. The proper rotative speeds and feeds are very important as they are the principal factors upon which the output of the machine depends. As the toughness and hardness of the differ- ent grades of the several metals varies so much, it is impossible to lay down any fixed rules to be followed. With cutters other than the most delicate the very fine feeds are to be avoided, as the cutting edges stand up better under a moderately heavy cut than when scraping the metal away. Milling cutters must be kept sharp. As soon as a cutter loses its keen cutting edges it dulls very quickly and does not produce smooth or accurate surfaces as it springs away from its work. A cutter must not be run backward when against its cut, as the teeth are not strong against a backing pressure and are apt to be broken off. For the standard carbon steel milling cutters, a surface speed of 30 to 40 feet per minute can be maintained on soft machinery steel, thoroughly annealed tool steel and wrought iron. In such cases, however, the cutters should be sharp and lubricated with screw cutting oil or some good compound. On cast iron cutting speeds of from 40 to 60 feet per minute can be maintained, de- pending on the hardness of the iron. On brass a speed of from 80 to 100 feet per minute is suitable. These speeds may, with cutters made of special air hardening steels, be materially in- creased. MILLING MACHINE WORK. 357 The depth of cut and rate of feed employed are dependent upon the hardness of the metal, its strength to resist the cut, rigidity with which it is held, and character of finished surface required. In general finishing cuts with plain axial mills are taken at quick speeds and fine feeds. With radial mills finishing cuts may be taken at coarse feeds, as the character of the cut due to the long cutting edge, does not show a waved or uneven sur- face. In the case of expensive gangs of cutters, and more especially on those where fixed dimensions necessitate great care in grind- ing, it is advisable to hold the cutting speed down somewhat. The following table will be found convenient for determin- ing the proper number of revolutions for cutters of different diameter to give cutting speeds up to 60 feet per minute. TABLE OF CUTTING SPEEDS. wtt 5' 10' 15' 20' 25' 30' | 35' 4 45' 50' 60' Diain. REVOLUTIONS PER MINUTE. X 38.2 76.4 114.6 152.9 191.1 229.3 267.5 305-7 344-0 382.2 458.7 X 30.6 61.2 91.8 122.5 I53-I 183-7 214.3 244-9 275-5 36.I 367.5 z /i 25.4 50.8 76.3 101.7 127.1 152.5 178.0 203.4 228.8 254-2 305.1 X 21.8 43.6 65.5 87.3 109.1 130.9 152.7 174-5 196-3 218.9 261.9 19.1 38.2 57-3 76.4 95-5 114.6 133.8 152.9 172.0 I9I.I 229.2 X 17.0 34.0 51.0 68.0 85.0 102.0 119.0 136.0 153-0 I7O.O 2O4.O X 15.3 30.6 45-8 61.2 76.3 91.8 106.9 122.5 1374 I53.I 183.6 y% 13.9 27.8 41.7 55-6 69-5 83.3 97.2 in. i 125.0 138.9 166.8 % 12.7 25.4 38.2 50.8 63-7 76.3 89.2 101.7 114.6 I27.I 152.4 X 1 1. 8 23.5 35-0 47-0 58-8 70.5 82.2 93-9 105-7 H7.4 I4I.O i /4 10.9 21.8 32.7 43-6 54-5 65.5 76.4 87.3 98.2 I09.I 130.8 i^ IO.2 2O.4 30.6 40.7 50-9 61.1 71.3 81.5 91.9 IOI.9 122. 1 2 9-6 ig.I 28.7 38.2 47-8 57-3 66.9 76.4 86.0 95-5 II4.6 2 /^ 8-5 17-0 25.4 34-0 42.4 51.0 59-4 68.0 76.2 85.0 IO2.O 2/2 7-6 15-3 22.9 30.6 38.2 45-8 53-5 61.2 68.8 76.3 91.8 2 /^ 6.9 13.9 20.8 27.8 34-7 41-7 48.6 55-6 62.5 69-5 83.4 3 6.4 12.7 19.1 25.5 31.8 38.2 44.6 51-0 57.3 63.7 76.5 3>^ 5-5 10.9 16.4 21.8 27-3 32.7 38.2 43-6 49.1 54-5 654 4 4.8 9.6 14.3 19.1 23-9 28.7 33-4 38-2 43-o 47.8 57-3 4/2 4-2 8.5 12.7 16.9 21.2 25-4 29.6 34-0 38.1 42.4 50-7 5 3-8 7-6 H-5 15.3 I9.I 22.9 26.7 30.6 34-4 38.2 45.9 5/2 3-5 6.9 10.4 13.9 17-4 20.8 24.3 27.8 3L3 34-7 41.7 6 3.2 6.4 9.6 12.7 15-9 19.1 22.3 25-5 28.7 31-8 38.1 7 2-7 5-5 8.1 10.9 13.6 16.4 19.1 21.8 24.6 27-3 32.7 8 2.4 4.8 7.2 9-6 II-9 14.3 16.7 19-1 21. 1 23-9 28.8 9. 2.1 4.2 6-4 8.5 10.6 12.7 14-9 17.0 I9.I 21.2 25.5 10 1-9 3-8 5-7 7-6 9-6 11.5 13-4 15.3 17.2 I9.I 22.8 The smaller milling cutters which are carried on an arbor are usually driven by the friction between their faces and the arbor collars. They should therefore be rotated in the direction 358 MODERN MACHINE SHOP TOOLS. which tends to tighten the arbor nut. With the large cutters which are keyed to the arbor the direction of rotation may be either way. For a given rotation of the cutter the direction of the feed should be such as to force the work against the cutter as shown at A, Fig. 492. When the rotation and feed are as above indicated, all slack or back lash between the nut and feed screw is taken up and the work is forced steadily to its cut. If the feed is as shown at B, the cutter tends to drag the work under it and as a result any slack whatever allows the work to move forward with an unsteady, irregular motion as the feed screw rotates. When the feed is as shown at A, the cutter teeth work from the bottom up, lifting the hard scale of castings and forg- ings rather than cutting down upon it, as is the case when the FIG. 492. feed is as shown at B. The keen edge of the cutter lasts much longer with the feed in the direction indicated at A. The under feed indicated at B has been advocated by some, but is generally considered as incorrect, as the wear on the cutter and the danger of accident from the work drawing under is much greater. With milling machines using the rack feed where the work table is held only when the feed is in, the most careful workman will some- times get into trouble if the under feed B is used. When the cutter is operating on the end of the work as shown at D, the feed should be up, as indicated by the arrow; if the work was on the other side of the cutter, the feed should be down. In this class of milling it is best to feed up, as that brings the pressure of the cut down upon the table and tends to close the joints of the table, saddle and knee, making the cut smooth and steady. When the table is to be fed vertically for MILLING MACHINE WORK. 359 work as shown at D, the table stops, provided with all milling machines, should be used and thus prevent any possibility of the work moving in or away from the cutter when correctly set. When it is necessary to use both sides of the cutter at the same time, as in Fig. 493, the direction of the feed should be deter- mined from a consideration of the amount of stock to be re- moved from the sides. If the rotation of the cutter is as indicated and the most stock is to be removed from the surface A, then the feed should be in the direction shown by the arrow. The cut on the upper surface then tends to retard the feed and the cut on the lower surface to draw the feed ; and since the cut on the upper surface is heavier than that on the lower, the re- tarding pressure is greater than the drawing, and a smooth, steady cut results, with a minimum danger of injury to the FIG. 493. work and cutter. If the cut was heaviest at the surface B, the cutter should be started from the opposite end and the direc- tion of the feed reversed. Plain surfaces may usually be milled either by the plain axial milling cutter or a radial or end mill. The axial cutter leaves a smoother surface and is more easily kept in order than the radial. The tendency to spring and distort the work is, however, greater with the axial cutter, as the pressure of the cut is very largely at right angles to the work surface, while with the end mill the pressure is almost wholly in the direction of the feed. The character of the work usually determines which class of cutter to use. At i and 2, Fig. 494, are shown two ways of milling a common hexagon nut. The straddle mills of No. 2 are radial cutters and, as arranged, finish two surfaces each time over the work. An end mill might be used, in which case but one surface would be finished at a time. In any case the diameter of the mill should be as small as strength and con- MODERN MACHINE SHOP TOOLS. venience will permit. An inspection of Fig. 495 shows the reason for this. If the portion D E F G of the work is to be removed by the cutter, it is evident that the smaller cutter X will travel the distance B in completing the cut, while the cutter Y must travel the distance A. If the width W of the work is small, the saving in time required for the work by using the small cutter becomes a considerable portion of the total time. MILLING MACHINE WORK. 361 The first cost of the smaller cutter is less and the power required to drive it also less than with the large cutter. In placing cutters on the arbor, the faces of the cutter and the arbor collars should be carefully wiped and thus insure a true running cutter. As shown in Fig. 496, a small piece of cutting or dirt A between the faces, causes a spring in the arbor and the cutter will run out of true. When made, the faces of these collars are carefully brought parallel with each other and, with reasonable care, they can be kept in this condi- tion. When, as in 2 and 3, Fig. 494, two cutters are to be used for straddle work, it is necessary when the distance between FIG. 495- FIG. 496. the faces of the work is to be of exact dimension, to have collars of suitable length. As the regular collars usually make up by eighths above one-fourth inch, suitable washers must be pro- vided for making up the exact dimension. These may be had with parallel faces and varying in thickness by .001 -inch, thus making it possible to obtain any desired dimension between the faces of the cutters. When it is required to machine the top surface of the work, a plain axial cutter can be used between the straddle mills in place of the collars and washers. At 4, Fig. 494, is shown the final operation in the milling of a T-slot. The neck of the slot and all the metal possible should 362 MODERN MACHINE SHOP TOOLS. be first removed with a plain axial cutter, as in Fig. 497, which leaves a minimum amount of work for the more delicate T-slot cutter to perform. If the nature of the work is such that a plain cutter cannot be used, the stock can be removed with an end mill. In this case, a cutter somewhat smaller in diameter than the required width of the neck must be used first, as the spring of so small a cutter when taking such a heavy cut would cause the work to be untrue. The neck can then be finished to exact width by passing a sizing cutter through or by trimming each side with a finishing cut with the roughing cutter. The mill- ing of a V-slot, 5, Fig. 494, is similar to that of the T-slot, the most of the stock preferably being first removed with a plain cutter or an end mill. The cutter shown could be used to com- plete the work at once, without the use of a stocking cutter as it is provided with teeth on its shank. This is not, however, the FIG. 497. FIG. 498. FIG. 499. customary method, as the necks of these cutters are not usually provided with teeth and the spring of the cutter makes smooth, accurate results very hard to obtain. At 6, Fig. 494, is illustrated a method of milling the guides of a housing. With a cutter of proper thickness and diameter, both sides and bottom of the guides are finished at one cut. This figure serves to suggest one of many similar operations that can be performed with a plain cutter. No. 7, Fig. 494, shows how the milling machine can be used for boring and facing work. The work is clamped to the table of the machine and a short boring bar placed in the spindle bearing. If the hole to be bored is of considerable length and diameter, the outer end of the bar should be formed to fit the bearing of the overhanging arm, thus making it firm and capable of producing a smooth, true bore. An automatic in-and-out feed is very de- sirable for work of this character. It will also be noted that the MILLING MACHINE WORK. 363 vertical and lateral adjustments to the work table enable the work to be set in any desired position for the boring of parallel holes. Take, for example, the piece of work shown in Fig. 498, where the two holes are to be bored parallel with each other. The work should be first squared up and the hole A bored; after which, by means of the graduated elevating screw, the work can be dropped exactly i l /% inches and by means of the graduated feed screw set over the 4*4 inches, which brings the center of the hole B into exactly the proper position for boring. In like manner any desired number of settings may be obtained quickly and with great accuracy. In making setting measurements by the use of the graduated screws precaution must be taken to avoid the error that might arise from neglecting to consider the back lash between the screw and its nut. Thus, if a vertical ad- justment is to be made, the table for the first operation should be dropped a little too low and brought up to the proper point. The index can then be set at zero and the work table raised the exact amount required by the graduated screw. If by accident the table is raised too high, it should be lowered somewhat below the proper point and again brought up to the correct reading. This insures against any error arising from the back lash and means that in all settings the slack between the nut and screw should be kept on the same side. A long tool with cutting edge at right angles to the boring bar may be used for facing off the end of the work after the boring operation. The end next to the spindle can, of course, be faced with an end mill if desired, or a facing attachment con- sisting of a slide and tool-carrying head can be mounted for this purpose on the nose of the spindle or on the boring bar. Twist drills and reamers mounted in the spindle of the milling machine can frequently be used to very good advantage on many classes of work. No. 8, Fig. 494, shows the method of keyseating a shaft in the milling machine. Where the keyway is not cut the entire length of the work, a rounded end is left, which is usually not objectionable. If a cutter of small diameter is used the length of the rounded end is not great. In cases where the keyway must be full depth to the end, an end mill of diameter equal to the width of the keyway can be used to finish out the rounded end. By placing several shafts together on the table and putting as many cutters on the arbor, properly spaced, all keyways may 364 MODERN .MACHINE SHOP TOOLS. be cut at one operation. This is advantageous where a large number are to be cut at one setting of the machine. When a keyway is to be cut in the shaft at some point between the ends, to receive a short key or feather, the end mill is used. If the mill is not of the center-cut type a small hole, a little larger than the diameter of the toothless center of the cutter, should be drilled at one end and to a depth equal to the depth of the re- quired keyway. This allows the mill to cut its way to the bottom and then feed out. For this work the cutter should run at a FIG. 500. comparatively high rotative speed and should be given a fine feed, as otherwise the spring is excessive and the work untrue. No. 9, Fig. 494, shows the method of fluting a reamer. The present example is that of a taper reamer. In this case the tail center is raised an amount sufficient to give the proper depth of cut at each end of the flutes. The cutters usually employed for this work are specially formed cutters and. should be set so that the face of the cutter that cuts the front face of the tooth stands on a radial line with the blank being fluted, as shown in Fig. 499. MILLING MACHINE WORK. 365 No. 10, Fig. 494, shows the method of cutting spur gears in the plain or universal milling machine. One or more of the gear blanks are mounted on a mandrel and placed between the centers, the gear cutter having been previously placed on the arbor and the table adjusted in and out so the center of the cutter falls in the line of the work centers. The index is set to give the correct number of divisions and the work elevated until the rotating cutter just touches the rim of the gear blank. The graduated dial on the elevating screw is then set to zero, the work moved out from under the cutter and raised an amount equal to the required depth of the tooth. Spur gears too large to swing between centers can often be cut by placing the index head spindle in a vertical position and carrying the blank on a vertical mandrel held in the spindle. This places the blank in a horizontal plane and the cutter is set to depth by the table feed screw and the work fed to the cutter by the vertical feed. In Fig. 500 is shown a method of cutting a large spur gear in a plain milling machine using a plain dividing head clamped to a knee plate. The gear shown is 30 inches in diameter. The greatest care must be taken in an operation of this kind as the leverage on the spindle of the dividing head is considerable and the chances of shifting the work great, especially if the cutter is a little dull. By previously gashing the work with a plain cut- ter, the chances for a true job are very materially improved. Another method of cutting large spur gears in the rattling machine is illustrated in Fig. 501. This is known as the under cutting method which is accomplished by raising the dividing head and tail stock by means of suitable elevating blocks and providing a substantial outer support for the milling arbor. An adjustable post in the tail stock raising block can be brought to bear against the rim of the blank immediately over the cutter, thus taking the cutter thrust and relieving the centers of this strain. The fluting of the tap shown at No. n is similar in all respects to the fluting of the reamer in No. 9. No. 12 shows the method of bobbing a worm gear, the blank having been pre- viously gashed. The hob is a cutter of exactly the same shape as the worm that is to mesh with the gear and simply forms out the teeth, the blank rotating free on the centers. In gashing the teeth of the worm gear before bobbing, it is placed on the man- drel between centers and the index set for the proper number of 366 MODERN MACHINE SHOP TOOLS. teeth. A gear cutter of suitable size to remove most of the stock, leaving only enough for the hob to finish, is placed on the arbor and brought central with the work. It is then necessary to swivel the table an amount C D E, Fig. 502, depending upon the pitch and diameter of the worm. The work is then raised to the cut- ter the proper amount and dropped for each succeeding cut. If the thread of the worm wheel is to be right-handed, the table is FIG. 501. swiveled to the right, and to the left if left-handed. For the hob- bing, the bed is set back to zero. Bevel and miter gears may be cut in either the plain or uni- versal milling machines when equipped with an elevating index head. The teeth so cut are of approximate outline, but suffi- ciently exact for all ordinary uses. As shown in Fig. 503, the gear blank is mounted on a suitable mandrel held in the chuck or, as shown, fitted to the spindle bearing of the elevating head. The head is then elevated until the root line of the tooth is MILLING MACHINE WORK. 367 w parallel with the work table. The proper cutter for the particu- lar pitch and number of teeth is placed on the cutter arbor and brought central with the work. For any pitch the depth and width A , at the outer end of the tooth is the same as for spur gears. As the inner end of the space is narrower, the cut- Q ters for bevel gears must be thinner --g- than for spur gears. The index hav- ing been set for the proper number of teeth a few center cuts are taken, The index pin is then advanced a few holes and the work moved out a few thousandths from the central position and the cutter again passed through the spaces already cut. This should remove some of the stock from the side of the teeth, taking more at the outer end than at FIG. 502. FIG. 503. the inner end. The index pin is next carried back double the number of holes it was advanced and the work moved in double 3 68 MODERN MACHINE SHOP TOOLS. the amount it had been moved out for the previous cut. This throws the cut on the opposite side of the tooth. As there is no fixed rule for the amount of these settings, the tooth must be measured and if not of proper thickness another trial setting must be taken. When the proper settings are found for any particular gear, they should be noted for future reference. The center cut is then not necessary as the tooth is finished by the two side cuts. In Fig. 504 is shown a method of cutting bevel gears in a plain milling machine using a plain dividing head. A spline is milled in the- face of the knee plate at the prbper angle to FIG. 504. receive the tongues in the base of the head thus fixing the cutting angle. A separate spline must be provided for each angle of gear cut. When a large .variety of gears, necessitating a number of different angles, are to be cut a plain graduated plate pivoted to the face of the knee plate and carrying the dividing head gives all angles. Where a graduated swivel base vise, as shown in Fig. 451, is available, it can be used to excel- lent advantage in cutting the splines in the knee plate at the re- quir .. angle. The method of cutting a twist drill in the universal milling machine is illustrated in Fig. 505. The settings are as for cutting a spiral gear, with this difference, that the depth of MILLING MACHINE WORK. 369 the flute in a twist drill should be less at the shank end than at the point. It is therefore necessary to elevate the point some- what. When the flute is to be cut from the very end of the blank, the shank must be held in a chuck on the spindle of the FIG. 505. universal head, and for the outer end, supported on a suitable steady rest. If, however, the work can be carried on centers and the cutter dropped into its cut as close to the point as. pos- sible, better results can usually be obtained with less liability to accident. In this case, the head spindle can be dropped a few J FIG. 506. degrees below the horizontal position, or the tail center raised to give the proper taper to the web of the drill. The backing off of the lands of the drill, as shown in Fig. 506, is a somewhat difficult operation, requiring good judgment on the part of the 370 MODERN MACHINE SHOP TOOLS. operator. The work table is swung through a small angle indi- cated by the line r a, which causes the end mill to cut deeper at c than at e, thus clearing the lip, as shown in the end view. FIG. 507. FIG. 508. Figs. 507, 508 and 509 show examples of vertical milling machine work. In Fig. 507 the end mill in the vertical spindle ir> machining spots on the inside surface of a feed bracket cast- MILLING MACHINE WORK. 371 ing. While this work, if clamped against a knee plate, could be done in a horizontal spindle machine with the same cutter, it would be much harder to hold and more difficult to get at for settings, measurements, etc. In Fig. 508, an angular cutter is shown, finishing the bevel face of a round casting, secured to a circular milling attachment. This work is done very rapidly and the same cutter is used to mill the internal face of the correspond- ing ring shown on the work table. Frequently where duplicate work is held in the vise and its nature will permit, two vises placed side by side will greatly FIG. 509. increase the output of the milling machine, as the work can be set up in one, while being machined in the other. A large portion of the work done in a milling machine is held in the vise. Plain base vises as shown in Fig. 450 are provided with tongues which fit the wards in the work table and insure correct settings of the vise jaws, either parallel with or at right angles to the cutter arbor. -With swivel base vises a graduation is usually applied with the zeros coincident when the jaws are parallel with the cutter arbor. To test the correct- ness of the zero setting, remove the collars on the arbor and move the table so as to bring the upper edge of the jaw at the height of the center of the arbor. Move the table longitudinally 372 MODERN MACHINE SHOP TOOLS. until the jaw touches the arbor. If the contact is uniform the full .length of the jaw, the setting is correct. This pre-supposes a true running arbor. Squaring from the front face of the column with an accurate square is equally satisfactory and the better method if the arbor is not dead true. For the 90 degree position square the jaw from the arbor. Vise jaws are nicely finished and made of hard or soft steel, the hard jaws being most used. They are so secured that they may readily be removed and special jaws applied in their place. The faces are at right angles to the work table, which insures the milling of the top surface of work at right angles with its sides when clamped squarely in the jaws. For the holding of round work a special V jaw as shown FK* 510. in Fig. 510 is well suited. This gives a three line contact be- tween work and jaws and prevents the work from tipping up or down. It also insures, on work of equal diameter, the same height of setting, a very important condition, which is difficult to obtain with certainty when the work is allowed to rest on the face of the vise slide, or on a parallel. For much special work, false vise jaws can be used to very excellent advantage as they may be formed to irregular contours of either work or cutter. In Fig. 511 is shown an example of heavy gang milling. In this case the seats for caps and quarter box cheaks are finished at once through. It involves the finishing of five horizontal and three vertical surfaces. The gang is made up of four stand- ard cutters and one special inserted tooth cutter. The diameter MILLING MACHINE WORK. 373 of the large cutter determines the rotative speed for the gang. On entering and leaving the cut a coarser feed can be employed than through the middle of the cut.-, The advantages of milling this piece of work over planing it, I FIG. lie in the possibilities for perfect duplication in the former, as well as the time saving element, it being milled in approximately one-third the time required for planing. In Fig. 512, is shown the stock, false vise jaws in which it is FIG. 512. .;.- held and gang of cutters for the finishing the tool steel piece shown. The stock has had a screw machine operation upon it before coming to the milling- machine. A suitable stop on one of 374 MODERN MACHINE SHOP TOOLS. the jaws locates the work in the vise with shoulder. The jaws are hardened with firmly gripping the stock, and a copious used on the work and cutter. As the cut for the size of the stock, y* inch square, held and a fine feed employed. In Fig. 513 is illustrated an example of jig milling. In this reference to the turned roughed surfaces for supply of lubricant is is very long and heavy it must be very firmly FIG. 513. case the jig consists of a plate secured to the work table of the machine and a second plate pivoted to it. The work which has been previously bored and faced on its lower side fits over a projection on the upper plate which holds it concentric with the pivot. The * work is squared up and the face mill machines one of the spots. The work is then rotated through 90 degrees, deter- mined by a pair of stop pins, and the second spot machined. The pair of straddle mills shown are next used to face off the ends MILLING MACHINE WORK. 375 of the hub of the upright part. It is possible in this way to machine any number of pieces and have them all alike. The methods for securing work to the table of the milling machine are quite similar to those used on the planer. The same bolts, clamps and blocking being equally suited in both cases. It is ordinarily necessary to clamp the work quite securely as the tendency to shift under heavy cuts is great. As milling ma- chine tables are not ordinarily provided with holes for stop pins, it is frequently necessary to bolt suitable stops to the table. A bar laid crosswise on the table and held with bolts in two or more of the T-slots makes an excellent stop. Round true iron washers bolted to the table may also serve as suitable stops. Bars of cast iron planed true and having tongues on the bot- tom side to fit in the wards of the table will be found very con- FIG. 514. venient for much work that requires two surfaces to be milled parallel with each other. Such a bar is shown in end view in Fig. 514. They are simply used for setting the edge of the work against serving as a stop and insuring quick and accurate align- ment. By making a casting in the form of a right angle triangle with tongues on one edge, a very satisfactory cross table stop is formed for milling surfaces at. right angles to each other. The knee plate is much used for holding work on the mill- ing machine, and especially in the case of special work where a plate serves as a jig. It should be provided with tongues for properly lining it on the table, and when used for general work the upright arm should have a goodly number of slots or holes for receiving the clamp bolts. Chuck work should be kept as close up to the jaws as possi- ble, thus making it rigid. When it is necessary to operate on a 376 MODERN MACHINE SHOP TOOLS. part of chucked work extending far out from the chuck jaws, it should be supported in some manner. A small adjustable center rest, usually furnished with universal machines or a small jack screw may be brought to bear immediately under that part of the work the cutter is to operate upon. With long work held between centers this support is also valuable. In universal machines, taper milling may be accomplished with work between centers, as shown at 9, Fig. 494, by either raising the tail center or depressing the head center. As this throws the centers out of line, the rotation of the work causes. the dog driving it to move in and out through the face plate. This is overcome by the use of the new dog and face plate FIG. 515. carrier shown in Fig. 515. When the work is held in the chuck it is necessary that the adjustment of head spindle be such that its center and the center line of the work remain in the same line r and point directly toward the tail center, as shown in Fig. 516. Although the milling of cams is usually performed on a special cam cutting attachment, they may frequently be milled in a plain or universal -head, using an -end mill as shown in Fig, 5i6A. From the round disk shown in the chuck, which is of a thickness somewhat less than the diameter of the cutter and having a hub upon which the chuck jaws' grip, the cam outline shown by the dotted lines is milled. As shown, the center of the mill is central with the disk. For the first or roughing cut, raise the table until the lower side of the cutter reaches the MILLING MACHINE WORK. 377 center line a a of the work. This roughs down one of the straight sides of the cam. Next rotate the chuck slowly by means of the worm and gear until the cutter has roughed all the sur- face around to the point b. By next dropping the work, the other i FIG. 51.6. straight side is milled. As machined the two straight sides wijl be flat but the circular portion will be somewhat concave, due to the high position of the cutter. For the finishing "cut the cutter should be set with its center at the height of the work center. FIG. 5l6A. This brings all of the work on the end of the cutter which leaves a straight surface, but does not cut as freely as when set for roughing. This class of work brings considerable strain and wear on the worm and gear of the dividing head. 3/8 MODERN MACHINE SHOP TOOLS. Cutter vibration can usually be traced to some slack in table joints or spindle bearings. Heavy cuts on frail work are apt to chatter. Straight cutter teeth are much more apt to cause chatter than spiral ones. A harmonic relation between the numbers of teeth in the back gears and the number in the cutter, when the machine is running in back gear, is without doubt a frequent cause of chattering. The graduated dials on all table feed screws are of great value in setting cutters in the proper position relative to the work. They should, when possible, be used for making these settings, care always being exercised in taking up the slack or back lash in the screws. In the milling of steel and wrought iron a cutter lubricant is used. Lard oil is generally considered the best for this pur- pose, although its high cost often precludes its use some form of compound being substituted. Many of the soap and soda com- pounds are very good substitutes. The object of lubrication is to supply, not only enough of the lubricant to keep down friction, but enough to carry away the heat of friction and thus preserve the cutting edges and make possible higher cutting speeds/ Cast iron and brass do not require a lubricant. Castings that are to be milled should be free from sand and hard, flinty spots. It is desirable to pickle them and in the case of small castings, which are very apt to be hard, to anneal them. These operations are inexpensive and rapid and will save many cutters and much grinding. CHAPTER XXVI. GEAR CUTTERS AND GEAR CUTTING. In the cutting or forming of gear-teeth two systems, known as the "duplication" and the "generation" systems, are em- ployed. The "duplication" system is the one most commonly employed and may be divided into two separate and distinct classes known as duplication by formed cutters and duplication by the templet- FIG. 517. planing process. Duplication by formed cutters is the more com- m6n method and the one with which most shop men are familiar. It involves the cutting of the tooth space with a rotating or re- ciprocating cutter, the side of the tooth of which, has a formed outline which is a negative of the side of the tooth outline re- quired. The accuracy of the tooth form is therefore dependent on the accuracy of the cutter's outline and theoretically a differ- ent form of cutter should be used for each number of teeth cut in each pitch. MODERN MACHINE SHOP TOOLS. In the templet-planing process the sides of the teeth are planed with a pointed tool, the path of the point being guided by a templet of the correct outline. This process is much slower than the rotat- ing formed cutter method and consequently is little used for other than the cutting of miter and bevel gears, to which work it is admirably adapted. In Fig. 517 is illustrated the Gleason templet bevel gear planer and in Fig. 5I7A an outline of its move- ments showing how it is possible to make the point of the cutting tool duplicate the templet outline to a uniformly reducing scale from the outer to the inner end of the tooth, thus giving a correct outline tooth, its accuracy depending upon the accuracy of the templet. With the formed cutter it is possible in bevel gear cut- 5I7A. ting to give a correct tooth outline only at one point in the tooth's length. The method is, however, much more rapid and for the finer pitches is much used. For the coarser pitches and relatively longer teeth', where quiet, smooth running gears are required, the planing process is used. , The generating of conjugate tooth outlines, or in other terms, the forming of the teeth upon cylinders that will cause" them to roll .together as the pitch 'circle' of the one would roll upon the pitch circle of the other without slipping, is a condition that can only be obtained by a molding process. When two newly cut gears run together, a molding process takes place, the high parts 'wearing down and gradually produc- ing a smooth running conjugate tooth. If the teeth of one gear GEAR CUTTERS AND GEAR CUTTING. were. covered with fine file-like teeth it would quickly mold the teeth of the other gear. The forming of teeth in this manner by a process known as the molding-planing process has but recently been put into a practical form for spur gear cutting in the Fellows gear shaper. The single-tooth molding-planing process, as applied in the Bilgrim machine, generates conjugate teeth on miter and bevel gear blanks. The making of formed gear cutters involves the laying out of the templet and making of the negative cutting tool as described in connection with Fig. 472. As the tooth outline varies with the number of teeth in the gear a cutter can be made exactly correct for but one number of teeth. In practice, however, the outline varies, so slightly, espe-. cially for the larger numbers of teeth, that one cutter, although exactly correct for but one number of teeth', is used for cutting quite a range of numbers. As the tooth outline changes very rapidly for the lower, numbers of teeth the range is small for these numbers. In the involute system the permissible range is much wider than in the cycloidal system. In the following table is given the numbers and range of Brown & Sharpe involute gear cutters : No. i will cut wheels from 135' teeth to a rack. " 134 teeth. " 54 " " 34- " " 25 ". " 20 " " 16 " ." 13 " In cases where a finer division is required in the number of teeth to be cut with each cutter, as sometimes occurs when very smooth running gears are required, intermediate cutters between those regularly used may be had on special order. The range of these cutters is given in the following table : 55 35 26 21 17 14 12 No. of Cutter. Range. No. of Cutter. Range. 3* 8o to 134 teeth. 42 " 54 " 30 " 34 " 23 " 25 " 19 to 20 teeth. 15 " 16 " 13 MODERN MACHINE SHOP TOOLS. In the cycloidal system 24 cutters are required for cutting all numbers from 12 teeth to a rack as given in the following table : Cutter A cuts 12 teeth. B cuts 13 " " C cuts 14 " D cuts 15 E cuts 16 <( " F cuts 17 " G cuts 18 " H cuts 19 " u I cuts' 20 " (t J cuts 21 tO 22 tf K cuts 23 to 24 " u L cuts 25 to 26 " o " P cuts 38 to 42 Q cuts 43 to 49 " R cuts 50 to 59 " " S cuts 60 to 74 " T cuts 75 to 99 " " U cuts loo to 149 " V cuts 150 to 249 " W cuts 250 or more. " X cuts Rack. For bevel gear cutting, involute teeth, eight cutters having the same range as above given are required. These cutters differ from those used for spur gearing in that they are considerably thinner, a condition made necessary by the cutters having to pass through the narrow end of the tooth space. The regular bevel Cutter M cuts 27 to 29 teeth. N cuts 30 to 33 cuts 34 to 37 cuts 38 cuts 43 cuts 50 FIG. 518. gear cutters are thin enough to pass through the narrow end of the space where the length of the tooth is not more than 1-3 the dis- tance from the outer end of the tooth to the point at which the axes intersect. Where an extra length of tooth is required, an especially thin cutter must be used. Cutters for spur gears have the pitch and the range of teeth stamped on them. Cutters for bevel gears have the pitch, but not the range stamped on them, inasmuch as the range does not or- dinarily correspond to that given for spur gears. The selecting of GEAR CUTTERS AND GEAR CUTTING. 383 the proper cutter for a spur gear is therefore a simple matter, as it is only necessary to know the diametral pitch and the number of teeth. With bevel gears, however, the following considerations are necessary. In any pair of bevel gears lay off the back cone radius a, b for the gear, and b, c for the pinion, Fig. 518. Con- sidering the gear, r is the actual pitch radius and upon which the pitch and number of teeth depend. The outline of the tooth, however, is the same as for a spur gear, having a radius a, b. Take, for example, r as equal to 4 inches, and assume No. 6 diametral pitch, which would give 48 teeth in the gear, requiring, if it was a spur gear, cutter No. 3. The back cone radius a, b measures 8 inches, requiring a tooth outline the same as a spur FIG. 519. FIG. 520. gear of 96 teeth, or cutter No. 2, which would be the correct cut- ter to use. In Fig. 519 is shown the Gould & Eberhardt duplex gang gear cutter, which consists of two or more cutters mounted to- gether and of such diameters and forms as to cut and correctly finish two or more teeth at each passage through the blank. An inspection of the figure shows the central cutter to be of normal diameter and symmetrical with reference to a central plane. The side cutters are somewhat larger in diameter and the center line of the front face of each tooth is coincident with a radius of the blank. It is evident that but one diameter of gear can be cut with each gang, and the larger the diameter of the blank for a given 384 MODERN MACHINE SHOP TOOLS. pitch, the more cutters it is possible to mount in one gang-. This condition at once makes the gang a purely manufacturing tool, which can be advantageously adapted only in cases where large numbers of each size of gears are to be cut. In using these gangs, care must be exercised in setting to the exact depth of cut and that the blanks are of exact diameter, as inaccuracies in these conditions will produce thick or thin teeth. These cutters are ground from the front face without chang- ing their form. With these gangs as many as ten finished teeth may be cut at one passage through the blank. Under ordinary conditions the excessive heat generated by the removing of so much stock necessitates a somewhat slower rate of feed and cutter rotation than can be employed with single cutters. A jet of com- pressed air directed against the work and cutters makes possible much higher speeds. The Clougri duplex cutter, as shown in Fig. 520, although a form, of .gang cutter, finishes but one tooth at a time. The object of this cutter is to produce gears having a widely different number of teeth,, that will interchange with a single cutter. Correct tooth outline must of necessity be sacrificed in accomplishing this end. Gears cut, however, with these cutters run fairly. well together and will work with gears cut with regular involute cutters. Gears having 30 teeth^or ov,er are finished entirely by-the inside faces of the cutter. For numbers lower than, 30 the flanks are finished by the outer faces' of the cutters. The. methods of cutting spur and bevel gears already described in Chapter XXV., require the continuous attention of the operator with a constant danger of his making an error in division. Auto- matic gear cutting machines insure better gear at very much lower cost. In Fig. 521 is shown an automatic gear cutter capable of cutting spur gears only up to 40 inches in diameter by 9 inches face. In Fig. 522 is shown an automatic gear Cutter for cutting both spur and bevel gears up to 18 inches diameter by 4 inches face. In these machines all movements are entirely automatic. The work is secured to the dividing head spindle ; the necessary change gear adjustments made for dividing the work ; the work set to the cutter so as to cut the proper depth of tooth, the correct cutter having previously been put on the cutter spindle, and the machine started up. When the feed is thrown in the cutter advances GEAR CUTTERS AND GEAR CUTTING. 385 through the blank at the required rate of feed, automatically re- versing when the cut has finished and returning the cutter slide at a quick speed. When the cutter on its return stroke has cleared the work, the dividing mechanism spaces for the next tooth and FIG. 521. Fill FIG. 522. the cycle of operation is again gone through, repeating itself without further attention until the work is finished. For the cutting of bevel gears in the automatic machine it is necessary that the cutter slide be so constructed that it can be set 386 MODERN MACHINE SHOP TOOLS. at .any angle between a horizontal and a vertical position. As with the cutting of Ibevel gear in the milling machine, the cutter must pass twice through each space, the automatic features of the machine, however, remaining the same as for spur gear cutting. Due to their smoothness of action, spiral gears running in oil are largely used for driving the cutter spindle. As the center of the cutter must, for spur gear cutting, be under the center of the work and as the cutters vary in thickness, it is necessary to give the spindle an adjustment endwise and to provide a suitable gauge for setting the cutter central. The feed to the cutter slide on the machines shown is accom- plished by a slow rotation of the feed screw, which rate can be varied within necessary limits by a change of gearing. The auto- matic disengaging by stops of the clutch, which engages the for- ward driving gear with the feed screw, stops the feed. The same movement engages the screw with a quick-running reverse gear which brings the slide back very rapidly.- The changes from the one movement to the other occur without pause or shock. The exactness with which the dividing mechanism performs its work is dependent upon an accurately cut worm gear and worm; accurately cut change gears; nicely fitting bearings and adjustments permitting of no back lash ; and an escapement move- ment which allows the locking disc-shaft to make exactly one revolution, or, as is the case with the Brown & Sharpe machines, two or four revolutions at the time the division is made. In these machines a side shaft rotating at a constant rate of speed carries a clutch which at the instant of the tripping of the escapement stop engages the locking disc causing it to rotate through one ? two, or four revolutions, depending on the setting. This has the advantage of reducing the number of change gears "necessary. Referring to Fig. 523, B is the gear on the locking shaft, C and D are intermediate gears on a stud, and E is the worm gear,, which transmits its motion to the worm through a pair of miter gears. The number of teeth in the worm divided by the number of teeth to be cut, represents the ratio that must be made up by the change gears. Thus if 120 teeth are required the ratio is one, and gears must be selected that will give this ratio, as B 50, C 50, D 60, and E 60. If, for example, 82 teeth are wanted, 120 60 2 30 82 j.i i si GEAR CUTTERS AND GEAR CUTTING. 3*7 giving gear B 100, C 50, D 30, E 41. As a gear with 41 teeth is not available, 60 and 82 may be used on D and E. If in the latter case 41 teeth were wanted, two revolutions of the locking disk could be employed, using the same change gears. Where work of small diameter is operated upon, the'outer end of the work mandrel is supported by an overhanging arm and no further support is necessary. If of large diameter the end of the mandrel is carried in an outboard support, and a rim support steadies the blank immediately back of the cutter. In setting the work to depth it should be lowered until the revolving cutter just touches the circumference, and the dial on the elevating screw then set at zero. It should then be dropped the required amount for LOCKING SHA FIG. 523. the cut by passing somewhat beyond the required distance and turning up to the mark, thus avoiding any error due to back lash in screw and connections. Gear cutting machines when used on steel gears are provided with an oil pump for supplying a liberal amount of screw cutting oil on cutter and work. In the cutting of steel gears, when prop- erly lubricated, a high rotative cutter speed with very fine feeds are usually advisable. The lubricant prevents the heating of the cutter and the fine feed overcomes its tendency to "hog" into the work. The cutting of bevel gears in the automatic machine shown in Fig. 522 does not differ materially from the milling machine method described in connection with Fig. 503. The side move- 3 88 MODERN MACHINE SHOP TOOLS. ment is given the cutter rather than the work, and the same care and judgment must be exercised in making the preliminary set- tings. In the cutting of heavy pitch and steel bevel gears, it is usually advisable to make a center cut, thus necessitating three cuts for each tooth. The cutting of racks may be accomplished in the milling ma- chine by use of a special attachment, as shown in Fig. 458; on the automatic gear cutter by means of a suitable attachment or FIG. 524. on a special automatic rack cutting machine. An attachment for the automatic gear cutter is shown in Fig. 524. A cross rail is secured to the front of the upright, and this is mounted on a slid- ing head with provisions for clamping the rack blank on its under surface. A pinion on the nose of the dividing spindle engages a rack on the head, thus making it possible to automatically move the head the correct spacing for each passage of the cutter through the blank. Gang cutters can be advantageously used in rack cutting. All cutters must be of exactly the same diameter and GEAR CUTTERS AND GEAR CUTTING. mounted on the arbor with their centers the exact pitch distance apart. Where large amounts of rack are to be cut, machines for that special class of work are employed. The Fellows gear shaper, above referred to, is shown in Fig. 525. The cut illustrates a front view of the machine at work on an internal gear. The cutters are illustrated in Fig. 526, and the method of securing them to the cutter spindle is shown in Fig. FIG. 525. 527. As already stated the cutter is a correctly formed gear dished on the cutting face in order to give it an angle of rake. The cutter, although resembling a spur gear, is in reality a bevel gear, having a very small center angle. This feature gives the cutter the neces- sary clearance in the work. Upon the correct forming of the cutter depends the accuracy of the work produced on this machine. Since the side of the tooth of an involute rack is a straight line, the substitution of the face of a cutting wheel for the side of the 390 MODERN MACHINE SHOP TOOLS. FIG. 526. < Clamp FIG. 527. GEAR CUTTERS AND GEAR CUTTING. 39 1 tooth would by the molding process produce a correct involute outline on the tooth of any gear that, meshing with the rack, was caused to pass this cutting face. Upon this fact is based the method by which the Fellows cutter is finished. The cutter hav- ing been planed from a blank, as shown in Fig. 528, and hard- ened, is put on a special grinding machine and the tooth outlines ground to the correct form, the operating of the machine depend- ing upon the principle above explained and clearly illustrated in Fig. 529. The rack, of which the face of the wheel forms the side of one tooth, is a fixed imaginary one and the cutter blank is given, by a suitable mechanism, a true rack, and pinion motion CUTTER BLANK FIG. 528. past the face of the emery wheel, which grinds the sides of the teeth, one at a time, to the correct form. In its operation the cutter and blank are so geared together that they rotate the same as two complete gears in proper mesh. After starting the machine, the cutter is fed toward the blank until it has cut the exact depth of the tooth. Rotation which cor- responds to a feed then begins, a small amount at the beginning of each stroke, when the cutter is clear of the work and continues until the cutting is finished. The method of holding the work is shown in Fig. 527, a suita- ble face-plate and clamp with a work support in connection with the draw stroke on the "cutter making a very rigid combination. "When the character of the work necessitates it, the cut can be 392 MODERN MACHINE SHOP TOOLS. taken on the down stroke, such usually being the case when cutting internal gears. The stroke of the cutter ram is adjustable^ as to length and position. Since the teeth of the cutter are conjugate to the generating- rack, all gears cut with the cutter are conjugate to it and to each other. One cutter will therefore cut all gears from a pinion to a rack. Bevel gears having the octoidal form of teeth are cut theoreti- *Emery Wheel Imaginary Racfe Cuttcc FIG. 529. cally correct by a molding planing process in the Bilgram bevel gear planer, Fig. 530. The generating tool has a straight cutting edge and is given a motion parallel with the root of the tooth and constantly moving toward the apex of the pitch cone. In this machine the gear blank is given a rolling motion as it swings under the cutting tool. This motion is accomplished by means of a pair of bands wrapped about a portion of a conical GEAR CUTTERS AND GEAR CUTTING. 393 surface, having its apex in the intersection of the axis, upon which the blank is mounted and the pivotal axis of the head. The adjustments of the machine are such that the motion given the blank is the same as it would receive if it was rolling in gear with a circular rack. As the cutting of the tool corresponds to the straight side of the rack tooth, its action is to generate a conjugate tooth on the blank. The indexing mechanism spaces the teeth and the feed rotates the blank slightly for each stroke of the cutter. In the cutting of worm gears by the hobbing process is illus- FIG. 530. trated a method of producing conjugate teeth by a rotating cutter. This operation as performed on the universal milling machine is described in connection with 12 Fig. 494 and Fig. 502. On machines designed specially for hobbing work and known as hobbing machines, the work spindle and hob are geared to- gether by means of a "suitable system of change gears, thus driv- ing the work blank at the proper speed relative to the cutter rotation. With machines of this class it is not necessary to pre- pare the blank by gashing, as the gearing insures correct spacing. This method is clearly shown in Fig. 531, which illustrates the Whitney attachment for the hobbing of worm gears on a plain 394 MODERN MACHINE SHOP TOOLS. milling machine. As clearly shown a pattern worm on the work .spindle, having the same number of teeth as required on the work, gears with the hob. Spiral gears are usually cut in the universal milling machine with a formed disk cutter mounted on the regular cutter arbor, or preferably on the spindle of a universal milling attachment, as shown in Fig. 454. In the latter case the setting for the spiral angle is made by swinging the auxiliary cutter arbor to the required angular position which is a very desirable feature in the cutting of short pitch spirals. As is the case with the teeth of bevel gears, spiral gear teeth can be formed theoretically correct by a planing process in which FIG. 531. the cutting tool is given a rolling feed that causes it to follow the outline of the tooth, the work being rotated as it advances to the tool at the proper rate to produce the required spiral. The teeth may also be correctly formed by using a planing tool of the same outline as the normal tooth space, the blank being again rotated to produce the proper spiral. Teeth of spiral gears in which the spiral angle is great, as in a worm, are usually formed by this method in a screw cutting lathe. As the planing process is necessarily an expensive one, the more rapid yet less accurate method of milling is usually used. For this method two forms of cutters are used, the disk cutter, the same as used for spur gear cutting, and the end or shank cutter. Of these the latter is used only when cutting low numbered pinions, GEAR CUTTERS AND GEAR CUTTING. 39 j where the root outlines of the teeth are so nearly parallel that a disk cutter would clip off the teeth too much, thus making the space wide and the tooth thin, as well as destroying the form of tooth section. The end cutter is given the same shape as the desired tooth space and rotates at right angles to the axis of the blank, both axes being in the same plane. The end cutter is a delicate tool that rapidly loses its form and does not produce a spiral groove or tooth space having exactly its outline. The disk cutter is best suited to this work, as it cuts faster and retains its shape well. When made of small diameter it can or- dinarily be used on low numbered pinions with satisfactory results. In its use the axis of the blank must be placed at 90 degrees, minus the spiral angle, from the cutter arbor, the direction in which the angle is measured depending upon whether the spiral is to be right or left handed. The blank as it is fed to the cutter is given the proper rotation to produce the required spiral. As the disk cutter operated in the universal milling machine forms the most practical method of producing spiral gears, we will consider that method of cutting in the following examples. In preparing to cut a spiral gear in the universal milling ma- chine the operator should observe the following points : Having selected the proper cutter and secured it well toward the outer end of the arbor in order to allow plenty of room to swing the table without striking the housing, or upon the spindle of the universal attachment, he will proceed as follows: First, move the saddle until the centers of the spindle and center plane of the cutter coin- cide. This will bring the center of the cutter over the center about which the work table rotates in setting for the spiral angle. Adjust the dividing mechanism to give the number of teeth desired the same as for spur gear cutting and release the pin on the back side of the index dial so that the dial may rotate with the worm spindle. The spindle must be geared with the feed screw in order to obtain the required pitch of the spiral. A table furnished with the machine will give the change gears to use for a large range of pitches. If the pitch required does not exactly coincide with any given in the table, it will usually be sufficiently correct to use the one nearest the proper pitch. The spindle will have right or left hand rotation, depending on whether the gear is to have right or left hand spirals. The 396 MODERN MACHINE SHOP TOOLS. direction of rotation is changed by driving through an idle gear carried on a second stud. Next swing. the table, or the universal spindle as the case may be, through the spiral angle and elevate the knee until the revolving cutter touches the circumference of the blank. Back the blank from under the cutter and again elevate the work, this time an amount equal to the depth to be cut in gear. In returning, lower the work a little so as to clear. CHAPTER XXVII. DRILLING MACHINES AND DRILLING WORK. Drilling machines constitute a class of machine tools which has developed from the lathe. The standard drilling machine in its various forms consists primarily of a revolving spindle for carry- ing the cutting tool ; a work holding table and a substantial frame connecting the two. The details of spindle adjustments and spindle drives and feeds, while differing in points of detail in the several designs and classes, all bear close mechanical relations with each other. The specific field for this class of tools is the drilling and boring of holes of comparatively small diameters. The reaming and tap- ping of these holes are in many cases added to the work of the drill and by means of special tools and fixtures much work for- merly done in the lathe is now being performed on drilling ma- chines. The relative importance of this class of tools in manufac- turing shops has been measured largely by their ability to do strictly drilling work. As a manufacturing tool, it is, however, due to its simplicity, the readiness with which it can be ganged, and its comparatively low cost, rapidly growing in favor. In Fig. 532 is shown a standard pattern upright drill. This is a back geared machine, the back gear mechanism being inclosed in the upper horizontal spindle cone. This gives the spindle eight speeds. The spindle has a three-speed automatic feed with an automatic stop for knocking the feed off at any required position of the spindle. Both wheel and lever feeds are also provided with a provision for quickly moving the spindle when the worm on hand wheel is disengaged from its gear. The rack and pinion method of moving the spindle is common to practically all jnakes and styles of drilling machine. The spindle has its lower bearing in a quill which is given a close sliding fit in the head. The feed rack is secured to the quill. The machine shown is of the sliding head pattern, the head having a vertical adjustment on the front face of the column to adapt the machine to work of different heights and drills and tools of varying lengths. The head is counter weighted by an equivalent weight on the inside of the column and 398 MODERN MACHINE SHOP TOOLS. attached to the head by the chain shown. The head can be firmly clamped in any position. The work table is supported on an arm, which is moved over the column by means of the screw and crank shown. It can be swung to a considerable angle either side of the spindle and firmly FIG. 532. .lamped in any position. For work too high to be supported on the adjustable table, the lower base table is used. On the smaller machines of this class, a stationary head is used, all the vertical adjustment being given the table. Machines of this general design are regularly made up to 52 inches capacity, the size indicating the maximum diameter of work, the center of which can be reached -by the spindle. For driving small drills, a light machine should be used in DRILLING MACHINES AND DRILLING WORK. 399 order to obtain the high speed required and the lightness of parts necessary to make the machine sensitive. By the term sensitive, as applied to small drilling machines, is commonly understood that lightness of parts, smooth running and perfect balance which enables the operator to judge as to the pressure he is applying to the drill and consequently lessen the danger of drill breakage. In addition to the above features some builders go a little farther and employ at some point in the drive an adjustable friction which can be so set as to just drive the drill being used. In Fig. 533 is shown a simple and efficient friction driven sen- . 533- FIG. 534. sitive drill. The friction driver is adjustable to compensate for wear only. The speed of the spindle is varied by the position of the driving friction wheel. In Fig. 534 is shown an example of a very heavy upright drill- ing machine. This machine is designed for very heavy work, as the boring and tapping of flanges. It is of massive proportions and powerfully geared. When, as illustrated in Fig. 535, a number of drilling spindles are driven from one main spindle, the machine is known as a mul- tiple spindle drill. In the drill shown, the spindles can be set at any desired position within the limiting circle. This is a manu- 400 MODERN MACHINE SHOP TOOLS. facturing tool adapted to the drilling of such work as cylinder heads, chest covers or any machine part where a number of parallel holes can be drilled at the same time and setting. These machines are also made in a horizontal style with one or two heads for such work, as the drilling of cylinder ends. When several complete machines, each having a single spindle, FIG. 536 are mounted upon a common base and driven either independently or as a single machine, they are known as gang drills. They possess many advantages and as manufacturing tools are coming into quite general use. In Fig. 536 is shown a four-spindle 14-inch gang drill, which DRILLING MACHINES AND DRILLING WORK. 4! illustrates favorably this class of drills in the smaller sizes. They are made with two to eight spindles in this general style. When larger numbers of spindles are required, as for the drilling of boiler plates, or bridge and structural work, the design is materially modified, the spindle heads being mounted on a cross rail which is supported at the ends by rigid housings resting on a heavy base with fixed or adjustable work table. With gang drills, as with multiples, the operating economy is evident when the work will admit of their advantageous use. With the gang drill when each operation on the work is short, a single piece of work is carried from spindle to spindle, but one spindle FIG. 537. working at a time. The saving here comes from not having to stop and start spindles and change tools. When the length of time required for each operation will permit the use of the auto- matic feed, each spindle may be kept constantly at work, it being only necessary to stop it long enough from time to time to take out the finished piece and put in another. When so operated the tim- ing should be so arranged, if possible, that all spindles except the one at which the work is being changed are working. The automatic feed and feed knock off are quite necessary for the latter class of operations. When work of large diameter is to be drilled near its center, 402 MODERN MACHINE SHOP TOOLS. the drilling spindle must be capable of sufficient radial adjustment to reach the required point on the work, hence the name and class radial drills. In Fig. 537 is shown a plain radial. The upright or column is carried on a stump, which is securely bolted to the base and extends through the column. The column rotates upon this stump and can be firmly clamped to it at any position. The radial arm has a vertical adjustment by power on the column, and the spindle head is radially adjustable on the arm. An extended base receives heavy work and a raised angle plate table the smaller work. The drive is through bevel and spur gear connections with shafts through the center of and down the outside of the column, along the arm and up the head to the upper end of the spindle. In the particular machine shown, a variable speed box, Fig. 537A, FIG. 537A. is substituted for the usual cone pulley. By means of a lever, operating friction clutches, either of four speeds may be instantly obtained. The back gear, which is mounted on the butt of the arm, is so arranged that four speed changes are obtained, thus giving sixteen speed changes for the spindle, all of which are ar- ranged in geometrical progression. Reversal of the spindle rota- tion for tapping is accomplished at the head, a friction clutch con- trolling same. As the efficiency of a tool of this class depends very largely upon the convenience of manipulation, special attention to the location and arrangement of operating levers is given. Radial drills are also made in what are known, as "half" and "foil" universal radial patterns. In the "half" universal radial, the DRILLING MACHINES AND DRILLING WORK. 403 drilling spindle is mounted on a swinging frame which allows the spindle to be set at any angle, in a vertical plane, parallel with the face of the arm. In the "full" universal radial the arm is pivoted to the butt in such a manner that its face can be rotated through a complete revolution, thus making it possible to drill holes at any desired angle with the base. For a large portion of the angular drilling work put on these machines, the universal drilling table, Fig. 538, in connection FIG. 538. with the plain radial machine, is well suited. In this case the work rather than the spindle is set at the required angle. On classes of work where each operation is short, and as a consequence it is not economical to attempt to work , on more than one piece at a time, turret head drills are well adapted. In Fig. 539 is shown a drilling machine of this class. The turret carries a number of spindles which can be successively thrown into position. Each spindle carries its particular tool for the work in hand and only the spindle in working position revolves. In Fig. 540 is shown a horizontal spindle drill of radial pat- tern. The value of this class of tool, not only for general work, 404 MODERN MACHINE SHOP TOOLS. but as a manufacturing drill, is not fully appreciated. This drill was originally designed for the drilling and tapping of holes in the ends of long work. Its advantages for this purpose are evident. For the drilling and tapping of holes parallel with a machined surface, on almost all classes of work this machine is superior to the standard upright drill, as the work can be more 539- readily set up on the table and without the use of knee plates and blockings. The machine is back geared and provided with auto- matic power feed. Reversal for tapping is accomplished by a double friction clutch counter shaft. Post drills as usually constructed consist of a substantial drilling head of suitable design to permit its being secured to a post or wall. DRILLING MACHINES AND DRILLING WORK. 405 Suspension and traveling drills comprise a special class used for the drilling of plates and other work too large to be handled under a radial. The suspension drill is made to bolt to the ceil- ing and the work is moved under it. With the traveling drill the head is mounted on a steel bridge which is carried on side tracks similar to a traveling crane. These machines have the spindles motor driven, and although limited in their vertical ad- justment are capable of wide lateral adjustment, making it possi- ble to reach any part of large heavy work without moving it. In Fig. 541 is shown a two spindle gang manufacturers' drill of entirely new design and construction. This tool is adapted FIG. 540. to the requirements of the manufacturing plant having many similar pieces to be drilled. In its action the operator throws in the feed lever and the spindle instantly advances by a quick movement until the drill comes in contact with the work surface, when the regular feed starts. When the hole is finished the spindle automatically returns. It is therefore only necessary for the operator to put into and remove the work from the carrying jig- In Fig. 542 is shown a portable drill operated by a compressed air motor through the flexible shaft. An electric motor or a rope transmission may be substituted for the compressed air motor 436 MODERN MACHINE SHOP TOOLS. \> hen desired. In many cases a small air motor is attached directly to the drill spindle. When a drilling spindle is to be used for tapping, it is neces- sary that some provision be made for reversing the spindle. The FIG. 543. DRILLING MACHINES AND DRILLING WORK. 407 common method is by using a double clutch counter shaft with one open and one crossed driving belt. This arrangement causes a reversal of all turning parts which is open to some objection. Some builders are employing a geared reversal, either directly on the spindle or on the first reducing shaft. In Fig. 543 is shown a combination of three bevel gears for this purpose. Gear C is keyed on the first reducing shaft, gears A and B run loose on the spindle, the clutch D is keyed to the shaft, but free to FICx. 544. slide up or down over the key. A suitable lever engages with the clutch, thus making it possible to lock gears B or A with D, caus- ing the spindle to rotate forward or back, depending on which gear is made to drive. This makes a very smooth and satisfac- tory working drive. It is frequently necessary to use small drills in a large machine. As the spindle speeds are entirely too slow for the proper running of these drills, the high speed drilling attachment Fig. 544 can 408 MOIiERN MACHINE SHOP TOOLS. be used to very good advantage. The box contains four gears, one cut on the lower end of the taper spindle, another on the spindle carrying the drill chuck with the two others mounted together on the stud shown. The arrangement is precisely like a back gear with an increasing rather than a decreasing spindle speed. The securing of work on the table of the drilling machine re- quires clamps, bolts, jacks and blocking, the same as for planer and milling machine work. The same care should also be exer- cised in the setting, as true work requires careful setting. The use of the square and surface gauge, and good parallel bars are indispensable in setting up work for drilling. For through drilling the work must be so located on the table that the drill in- passing through will enter a slot or the central hole on the table. If the drill is too large or for any other reason this can- FIG. 545- not be done, the work should be placed on parallel bars sufficiently thick to raise the work enough to allow the drill to pass through without spotting into the table. The work table should be kept in good condition, and to drill a hole into it should be an unpardonable offense. As the work table on upright drills turns about its center and the table arm turns on the column, it is possible to so adjust the table that any point on a piece of work clamped to it can be brought under the center of the drill. For drilling surfaces at right angles to a plain surface, the work can be secured to a knee plate or preferably to the table of a horizontal spindle drill. Round work can be advantageously clamped in a pair of 90 degree V blocks. For the holding of small and medium sized pieces of work the drilling vise is much used. In Fig. 545 is shown a form of DRILLING MACHINES AND DRILLING WORK. 409 drilling vise with an angular adjustment to the sliding jaw for holding tapered work. Nearly all pieces of work can be held in some manner in a vise, and in some cases when a large number FIG. 546A. FIG. 5468. of irregular shaped pieces are to be drilled it is found advisable to make special false vise jaws for holcling them. In Fig. 546 is shown, at A, a new drilling vise with a cross section at B. The method of operating the sliding jaw in this vise is such as to always hold the jaw tight down to its slide, FIG. 547. which prevents lifting and drawing the work out of true in tight- ening. In Fig. 547 is shown a special jig drilling vise. It consists of a substantially made plain drilling vise with the jig drilling attachment shown. The attachment is secured to the stationary 410 MODERN MACHINE SHOP TOOLS. jaw. The post C permits a vertical and a turning adjustment, and is firmly clamped in position. The yoke D, which carries the drilling bushing B, can be adjusted for length. The stops, H and K, are also adjustable. When a number of pieces are to be drilled alike, the first one is clamped in the vise and the stop K or H adjusted to it. The work should rest, if possible, on the ways of the vise or on suitable parallels in order that all pieces can be put into the vise in the same relative position. The bushing, when properly adjusted, insures the drilling of the hole in the same relative position, within reasonable limits, on all the pieces. A vise of this description proves an efficient tool for many drilling operations. No class of work in the manufacturing shop presents as many B FIG. 548. FIG. 549- possibilities for jigging as does the work handled in the drilling machine. Drilling is really a connecting operation between the machining and assembling of machine parts. These parts are turned, planed and milled to dimensions, but the accuracy with which they go together, and their interchangeability is dependent entirely upon the manner in which the drilling is performed. Carefully made drilling jigs not only make possible exact dupli- cation, but save much time that would otherwise be devoted to the laying out of the work. Jigs are manufacturing tools of, as a- rule, high first cost and their economy depends very largely on the number of pieces to be drilled. Drilling jigs can be divided into two general classes, plate jigs and box jigs. A plate-drilling- jig is one which can be laid flat upon the surface of the work, properly located and clamped DRILLING MACHINES AND DRILLING WORK. 411 in position. All holes drilled through plate jigs are parallel with each other. A box jig is one which contains the work and may be used for drilling holes at any angle with each other. The character of the work frequently necessitates the use of a box jig in cases where all holes required are parallel with each other. Jigs are usually made of cast iron with bushings of hardened steel. The form of bushing usually used is shown in Fig. 548. At A is shown a shoulder bushing for use in jigs to be used from the one side only. At B is shown a plain bushing, as used in plate jigs which are reversed for drilling from either side. When two bushings, as a drilling and a reaming bush, must be used in the same hole in a jig they are usually made as shown in Fig. ^49- The knurled head facilitates removing, and the pin A prevents the bush from turning and wearing loose in the jig. Bushings FIG. 550. should be nicely fitted in the plate and for the most exacting re- quirements should be ground internally and externally after hardening. An example of a plane plate jig is shown in Fig. 550. This jig is used in the drilling of the cylinder head shown. The jig is centered by a short bush, which fits the central reamed hole in the head. As the character of the head casting necessitates the jig being put on in a certain position, with reference to a core, a zero line established on each casting and the zero mark on the ear shown on the jig, are in each case made to coincide. In Fig. 551 is shown a reversing plate jig and the work it is used upon. In this example the holes in the bed are drilled and those in the cylinder drilled and tapped to receive turned bolts which fit the holes exactly. It is also necessary that the flat face, shown on the side of the cylinder, comes exactly at right angles 412 MODERN MACHINE SHOP TOOLS. with the planed bottom of the bed. The jig is first slipped over the extended barrel of the cylinder and its flat side squared with the face above referred to on the cylinder. The jig is clamped in this position and the holes drilled tapping size. The jig is then removed and the holes tapped at the same setting. The tap drill bushings are next removed from the jig and FIG. 551. the bolt size bushing put in from the opposite side. The ring shown in the cut is now slipped into the bore of the bed and left extending from the face a distance sufficient to receive and center the jig, which is squared as before, this time from the drilling ma- chine table. In all cases, after drilling the first hole, the stop pin FIG. 552. shown should be inserted in it to prevent any possibility of the jig shifting on the work. In Fig. 552 is shown a form of box jig, and the-piece of work it is used upon. In this case all the holes are parallel with each other and three of them do not pass through. The work is first DRILLING MACHINES AND DRILLING WORK. 413 faced and bored. All holes in the jig are located with reference to the bore of the work. The lower portion of the jig holds the work central and the upper portion carries the bushings. These parts are nicely fitted together and suitable dowels insure their always remaining in the required position, relative to each other. For the holes that are low on the work surface, extended bush- ings are used. In Fig. 553 is shown a simple form of box jig used for drill- ing holes in round work at right angles to each other. The construction is evident from the cut. The work is slid to a stop in the jig and clamped in position. The hole E is drilled through the bushing C, and F is drilled through the bushing D with the jig resting on its faces A and B respectively. When the angle A O B is a right angle, the holes will be drilled at right angles with each other. By making the angle A O B any re- quired angle the same angular relation between the holes drilled will result. From a consideration of Fig. 552 it is evident that when holes are to be drilled in a piece of work at any angle with each other, a box jig can be used. This jig must contain the work and have two parallel faces, one to receive the bush and the other to rest upon the work table, at right angles to each required hole. The drilling of steel and 'wrought iron requires lubrication 414 MODERN MACHINE SHOP TOOLS. for the cutting tool. Cast iron and brass are drilled dry. As with other cutting tools lard oil makes the most satisfactory lub- ricant. It is expensive, however, and as a result cheaper oils and drilling compounds comprise the lubricants most used. As the lubricant conducts away the heat of friction generated in the cut- ting of stock, it should be freely applied and provisions made for delivering it to the very cutting edge. This, as previously de- scribed, is accomplished by means of oil tube drills. These when used in a revolving spindle require a special form of socket which can be connected by pipe or tubing with a pump, for forcing the lubricant. The drilling of deep holes is usually accomplished in special drilling machines using pod drills. Long twist drills are not FIG. 554- well suited to the drilling of deep holes inasmuch as the strain tends to untwist and make them vibrate and catch in the work. There is also not sufficient land area to .satisfactorily guide the drill, thus making it difficult to drill true, straight deep holes. The pod drill is shown in Fig. 554. It is of semi-circular cross section, the radius of the section being equal to the radius of the required hole. All the cutting is done by the end face at A B which is given the necessary clearance, and for drilling steel a small amount of top rake. An oil tube D, bedded in the shank, supplies the lubricant to the cutting edge. For this class of drilling it is usual to rotate the work to a sta- tionary drill. The feed, however, is usually given the drill. For the drilling of deep holes of large diameter, the drills used have an inserted cutter which can be removed for grinding and set out to compensate for wear. DRILLING MACHINES AND DRILLING WORK. 415 Spotting and facing of small surfaces is usually accomplished with a counter boring tool of the class shown in Fig. 555. In this tool the cutter is held in place by the small screw in the end of the teat. The teat bushings are removable, several sizes being furnished with each counter bore. For special work it is advis- able to have a separate counter bore for each piece. They should be made of tool steel and the teat or pilot point hardened after the FIG. 555. tool is finished. A plain mortise through the stock with a small set screw in the center of the teat is a satisfactory method of holding the cutting blade. By reversing the blade this tool is also well suited for back facing operations. In Fig. 556 is shown the usual method of doing this work. The character of the work is such that the face F cannot be ma- chined from the inside. The counter bore B should be made to fit nicely in the hole and it is also advisable to mill away some. of FIG. 556. the stock D D on the side of the cutter, in order to give a clean cutting edge close down to the bar. A set screw S, or some other means must be provided for preventing the bar from draw- ing out of the socket. When large holes are to be drilled in plates, the twist drill is not well adapted, since its point strikes through before the land enters the full size hole, thus leaving nothing to support the cutting edges. It is also necessary for the drill to reduce to chips all the stock removed. For this work the annular or sweep 416 MODERN MACHINE SHOP TOOLS. drill is well adapted. Such a tool is shown in Fig. 557. The head H carries two cutters C C and the pilot P. The small hole for the pilot is first drilled, after which the tool shown sweeps out the balance of the stock with the least possible amount of cutting duty. When a large hole of considerable length is to be drilled it is good practice to drill a small lead hole the required depth first. This not only aids in starting the large drill true, but prevents the grinding action on the inefficient cutting edge, at the end of the web. In cases of this kind and for the enlarging of cored holes, the three-flute drill is superior to the ordinary form. For the handling of work on the table of the gang drill where it is necessary to move the work from spindle to spindle, some FIG. 557 form of universal vise or chuck, that will permit the work to read- ily center, must be employed. If the operations require but little power and consequently cause only a slight turning effort, the work can be held in a drilling vise and moved to the spindles, the operator centering and holding it while the work is done. On heavier work, however, and in cases where all spindles are operating at the same time a special arrangement must be em- ployed. Take for example the finishing of the collar shown in Fig. 558, which is regularly a turret lathe job. The guide shown * n Fig. 559 is the same length as, and secured to the table in such a position that the center line A B is in the plane of the spindles. The chuck or vise for holding the work is fastened to, or made DRILLING MACHINES AND DRILLING WORK. 417 a part of the slide, shown in Fig. 560. This slide fits over the guide, Fig. 559. The work is secured to the upper half of the slide which due to the two motions readily centers itself under FIG. 558. the spindle. After the first spindle has performed its operation the slide is moved along the guide to the next spindle and another slide with another piece of work is put on the guide and brought T FIG. 559. to the first spindle. After each operation the work is moved to the next spindle and when finished the slide is taken off the end of the guide, and returned to the starting end for another piece. MODERN MACHINE SHOP TOOLS. ' i -__ 4 _ f 1 1 :__4~ I 1 1 i ! 1 i ! I 1 1 """, \ ^X-^ FIG. 560. DRILLING MACHINES AND DRILLING WORK. 419 In this manner several spindles are kept busy, each doing its particular work. In the present example, Fig. 558, the chuck used can be made as shown in Fig. 561. The ring R is secured to the top of the slide, and the work W gripped by the three set screws S S S. In removing the work, but one of these screws is loosened. The work is put in with the top face F down. The first spindle car- FIG. 562. FIG. 563. ries a three-fluted drill 1-64 inch under the finished diameter of the hole. The second spindle carries a reamer which sizes and finishes the hole. The third spindle carries the facing head shown in Fig. 562, which consists of a cast iron head H with the hardened and ground pilot pin P and the inserted cutter with a cutting edge at C which sweeps the face E of the work, leaving it smooth and true. By grinding the cutting edge perfectly par- 42O MODERN MACHINE SHOP TOOLS. allel to the opposite edge of the cutter and securing it squarely against the seat S in the head this tool will face square. The work is now removed from the chuck, the upper half of the slide taken off, and the fixture X shown in Fig. 563 put on. P is a hard- ened pilot, the upper end of which is made into an expanding chuck, as shown. The frame Y Y has a bearing fit at S S on the pilot post and is threaded on the nose of the spindle. A turning tool T and a facing cutter C are secured in the proper positions in the frame. The work is secured to the post as shown with the unfinished face F up. The downward feed of the spindle first turns and then faces the work. The above example, although involving simple operations on a very plain piece of work, serves to illustrate how many pieces of work can be put on a gang drill and produced at a much lower cost than is possible on a single spindle turret machine. Small pulleys, cones and plain work up to 6 and 8 inches in diameter can be advantageously bored and turned by the above method in the drilling machine, when they can be gripped suffici- ently rigid by the bore. When that cannot be done the arrange- ment shown in Fig. 372 can be applied and the work rotated to a stationary cutter. The boring and reaming of large parallel holes in the drilling machine is accomplished in a very satisfactory manner by the method shown in Fig. 564. In this case a 5*4 -inch cylinder 14 inches long is accurately bored in the heavy standard pattern 32-inch upright drill, shown in Fig. 532. As the bottom of the engine bed shown is closed an extended boring bar cannot be used. The work is squared up on the machine table T and firmly clamp- ed ; an arm A supporting the" upper end of the work. The yoke Y is bolted to the table and extends into the work through an opening in the side. This yoke carries a pilot bar P which fits in a tap- ered bearing at E. The boring bar B threads on the nose of the spindle and has a reamed hole H through it to receive the pilot bar P. The cutters C C are secured in the end of the bar and rough out the stock at the first passage through the bore. Sizing cutters are next substituted for C C and the bore brought to reaming size. At the end of this cut the facing cutter F which is secured in the head of the bar, as shown, is carried down and the end of the cylinder faced by a sweep cut. The construction of the end of the bar is such that the cut- ters C C and the sizing cutters can be changed without altering DRILLING MACHINES AND DRILLING WORK. 421 their dimensions. This is especially important with the sizing cutter, as it will carry through several bores without regrinding. The pilot bar P is now taken out and an inserted blade reamer FIG, 564. secured on the end of the boring bar is floated through the bore leaving it smooth, round and parallel. The reamer used on the above work comes from the shop of 4 22 MODERN MACHINE SHOP TOOLS. the B. F. Barnes Company, and its size retaining features are of special interest. It is shown in Fig. 565. The cutters, one of which is shown at A and B, are inserted in the head, as shown. The shank of each cutter is tapered and drawn firmly to its seat by the bolt shown in B. The cutter disc corresponds to one thread of a coarse pitch square thread screw, a portion of which is ground away, as shown at C. In obtaining the required size, the cut- ters are numbered, hardened and fitted in the head. The head is then placed on a mandrel between centers in the grinding ma- chine and the cutters ground to the circle D D of the exact di- ameter required. They are then removed and each cutter ground FIG. 565. *+ to the diameter E E, and replaced in the head, each cutter in its respective bearing as indicated by the numbers. This is im- portant inasmuch as the locations of the bearings vary somewhat and consequently all the cutters are not of the same diameter. The cutting edge can be set to a line across the face of the head and by grinding from the face X only in sharpening, the exact diameter of the tool can be maintained until the cutters are entirely ground away. By keeping a record of the diameter of each cutter, others can be made at any time without the ne- cessity of the first grinding operation above referred to. The objection to this tool is its comparatively short cutting edges. It is only adapted to reamers of the larger sizes, as enough cutters cannot be put in a head of small diameter. CHAPTER XXVIII. GRINDING MACHINES AND GRINDING. Grinding operations in the machine shop depend upon the abrasive or cutting qualities of stone, emery, corundum, and car- borundum, when suitably held and presented to the work. The use of the solid grinding wheel has made it possible to attain many refinements in machine construction that would have been FIG. 566. impossible without it. It has made it practical to economically finish parts in hardened steel that could not possibly be machined with cutting tools in the lathe or . planer ; and on the softer materials, surfaces smoother and truer can be obtained by grind- ing than by any other method. Grinding operations may be divided into the following classi- 424 MODERN MACHINE SHOP TOOLS. fications: 1st, hand grinding; 2d, tool and cutter grinding; 3d, cylindrical grinding; 4th, surface grinding. Hand grinding in- cludes all the grinding operations in which the work is held to the wheel by hand or with a rest, as in rough grinding, ordinary lathe tool grinding, buffing and polishing. The class of machine used for this work is of the simplest form, consisting of the wheel-carrying spindle mounted in suitable bearings on a sub- stantial head or pedestal. In Fig. 566 is shown a simple grind- FIG. 567. ing stand, designed to carry two wheels. It is provided with ad- justable rests upon which the work being ground is steadied. This grinder is intended for dry grinding of the rough and heavy class, where there is little danger of heating the work. When tempered work is to be ground, or any class of work that would be injured by heating, a wet grinder of the class shown in Fig. 567 is used. With tools of this class a supply of water is delivered constantly to the rim of the wheel, thus keeping the GRINDING MACHINES AND GRINDING. 425 work cool. Fig. 568 shows a buffing head or spindle. The spindle extends well out from its bearings for convenience in handling the work being operated upon. These spindles are fitted to receive wheels of wood, leather, or cloth, which are charged with the emery or other grinding material. The work is held to the wheel without the aid of a rest. Tool and cutter grinding requires a better class of grinding machinery than is required for the hand-grinding operations. What is here referred to as tools does not include the ordinary hand and lathe tools, commonly ground on the machine shown in Fig- 567, but refers to drills, reamers, milling cutters, and the finest class of tools. Fig. 569 illustrates a universal cutter and FIG. 568. reamer grinder. As the name implies these tools are provided with all the necessary adjustments and attachments for grinding the cutting edges of all classes of reamers and milling cutters, and in many cases may be used for doing a limited amount of cylindrical grinding both internal and external. A much simpler machine, shown in Fig. 570, constitutes a very satisfactory cutter grinder of small proportions. By the use of the swivel head shown, cutters of all angles may be readily ground, and by plac- ing centers on the slide which is operated by the lever shown under the table, reamers up to the capacity of the machine may be ground. The extensive use of the rotating cutter in machining opera- tions and the necessity of keeping these cutters true and sharp makes necessary the use of the cutter grinder whenever this class 426 MODERN MACHINE SHOP TOOLS. FIG. 560. GRINDING MACHINES AND GRINDING. 427 of tools are used. In the grinding 1 of cutters care and judgment must be exercised and not until the operator has become thor- oughly familiar with all the setting combinations of the machine can he expect to get the best results. As water is not used on the wheels of cutter grinders and the wheels are for this work usually quite hard and fine, light cuts FIG. 571. must be taken in order not to draw the temper of the tool at its cutting edge. The cutter support should be adjusted to bear against the tooth being sharpened and its position relative to the wheel should be such as to give the necessary amount of clear- ance to the cutting edge. Polishing and buffing operations involve the removal by a grinding process of a small part of the work surface, the grind- MODERN MACHINE SHOP TOOLS. ing material used being of such a fine character as to leave a smooth, highly-finished surface. This class of work is usually done on the burring spindle shown in Fig. 568. Buffing does not leave a true surface and is consequently confined strictly to polishing work. The grinding of twist drills is a very particular operation, requiring a skillful operator, if performed by hand. In Fig. 571 is shown a twist-drill grinder in which the twist drills may be ground with the assurance that the angle and clearance will be correct and equal on both sides. In the machine shown, the construction is such that drills of any diameter within the limits of the machine may be ground with but one preliminary adjustment for each size. Unfortunately a twist drill can be ground by hand on a plain emery wheel, which fact keeps the twist drill grinder out of many shops where its use would add materially to the efficiency of the drilling equipment. Correctly ground drills cut faster, stand up longer between grindings and produce the proper size of hole, A correctly-ground drill seldom breaks, as it cuts freely ahead of its feed 'and does not scrape and jam, as is the case when clear- ance and angle are wrong. Grinding machines for the grinding of common forged lathe and planer tools are manufactured, and in shops where large numbers of forged tools are used have proved very efficient. In the working of these grinders the tool is clamped in a suitable head and presented to the emery wheel at the proper rake and clearance angles. Cylindrical grinding as a class, covers all forms of grinding operations upon external and internal cylindrical surfaces. The universal grinding machine, or, as it is sometimes termed, grind- ing lathe, shown in Fig. 572, is specially adapted to this very ex- acting class of work. All machines of this class consist of a swivel table carrying a suitable head and tail stock, and of a wheel stand carrying the grinding wheel. The arrangement of parts is such that either the wheel stand is given the feeding mo- tion past a stationary table or the platen is given the feed past the wheel. The adjustments are such that the wheel can be set in or away from the line of the work center, or can be turned to stand at any desired angle with the line of the feed travel, which is necessary for face and steep angle grinding. The swivel table can be set at an angle with its travel, or the line of travel of the GRINDING MACHINES AND GRINDING. 429 wheel where the table is stationary, thus making possible the grinding of long tapers. For internal grinding, a small spindle, run at a high rate of speed and carrying an emery wheel small enough in diameter to operate in the bore to be ground, is used. These machines are provided with suitable pumps for supplying an abundance of water to the wheel and work, when the character of the work is such as to require it. As these machines are ex- pected to produce work smooth and cylindrically true, they are most carefully built, and should embody all the refinements known in machine tool construction. The spindle for carrying the emery wheel is perfectly balanced and runs in very close-fitting boxes, as any slack in the bearings or lack of balance proves fatal to the production of correct results. Provisions are made for rotating the .work, when held between dead centers, with a spring tension adjustment on the tail center, thus reducing the danger due to expansion and the unequal wearing of the center bearings. The screw adjustment for setting the wheel up to work is graduated to thousands of an inch, thus forming an excellent guide in de- termining the amount of stock removed. The application of an automatic cross feed to the wheel stand is a valuable addition to the plain and^universal machines, as. it advances the wheel to the work by fixed amounts at the begin- ning of each cut, thus making the conditions more uniform and requiring less attention on the part of the operator. The amount of feed for each passage of the wheel over the work can be varied to suit the condition. A feed as fine as' y% of TTr V-o can be ob- tained, which would reduce the work l / 4 of T oVo for eacn passage of the wheel across it. An automatic stop throws- out the feed when the wheel has advanced the required amount. As this mechanism is necessarily very sensitive and delicate it must be kept perfectly clean and well lubricated. Plain grinding machines are in many respects similar to the universal machines. As they are, however, used for straight cylindrical and long tapered work, many of the universal features are dispensed with, making them strictly a manufacturers' ma- chine. The wheel for any class of grinding should be properly adapted to its work as to shape, grade, and hardness. The shape and character of the work determine in any case the shape of the wheel to use ; while the material of which the work is composed, the amount of metal to be removed, and the condition of the 430 MODERN MACHINE SHOP TOOLS. finished surfaces must determine the quality of the wheel. Emery and other wheels of that class are composed of two elements the abrasive and the cementing materials. The cement as clay, glue, or rubber holds together the grains of emery, and in use as the grains become worn and dulled, they break away from their settings in the cement, and fresh grains are uncovered to go on with the cutting process. If this breaking down process is comparatively rapid, the wheel cuts very freely, but reduces in diameter correspondingly fast. If the cement, on the other hand, does not give up the worn grains of emery, the wheel glazes, cuts slowly, and heats the work. The surface velocity of the wheel should be correct for the different classes of work and grade of wheel. The wheel is ordinarily most efficient just before it stops breaking away and begins to glaze. Up to this point, the higher the speed the more metal it will remove in a given length of time. When run at lower speed, it cuts somewhat easier, and does not heat the work as badly. Glazing is usually prevented by reducing the speed. Soft wheels stand up better at high, than at low speeds. The wider the faces of the wheel presented to the work, the more cutting surface, and the faster the metal is ground away. The feeds must be correspondingly coarse. The wider-faced wheels should be comparatively soft, and as the face reduces in width the wheel should increase in hardness. The surface speed of the work should be proportionate to the speed of the wheel, and in any case should be sufficiently slow to allow the wheel ample time to cut away the metal without crowding, as otherwise the work is sprung away from the wheel more or less, and untrue work results. A free cutting wheel, run at the proper speed and with a light cut, is best for accurate grinding, as it removes the metal without pressure and consequently cuts the high spots most and does not heat up the work. It is, however, necessary on very accurate -work to use water on the wheel, as a slight change of tempera- ture affects the work noticeably. When long cuts are to be taken, it is sometimes difficult to get the wheel to stand up so as to give a parallel cut. In such cases, the wheel must be properly adapted, and each grain of emery must cut as long as possible before drop- ping out. As the harder wheels hold the emery longer, and can be run somewhat slower, they are best adapted to this condition. The wheel should have a wide face, and should be of large diam- eter, so as to present as many grains of the abrasive as possible GRINDING MACHINES AND GRINDING. 431 to perform the required work. It is also necessary to use the coarser feed and light cuts in order that the wheel may cover the entire surface before it drops materially in diameter. The direction of feed is changed for each time over the work, which also tends to even up the wear on the wheel. All manufacturers of grinding wheels, however, give a table of speeds for the different diameter of wheels they manufacture, but these speeds are not always best suited to the work. All wheels should fit easily, yet closely, on their spindle to prevent danger from cracking, and a soft washer of uniform thickness should be placed between the sides of the wheel and the clamp- ing washer. The wheel should be firmly clamped and trued be- fore using. Manufacturers test all wheels by running them at a speed considerably above their rated speed. In the grinding 'of long work it is quite necessary to support it at one or more points between its end bearings, as otherwise it will spring and chatter, making true smooth work impossible. For this purpose, suitable steady and follow rests are provided with the machine. * In Fig. 573 is illustrated the method of grinding slight tapers 573- 43 2 MODERN MACHINE SHOP TOOLS. in the universal or plain grinding machines. By means of a screw and graduation at the end of the table it is swiveled to the required angle with the line of travel of the slide. In this man- ner tapers up to i*/2 or 2 inches per foot may be ground. When a steeper taper is required it can be obtained in the universal ma- chine by setting the wheel slide to the required angle, as shown in Fig. 574. In this particular case, two tapers, one of 45 de- grees and one of 5 degrees are required on the work. By swing- FIG. 574. ing the swivel table to 5 degrees from the line of its travel the slight taper can be ground by the travel of the table past the wheel. By setting the wheel slide to 50 degrees, as shown, the steep taper is ground by operating the wheel slide, the swivel table re- maining stationary. If but the 45 degree taper was required, the table would be left central, and the wheel slide set to 45 degrees. As shown in the cut, the corner of the wheel is dressed to give a cutting face of suitable width. GRINDING MACHINES AND GRINDING. 433 In Fig. 575 is shown the usual method of face grinding. The work is held in the chuck or on a face plate as shown. If the face is to be a plane surface, the head spindle axis is set at right angles to the wheel spindle. By varying this angle concave or convex, conical surfaces may be obtained. In Fig. 576 is shown the method of grinding internal surfaces FIG. 575. with the internal fixture. The example given serves to illustrate, as in Fig. 574, the settings for both slight and steep tapers. The small taper is obtained by setting the swing table to the required angle with the travel of the table slide and the steep taper, by using the wheel slide set to give the wheel the required line of travel. It will be noted that in using the internal grinding fix- ture, the position of the wheel table is reversed from its universal 434 MODERN MACHINE SHOP TOOLS. position and the fixture secured to the end of the table. A belt- ing jack is substituted for the emery wheel spindle and the spindle of the internal fixture driven by a light canvas belt from the jack. Although the spindle of the internal grinding fixture is driven at a very high speed, the diameters of the wheels used are so small that it is not possible to obtain a periphery speed as high as would FIG. 576. be desired. It therefore is necessary to use a free cutting wheel and to rotate the work to it at a comparatively slow speed. On these machines all work and wheel settings are to care- fully graduated arcs. These graduations cannot, however, be relied upon for exact settings within the accuracy limit of the machine. If, for example, the machine is set for parallel grind- ing on a certain class of work, the head stock is undamped and the spindle thrown out of parallel with the table's line of travel ; it will be found practically impossible to set the head back to its GRINDING MACHINES AND GRINDING. 435 original position, sufficiently close to make the machine grind parallel again. In Tact, so minute are the variations that the wheel will detect that the unclamping of the tail stock, moving it out of 'position and then back will show an unparallel condition of the work. It therefore becomes necessary after each setting of head or tail stock to readjust the work table by means of the end ad- justing screw in order that the line of rotation may be brought parallel with the line of motion of the table slide. Surface grinding bears the same relation to planing that cyl- FIG - indrical grinding does to turning. The surface grinders use the same form of wheels as the cylindrical grinding machines. The work, however, is secured to the work table, which is fed under or over the wheel. In Fig. 577 is shown a surface grinding ma- chine. The construction of the machine is clearly shown. The wheel is adjustable vertically to give depth of cut, the arrange- ment of pulleys being such as to give constant tension on the belt for all positions of the wheel. The cross feed is obtained by moving the table toward or away from the housings on suit- 43^ MODERN MACHINE SHOP TOOLS. able cross slides. Provisions are made for supplying water to the wheel when necessary. In Fig. 578 is shown a plain grinder provided with a surface grinding plate. In this case the wheel projects above the surface of the plate only the amount of the cut required, and the work is passed over it by hand. To give satisfactory results, the spindle and its bearing should be first class, and the wheel in perfect bal- ance. A grinder of this class is a most satisfactory tool for FIG. 578. smoothing and polishing surfaces where finish and not truth is required. A more refined grinder, somewhat after the same order, and known as a disc grinder is shown in Fig. 579. These are very nicely constructed grinders in which the grinding is done by sheet emery glued to the faces of the discs. The rests swing across the face of the disc, the work being held on top of the rest. For the finishing of one or more plane surfaces on small parts, this tool is very well adapted. GRINDING MACHINES AND GRINDING. 437 In Fig. 580 is shown a form of portable hand emery grinder driven by a rope transmission through a flexible shaft. These grinders are very satisfactory tools for the grinding of heavy castings that cannot be held to a wheel. For truing the emery wheels used on the better classes of grinding machinery nothing but a black diamond truer is suitable. Such a tool is shown in Fig. 581. The diamond is mounted in the end of the round steel holder, as shown. The round holder FIG. 579. enables the stone to be presented to the wheel in various posi- tions, so as to bring the several cutting points of the stone into action. As the diamond is harder than the emery, it actually cuts the wheel away. A suitable fixture is usually provided for holding the truer in such a manner that it can be passed squarely by the part of the wheel being trued. Water should be used on the wheel in true- ing and the cuts should be light in order to obtain good results and to preserve the diamond. For the coarser wheels, dressers of the character of the one 438 MODERN MACHINE SHOP TOOLS. shown in Fig. 582 are used. Several forms of discs are used. The discs are made of hard steel or chilled iron and turn freely upon a pin. In their action the teeth of the discs break up the surface of the wheel as they roll together and dislodge the high particles of the wheel by a picking action. Lapping is a refined grinding process used for the final finish- ing of machine ground surfaces, usually of hardened steel. A lap is usually made of cast iron, copper or lead, the surface being FIG. 582A. FIG. 580. FIG. 581. FIG. 582B. coated with very fine washed emery. In Fig. 583 is shown a form of lap well suited to the finishing of cylindrical surfaces. The body of the lap is of cast iron with lead or copper strips a a a a extending through it. These soft strips serve to hold the emery better than a harder material. By slightly reducing the diameter of the lap by means of the thumb screw, as the grind- ing proceeds, the work may be brought to the required size. In its use, the work is usually rotated at a comparatively high speed, and the lap held by the hand. By moving it slowly from end to end of the surface being finished, parallel work can be obtained. GRINDING MACHINES AND GRINDING. 439 It is in this manner that hardened steel plugs receive their final sizing. For the finishing of bores the same general method is em- ployed. A plug, preferably with the lead or copper strips, so constructed that it can be slightly expanded, is the form usual- ly employed. In Fig. 584 is shown a form well suited to most classes of work. It is preferably of cast iron but may be made of soft steel. The slot is cut through and the wedges w w serve to give the slight expansion necessary. For the lapping of flat surfaces, a cast iron plate drilled full FIG. 583. FIG. 584. of holes with plugs of lead or copper inserted and the surface then planed as true as possible can be used. This surface is charged with emery and oil and the work rubbed over it, the di- rection of motion and part of the surface used, being constantly changed in order to wear the lap equally all over. Although it. is impossible to give any fixed rule for the cor- rect periphery speed of emery wheels of different makes and for varying service, the tables given in Chapter XXXIV. will serve as suitable guides. CHAPTER XXIX. HARDENING AND TEMPERING. The hardening and tempering of tool steels present many problems which can only be solved by a wide and varied experi- ence at the temperer's forge. The simpler cases are mastered with little trouble, but when it comes to the tempering of difficult and expensive pieces the trained judgment of the expert temperer is usually sought. Hardening and tempering of steel brings about such a change in its physical condition that it may be used in places where cut- ting edges, resistance against wear and elasticity are required. The hardening and tempering of steel are two quite different things although often referred to as the same. By hardening we change the physical condition of the steel, transforming it from a relatively soft material to an exceedingly hard one and at the same time, rendering it brittle and weak. By tempering we reduce the hardness to the degree required for performing the work it is intended for, and in so doing restore much of its origi- nal strength and toughness. For tempering it is therefore neces- sary that a degree of hardness equal to or greater than that re- quired must first be given the steel. The amount of carbon contained in a piece of steel determines its temper. The more carbon, the higher the temper. Thus J % P er cent of carbon makes a steel capable of very high temp- ers, such as are required for the turning of chilled rolls and other very hard materials. One per cent is the amount usual when the steel is used for the more common tools, as cold chisels,, drifts, etc. Lathe tools, milling cutters, taps, drills, and reamers come between these two limits. In general, the more the carbon, the greater the care required in the heating and handling of the steel. A 1% per cent carbon steel burns very easily while a one per cent steel can be heated with little danger from this source. Cutting tools that are forged to shape are given a short temper ; that is only a short portion at the cutting edge is made hard, the balance of the tool being left tough to support the cut- ting edge, and when that edge is worn or ground back into the softer part the tool is redressed and retempered. When, as with HARDENING AND TEMPERING. 441 a drill or milling cutter, the tool must be repeatedly sharpened until worn completely out without retempering, it is necessary to harden it through and then draw down for toughness as far as the character of the tool will permit. Cutters,- reamers and mandrels of comparatively large diameter are usually given a hard surface temper, leaving the core soft. When a piece of steel is of sufficiently high temper to be used as a metal cutting tool it is too hard to permit of any bending. By drawing the temper sufficiently low, however, the steel gains in toughness at the expense of its hardness and what is termed a spring temper is obtained. The tempering of steel machine parts to make them resist wear is frequently necessary. The higher the temper the better the wear reducing quality ; the hardness, however, being limited by the strength required. The manufacturers of tool steels usually prefer to recommend the grade and temper of steel for any specific purpose. In gen- eral, the higher the carbon the finer the steel, but not necessarily the better for many classes of work. For general purposes a grade of steel of medium temper costing about twelve cents per pound, as furnished by any of the reputable makers, will be found satisfactory. The extra qualities at 16 to 20 cents per pound are suitable for the most exacting requirements, while a lower grade at eight cents can be used for the less important work. For many machinery parts, when a temper to resist wear only is required, the lowest grades of tool steel or even machinery steel can be used. The latter is not considered as a tempering steel, but can be somewhat hardened by tempering methods; and can be given a hard surface by case hardening. There are many special grades of steel running much higher in price; their uses being restricted to certain lines. The heating of steel may be classed under three distinct heads ; first, for forging; second, hardening, and third, for tempering. For forging, a clean, thick fire should be used with a steady blast, so regulated as to give a uniform heat to the work. It is very important that the work be heated uniformly and at the same time it is advisable to get this heat as quickly as possible, as it usually injures the quality of the steel to leave it too long in the fire. If the steel is not uniformly heated, the forging produces surr face cracks, makes the grain of the steel coarse and is otherwise injurious. Heavy forging at moderate heats refines and improves 442 MODERN MACHINE SHOP TOOLS. the quality of the steel. In hardening, a coke, charcoal or gas fire should be used for heating the steel. The blast should be moderate in order to raise the temperature uniformly and without overheating corners and delicate cutting edges. The heat should be the lowest possible at which the steel will properly harden. Too high a heat injures the quality of the steel and increases the strains and consequent chances for cracking. An uneven heat is also very apt to produce excessive strains and cracks, when the steel is quenched. For small flat pieces the heating is frequently done in the open flame of a gas or charcoal fire. A level .charcoal fire with a dis- tributed blast is much used for heating thin work, as for example, metal saws, gear cutters and similar work which can be laid flat on the surface of the fire. A fire of this kind is also suitable for heating small round work. When the work is long and com- paratively small in diameter a muffler is often used. This may consist of a piece of pipe buried in the fire and heated to a bright red. The work is held in the center of the pipe and by constant- ly rotating it a very uniform heat is obtained. The heating of work for hardening in melted lead or a flux of salt and cyanide of potassium is extensively employed by many manufacturers of small tools. In each case the method is similar. A deep cast iron pot of from four to six inches diameter is placed in a special furnace where a suitably regulated fire can be main- tained under and around it. This pot is filled to within a few inches of the top with lead. By a proper regulation of the fire the temperature of the lead is maintained at the point it is desired to heat the steel to. To prevent the oxidation and resulting waste of the lead its surface should be covered with powdered charcoal. A study of the appearance of the surface of the lead provides a reliable means of determining the proper heat. It is quite pos- sible to obtain a temperature of the lead sufficiently high to injure a high carbon steel ; care must therefore be taken in the matter of regulating the heat. The article to be hardened is immersed in the lead and allowed to remain until it has acquired, throughout its entire body, the same temperature as the lead. It is evident that all parts of the work surface are subject to the same degree of heat, which insures the greatest uniformity in its heating. After heating, the hardness is obtained by quickly cooling the steel. The usual method is to plunge it into cold water, brine or HARDENING AND TEMPERING. 443 oil, immediately after taking it from the fire. This sudden cool- ing of the steel is necessary, and the success of tempering depends very largely upon the manner in which it is done. The shape and character of the work must in every case determine the manner in which the steel is presented to the cooling bath. Salt added to the water in which the quenching is performed intensifies the hardening effect. If the body of steel is large, a large volume of cooling solution is necessary. When the work is of a bulky character, that part which first enters the cooling bath is quite apt to harden better than the top, inasmuch as the boiling action prevents the water from coming in actual contact with the surface longer at the upper parts of the work than at the lower. For this reason, on heavy work, a large jet of water is frequently forced against the upper portion of the work. Cooling in oil is for many classes of work considered superior to water or brine. In its softer action and more rapid conduction of the heat from the steel, lie the advantages in oil quenching. Sperm or cottonseed oils are those usually employed. In using the fish oils, some means of ventilating that will carry away the disagreeable odor should be employed. Springs of all classes are usually hardened in oil. When the lead bath is used for heating more or less of the lead and its dross will adhere to the work if it is put in dry. By covering the work with a thin coating of soft soap before im- mersing it, a thin charred covering will form over the surface of the steel which prevents the lead from adhering to it when re- moved from the bath. By first plunging .the work into a brine solution this coating is removed, .leaving a clear gray surface on the work. When the workman is not familiar with the hardening of a particular brand of steel from which some expensive tool is made, it is usually advisable for him to experiment upon a small piece from the .same bar and thus determine the lowest heat at which the steel will properly harden. It is important that the article hardens on the first heat as reheating is quite apt to injure the quality of the steel and adds to the possibility of loss by cracking. Having hardened the work to a degree considerably beyond that required, it is then necessary to temper it, which involves the reduction of the hardness to the point necessary for the work required of the tool. The tempering of steel is accomplished by 444 MODERN MACHINE SHOP TOOLS. gradually raising its temperature until the hardness has drawn or let down to the required point, when plunging the steel into water fixes the hardness. When the temperature has reached about 600 degrees Fahrenheit the hardness has been drawn down through the several points at which cutting tools for the various uses are tempered. If the rise in temperature continues past this point the hardness continues to disappear in proportion to the amount of heat given it. When a red heat is reached it has lost all the hardness given it in the hardening process and is again back to its normally soft condition. The correct tempering of a piece of hardened steel for any class of work must therefore depend upon the workman's ability to raise the temperature to the proper degree before cooling. This he accomplishes by one of two methods ; first by actually measuring the temperature with a thermometer and second, by what is known as the color method. Except in cases where tem- pering is done in a manufacturing way the latter method is the one always employed. An understanding of the colors, the corresponding tempera- tures and the relation between color and hardness are quite necessary. Lathe and planer tools are given a hard temper. Their color is a straw yellow, which comes at a temperature of 460 de- grees. A brown yellow at 500 degrees is used for milling cut- ters, taps, dies, and reamers. Light purple at 530 degrees is about right for twist drills and wood working tools and dark purple at 550 to a dark blue at 570 degrees is usual for cold chisels, screw drivers, and wood saws. In determining the proper temper by means of a thermometer the following method is employed : Take 1 for example the tem- pering of a quantity of small taps. Having been properly hard- ened they are placed in a wire basket and the entire mass sus- pended in an iron vessel filled with sperm oil. The vessel is covered with a closely fitting cover having a hole through the top sufficiently large to permit the stem of a thermometer, which is in the oil, to extend through for reading. As the tempera- tures required are considerably below the boiling point of mer- cury, a mercurial thermometer having the necessary range may be employed for determining proper temperatures. It is neces- sary to cover the oil closely, as otherwise it would flash up at the high temperatures employed. Heat is applied to the bottom of the vessel and the temperature of the oil and the articles in it HARDENING AND TEMPERING. 445 gradually raised until, in the present example, the thermometer indicates a temperature of 500 degrees. In order to obtain a perfectly even temperature in the oil it is advisable to arrange for some means of stirring it while the heat is being applied. The basket and its contents are taken out when this point is reached and immersed in cold water with the assurance that a uniform temper has been obtained in the entire batch. In tempering by color, the article after being hardened is made bright by grinding or buffing. Taps and reamers for example are, after hardening and before tempering, ground in the flutes, thus leaving bright surfaces to show the run of the color. The article is then held over the fire, being constantly turned in such a manner that all parts are equally exposed to the heat. The raising of the temperature should be gradual and the surface closely watched for the first show of color. The color will start with a very light tinge of yellow which gradually changes into a straw yellow and next into the brownish yellow. If it is a tap or a reamer it is quickly immersed in cold water just as the yellow blends into the brown. If it was, for example, a cold chisel, the colors would be allowed to run from the yellow through the purples and into the dark blue. As is the case when heating for hardening, difficult work, especially if long, can usually be heated for tempering in a muffler to very good advantage. An excellent method of heating for tempering small tools, as taps, reamers, cutters, etc., is in a bath of sand. A suitable tray covered with about one inch of pure white sand supported over a series of gas burners is employed. By first burning all the im- purities out of the sand false colors will not be shown on the articles being tempered. The article, if small or thin, can be laid on the top of the sand, but if larger, it should be buried in it, only a small part of the surface being exposed to show the starting of the color. In the tempering of a piece of steel, the strains are such that the form of the article usually undergoes a change. This may occur in either the hardening or the tempering or both. In such tools as milling cutters and reamers which receive their final finishing by grinding after they are tempered slight changes in form are not troublesome. With long taps, drills, formed cut- ters, etc., it becomes a more serious question. Take, for ex- ample, a stay bolt tap two feet long. Although the greatest care 446 MODERN MACHINE SHOP TOOLS. is exercised in tempering, it usually comes out badly bent. In straightening work of this kind it is necessary to heat it up very nearly to its temper point, place it between a pair of centers, revolve it quickly by drawing the hand over it and note with a piece of chalk the high point or belly. Place it with the belly down and by means of a lever or small jack having a quick pitch screw, spring the work in the direction opposite to its curvature and beyond its proper position an amount somewhat greater than its temper bend. Hold it in this strained position for a few seconds, remove quickly and immerse in cold water. The ex- perience gained in a few trials will usually enable the operator to successfully straighten work of this character. As a general rule it is not advisable to leave tool steel long in the fire as "soaking" is usually injurious to its structure. Oc- casionally, however, a piece of steel known to be of good quality will resist hardening properly when treated by the regular meth- ods. In such cases it can usually be hardened if allowed to re- main in an even fire and "soak" for a considerable length of time. When a hard surface and soft center are required, as is often the case when the tool must stand severe strains and shocks, it is given a quick surface heat, the core remaining comparatively cool, and then plunged into the cooling solution. This hardens the surface and leaves a soft strong core. Large mandrels, punches, dies and articles of that class are usually hardened in this manner. As the high carbon steels harden at comparatively low heats they should never be given a high heat either for forging or hard- ening as the dangers of burning them are great. Forged articles, as lathe tools and cold chisels, are usually hardened and tempered with the same heat. In such cases only a small portion at the cutting edge is tempered. It is heated for a considerable distance back from the part to be tempered and the heat in this portion is used in drawing to temper the cutting portion. For example, a cold chisel which should be tem- pered for only a short distance back from -the point, is given a proper heat for hardening at the point and this heat allowed to run back two or three inches. In quenching only the point for a half inch or so back is immersed and held until the red has nearly faded out of the heated portion. It is then removed and the bit brightened up, by a few quick strokes over its surface with a piece of -emery cloth, sand stone or any grinding material at HARDENING AND TEMPERING. 447 hand. The operator then watches for the color, the heat in the balance of the tool being sufficient to draw the point. The straw colors will start first and move toward the point; these will be quickly followed by the purples and the blue, and just as the required color reaches the point the tool is plunged in the water. When too much heat remains in the tool after the hardening of the point, the temper draws too fast and the point must be im- mersed a second time to check the drawing, as it would not do to immerse the whole tool while so much heat remains in it. On the other hand if too little heat remains with which to draw the temper, it will be necessary to draw in the open fire as above explained. What are known as tungsten or self-hardening steels have come into very general use for machine shop cutting tools which require no machine work upon them and little or no forging. These steels are produced by adding several per cent of the metal tungsten to the carbon steel. This makes a steel possess- ing great hardness without the necessity of tempering. It is very "short" when heated and requires great care and skill in forging. It is usually used in special holders and ground to shape without the necessity of forging. After heating for forg- ing the steel must be allowed to cool in the air as immersion in water is sure to crack it. It must be nicked on an emery wheel and broken to required lengths, as it cannot be cut when cold. The demand for high cutting speeds and the comparatively recent introduction of high speed cutting steels to meet this re- quirement is creating a vast amount of interest. These steels are, unlike tungsten steel, capable. of annealing and consequently can be used for making tools of finer class, as milling cutters, reamers, etc. In some recent experiments by the author with "Novo" air-hardening steel, cutting speeds as high as no feet per minute at coarse feed and moderate cuts on mild steel forging without lubrication, were successfully maintained. Although the cutting edge quickly drew to a dark blue it held its keenness for an unusual length of time. It is quite evident that for heavy roughing work these steels are remarkably well adapted and that the rigidity and ordinary spindle speeds of standard engine lathes are not sufficient for its most effective use. In forging the "Novo" steel it is at all temperatures other than a white heat "hot short" and crumbles or crushes away. It cannot be burnt and for forging and hardening must be given MODERN MACHINE SHOP TOOLS. a uniform white welding heat. When thus heated, for harden- ing, it is placed immediately under the strongest and coldest air "blast available and left until quite cold. It is not drawn or tempered after hardening. These steels, although extremely hard, possess reasonable strength. It is advisable, however, for heavy work to use as large a bar as possible, not only because better support to the cutting edge can be had, but because the large body of steel conducts away the heat caused by the cutting much more rapidly than can a small tool. The case hardening of iron and mild steel is a process where- by the surface of the work is converted into tool steel and hard- ened. This is accomplished by heating the work in contact with a material, rich in carbon, which gives up its carbon to the work. When large numbers of pieces are to be case hardened they are packed in an iron box with granulated rawbone and fine charcoal mixed in about equal proportions. For the rawbone may be substituted bone black, charred leather or some one of the various special preparations for this work. The box is sealed with an iron coyer and fire clay at the joints to exclude the air and prevent the escape of the gases as far as possible. It is then placed in the furnace and allowed to slowly heat up to a low red heat, at which temperature it is maintained for a length of time depending upon the depth it is desired to convert the surface of the work into tool steel. Under favorable conditions the surface will harden to a depth of 1-32 inch, by heating about two hours; 1-16 can be obtained in from five to six hours and by heating for eighteen or twenty hours, a hardened surface as thick as *4~ inch can be obtained. After heating the contents of the box, it is dumped into a tank of cooling water preferably of considerable depth, as the articles should be well cooled before they reach the bottom. By allowing the articles to fall a short distance through the air before strik- ing the water, the coloring of the surface will be improved. When only a few pieces are to be treated, they may be heated in an open fire to a bright red ; the surfaces to be hard- ened then covered with cyanide of potassium and again heated before cooling in the water. The thickness of the case Hardened surface thus obtained is quite thin. By several applications of the cyanide it can be made sufficiently thick for most require- ments. HARDENING AND TEMPERING. . 449 Another and very satisfactory method is to melt in a black lead crucible, equal parts of cyanide of potassium and fine salt. Bring this up to a bright red heat and immerse the articles to be hardened in it, leaving for a length of time depending on the de- gree of hardness required. Five to ten minutes will give a thick- ness sufficient for all ordinary requirements. When finely mottled surfaces are desired, the work should be polished and thoroughly cleaned before treating. The blowing of air through the cooling water at the time the work is cooled will add much to the beauty of the markings on its surface. CHAPTER XXX. FASTENINGS. The term "fastening" applies to those devices used by the machinist for holding together in their relative positions the various elements that make up a machine. Their importance in mechanical work cannot be overestimated, and a brief description of the more important cases seems advisable. With few exceptions, all threaded fastenings use the sharp V or United States standard form of thread. In Fig. 585 are shown the three forms of machine bolts most used. The manu- facturers of machine bolts have adopted the United States stand- ard form of thread and as a consequence these bolts run reason- ably close to size, but a trifle small. A ^j bolt, for example, will pass through a ^ drilled hole. The square head and nut bolt as shown at A is most used on general work. When the nut comes in a place where it is difficult to get at it with a wrench, the hexagon nut is substituted for the square. At B the bolt has both hexagon head and nut, presenting a more finished appear- ance. The snap or round head machine bolt is shown at C. It differs from the others only in its form of head. Carriage bolts are similar as to diameter and form of thread to the machine bolt shown at C with the exception of a square under the head which prevents them from turning when used in wood. The length of this square section is approximately equal to the diameter of the bolt. On square and hexagon head machine bolts, the thickness of the head is 24 the diameter of the bolt and the thickness of the , nut is i^s the diameter. The width of the head and nut be- tween flats is I J4 the diameter of the bolt in both the hexagon and square. The width from angle to angle on the hexagon is two times the bolt diameter. A table of weights and dimensions of machine bolts is given in Chapter XXXIV. Turned machine bolts, commonly known as coupling bolts, are much used for holding together machine and engine parts. In such cases they fit closely in reamed holes. Machine bolts with specially formed heads and nuts are fre- quently used. As they are not regularly carried in stock by the FASTENINGS. 451 manufacturers and must be made up to order, any desired form may be had. When the character of the work is such that one of the parts that are being secured together can be tapped, a stud bolt or cap screw may be used. In Fig. 586 at A is shown the standard form of milled stud. The short thread is usually made slightly larger than the long one, as it is intended to fit closely the tapped hole in the work. The stud when set extends above the surface an amount sufficient to receive the work and a nut on the outside. FIG. 585. ==H_" FIG. 586. FIG. 587. At B and C are shown two forms of special collar studs used only on special work. In Fig. 587 is shown a simple device for set- ting studs. A piece of hexagon steel with a tapped hole through it as shown, is screwed on the end of the stud and the special set screw tightened against the end of the stud. The set screw should be cupped slightly as shown, and hardened. It is also ad- visable to case harden the body. By using two wrenches the device is readily removed after the stud has been set. It is frequently necessary to lock the nuts on bolts and studs to prevent them from working loose. The use of two nuts, as 452 MODERN MACHINE SHOP TOOLS. shown in Fig. 588, at A, is a very common method. The thinner nut is called a lock or check nut and is usually one-half the bolt diameter in thickness. The check nut is usually put on the outside; a better distribution of the strains, however, is ob- tained when the thin nut is placed on the inside. This arrange- ment of nuts while not absolutely proof against their working loose, can usually be relied upon. By allowing the bolt to ex- tend through the nut an amount sufficient to permit drilling a hole and inserting a cotter key, as shown at B, a most satisfac- tory safeguard against loosing the nut is obtained. The cotter key in connection with the jam nut is perfectly safe. Devices of the character of the one shown in Fig. 589 are A. B. FIG. 588. occasionally used in connection with standard nuts. More often, however, a special nut having a notched rim is used in connection with a dog to engage the notches and secured to the body of the work. Cap screws are similar to coupling bolts without nuts. In Fig. 590 are shown three styles; at A, a square head; at B, a hexagon head, and at C, a form known as a tap bolt which is threaded close under the head. When cap screws are used in places where they must often be turned, they are usually of the forms shown in Fig. 591 and known as collar cap screws. Cap screws with slotted heads for a screw driver, are shown FASTENINGS. 453 in Fig. 592 ; the flat head at A ; the round or button head at B, and the fillister head at C. These are known as machine screws when of machine screw diameter and threads. Set screws are made of steel and tempered or of iron and case hardened. They form a convenient and largely used means of securing pulleys, collars, etc., to shafting, and in their headless FIG. 591 forms for holding liners and other machine parts. Set screws are not well suited to the holding of pulleys that must transmit much power, as they do not get much bearing on the shaft and as a result are very apt to slip. The standard form of set screw is shown in Fig. 593, as is also the headless pattern. What are known as low head or collar set screws have square heads of FIG. 592. about one-half the height of the regular head. In this figure are also shown the various forms of points used on set screws. A and B, the cupped and ovai points, are regular patterns. The flat point C, the cone point D, and the pivot point E are specials. Studs, cap, and set screws are regularly made with both the 454 MODERN MACHINE SHOP TOOLS. sharp V and United States standard threads ; unless the latter is specified, orders are always filled with V threads. Square and hexagon nuts may be had either hot or cold press- ed, commonly known as black and bright. The cold pressed nuts are those usually used on machine and engine work. A plain nut, tapped and faced on the work side meets the necessities of any case. It is not, however, when applied to well-finished work, in keeping in appearance. It is therefore usual to use what are termed semi-finished, finished or finished and case hardened nuts on good work. A semi-finished nut is faced bottom and top and chamfered on the top. A finished nut has its - faces buffed or FIG. 594. ground smooth in addition to the facing, and the case hardened nut, as its name indicates, is hardened after being finished. Keys and feathers are much used in machine construction in the fastening of the parts to shafts. In Fig. 594 are shown the three forms of keys most used. The round key, shown at A, is used in places where little power is to be transmitted and on light work only. A small hole drilled half in the hub and half in the shaft receives the round key, which is usually not tapered and driven firmly in. By tapping the hole, a headless screw can be substituted for the round key. This not only provides a mean? for removing if necessary, but prevents the possibility of any FASTENINGS. 455 motion in the direction of the shaft's length. Keys of this kind can be properly applied only when the end of the shaft and hub are in the same plane. When the hub and shaft are of different materials, as is usually the case, difficulty is experienced in mak- ing the drill follow the joint, as it will tend to crowd toward the softer metal. Where the strains transmitted are moderate, the flat key shown at B may be employed. As the flat on the shaft can, if necessary, be filed, this forms a most convenient method of key- ing after a shaft is in place. The width of the key should be from one-quarter to one-third the diameter of the shaft. If the key way is tapered in the hub the key should have the same taper and can be driven firmly to its seat. If the key way is straight it is necessary to use two set screws over the key. The flat key sunk in the shaft, as shown at C, is the most reliable and consequently most used. It is a tapered key fitting closely in the sides and driven to a tight top and bottom fit. By using a straight key way with set screws over each end the key may be made straight. Practice as to the taper and dimensions of keys is somewhat at variance. Good practice, however, indicates the use of 3-16 of an inch taper per foot with a width of key equal to one-quarter the shaft diameter and a thickness equal to. one-sixth the shaft diameter. For shafting a width equal to one-quarter the diameter and a thickness 1-16 of an inch less than the width is much used. Tapered keys are little used by machine tool builders owing to their tendency to throw the parts out of true, due to the radial strain. For such work straight square keys fitting neatly on the sides but loose top and bottom are much used. Straight keys should be set one-half their thickness in the shaft and the depth of key seat should be measured from the sides, not the center, With tapered keys the depth of key way in shaft should be one- half the thickness of the key at its middle section. A recom- mended practice is that the depth of key way in shaft should equal two-fifths the thickness of the key at its thick end. Feather keys are much used by machine tool builders. They are usually of a thickness greater than their width and are not fitted tight top and bottom. When fitted in this manner the key does not hold against motion along the shaft, consequently very close fits between shaft and bore are necessary. Sliding feathers are those which are doweled in the hub 45^ MODERN MACHINE SHOP TOOLS. where a sliding fit of the spindle through the hub is required, as with drilling machine spindles, feed rods, etc. Feathers of this kind should be long in order to resist wear, and as they must fit the spline in the spindle freely they drive from the hub seat and should therefore have a close deep bearing in this seat. It is. usual to make sliding feathers of a thickness equal to one an 1 o 1 o o a |j 3 cr 3 o \ sl i 04 3 SJ g 1 2 /^ 3 tfi 3 3 n C/i 3 3 s s " E O 1 314 7854 1 1. 714 2278 41 28 52.56 381 08 2.692 1 935 A 3.34 .886 1.13 1.19 1.031 1.020 23.56 44.18 56.25 421.88 1.957 IX 3.53 .994 1.27 1.42 1.060 1.040 7% 24.35 47.17 60.06 465.48 784 1.979 I 3 B 3.73 1.107 1.41 1.67 1.089 1.059 8 25.13 50.26 64 612. 2.828 2. IX * 8.93 1.227 1.56 1.95 1118 1.077 8x4 25.92 53.46 68.06 561.52 2.872 2.021 4.12 1.353 1.72 2.26 1.146 1.095 26.70 6675 72.15 614.12 2.915 2.041 x*l 4.32 1.485 1.89 2.60 1.173 1.112 8fS 2749 60.13 76.56 669.92 29J8 2.C61 T 4.52 1.623 2.07 2.97 1.199 1.129 9 28.27 63.62 81. 129. 3. 2.080 ff 4.71 1.767 2.25 3.38 1.225 1145 9/4 29.16 67.20 85.56 791.45 3041 2.098 9 4.91 1.917 2,44 3.82 1.250 1.161 9V& 29.85 70.88 90.25 857.37 3.082 2.118 RX 5.11 2.074 2.64 4.29 1275 1.176 S3^ 30.63 74.66 95.06 926.86 3.122 2.136 1? 5.30 2.236 2.85 4.80 299 1.191 10 31.41 78.54 100 1000 3.162 2.154 M 5.60 2.405 3.06 5.36 .323 1.205 111 34.66 95.03 121 1331 3.317 2.224 1| 5.69 2.580 3.29 5,95 .346 1.219 12 37.69 113.0 144 1728 3.464 2.289 7X 5.89 2.761 3.52 6.69 .369 1.233 13 40.84 132.7 169 2197 3.606 2.351 ll 6.09 2.948 3.75 7.27 1392 1.247 14 43.98 1539 193 2744 3.742 2.410 2 6.28 3.142 4. 8. 1.414 1.260 15 47.12 1767 225 3375 3.873 2466 6.48 3341 4.25 8.77 1.436 1.273 16 50.26 2010 256 4096 4. 2.f>20 2^6 6.68 3547 4.52 9.59 1.458 1.286 17 53.40 2269 289 4913 4.123 2.571 2l 3 5 6.87 3758 4.78 10.47 1.479 1.298 18 56.54 254.4 324 5832 4243 2.621 2,4 7.07 3.976 5.06 11.39 15 1.310 19 59.69 2fc3 5 361 6859 4.359 2.668 7.26 4.200 5.35 12.36 1521 1.322 20 62.83 314!l 400 8000 4.472 2.714 7.46 4.430 5.64 13.40 1.541 1.334 21 65.97 846.3 441 9261 4.583 2.759 7.66 4.666 5.94 14.48 1 f'6L 1.346 22 69,11 380.1 484 10648 4.690 ;_si i2 7.85 4.909 6.25 15.63 1.581 1.358 23 7225 415.4 529 12167 4.796 2 844 2i4 8.05 5.157 6.57 16.83 1600 1.369 24 75.39 452.3 576 13824 4 899 1 2.885 gax 8.25 5.412 6.89 18.08 1.620 1.380 25 78.54 480.8 625 15625 5. 2924 2re 8.44 5.673 7.22 19.41 1.639 1.391 26 81.68 530.9 676 17576 5.099 2.963 2M 8.64 5.940 7.56 20.79 16.)8 1.402 27 84.82 572.5 729 19683 6.1S6 3. 2is 8.84 6.213 7.91 22.25 1.677 1.412 28 87.96 615.7 784 21952 5.292 3.037 2% 9.03 6.492 8.27 23.76 1.695 1.422 29 91.10 6605 841 24389 5.385 3.072 2rl 9.23 6.777 8-63 2534 1.714 1.43^ 30 9424 706.8 900 27000 5.477 3.107 3 9.42 7.07 9 27. 1.732 1.442 31 9759 754.8 961 29791 5.568 3141 9.82 7.67 9.77 30.52 1.768 1.462 32 100.5 804.2 1024 32768 5.657 3.175 3^4 10.21 8.30 1055 34.32 1.803 1.482 33 103.7 855.3 1089 35937 5.745 3.208 3$ 10.60 8.95 11.39 38.44 1.837 1.5 34 106.8 907.9 1156 39304 5.831 3.240 3Jl2 11.00 9.62 12.25 42.88 1.871 1.518 35 110. 962.1 1225 42875 5916 3.271 3?6 11.39 10.32 13.14 47.63 1.904 1.535 36 113.1 1017.9 1296 46656 6. 3.302 3% 11.78 11.05 14.06 62.73 1.936 1.553 37 1162 1075.2 1369 50653 6.083 3332 3% 12.17 11.79 15.02 58.17 1.968 1.57H 38 119.4 1134.1 1444 54872 6164 3.362 4 12.67 12.57 16. 64. 2. 1.587 39 122.5 1194.6 1521 59319 6.245 3.391 13.35 14.19 18.06 76.78 2081 1.619 40 125.7 1256.6 1600 64000 6.325 3.420 4 1/ 14.14 15.90 20.25 91.13 2.121 1.651 41 128.8 1320.3 1681 68921 6403 3.448 4*& 14.92 17.72 22.56 107.16 2.179 1.681 42 131.9 1385.4 1764 74088 6481 3.476 5 15.71 19.63 25. 125. 2.236 1.710 43 1452.2 1849 79507 6.557 3.503 5x4 16.49 21.64 27.56 144.70 2.291 1.738 44 13&2 1520.5 1936 85184 6.633 3.530 5V^ 17.28 23.76 30/45 166.37 2.345 1.765 45 141.4 15904 2025 91125 6.708 3.fi57 5M 18.06 >5.97 3306 190.11 2.398 1.792 46 1445 1661.9 2116 97336 6.782 3.583 6 18.85 28.29 36 216. 2.449 1.817 47 147.7 1734.9 2299 1013823 6.856 3.609 19.64 30.68 39.06 244.14 25 1.832 48 150.8 1809.6 2304 110592 6.928 3.634 6/^8 20.42 33.18 42.26 274.63 2.550 1.866 49 153.9 1885.7 2401 117649 7. 3.659 6x4 21.21 35.78 45.56 307.55 2.599 1.890 50 157.1 1963.5 2500 125000 7.071 3.684 7 2L99 38.48 49. 343. ?.646 1913 NOTE. To find the 4th power (or biquadrate) of a number, multiply the square by the square. To find the 4th root, extract the square root twice in succession. TABLES AND USEFUL DATA. 531 WEIGHTS OF SQUARE AND BOUND BARS OP WROUGHT IRON IN POUNDS PER LINEAL FOOT. KENT. Iron weighing 480 Ibs per cubic foot. For steel add 2 per cent. Thickness or Diameter in Inches. Weight of Square Bar One Foot Long. Weight of Round Bar One Foot Long. Thickness or Diameter in Inches. Weight of Square Bar One Foot Long. Weight of Wound Bar One Foot Long. , .013 .010 4 * 55.01 43.21 iz .052 .041 4^} 56.73 44.55 i 3 a .117 .092 '4i 3 e 68.45 45.91 24 .208 .164 4J4 60.21 47.29 Iff .326 .256 4i 8 e 61.99 48.69 % .469 .368 4% 63.80 60.11 7 .638 .501 4/6 65.64 51.55 /4 .833 .654 4/4 67.50 53.01 9 1.055 .828 4l6 69.39 54.50 RX 1.302 1.023 4^2 71.30 56.00 IT 1.576 1.237 4 B 7324 57.52 J 1.875 1.473 4M 75.21 59.07 n 5i 2.201 2.552 1.728 2.004 1 77.20 79.22' 60.63 62.22 (l 2.930 2.301 4ii 81.26 63.82 1 3.333 2.618 5 83.33 6545 1/6 3.763 2.955 85.43 67.10 1J4 4.219 3.313 5^6 87.55 68.76 1A 4.701 3.692 5 16 89.70 70.45 5.208 4.091 5)4 91.88 72.16 1 * 6.742 4.510 5 IB 94.08 73.89 -,/ 6.302 4.950 5% 98.30 75.64 1 6.888 6.410 6/6 98.55 77.40 1 tl 7.500 5.890 5' ; 100.8 79.19 Il 9 5 8.138 6.392 5> a 103.1 81.00 8.802 6.913 5% 105.5 82-83 lie 9.492 7.455 5il 107.8 84.69 10.21 8.018 5M 110.2 86.56 Ml 10.95 8.601 5j| 112.6 88.45 17/1 11.72 9.204 5% 115.1 90.36 lit 12.51 9.828 5il 117.5 92.29 2 13.33 10.47 6 1200 94.25 14.18 11.14 125.1 98.22 2vl 15.05 11.82 6}4 130.2 103.3 2 ** 15.95 12.53 6fH 135.5 106.4 2M 16.88 13.25 6V( 140.8 110.6 95 17.83 14.00 $% 146.3 1149 23/ 18 80 14.77 6M 151.9 119.3 g 7 19.80 15.55 6j| 157.6 123.7 2?5 2083 16.36 7 163.3 128.3 09 2189 17.19 7/^ 169.2 1339 gs| 22.97 18.04 7J4 1752 137.6 Oil 24.08 18.91 746 181.3 142.4 2p 19.80 7Va 187.5 147.3 oil 26'.37 20.71 7% 193.8 152.3 97/ 27.55 21.64 7% 200.2 157.2 Olli 28 76 23.59 7% 3067 163.4 3 30.00 2356 8 213.3 167.6 31 26 24.55 236.9 178.3 g[5 32.55 25.67 " Ui 240.8 189.3 03 33.87 26.60 H5^ 255.2 200.4 of/ 35.21 27.65 9 270.0 212.1 3^ 36.58 2873 9/4 285.8 224.0 ojff 37.97 29.82 9*2 3(0.8 236.3 07 3939 3094 9% 316.9 348.9 g?f 4083 3-i.or 10 3333 361.8 O^JP 4230 3323 io/4 350.8 275.1 xl| 4380 3440 lO^c 367.5 2886 3il 45.33 46 88 3560 36.82 11. 385.2 403.3 302.6 316.8 3j| 48.45 50 05 38.05 39.31 iivl 421.9 4408 331.3 346.2 016 51 68 40.59 11% 460.2 361.4 4 IB 53.33 41.89 13 480. 377. 532 MODERN MACHINE SHOP TOOLS. WEIGHT OF FLAT BAR IRON. fi THICKNESS IN INCHES. A ^ i 3 B Vt A % i 7 S ^ % % % 1 Ibs. Ibs. Ibs. Ibs. Ibs. Ibs. Ibs. Ibs. Ibs. Ibs. Ibs. IX .11 .21 .31 .42 .f2 .63 .73 .84 n .13 .26 .40 .63 .66 .79 .92 1.06 1.32 ax .16 .32 .47 .63 .79 '.95 1.11 126 1.58 1.89 % .18 .37 .55 .74 .92 1.1L 1.29 1.48 1.85 222 2.58 I .21 .42 .63 .84 1.05 1.26 1.47 1.68 2.11 2.53 2.95 3.37 16 .24 .47 .71 .95 1.18 1.42 1.66 1.90 2.37 2.84 3.32 3.79 .26 .53 .79 1.05 1.32 1.58 1.84 2.11 2.63 3.16 3.68 4.21 az .29 .58 .87 1.16 1.45 1.74 2.03 2.33 2.89' 3.47 4.05 4.63 ^ .32 .63 .95 126 1.58 1.90 2.21 2.53 3.16 3.79 4.42 5.05 KZ .34 .68 1.03 1.37 1.71 2.05 2.39 2.74 3.42 4.1 1 4.79 5.47 % .37 .74 1.11 1.47 1.84 2.21 2.58 2.95 3.68 4.42 5.16 5.89 72 .40 .79 1.18 1.58 1.97 2.37 2.76 3.16 3.95 4.74 5.53 6.32 2 .42 .84 1.26 1.68 2.11 2.53 2.95 3.37 4.21 505 5.89 6.74 .45 .90 1.34 1.79 2.24 2.68 3.13 3.68 4.47 5.37 6.26 7.16 IX .47 .95 1.42 1.90 2.37 2.84 3.32 3.79 4.74 5.68 6.83 7.58 % .50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 5.00 6.00 7.00 8.00 IX .53 1.05 1.58 211 2.63 3.16 3.68 4.21 5.26 6.32 7.37 8.42 KX .55 1.11 1.66 2.21 2.76 3.33 3.87 4.42 553 6.63 7.74 8.84 94 .58 1.16 1.74 2.32 289 3.47 4.05 4.63 5.79 6.95 8.10 9.26 i/ .61 1.21 183 2.42 3.03 363 4.24 4.84 6.05 7.26 8.47 9.68 3 .63 1.26 1.90 2.53 3.16 3.79 442 5.05 6.32 7.58 8.84 10.10 IX .68 1.37 2.05 2.74 3.42 411 4.79 5.47 6.84 8.21 9.58 10.95 /4 .74 1.47 2.21 295 3.68 4.42 5.16 5.89 7.37 8.84 10.32 11.79 ax .79 1.58 2.37 3.16 3.95 4.74 5.53 6.32 7.89 9.47 11.05 12.63 4 .84 1.68 2.53 3.37 4.21 5.05 5.89 6.74 8.42 10.10 11.79 13.47 .90 1.79 2.68 3.58 4.47 5.37 6.26 7.16 8.95 10.74 12.53 14.31 1Z .95 1.90 2.84 379 4.74 5.68 663 7.58 9.47 11.38 13.26 15.16 ax 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 10.00 12.00 14.00 16.00 5 LOS 2.11 3.16 4.21 5.26 6.32 7.37 8.42 10.53 12.63 14.74 16.84 111 2.21 3.32 4.42 5.53 6.63 7.74 8.84 11.05 13.26 15.47 17.68 12 1.16 2.32 3.47 4.63 5.79 6.H5 8.10 9.26 11.58 13.89 16.21 18.52 ax 1.21 2.42 3.63 484 6.05 7.26 8.47 9.68 12.10 14.53 16.95 19.37 6 1.26 2.53 3.79 5.05 6.32 7.58 8.84 10.10 12.63 15.16 17.68 20.21 PLATE IRON. WEIGHT OF SUPERFICIAL FOOT. Thickness in inches. Weight, Ibs. Thickness in inches. Weight, Ibs. ,', = .03125 1.25 ft = .3125 12.n8 V = -0625 2.519 96 = .375 15.10 '& = .0937 3.788 i 7 a = .4375 17.65 ^ = .125 5.0-">4 V 5 K0.20 & = .1563 6.305 A = .5625 22.76 & = .1875 7.578 % = .62) 25.16 3 7 a = .2187 8.19 94= .75 30.20 !4 = .25 1009 %= .875 35.30 & = .2812 11.38 1 =1. 40.40 TABLES AND USEFUL DATA. 533 SPECIFIC GRAVITY AND WEIGHT OF VARIOUS METALS. METAL. Specific Gravity. Aluminum, cast 2660 wrought 2.WO Antimony 6713 Brass, Sheet, Copper 75, Zinc 25 8 450 Yollow, Copper 66, Zinc 34 8 300 Plate 8.*380 ' Cast 8.100 Wire 8.214 Bronze, Gun Metal 8 750 Copper 84, Tin 16 8'833 Copper 81, Tin 19 8.700 Phosphor Bearing- Meta> 9.214 Copper, cast 8788 plates 8.6P8 wire and bolts 8.860 Gold, pure, cast 19.258 hammered 19.361 k 22 carats fine. . 17.486 1 20 carats fine 15.709 Iridium, hammered 33.000 Iron, cast, gun metal 7.308 ' ordinary, mean 7.207 wrought bars 7.788 wrought wire 7.774 wrought rolled plates . . 7.704 Lead, cast 11.352 " rolled n.388 Mercury-40 deg 15.632 +32deg 13.598 -}-60deg 13.569 212deg 13.370 Nickel. 8800 cast 8.279 Platinum, hammered 20.337 native 16.000 rolled 22.069 R^d Lead 8.940 Silver, pure, cast 10.474 " hammered 10.511 Steel, tempered and hardened 7.818 " plates , 7.806 " crucible .... 7.842 " Bessemer 7.852 Tin, Cornish, hammered .... 7.390 pure 7.891 Zinc, cast 6.861 " rolled.. 7.191 Weight of a Cubic Inch in Lbs. .0926 .0906 .2428 .3056 .2997 .3026 .2930 .2972 .3165 .3194 .3179 .3146 .3212 .6965 .7003 .6325 .5682 .8319 .264 .2607 .2817 .2811 .2787 .4106 .4119 .5661 .4918 .4908 .4836 .3183 .2994 .7356 .5787 .7982 .324 .3788 .2836 .284 .2673 .2637 .2482 Weight of a Cubic Foot in Lts. 160. 156.5 419.5 528. 517.9 506.3 513.5 546.9 5519 506.1 575.8 B47.2 643.7 555.1 1204. 1210. 1093. 981.8 1437. 456.2 450.4 486.8 485.8 481.6 709.5 711.7 978.2 849.8 848.1 835.7 650. 517.4 1271. 999.9 13.9. 559.9 654.6 657. 488.7 487.7 490.1 490.7 461.9 455.7 428.8 449.4 WEIGHT OF VARIOUS SUBSTANCES. RICHARDS. Name of Substance. Weight of 1 Cubic Foot in Lbs. Name of Substance. Weight of 1 Cubic Foot in Lbs. Brickwork Clay Coal Coke Earth, Loose. . . . Earth, Hammed. Granite.. Sandstone Water, Fresh . Water, fait Alcohol . 100 to 120 120 to 130 80 to 82 45 to 62 76 to 90 100 to 120 160 to 165 135 to 150 62.3 to 62.5 63 to 65 50 to 60 Oils, various Acid, Sulphuric. Oak Wood Pine, White Pine, Yellow . . . Air Steam Snow Coal Gas . Carbonic Acid... 54 to 57 114 to 116 42 to 63 27 to 30 35 to 45 .08 to .080 .05 to .056 5 2 to 6.5 .035 to .036 .122 to .123 534 MODERN MACHINE SHOP TOOLS. WEIGHT OF CASTINGS FROM PATTERNS. Simpson Bolland. A Pattern Weighing One Pound, Made of- Will Weigh when Cast in Cast Iron. Zinc. Copper. Yellow Brass. Gun Metal. Mah ogany Nassau Lbs. 10.7 12.9 8.5 12.5 16.7 14.1 9. Lbs. 10.4 12.7 8.2 12.1 16.1 13.6 8.6 Lbs. 12.8 15.3 10.1 14.9 19.8 16.7 10.4 Lbs. 12.2 14.6 9.7 14.2 19. 16. 10.1 Lbs. 12.5 15. 9.9 14.6 19.5 16.5 10.9 Honduras.. . . Spanish. . Pine-Red " White " Yellow .. Oak . . UNITS OF HEAT IN ONE POUND OP FUELS. Anthracite 14,500 Bituminous 14,000 Petroleum, light 22,600 Petroleum, heavy :. 19,440 Petroleum, refined.. Petroleum, crude. . . Coal Gas Water Gas . 19,260 19,210 20,200 8,500 TABLE OP RELATIVE VALUE OF NON-CONDUCTORS. Chas. E. Emery. Non-Conductor. Value. Non-Conductor. Value. Wood Felt 1000 Loam dry and open 550 Mineral Wool No 2 832 Slaked Lime 480 Mineral W ool with Tar .715 Gas House Carbon. .. . 470 Sawdust 680 Asbestos 363 Mineral Wool No. 1 .676 Coal Ashes 345 Charcoal .632 Coke in lumps . . 277 Pine Wood, across fiber .553 Air space undivided !l36 PROPERTIES OF METALS. RICHARDS. Names of materials. Weight in Ibs. of a cubic foot. Weight in Ibs. of a cubic inch. Relative Weight. Water, 1,000 Tensile strength Ibs. per in. section. Melting point in degrees Fahrenheit. Wrought iron, avge. Cast iron. 485.0 450.0 .277 .260 7,700 7,200 56,009 16,000 3.000 2,300 Cast steel, 487.0 .280 7,800 100,000 2,500 Bessemer steel, " 480.0 .280 7,852 90,000 2,500 Copper, i 547.0 .316 8,780 33,000 2,0(!0 Brass, 500.0 .281 8,100 20,000 1,800 Tin, 455.0 .210 7,290 5,000 446 Lead, 709.0 .410 11,352. 2,000 600 Silver, 653.0 .378 10,474 30,000 1,800 AL9JOS JO qoui d spBo jo -o TABLES AND USEFUL DATA. ^-COOO * * r-l 1-1 - i IOOOOOOCO 535 OO QO CO QO GO QO IBUiuio., 500 J oiqno 9UQ aoBj-mg j~-osaot- -^aot-cciosos i 1 8 i 5 S a i g [Buaajuj T-5 r-i *i i53! - " " SS ISSSSS^S 5 1 1 111 " a -o O I 5 h o, 2: ^ If - g S'85 B 1 5 ^ H S| g J-j ^ S '"" '"' *^ ^ -|1 I o o> ^c , S =i III = 1 o W 1 r-5 (> CO -* TABLES AND USEFUL DATA. 537 TABLE OP EMERY WHEEL SPEEDS. Diam. Whee\ Rev. per Minute for Surface Speed of 4,000 Feet. Rev. per Minute for Surface Speed of 5,000 Feet. Rev. per Minute for Surface Speed of 6,000 Feet. 1 inch. 1\279 19,099 22,918 2 " 7,639 9,549 11,459 3 ll 5,093 6,366 7,639 4 " 3,820 4,775 5.730 5 " 6 " 3,056 2,546 3,820 3,183 4,584 3,820 7 " 2,183 2,728 3,274 8 " 1,910 2,387 2,865 10 " 1,528 1,910 2,292 12 " 1,273 1,592 1,910 14 " 1,091 1,364 1,637 16 " 955 1.194 1,432 18 " 849 1,061 1,273 20 " 764 955 1,146 22 " 694 868 1 042 24 " 637 796 935 26 " 586 7:?3 879 28 '* 546 683 819 30 " 509 637 764 32 " 477 596 716 34 " 449 561 674 36 " 424 531 637 38 " 402 503 603 40 " 382 478 573 42 " 364 455 548 44 " 847 434 521 46 " 332 415 498 48 " 318 397 477 50 ' 306 383 459 52 ' 294 369 441 54 ' 283 * 354 425 66 * 273 341 410 58 * 264 330 396 60 255 319 383 THE SPEED OF DRILLS. Cleveland Twist Drill Co. Diam. of Drill. Speed for Soft Steel. Speed for Iron. Speed for Brass. Diam. of Drill. Speed for Soft Steel. Speed for Iron. Speed for Brass. 1,824 912 608 2,128 1,064 710 3,648 1,824 1.216 || 108 K-2 96 125 118 112 215 203 192 8 456 532 912 iS 91 106 182 A 365 425 730 lr s 87 101 174 a/ 304 355 608 m 83 17 165 7 260 804 520 1 T 7 80 93 159 11 228 266 456 18 76 89 152 . 203 236 405 Hi 73 85 145 g/ 182 213 365 1% 70 82 140 il 166 194 332 ill 68 79 135 B 153 177 304 1 65 76 130 ,8 140 130 122 114 164 162 142 133 280 260 243 228 V 2 fl 63 60 59 57 73 71 69 67 125 122 118 114 538 MODERN MACHINE SHOP TOOLS. TABLE OP SIZES OF TAP DRILLS. Tap Diameter. Threads per Inch. Drill for V Thread. Drill for U. S. Standard. M 16 18 20 3 B 2 3 5 2 li ft 9 16 18 20 7 T 3 S IB *| *3 T 5 S 16 18 J4 32 16 18 32 J4 S *i! 14 r 16 18 M 32 3 9 5 a 9 ^ % 11 14 16 18 11 li li IS 14 16 * 32 A? 3 | 14 16 12 13 14 % B * If 11 3 1 9 6 12 14 & if 10 11 12 H iJ 11 12 10 11 12 IS 96- 96 96 it 10 li % 9 10 If li U it 9 II 8 li N TAP DRILL SIZES. For Gas Taps. Diameter of Tap or Size of Pipe. Diameter of Drill. Diameter of Tap or Size of Pipe. Diameter of Drill. ^ inch 1 4 Ik inch 5 ! 1M inch ri 3J4 " a lli inch 3*1 i* : MACHINE SCREW TABLE. Screw Gauge Size. Diameter in Decimals. Approximate Diameter. No. Threads per Inch. Size of Tap Drill. 2 .0842 * 56 49 3 .0973 h 48 45 4 .1105 & 36 42 5 .1236 X 36 38 6 .1368 A 32 35 7 .1500 A 32 30 8 .1631 A 32 29 9 .1763 tt 30 27 10 .1894 TS 24 25 U .2026 if 24 21 12 .2158 & 24 17 13 .2289 U 22 15 14 .2421 U 20 13 15 .2552 *4 20 8 16 .2684 ki 18 6 17 .2816 32 18 2 18 .2947 if 18 1 19 .3079 T7T 18 c 20 .3210 Ii 16 D 22 .3474 y 16 J 24 .3737 % 16 N 26 .4000 u 16 P 28 .4263 15 14 R 30 .4526 IS 14 U TABLES AND USEFUL DATA. 539 TRANSMISSION OF POWER BY LEATHER BELTINO. Single Leather. Belt Speed. GOO 1200 1800 2400 3000 3600 4200 4800 5400 6000 Width of Belt. H P H P H P H P H P H P H P HP H P H P 1 in \ 2 g A 2 in 2 4 g 8 10 10 14 10 3 in. 3 6 g 12 15 18 9-1 4 in 4 8 12 16 20 24 28 Q> Oft 5 in. 5 10 15 20 25 30 OK 4/1 6 in g 12 18 24 30 ia JO 8 in. . . 8 16 24 32 40 48 56 fi4 72 Of) 9 in. 9 18 27 36 45 64 ftQ 79 01 10 in 10 20 30 40 50 60 70 80 'III 100 12 in. .... 12 24 36 48 60 72 84 96 108 1'*ll 14 in... 14 28 42 56 70 84 98 112 126 140 16 in... . 16 32 48 64 80 96 112 128 144 IfiO Double Leather. Belt Speed. 4GO 800 1200 1600 2000 24CO 2800 3.tO 36CO 4000 5000 Width of Belt, H P H P H P H P H P H P H P HP H P H P H P 4 in. 4 8 12 16 20 24 28 32 36 40 50 6 in... 8 in 6 8 12 16 18 24 24 32 30 40 36 48 42 56 48 64 54 72 60 80 75 100 10 in 10 20 30 40 50 60 70 80 90 100 125 12 in 12 24 36 '48 60 72 84 96 108 120 150 16 in 16 32 48 64 80 96 112 128 144 160 200 20 in 20 40 60 80 100 120 140 160 180 200 250 24 in 24 48 72 96 120 144 168 192 216 240 300 30 in 30 60 90 ItiO 150 180 210 240 270 300 330 36 in 86 72 108 144 180 216 252 288 334 370 450 40 n 40 80 120 160 200 240 280 320 360 400 500 ROPE DRIVING. TABLE OF THE HOKSE POWER OF TRANSMISSION ROPE BY O. W. HUNT. The working strain is 800 Ibs. for a 2-inch diameter rope and is the same at all speeds, due allowance having been made for loss by centrifugal force. Diameter Rope. Speed of the Rope in Feet per Minute. Smallest Diameter Pulleys. l^OO 200J 2500 3000 3500 4000 4500 5000 6000 7000 1 in". !".'!!!.' .' 14 in 2 in. ! 3.3 4.5 5 8 9.2 13.1 18 23.1 4.3 5.9 7.7 12.1 17.4 23 7 30.8 62 7.0 92 14.3 20.7 28.2 36 8 5.8 8.2 10.7 16 8 23.1 32 8 42.8 6.7 9 1 11 9 186 26.8 36 4 47.6 7.2 9 8 128 20.0 28.8 39.2 51.2 7.7 10.8 13.6 21 2 30.6 41 5 64 4 7.7 10.8 13.7 81.4 30.8 41.8 54.8 7.1 9.3 12 5 19.5 28.2 7.4 5UO 4.9 6.9 8.8 27\6 35.2 30 in. 36 in. 42 in. 64 in. 60 in. 72 in. 84 in. 540 MODERN MACHINE SHOP TOOLS. TRANSMITTING IFFICIENCY OF TURNED IRON SHAFTING AT DIFFERENT SPEEDS. As Prime Mover or Head Shaft carrying Main Driving Pulley or Gear, well supported by bearings. Diameter of Shaft. Number of Revolutions per Minute. 60 80 ICO 125 150 175 00 225 2:0 275 300 1M in H P 2.6 3.8 5.4 7.5 10 13 16 20 25 3 127 180 250 H P 11.8 17.6 22 34 44 55 74 93 115 140 198 275 H P li.9 19.3 24 37 48 60 81 102 12$ 153 216 300 2 in ft/A in ;& in 2% in 3 in . 314 in , 3ju in 4 in 4^i in. 5 in. ... . TRANSMITTING EFFICIENCY OF TURNED IRON SHAFTING AT DIFFERENT SPEEDS. As Second Movers or Line Shafting. Bearings 8 Feet Apart. Number of Revolutions per Minute. Diameter or Sbalt. 100 125 150 175 200 225 250 275 300 325 850 Inches. H. P. H. P H.P H. P. H.P. H.P. H.P. HP. H.P.IH. P.!H. P. 6 7.4 8.9 10.4 11.9 13.4 14.9 16.4 17.9 19.4 iO.9 1% . 7.3 9.1 109 12.7 145 16.3 18.2 20 21.8 23.6 25.4 2 8.9 11.1 13.3 15.5 17.7 20 23.2 24.4 26.6 28.8 31 2V6 10.6 132 15.9 185 21.2 23.8 26.5 29.1 31.8 34.4 37 12.6 15.8 19 22 25 28 31 35 38 41 44 2% 15 18 22 26 29 33 37 41 44 48 h2 2^6 17 21 26 30 34 39 43 47 52 56 60 2i 23 29 34 40 46 52 58 64 69 75 81 3 30 37 45 62 60 67 75 82 90 97 105 3M 38 47 57 66 76 85 H5 104 114 123 33 3V 47 59 71 83 95 107 119 131 143 155 167 3?| 58 73 88 102 117 132 146 162 176 190 205 4 71 89 107 125 142 160 178 196 213 231 249 TRANSMITTING EFFICIENCY OF TURNED IRON SHAFTING AT DIFFERENT SPEEDS. For Simply Transmitting Power. Number of Revolutions per Minute. Diameter of Shaft. 100 125 150 175 200 233 267 300 333 367 400 Inches. H. P. H. P. H. P. H. P. H. P. H. P. H. P. H. P. H. P. H. P. H. P. UjC 6.7 8.4 10.1 11.8 13.5 15.7 17.9 20.3 22.5 24.8 27 i2 8.6 10.7 12.8 15 17.1 20 22.8 25.8 28.6 31.5 JJ4 3 19* 10.7 13.4 16 18.7 21.5 25 28 32 36 39 43 JB 13.2 16.5 19.7 23 26.4 31 ;5 39 44 48 52 2 16 20 24 28 32 37 2 48 53 58 64 fU 19 24 29 33 88 44 51 57 63 70 76 2/4 22 28 34 39 45 52 60 68 75 83 90 M 27 33 40 47 53 62 70 79 88 96 105 IM 31 39 47 54 62 73 83 93 104 114 125 2% 41 52 62 73 83 9: 111 125 139 153 167 3 54 67 81 94 108 123 144 162 180 198 216 3M 68 86 103 120 137 160 182 205 228 250 273 m 85 107 128 150 171 200 ,223 257 ,'85 313 342 TABLES AND USEFUL DATA. 541 IIP cc o. a si 1 . T-H c f SJj 2 1 11 1 i 'jj.S S "3 JO 1 5 1 IS * O O 3 S 55 O 5 1 s OcS 14 .0208 .0003 .0026~ %y .5625 .2485 1.859 19 1.583 1.969 14.73 5 .0260 .0005 .0040 I .5833 .2673 1.999 1.625 2.074 15.52 % .0313 .0008 .0057 .6042 .2868 2.144 20 1.666 2.182 16.32 T'S .0365 .0010 .0078 7 /'is .6250 .3068 2.295 20^ 1.708 2.292 17.15 1 .0417 .0014 .0102 7"M .6458 .3275 2.450 21 1.750 2.405 17.99 A .0469 .0017 .0129 8 .6667 .3490 2.611 1.792 2.521 18.86 % .0521 .0021 .0159 8/4 .6875 .3713 2.777 22 S 1.833 2.640 19.75 ii .0573 .0026 .0193 ty& .70^3 .3940 2.948 22^ 1.875 2.761 20.65 3X .0625 .0031 .0230 t*% .7292 .4175 3.125 23 1.9)7 2.885 21.58 il .0677 .0036 .0270 9 .7500 .4418 3.305 2% 1.958 3.012 22.53 % .0729 .0042 .0312 9M .7708 .4668 3.492 24 2.000 3.142 23.50 15 .0781 .0048 .0359 <|L .7917 .4923 3.682 25 2.083 3.409 25.50 1 .0833 .0055 .0408 9M .8125 .5185 3.879 26 2.166 3.687 27.58 .1042 .0085 .0638 10 .8333 .5455 4.081 27 2.250 3.976 29.74 ]1^ .1250 .0123 .0918 .85 '2 .5730 4.286 28 2.333 4.276 31.99 194 .1458 .0168 .1250 1014 .8750 .6013 4.498 29 2.416 4.587 34.31 2 .1667 .0318 .1632 10M .8958 .6303 4.714 30 2.500 4.909 36.72 2J4 .1875 .0276 .2066 11 .9167 .6600 4.937 31 2.583 5.241 39.21 2ji .2083 .0341 .2550 .9375 .6903 5.163 32 2.666 5.585 41.78 2% .2292 .0413 .3085 lli/ig .9583 .7213 5.395 33 2.750 5.940 44.43 3 .2500 .0491 .3673 11*1 .9792 .7530 5.633 34 2.833 6.305 47.17 2708 .0576 .4310 12 1 foot .7854 5.876 35 2.916 6.681 49.98 8j| .2917 .0608 .4998 12V<9 1.042 .8523 6.375 36 3.000 7.089 52.88 .3125 .0767 .5738 13 1.083 .9218 6.895 37 3.083 7.468 55.86 4 .3333 .0873 .6528 13V<8 1.125 .9940 7.435 38 3.166 7.876 58.92 .3542 .0985 .7370 14 1.167 1.069 7.997 89 3.250 8.296 62.06 41^ .3750 .1105 .8263 14V4 1.208 .147 8.578 40 3.333 8.728 65.29 4% .3958 .1231 .9205 15 1.250 .227 9.180 41 3.416 9.168 68.58 5 .4167 .1364 1.020 1.292 .310 9.801 42 3.500 9.620 71.96 6J4 .4375 .1503 1.124 16 S 1.333 .396 10.44 43 3.583 10.084 75.43 6*3 .4583 .1650 1.234 1.375 1.485 11.11 44 3.666 10.560 79.00 5% .4792 .1803 1.349 17 8 1.417 .576 11.79 ' 45 3.750 11.044 82.62 6 .5000 .1963 1.469 1.458 1.670 12.50 46 3.833 11.540 86.32 6*4 .5208 .2130 1.594 18 8 1.500 .767 13.22 47 3.916 12.048 90.12 6>i .5417 .2305 1.724 1.542 .867 13.97 48 4.000 12.566 94.02 CAPACITIES OF RECTANGULAR TANKS IN UNITED STATES GALLONS, FOR EACH FOOT IN DEPTH. 5 * ss * fi Ft.In. 2 ~6 3 3 6 4 4 6 5 5 6 6 6 6 Length of Tank. Feet 2 Ft. In. 2 6 Feet 3 44.88 56.10 67.32 Ft. In. 3 6 52.36~~ 65.45 78.54 91.64 Feet 4 59 84 74 80 89.77 104.73 119 69 Ft. In. 4 6 Feet. 5 74.81 93.51 112.21 130.91 149.61 168.31 187.01 Ft. In. 5 6 Feet. 6 89.77 112.21 134.65 157.09 179.53 201.97 224.41 246.8B 2(39.30 Ft. In. 6 6 97.25 121.56 145.87 170.18 194.49 218.80 243.11 267.43 291.74 316.05 Feet, '7 104.73 130.1)1 157.09 183.27 209.45 235.3 261.82 288.00 314.18 340.36 29.92 37.40 46.75 G7.32 84.16 100.99 117.82 134.65 151.48 82.29 102.86 123.43 144.00 164.57 185.14 205.71 22d.28 .... .... .... TABLES AND USEFUL DATA. 543 METRIC CONVERSION TABLE. Arranged by C. W. Hunt, New York. Millimeters X .03937 = inches. Millimeters -*- 25.4 = inches. Centimeters X .3937 = inches. Centimeters +- 2.54 = inches. Meters X39.37 = inches. (Act Congress.) Meters X 3.281 = feet. Meters X 1.094 = yards. Kilometers X .621 = miles. Kilometers -*- 1.6193 = miles. Kilometers X 3280.7 = feet. Square Millimeters X .015') = sq. inches. Square Millimeters -s- 645.1 = sq. inches. Square Centimeters X .155 = sq. inches. Square Centimeters -*- 6.451 = sq. inches. Square Meters X 10.7(54 = sq. feet. Square Kilometers X 247.1 = acres. Hectare X 2.471 = acres. Cubic Centimeters *- 16.383 = cubic inches. Cubio Centimeters-*- 3.69 = fl. drachms. (U.S. P.) Cubic Centimeters-*- 29.57 = fl.oz. (U.S.P.) Cubic Meters X 35.315 = cubic feet. Cubic Meters X 1.308 = cubic yards. Cubic Meters X 264.2= gallons (231 cu. in.) Liters X 61.022 = cubic in. (Act Congress ) Liters X 33 84 = fluid ounces (U. S. Phar.) Liters X .2642 = gallons (331 cu. in.) Liters H- 3.78 = gallons (231 cu. in.) Liters -*- 28.316 = cubic feet. Hectoliters x 3.531 = cubic feet. Hectoliters X 2 84 = bushels (2150.42 cu. in. Hectoliters X .131 = cubic yards. Hectoliters -*- 26 42 = gallons (231 cu. in ) Grammes x 15.432 = grains.(Act Congress.) Grammes -t- P81 = dynes. Grammes (water) -+- 29.57 = fluid ounces. Grammes -+- 28.35 = ounces avoirdupois. Grammes per cu. cent. +- 27.7 = Ibs. per cu. in. Joule X . 7373 = foot pounds Kilogrammes X 2.2046 = pounds. Kilogrammes X 35.3 = ounces avoirdu- pois. Kilogrammes +- 1102 3 - tons (3,000 Ibs ) Kilogrammes per tq. cent, x 14.2,'3 = Ibs. per sq. in. Kilogram-meters X 7.233 = foot Ibs. Kilo per Meter x .672 = Ibs. per foot. Kilo per Cu. Meter x .062 = Ibs. per cu.ft. Kilo per Cheval x 2.235 = Ibs. pe. H. P. Kilo- Watts X 1.34 = Horse Power. Watts +- 746. = Horse Power. Watts -s- .7373 = foot pounds per second. Calorie x 3.968 = B. T. U. Cheval vapeur x .9863 = Hor?e Power. (Centigrade X 1.8) + 32 = d gree Fahren- heit. Fran9 X .193 = Dollars. Gravity Paris = 980.94 centimeters per second. DATA ON WATER. 1 cubic foot of water = ..... 62.3791 Ibs. 1 cubic inch of water = .03612 1 bs. 1 gal Ion of water = 8.338 Ibs. 1 gallon of water = 231. cubic in. 1 cubic foot of water = 7.480 gallons. 1 pound of water = 27.7 cubic in. The above data is calculated for distilled water at 40 Fahrenheit. The pressure of a column of water in pounds per square inch is equal to the height of the column in feet multiplied by .433. The pressure per square foot is equal to the height of th* column in feet multi- plied by 62.44 The power required to elevate water is equal to the weight of the water multiplied by the height in feet through which it is lifted (foot pounds divided by 33,00 . An allowance of 25 per cent should ordinarily be made for frictional Josses. DATA ON POWER. The Unit of Work is the foot pound or the work necessary to raise a weight of one pound one foot. The Unit of Heat is the British Thermal Unit or the amount of heat necessary to raise the temperature of one pound of pure water from 39 to 40 Fahrenheit. The Mechanical Equivalent of one British Thermal Unit of he .t is 778 foot pounds of work, and upon this value are based all heat and power determinations. A Horse Power is the amount of work necessary to raise 33,000 pounds one foot high in one minute. It is dependent upon three factors : force, distance and time. Indicated Horse Power is the measure of the work developed in the cylinder of an engine and equal to the following expression : Horse Power = Pressure X Area X Double Stroke X Revolutions 33,000 where pressure = the mean or average pressure per square inch on the piston : Area = the area of the piston in square inches ; Double Stroke the distance traveled by the piston in feet for each revolution, and Revolutions = the number of revolutions the engine makes in one minute. In this expression the pressure and area represent the force, and the stroke and revolutions the distance. Brake Horse Power is the measure of the power given off at the shaft, and is always less than the indicated horse power by an amount equal to the work necessary to overcome the frictional resistance of the engine. In measuring the brake horse power a suitable brake is applied to the fly wheel of the engine as shown in Fig. 673. 544 MODERN MACHINE SHOP TOOLS. A band a a a a of rope, leather or steel is placed on the wheel. The rod R attached to the brake at the distance L from the center of rotation holds the brake from rotating with .the wheel. This rod is attached to a suitable scale beam by means of which the pull P can be weighed. By means of the nut H and screw S the brake can be adjusted to absorb the full power of the engine. We then have a force P acting through a distance represented by the radius L and FIG. 673. the number of revolutions the wheel makes, or, in other words, the Distance the point P would move in one minute if free to turn. force X distance P. X 2L X * X N The brake horse power = horse power = = "- 33,000 foot pounds 33,000 when P = the force in pounds ; 2L = the diameter in feet of the circle through which tku- force acts ; it = the constant 3.1416 by which the diameter is multiplied to obtain the Circumference, and N = the number of revolutions per minute. INDEX. Addendum circle 465 Adjustable hollow milling tool 208 Adjustable reamers 114, 120 Adjustable limit gauges 91 Adjustable dies 130 Advantage of radial mills 318 Advantage of collapsing taps 133 Advantages of expansve mandrels. . 158 Advantages of patent lathe tools. . 201 Alining shafting 512 Angular and notch gauges 84 Angular milling cutters 336, 339 Angular velocity 463 Angular drilling 415 Arbors . . . 154 Arbors, milling 348 Arbors, shell end mill 346 Arbors, thread 347 Arch stays 462 Automatic gear cutting machines. . 384 Automatic screw machine 191 Back facing 415 P>ack gearing, computation of 167 Back gear, friction 391 Back gearing, triple 167 Back lash, effect of on taper turn- ing 230 Balancing of pulleys . . .. 521 Balancing way .' 521 Bearing, shaft 511 Bell center punch. . 220 Ball turning 243 Belting 490 Belting, care of leather . 493 Belting, double, triple, etc 492 Belting, examples of drives 497 Belting, hides used for leather 490 Belting, leather 490 Belting, leather strongest section of 492 Belting, methods of lacing 495 Belting, methods of lapping 494 Belting, power transmitted by 493 Belting, preparation of leather 401 Belting, reasons for running hair side next to the pulley 496 Belts, run of on pulleys 501 Bevel gear cutting 365-387 Bevel gear cutting in milling ma- chine 365 Bevel gear cutting, selecting of cut- ters for 382 Bevel gears 467 Bevel gears, laying out 474 Bevel gear planer, Belgram 392 Bevel gear planer, Gleason 392 Blocking for planer 299 Bolts, carriage 450 Bolts, machine 450 Bolts, stud 451 Boring bars 2.~o Boring large parallel holes in heavy drilling machines 420 Boring mills, floor 268 Boring mills, horizontal .......... Boring mills, relation to the lathe. Boring mills, universal ........... Boring mill work, securing ........ Boring parallel holes in the lathe. Boring mills, vertical ............. Boring, setting up work for ...... Boring spherical sockets .......... Boring tapered holes with boring bars ....................... Boring tools ............. 200-202 Boring work secured to the lathe carriage .................... Box cut-off slide ................ Box tools ........ ............... Buffing spindle ................. Bushings, for jigs ............... Brazing furnace ................. Brown and Sharpe tapers ......... 266 264 269 269 2.v. 264 jr.:; 252 203 252 209 207 425 410 522 346 Circulating speed of pulleys 514 Calculation of cutting speeds 224 Calculations for indexing on auto- matic gear cutters 386 Caliper dividers 220 Calipers 64 Calipers, firm joint 64 flaliper gauges 60 Calipers, hermaphrodite 68 Calipers, how held 65 Calipers, keyhole 68 Calipers, lock joint 64 Calipers, micrometer 70 Calipers, recording 64 Calipers, spring joint 65 Calipers, thread 68 Calipers, transfer, types of 64-68 Calipers, use of 65-67 Calipers, vernier 68 Cam cutting attachment 333 Cam milling, example of 376 Cape chisels "ase hardening 448 Care in heating tool steel 446 Care in indexing ">">"> Care and use of drill chucks 1.">i Care of centers -"' Care of files . , 45 Care of lathe centers 181 Care of mandrel centers 161 Care of surface plates ."4 Care necessary in chucking 255 Care to exercise in putting on arbor cutters 361 Carriage bolts 450 ;^at head -'-J Causes of inaccurate work with flat drills . 104 Center bearing reamers I Center bearings, form of 222 "enter bearings, lubrication of.... 222 Center gauges . , 86 'enter head square, use of 221 Center reamer, combination 2 Center rest 225 enter rest work, example of 227 546 INDEX. Centers, care of 236 Centers, drawing over ---' Centers, drilling of 222 Centers, pipe 288 Centers, index 29b Centers, locating of 220 Centers, planer 29b Check nuts . 4ol Chucking reamers lib, 118 Circular milling attachment 330 Circular pitch 465 Clamp dogs fll Clamping work on planer 299-301 Clamps, belt 49-1 Clamps for planer 300 Classes of milling cutters 330 Classification of drilling jigs 410 Classification of files 2o Classification of grinding operations 423 Cleaning castings 46 Cleaning files 44 Clearance angle 108 Clearance in tap threads 1 Clearances in twist drills 105 Cold chisels; forms of Cold chisels, how forged 18 Cold chisels, correct grinding of... 19 Cold chisels, how held 21 Cold chisels, machinist 18 Cold chisels, temper of 21 Cold chisel, tempering of 446 Collet chucks 105 Collets, milling machine 346 Collets, spring chuck 348 Combination center reamer 222 Combination drill and pipe taps. . . . 133 Combination chucks 216 Combination squares 96 Comparison of wire gauges 82 Combination wrenches 102 Compound indexing 351 Compound rest 170 Compressed air in the shop 517 Computation of back gearing 167 Cones, rapid finishing of 259 Correct grinding of cold chisels. . . . 19 Correct use of hack saw blades .... 99 Correct use of hammers 18 Correct use of monkey wrenches. . . 100 Cotter pins 458 Counter bore 415 Counter shafts 396 Couplings, shaft 508 Change gears in gangs 177 Chucking, care necessary in 255 Chucking work 254 Chucking work from outside 255 Chucks, drill 150 Chucks, drill, care and use of 151 Chucks, combination 216 Chucks, face plate 218 Chucks, independent 215 Chucks, lathe 214 Chucks, revolving 219 Chucks for special work 254 Chucks split 266 Chucks, universal 215 Collapsing taps, advantages of 133 Crank driven shapers 283 Crank pins, turning of 232 Cross-filing 30 Cross sections of files 22 Cutter and reamer grinder 425 Cutter bar for keyseater 310 Cutter head for boring 270 Cutters, care to exercise in putting on arbor 361 Cutters for keyseaters .'!()!) Cutters, Importance of keeping sharp .SDO Cutters, milling, driving of . . . .349-359 Cutting angle for drills 106 Cutting bevel gear. . 305-387 Cutting edges 197-199 Cutting double threads 235 Cutting key ways 364 Cutting worm gears 3b5 Cutting off machine 196 Cutting speeas 223 Cutting off tools 200 Cutting speeds, calculation of 224 Cutting speeds, effect upon output. 224 Cutting spiral gears 394 Cycloidal curve 472 Cycloidal gearing system 407, 471 Cycloidal tooth curves 472 Cylinder boring, example of 271 Cylinder boring machine 27O Cylindrical grinding 428 Data for spiral gears 482 Data on water 542 Definition of forced fit 262 Definition of horse power 542 Definition of working tit 262 Diametral pitch 465 Diamond point chisels 21 Diamond truers 437 Die sinking machine 320 Dies, adjustable 136 Dies, two classes of 135 Dies, effect of tempering 011 140 Dies, self-opening 138 Dies, how sharpened 137 Dies, solid 136-138 Dies, use of on oversize stock 140 Dimensions of lathe 1 Klles, double cut 25 Files, effect of sand and scale on. . 46 Files, grades as to coarseness 25 Files, hand cut 27 Files, how held in operating 31-38 Files, lengths 23 Files, machine cut 26 Files, names of 22-23 Files, necessity of belly in 29 Files, pinning of 45 Files, preparation of blanks for cut- ting 25 Files, racks for 46 Files, rasp 1-5 Files, safety edges on 36 Files, selecting of, for any class of work 30-34-46 Files, single cut 25 Files, use of chalk and oil on 45 Filing, direction of strokes 34 Filing, effect of narrow surface on file teeth 34 Filing, fillets . . . 37 Filing, flat surfaces 35 Filing, interior surfaces 36 Filing, mortises 38 Filing, position of work for 33 Filing rotating discs 44 Filing rotating work 41 Filing, position of workman 33 Filii ? square corners 37 Filing square and round holes. ... 35 Filing thin work 39 Finishing cuts after roughing 253 Filtering of oil ; 523 Finishing for planer tools 293 Fitting surfaces by "bedding".... 52 Flat drills 103 Flat keys 455 Flat turret lathe 1 94 Fly cutter 342 Follow rest 227 Forced fit, definition of 262 Forged drills . . .x. 106 Formed cutters 24.", Formed gear cutters 381 Forming tools 207 Form of center bearings 222 Forms of cold chisels 20 Form of flutes and teeth taps... . 131 Forms of hammers 17 Forms of scrapers 48 Frictional tap holders 147, 149 Frictional gearing 463 Gang drill work, examples of 416 Gang drills 400 Gang drilling jigs . , 417 Gang milling cutters 3 Gang milling, example of heavy. . . . 372 Gang milling, importance of 313 Gang planer tools 291 Gauges, adjustable limit 90 Gauges, angular and notch 84 Gauges, caliper 60 Gauges, center 86 Gauges, corrective 62 Gauges, depth 89 Gauges, drill 84 Gauges, end measure 59 548 INDEX. Gauges, limit 61 Gauges, manufacture of 63 Gauges, nut and washer 85 Gauges, plug and ring 59 Gauges, scratch 89 Gauges, screw thread 88 Gauges, standard care in use of . . . 61 Gauges, standard 59 Gauges, standard thread 02 Gauges, surface 'JO Gauges, thickness 88 Gauges, thread 87 Gauges, use of t>l Gauges, wire 85 Gear cutters 340 -Gear cutting, duplication system... 379 Gear cutters, duplex 383 Gear cutters in gangs 383 Gear cutting in plain milling ma- chine, by under cut method. . . 365 Gear cutting, laige spuV, in plain milling machine 365 Gear cutting machines, automatic. . 384 Gear cutting, molding planing method 380 Gear cutting, templet planing method 380 Gear suaper, Fellows 389 Gears, bevel 40 <' Gears, toothed . '. 464 Gears, worm 467-475 Gearing 463 Gearing, cycloidal, system. 467-471 Gearing, efficiency of toothed 474 Gearing, f rictional . . . 463 Gearing, involute system 46 i Gears, internal ^ 4/3 Gears with axes at varying dis- tances 471 Gears, spiral 407 Gears,, spur 467 Graduated dials on feed screws, use of 362 Graduate machine dials, value of. . 378 Grinder, cutter and reamer 425 Grinder, twist drill 428 Grinding, cylindrical 428 Grinding, importance of 423 Grinding, internal 429-433 Grinding machine, plain 293-429 Grinding machine, universal 428 Grinding operations, classification of 423 Grinding steep tapers 434 Grinder, portable 437 Grinder, tool 424 Hack saw blades 99 Hack saw blades, correct use of . . . 99 Hack saw frames 100 Hack sawing machines 520 Hammers, correct use of 18 Hammers, dressing and regrinding. . 18 Hammers, forms of 17 Hammer handles 18 Hammers, machinist 17 Hammers, pneumatic 518 Hammers, weight of 17 Hand cut files 27 Hand caps 129 Handles, of hammers 18 Hardening in oil 443 Hardening in steel 440 Heat, unit of 542 Heating of steel 443 Heating of tool steel, care in 446 Hermaphrodite calipers 220 I Hides used for leather belting..... 4901 Iliirh speed milling attachment .331, 407 Hints on planer manipulation 305 Ilobbing machine 393 Hobs, worm 340, 365-393 Hoists, hand " 520 Hoists, pneumatic .' 517 Hollow hexagon turret lathe 196 Hollow milling tool, adjustable 208 Horse power, brake 542 Horse power, definition of 542 Horse power, indicated 542 ilorse power, measuring of 542 How to find tap drill sizes 141 How to sharpen dies 137 Hypocycloidal curve 472 Importance of drill and tap holders. 142 Importance of gansr milling 313 Importance of grinding 423 Importance of keeping sharp cutters 356 Importance of milling machines. . . . 312 Increase twist in drills 106 Independent chucks 215 Indexing, care in 353 Indexing, centers 323 Indexing, compound 351 Indexing, differential 352 Indexing on automatic gear cutters, calculations for '. . 386 Indexing, plain 324 Indexing, rule for 350 Indicator, use of test. 92 Influence of form and number of teeth in reamers 114 Inside micrometer calipers 81 Internal grinding 43e Involute curve 467 Involute tooth outline, approximate method of laying out 468 Jacks, planer 300 Jig, box, example of 412 Jigs, drilling, classification of 410 Jigs examples of 411 Jigs^ for drilling 410 Jigs of gang drilling 417 Jig milling, example of 374 Key rule blocks 97 Key seater 308 Key seaters, portable 311 Key seating in a shaner 298 Key ways, cutting of 364 Keys, drawing of 457 Keys, flat 455 Keys, gib head 457 Keys, round 454 Keys, taper of 455 Keys, Woodruff 456 Knee plate, securing work to 254 Knee plate, use of 375 Knurling tools 206 Large micrometer calipers 74 Lapping 438 Laps 439 Lathe beds 1 (55 Lathe carriage 169 Lathe centers, care of 181 Lathe change gears 174 Lathe change gear calculations.... 175 Lathe change gears, compound.... 175 INDEX. 549 Lathe chucks 214 Lathe, dimensions of 177 Lathe dogs 210 Lathe, elements of 165 Lathe, engine 165 Lathe, gap . . . 184 Lathe head stock 165 Lathe, importance of 163 Lathe, monitor 189 Lathe pans 525 Lathe, pit 184 Lathe, pulley 185 Lathe racks 525 Lathe, relationship with other tools 163 Lathe, speed or hand 164 Lathe spindle bearings 106 Lathe tail stock 168 Lathes, testing of. 179 Lathe tools 197 Lathe, tool makers 182 Lathe tools, patent 200 Lathe tools, patent, advantages of. . 201 Lathe tools, threading 203 Lathe tools, setting of 199 Lathe, two spindle 183 Lathe, turret 186 Lathe, turret chucking 188 Lathe, wheel 184 Laying out bevel gears 474 Lead screw 169-174-177 Lead screw nut 174 Lead screw threads 177 Leather belting 490 Left-hand screw cutting 234 Leveling wedges 299 Linear velocity 463 Line of action in gearing 473 Link leather belting 496 Lining up line shafting 512 Link planing attachment 295 Limit gauges 61 Locating drilled holes 112 Lock nuts 451 Lubrication of center bearings.... 222 Lubrication of drills 41 Lubricating machine centers 161 Lubricating, planer ways 280 Lubrication of milling centers 378 Lubrication of taps and dies 140 Machine bolts 450 Machinists' cold chisels 18 Machine cut files 26 Machinists' hammers 17 Mandrel block 161 Mandrel centers 154 Mandrel centers, care of 161 Mandrel presses 162 Mandrels 153 Mandrels, driving in bores 161 Mandrels, expanding 154, 156 Mandrels, expansive, advantages of. 158 Mandrels for conical bores 158 Mandrels for large bores 159 Mandrels, hardened and ground.... 155 Mandrels, influence of on sizes of bores 156 Mandrels, nut 159 Mandrels, solid 154 Mandrels stub 160 Mandrels, taper of 150 Mandrels, with ends only hardened. . 155 Manufacturers' drilling machine. . . 406 Measuring machine, Pratt & Whit- ney 7" Measuring machine, Rogers-Bond. . 57 Measuring machines. Swp^ts _79 Mechanical equivalent of heat 542 Methods for testing sijimn-s 95 Method of lacing Peking 495 Methods of lapping beluug 4:14 Methods of producing screw threads 129 Micrometer calipers, beam 76 Micrometer calipers, bench 77- Micrometer calipers, for measiiung screw threads 73 Micrometer calipers, inside '.'. 81 Micrometer calipers, large 74 Micrometer calipers, reading of Micrometer calipers, use of Milling arbors ' [ ' ' 34^ Milling, advantages for certain classes of work over planing. . 312 Milling attachment for planer. . . . 293 Milling cutters, forms of 'teeth 345 Milling cutter vibration, causes of. . 378 Milling cutters, advantages of small diameters of 3 Oil, filtering of 522 Oil pump 334 Oil separator 522 Oil tube drills Ill Open side planer 279 Open sid^ shaper 288 Overhanging arm supports 321 Oversize in taps 131 550 INDEX. Parts of planer head 281 Patent lathe tools '200 Pickling brass castings 47 Pickling castings 47 Pilot bars 25 ( Pipe centers 238 Pitch circle 46o Pitch of screw thread 12 1 Planer attachments 293 Planer clamps 300 Planer jacks 300 Planer, characteristic parts 273 Planer and its modifications 2<3 Planer and shaper tools 21)1 Planer feeds 2'< u Planer head, parts of 281 Planer, open side 279 Planer, table drives 21-1 Planer table reversing mechanism.. 27o Planer table stop pins 302 Plane surface, method of producing 53 Planing, care necessary in 30o Planing, clamping of work 299 Planing, lining up work 304 Planing, securing work in vise.... 304 Planing, springing of work in 303 Pneumatic drilling machine 518 Pneumatic hammers 518 Pneumatic hoists . . 51 Y Pinning of files 45 Plain grinding machine 293, 429 Plain milling machine 314 Plain turret screw machine 191 Planer centers 290 Planer, jacks 300 Planer tool clamps 282 Plug and ring gauges . . . . : 59 Portable drills 405 Portable grinding head 437 Portable key seater 311 Position of tool for screw cutting. . 233 Position of work for filing Position of workman filing 33 Power required to elevate water. . . . 542 Power transmitted by belting 493 Pratt & Whitney measuring machine 78 Pratt & Whitney's standard gradu- ated line-measure bar 56 Preparation of leather belting 491 Problems in spiral gearing 483 Proper care and use in reamers. . . . 122 Pulleys 510 Pulleys, balancing of 521 Pulleys, calculating speed of 514 Pulleys, clutch 510 Pulley drivers 213 Pulley lathe 185 Pulley taps 131 It Rack cutting attachment 332, 388 Racks, cutting of 388 Rack-driven shapers 283 Racks for files 46 Rack teeth, involute 469 Racks, movable 525 Radial drills 401 Radial mills, advantages of 318 Raising blocks 182 Rake angles 198 Reamer, special large 421 Reamers, adjustable 114-120 Reamers, arbors for shell 119 Reamers, center bearing 123 Reamers, chucking 1 1 <>-1 1 8 Reamers, expansive 1 20 Reamers, fluting of 364 Reamers, hand 116 Reamers, influence of form and num- ber of teech in 114 Reamers, life of ll'd Reamers, points on manufacture of. lit! lieamers, the proper care and use of 12:.' iieamers, shell 119 Reamers, solid 114 Reamers, stocking ] 22 Reamers, taper 1 20 iteamers, tooth clearance in 1 1 7, Reamers, undersized, reclaiming of 120 Reamers with three flutes 119 Reamers with spiral flutes 119 Reaming by hand 1 2-i Reaming in machines 124 Reaming in the lathe 249 Recording calipers 64 Regrinding and dressing hammers.. 18 Relationship of lathe with other tools 163 Relieving attachment for lathes . . ^4 Reversing drill and tap holders.... 148 Revolving chucks 219 Riveted joints -J5S Rivet holes 460 Rivets 458 Rivets, setting of 461 Rogers-Bond comparator 57 Rogers-Bond measuring machine .... 57 Rolled drills 106 Root circle 465 Rope drives 502 Rope drives, flexibility of 500 Rope splicing 502 Rope transmissions, systems of ....... 505 Ropes, speed of in drives 507 Hound keys 454 Rule for drill sneeds 110 Rule for indexing 350 Rules for determining gear parts . . 46(5 Rules, gear 94 Rules, hook 94 Rules, key seat 97 Rules, standard steel 93 Rules with end graduation 93 Safety edges on files 36 Scrapers and surface plates. 48 Scrapers, forms of 48 Scrapers, how held and used 51 Scrapers, use of 48 Scraping, plane surfaces . 52 Scraping, preparation of work sur- face for 50 Scratch gauges 89 Screw cutting, by use of compound rest 236 Screw cutting, catching thread in ... 237 Screw cutting, exercise of care in . . 235 Screiy cutting, in the lathe 233 Screw cutting, left-hand 234 Screw cutting, position of tool for. 233 Screw cutting, square threads 236 Screw drives and how ground 100 Screw machine, plain turret 191 Screw machine, automatic 191 Screw thread gauges 88 Screw thread, pitch of 127 Screw threads 125 Screw threads table 128 Screw threads for fastenings 125 Screw threads fo; transmitting mo- tion 125 Screw threads, methods of producing 129 Screw threads, square, trapezoidal and Powell's 127 Screws, cap 452 Screws, set 453 Securing work on planer 299, 304 Securing work to knee plate. ...... 254 INDEX. 551 Selecting flies for any class of work 30, 34, 46 Self-hardening steel 200 Self-opening dies 138 Sellers' planer table drive 274 Sensitive drills :'.'.)7 Shaper attachments 285-297 Set screws 453 Setting of lathe tools 199 Setting of rivets 461 Setting tool for taper turning 231 Setting up work for boring 253 Shaft, bearing 511 Shaft, couplings 508 Shafting-, alining 512 Shaper, draw stroke 289 Shaper, movable head 289 Shaper, open side. ." 288 Shapers, characteristic parts 282 Shapers, crank driven 283 Shapers, rack driven 283 Sheaves, rope 506 Shell reamers 119 Shrink fit. definition of. *. 262 Single cut files 25 Slabbing cutter 343 Sleeves, drill 144 Slide rest 1 70 Slotted link, for shnper 284 Slotting attachment 334 Slotting machine 306 Slotting machine work, example of. . 307 Sockets, drill 142 Sockets, special form of drill 144 Sockets for oil tube drills 248 Sockets, frictional driven 147 Sockets, grip 145 Sockets, lathe :,. 145 Solid dies 136, 138 Solid mandrels 354 Solid reamers 114 Special form of drill sockets 144 Special tool for planing circular surfaces 296 Speeds for milling cutters 356 Spherical turning 243 Spherical socket boring 261 Speed of emery wheels 430 Speed of hand lathe 364 Spindle ends squaring off 223 Spiral cutting attachment 332 Spiral, cutting of a '. 354 Spiral gears 467 Spring for planer tools 292 Spring joint calipers 65 Spiral gears, data for 482 Spiral gears, elements of 479 Spiral geared planer 276 Spiral gearing, problems in 483 Spiral gears, cutting of 394 Spirals, calculations for the change gears 354 Sour gears 467 Square, box 97 Square corner filing 37 Squares, combination 96 Squares, methods for testing 95 Squares, standard steel 94 Squares, thin steel 96 Squaring off snindle ends 223 Standard gauges 59 Standard graduated line-measure bar. Pratt & Whitney 56 Standards of measuvo 55 Standard pattern drilling machines. 397 Standard steel rules . . 93 Standard steel squares Standard thread gauges 62 Straightening of tempered work... 4*:i Straight edsres. cast iron 98 Straight edges, steel 97 Stay bolts 461 Stay bolt taps 132 Stays, crown sheet ;. 462 Stays, diagonal '. 461 Steady rest --., Steel, air hardening tool 447 Steel, effect of carbon in 44<> Steel hardening 440 Steel, heating of 441 Steel, quenching of ' 44;', Steel, self-hardening tool 447 Stock, keeping of 7, \ Stops, milling machine table.. .' 875 Stud bolts 451 stud set ; ; ; 451 Supporting work not round 22<> Surface disc grinder \:\c, Surface file holders 32 Surface gauge, use of 22t Surface grinder 435 Surface plates 50-54 Surface plates, care of 54 Sweep cutter 419 Sweep drilling 415 Sweet's measuring machines ...... 79 Systems of rope transmission 505 Table of capacities of rectangular tanks 541 Table of capacities of round tanks. 541 Table of circumferences, areas, squares, etc., of circles 52! Table of cycloidal gear cutters.... 382 Table of decimal equivalents 520 Table of dimensions of keys and key ways *. 527 Table of drill speeds 110 Table of emery wheel speeds 536 Table feeds on milling machines . . 321 Table of gas tap sizes 133 Table of horse power of transmis- sion rope 538 Table of involute gear cutters 381 Table of machine screws 537 Table of metric conversions. . 542 Table of milling speeds 357 able of properties of metals' 533 Table of relative values of non-con- ductors 533 Table of size of tap drills 537 Table of screw threads 12S Table of sizes of chimneys with ap- proximate horse power boilers. 541 Table of specific gravity and weight of various metals 5.",2 Table of speed of drills 536 Table of standard dimensions of wrought iron steam, gas and water pipes ":: I Table of different standards for wire gauge in the TL S 528 Table of standard hexagon bolts and nuts 535 Table of tap drill sizes for gas pipe 537 Table of tap drill sizes 112 Tables for transmitting efficiency of turned shafting 539 Tables of transmission of power by leather belting . 538 Table of units of heat in one pound of fuels 533 Table of weight of flat bar iron. . . . 531 Table of weight of plate iron 531 Table of weight of castings from patterns '"" Table of weights of square and round bars of wrought iron. . . . 530 Table of weight of various sub- stances 532 Table fe^d rack, dangers of 321 r> flpd die action when dull.... 141 Tap drill sizes 11-' 552 INDEX. Tap drill sizes, how found 141 Tap holders, f fictional 147-140 Tap wrenches 151 Taper attachment 180 Taper drill shanks 108 Taper grinding 431 Taper keys 455 Taper milling 376 Taper pins . . 458 Taper reaming 122 Taper turning 226-229-232 Taper turning attachment 230 Taper turning lathe 231 Taper turning with compound rest. 231 Taper turning, setting of tool for. . 231 Tapers, Brown & Sharpe 346 Taps, care in the use of. 134 Taps collapsing 133 Taps, combination drill and pipe. . 133 Taps, form of flutes and teeth 131 Taps, hand 120 Taps, hob and pipe . 132 Taps, pulley 131 Taps, square, starting of 135. Taps, stay bolt 132 Taps, taper, plug and bottoming. : . 130 Taps, use of two on heavy tapping 135 Temper, drawing of in sand 445 Temper of twist drills 107 Tempered work, straightening of . . . 445 Tempering by color 444-447 Tempering in oil 444 Tempering, object of '. 441-443 Tempering of steel ._. 440 Tempering, warping of articles in . . 44T> Testing of lathes 170 Thread calipers 68 Three flute drills 107 T slot cutters 330 Tool grinder 424 Tool clamps, planer 282 Tool, for planing key-ways 201 Tool setting, influence of on taper turning 227 Tool, special , for planing circular surfaces 296 Tools for slotting machine 308 Tools, spring for planer 292 Tools, finishing for planer 293 Tools, under cut for planer 292 Toothed gears 464 Tote boxes 525 Transmission of electric power.... 515 Transmitting motion for screw threads 125 Turning a plain spindle 220 Turning cams 246 Turning concave and convex sur- faces 245 Turning cross-head pins 239 Turning crank pins 232 Turning, exercise of judgment in. . 224 Turning irregular outlines 242-245 Turning long work by use of hol- low rest 227 Turning, offset work 232 Turning shafting 239 Turning spherical work 243 Turning taper work 226-229-232 Turret boring, example of 257 Turret chucking lathe, automatic.. 192 Turret chucking lathes 192 Turret drilling machines 403 Turret facing, example of 257 Turret machine operations 256 Turret, on carriage 1 86 Turret on shears 1 88 Turret tools 195-207 Turret work, exampl^ of V>HVV. . . . 258 Twist drill cutting in milling ma- chine 368 Twist drill grinder 428 Twist drills 305 Twist drill, relieving of 369 Two classes of dies 135 Two spindle lathe 183 U United States standard of measure 55 United States standard thread 125 Universal boring mills 260 Universal chucks 215 Universal drilling tables 403 Universal grinding machine 428 Universal indexing head 325 Universal milling head 328 Universal milling machine 313 Unit of heat 542 Unit of work 542 Use of calipers 65, 67 Use of center head square 221 Use of chalk and oil on flies 45 Use of gauges 61 Use of graduated dials on feed screws 362 Use of knee plate 375 Use of micrometer calipers 72 Use of oil tube drills 248 Use of scrapers 48 Use of surface gauge 221 Use of test indicator 92 Value of graduated machine dials.. 378 V blocks 303 V threads 125 Velocity ratio 466 Velocity ratio in elliptical gearing 4(>< Vernier calipers, reading of 69 Vertical boring mills 264 Vertical milling, examples of 370 Vise, drilling 408 Vise jaws, soft 38 Vise jaws, spring 38 Vise, jig drilling 409 Vise jigs 38 Vises, milling machine 327 Vises, planer 295 Vise, planer and shaper, securing work in 304 Vises, special jaws for 372 Vises, use of two in milling 371 W Warping of articles in tempering . . 445 Waste cans 523 Water, data on 542 Water, power required to elevate.. 542 Weight of hammers 17 Whitworth quick return motion . . 286 Whitworth standard thread 125 Wire belt lacing 495 Wire gauges, comparison o'f 82 Work supports 224 Work,' unit of 542 Work, securing of on planer. . . 299-304 Working fit, allowance for 262 Working fit, definition of 262 Worm gears, cutting of 365 Worm gears, forms of te^th 477 Wrenches, box, socket and ratchet.. 102 Wrenches, combination 102 Wrenches, correct use of monkey.. ?00 Wrenches, monkey 100 Wrenches, solid 15 degree 102 Are You Awake to the vast amount of valuable and interesting matter which is afforded the readers of Cassier's Magazine The Leading ENGINEERING MONTHLY 25 Cents a copy. $3.00 a year. it contains articles of the greatest importance in each issue, and should be read not only by every Engineer, but by every thinking man in order to keep in touch with industrial progress. It is impossible to tell half of its good features here and we prefer anyway to let the magazine speak for itself. Why not send for a sample copy ? We will send you one free or we will send you the current number and two previous ones for twenty -five cents. THE MAGAZINE OF INDUSTRIAL PROGRESS Send for "AS OTHERS SEE US" it is of interest to every advertiser and will interest you. A COPY FOR THE ASKING The Gassier Magazine Company 12 West 31st Street, New York THE PEERLESS Piston and Valve Rod Packing It will hold 400 pounds of steam. Will run twelve months in high- speed engines. In boxes 3 to 8 pounds. 1 -4 to 2 inches diameter. Made in three different shapes: Straight, Spiral and Square Spiral. SOLE MANUFACTURERS OF THE Celebrated "Rainbow Packing," "Eclipse Sectional Rainbow Gasket," "Hercules Combination," " Honest John," " Success," " Arctic," and "Germane" Packings Manufacturers of a full and complete line of superior Rubber Goods, including Gas Bags, Belting, Fire Buckets > Diaphragms, Disks for Valves, Rubber Gaskets, Air, Steam Hydrant, Garden and Suction Hose, Landing Pads, Mats and Matting, Nipple Caps, Packing, Pails, Pump Valves, Gauge Glass Rings, Springs, Tubing, etc. COPYRIGHTED AND MANUFACTURED EXCLUSIVELY BY PEERLESS RUBBER MANUFACTURING CO. 16 WARREN STREET - - - - . NEW YORK FOR SALE BY ALL FIRST-CLASS DEALERS RAINBOW PACKING Thousands f^Tfj^^^^_ -> Don't Have to of Imitators. [ Use Wire and No Equal. I cloth to Hold Will Hold RAINBOW. Highest I Can't Blow Pressure. **m --___ ; It Out. THE COLOR OF RAIXBOW PACKING IS RED Notice our trademark of the word "Rainbow" in a diamond, in Three Rows of Diamonds in Black, extending throughout the entire length of each and every roll of Rainbow Packing Sole Manufacturers of the Famous Eclipse Sectional Rainbow Gasket Peerless Piston and Valve Rod Packing Honest John Hydraulic Rainbow Core Packing Hercules Combination Arctic Ammonia Ring Packing A FULL AND COMPLETE LINE OF FINE MECHANICAL RUBBER GOODS INCLUDING RUBBER HOSE FOR ALL PURPOSES SEND FOR OUR NEW CATALOGUE Copyrighted and Manufactured Exclusively by PEERLESS RUBBER MANUFACTURING CO. 16 WARREN STREET NEW YORK 1911 CATALOGUE of Practical Books Published and for sale by The Norman W, Henley Publishing Company Publishers of Scientific and Practical Books 132 NASSAU STREET NEW YORK, U.S.A. All books in this Catalogue sent prepaid on receipt of price. SUBJECT INDEX Air Brakes 3, 12, 13 Arithmetics 7, 15, 20 Balloons 3 Bevel Gears 10 Boilers 3, 13, 16 Brazing 3 Cams ii Car Charts 3 Change Gear n Charts 3 Chemistry 10, 17 Coal Mining 17 Coke 4 5 4 Compressed Air Concrete Cyclopedia Dictionaries Dies Drawing Drop Forging Dynamo Electricity Engines and Boilers Flying Machines Fuel Gas Manufacturing Gas Engines Gears Heating, Electric Hot Water Heating Horse-Power Chart Hydraulics Ice Making India Rubber Interchangeable Manufacturing Inventions Lathes Lighting ([Electric) Link Motion Liquid Air Locomotive Engineering 12, 13, Machinist's Books 14, 15, PAGE Manual Training 16 Marine Engines 16 Mechanical Movements 15 Metal Turning n Milling Machines 16 Mining 17 Oil Engines 10 Patents n Pattern Making 17 Perfumery 17 Pipes ' 20 Plumbing 18 Producer Gas 10 Punches Receipt Book Refrigeration Rubber Stamps Saws -r. . Sheet Metal Working Shop Tools Shop Construction Shop Management Sketching Paper Smoke Prevention 9, i: Soldering ; Steam Engineering . 19, 2c Steam Heating 2c Steam Pipes 2c Steel 2 Superheated Steam i Switchboards 7, Tapers i Telephone < Threads . . t Tools. 14, 15, Ventilation Valve Gear Valve Setting Walschaert Valve Gear Watchmaking Wiring 7, Wireless Telephones INDEX BY AUTHORS PAGE Alexander, T. H 3 Askinson,G. W 17 Barr, Wm. M 9, 12 Barrows, F. W 17 Bauer, Dr. G 16 Baxter, Wm 7, 8 Benjamin, Park 16 Blackall, R. H 12, 13 Booth and Kershaw 9 Booth, Wm. H 20 Buchetti. J 19 Byrom, t. H 17 Byrom and Christopher 4 Cockin, T. H 17 Colvin, Fred H 12, 13 Colvin-Cheney is, 20 Colvin-Stabel 16 Crane, W. E 19 Dalby, H. A 14 Engstrom, D. Ag 10 PAGE Erskine-Murray 9 Fowler.Geo. L 3, 13 Garbe, Robert 12 Goddard, Dwight 19 Grimshaw, Robert 13, 16, 18, 19 Harrison, Newton 7 Haslam, Arthur P 8 Hiscox, G. D. .4,10,11, 15, 17, 18, 19 Hobart, T. F 3 Horner, J. G 4, n, 14, 10 Houghton, A. A 4, 5 Johnson, J. P 17 King, A. G 20 Kleinhans, F. A 13 Kraus, H.T. C 6 Lewis, t M. H Lummis-Paterson 8 Markharn, E. R 20 Mathot, R. E 10 Parsell and Weed 10 PAG Perrigo, Oscar E 9, n, i Pratt, H .... Putnam, Xeno W i Radcliffe and Cushing Richards-Colvin Rouillion, Louis u, Royle, H.M Saunier, Claudius Sloane, T. O'Conor . . .5, 7, 8, 12, Starbuck, R. M Sylvester and Oberg Usher, John T Vandervoort, W. H Walker, S. F Wallis-taylor, A. J i Weed, A. J...... Wood, Wm. W i Woodworth, J. V 6, 14, : \Vright, J (|gr-ANY BOOK ADVERTISED IN THIS CATALOGUE WILL BE SENT PROMPTLY TO ADDRESS IN THE WORLD, CHARGES PREPAID, UPON RECEIPT OP PRICE. 1 How to Remit. Remit by Postal Money Order, Express Money Order, Bank Dra or Registered Letter. RETURN CIRCULATION DEPARTMENT TO +> 202 Main Library 836, LOAN PERIOD 1 HOME USE 2 3 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS RENEWALS ANO RECHARGES MAY 3E MADE 4 DAYS PRIOR TO DUE DATE. LOAN rlifiiOD;; Ant 1-V.OM'H. 3-MONTHS, AND 1-YEAR. 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