AUTOMATIC SCREW MACHINES AUTOMATIC SCREW MACHINES AUTOMATIC SCREW MACHINES A TREATISE ON THE CONSTRUCTION, DE- SIGN, AND OPERATION OF AUTOMATIC SCREW MACHINES AND THEIR TOOL EQUIPMENT BY DOUGLAS T. HAMILTON ASSOCIATE EDITOR OF MACHINERY AUTHOR OF " AUTOMATIC SCREW MACHINE PRACTICE," " SHRAPNEL SHELL MANUFACTURE," " MACHINE FORGING," " BOLT, NUT, AND RIVET FORGING," ETC. AND FRANKLIN D. JONES ASSOCIATE EDITOR OF MACHINERY AUTHOR OF " TURNING AND BORING," " PLANING AND MILLING," " GAGING TOOLS AND METHODS," ETC. FIRST EDITION NEW YORK THE INDUSTRIAL PRESS LONDON: THE MACHINERY PUBLISHING CO., LTD. 1916 COPYRIGHT, 1916 BY THE INDUSTRIAL PRESS NEW YORK Composition and Electrotyping by THE PLIMPTON PRESS, Norwood, Mass PREFACE THE class of automatic machine tools commonly known as screw machines represents one of the most important develop- ments in the machine tool field, and includes ingenious mecha- nisms which may be studied with profit by all who are interested in mechanical movements and modern methods of manu- facture. This book deals with five distinct branches of auto- matic screw machine practice. It covers the design and construction of different well-known types of single- and mul- tiple-spindle machines, the tool equipment used for various classes of work, the methods of adjusting or setting-up machines made by different manufacturers, the design of screw machine cams, and the application of machines of this type to both typical and unusual operations. The descriptions of machines are confined principally to the important fundamental features of the design, and deal especially with those mechanisms which control parts that must operate automatically and in accordance with the nature of the work being produced. The machines illustrated were selected as representative types, each embodying important developments in screw machine design. While designers have incorporated many ingenious ideas in automatic screw machines, the tool equipment and auxiliary attachments used in conjunction with these machines are not lacking either in cleverness of design, or effectiveness in in- creasing the efficiency and range of machine tools of this class, to include an endless variety of work. The various types of tools used for turning, boring, recessing, threading, knurling, etc., are described, and the methods of applying these tools are illustrated by practical examples. Different attachments are also described, such as are commonly used for slotting 392309 vi PREFACE screw-heads, milling, cross-drilling, and automatically feeding separate castings or forgings to the machine from a magazine. Information on the adjustment and setting-up of screw ma- chines is given to supplement the general descriptions and show just what changes are necessary when a machine must be arranged for producing different parts. In dealing with the subject of cam design, the exact method of laying out a set of cams for a given operation has been described in detail, in order to clearly indicate the fundamental principles involved. This treatise is intended especially for the users of screw machines and the designers of tools and auxiliary equipment, and, in order to make it of greater practical value to the men responsible for the economical operation of these machines and the production of parts which conform to required stand- ards of accuracy, many different classes of work and a large variety of standard and special tools have been described in detail. The cooperation of screw machine manufacturers in supplying illustrations and data is much appreciated. THE AUTHORS. NEW YORK, September, 1916 CONTENTS CHAPTER I SCREW MACHINE CLASSIFICATION AND DEVELOPMENT PAGES Origin of the Term "Screw Machine" Distinction between Automatic and Semi-automatic Machines Gen- eral Features of Automatic Screw Machines . Classification of Automatic Screw Machines Development of Single- and Multiple-spindle Types General Application of Auto- matic Screw Machines Advantages of Single- and Mul- tiple-spindle Designs i-io CHAPTER II SINGLE-SPINDLE AUTOMATIC SCREW MACHINES Brown & Sharpe Automatic Screw Machine Cleve- land Automatic Screw Machine Gridley Single-spindle Automatic Turret Lathe Chicago Automatic Screw Machine 11-38 CHAPTER III MULTIPLE-SPINDLE AUTOMATIC SCREW MACHINES Acme Four-spindle Automatic Screw Machine Daven- port Five-spindle Automatic Screw Machine Hayden Five-spindle Automatic Screw Machine Gridley Four- spindle Automatic Screw Machine New Britain Six- spindle Automatic Screw Machine 39-83 CHAPTER IV AUTOMATIC SCREW MACHINE TOOL EQUIPMENT Circular Forming and Cutting-off Tools Tool-holders foi Flat Forming Tools Box-tools Methods of Apply- ing Box-tool Cutters Work Supports for Box-tools Viii CONTENTS Hollow Mills Centering and Facing Tools Drills and Drill-holders Counterboring Tools Reamers and Reamer- holders Swing Tools for Turning and Recessing Shaving Tools Dies for Screw Machine Work Die-holders Taps for Screw Machines Knurling Tools 84-147 CHAPTER V ADJUSTING OR SETTING-UP AUTOMATIC SCREW MACHINES Setting-up the Brown & Sharpe Machine Adjustments on the Cleveland Automatic Method of Setting-up the Acme Multiple-spindle Machine Setting-up the Daven- port Multiple-spindle Automatic 148-196 CHAPTER VI ATTACHMENTS FOR AUTOMATIC SCREW MACHINES Screw Slotting Attachment Slotting and Slabbing Attachment Index Drilling Attachment Cross-drilling Attachments Turret Drilling Attachment Burring At- tachment Tap and Die Revolving Attachment Accel- erated Reaming Attachment Drilling and Milling Attach- ment Vertical-spindle Milling Attachment End-milling or Slotting Attachment Attachment for Forming Squares and Hexagons Attachment for Robbing Worms and Spiral Gears Magazine Feeding Attachments 197-223 CHAPTER VII DESIGNING SCREW MACHINE CAMS Effect of Cutting Speed on Cam Design General Method of Designing Cams Laying Out Cams for a Spe- cific Operation Development of Cam Lobe for Control- ling Movement of Threading Die Allowance for Tool Clearance Use of Cam-lever Templets Laying Out Cams for Recessing Cam Rise for Drilling Designing Cams for Deep-hole Drilling 224-257 CONTENTS IX CHAPTER VIII OPERATIONS ON SINGLE- AND MULTIPLE- SPINDLE SCREW MACHINES Examples of Forming Operations Recessing Drill- ing and Counterboring from Cross-slide Making Watch Parts in Screw Machine Examples of Work on the Cleve- land Automatic Operations on Acme Multiple-spindle Machine Use of Screw Machine for Producing and Assembling Parts Thread Rolling in the Screw Machine - Different Types of Tools for Thread Rolling Cutting Helical Gears in Screw Machine Speeds and Feeds for Screw Machine Operation 258-335 AUTOMATIC SCREW MACHINES CHAPTER I SCREW MACHINE CLASSIFICATION AND DEVELOPMENT MACHINE tools which are either automatic or semi-auto- matic in their operation have replaced many hand-operated tools, especially wherever large numbers of duplicate machine parts are required. There are many different classes of auto- matic machine tools used at the present time, but the most important class or group is that which originated from the lathe and in which are included the machines designed primarily for turning and boring operations. In this general class there are several distinct types which have their own particular field and also many different designs. The machines which are dealt with in this treatise are commonly known as automatic screw machines because the work for which they were originally designed was the making of screws. This field, however, was soon enlarged to include the making of all kinds of small nuts, washers, pins, collars, etc., and, at the present time, machines of this class are capable of a great variety of operations, not only on parts which are turned from bars of stock, but on separate castings or forgings when magazine feeding attachments are employed. It is evident, therefore, that the term " screw machine" as applied to modern machines of this type is a misnomer, because the making of screws constitutes only a small part of screw machine production. While the smaller machines are naturally adapted to making various kinds of standard and special screws, in many shops and factories they are used almost exclusively on other classes of work. The term " screw machine " is even less 2 CLASSIFICATION AND DEVELOPMENT accurate or descriptive when applied to the large automatic machines now used extensively for general bar and chuck work, in direct competition with the semi-automatic and hand- operated turret lathes; in fact, some manufacturers of such machines do not list them as screw machines, but as automatic machines, automatic turret lathes, or simply as "automatics." Application of the Term " Automatic." The term "auto- matic," as applied to various classes of machine tools, does not always have the same meaning, and a machine which one manufacturer classifies as automatic would be considered semi- automatic by another manufacturer. For instance, some machines which are designed to perform a certain cycle of operations, but are not capable of presenting unfinished parts to be operated upon to the tools, may be referred to as auto- matic machines. While such a machine is automatic or self- moving, in that it controls the movements of the cutting tools, the attention of an operator is required when each part is com- pleted, so that such a machine is really semi-automatic. There are other types of machines, such as the automatic screw machines, which not only control all the movements of the cutting tools, but are equipped with work-feeding mecha- nisms so that, when one part has been finished, other dupli- cate parts may be produced automatically. The operation of such a machine is continuous until it needs to be supplied with raw material, which may either be in the form of bar stock, or separate castings or forgings, when a magazine feeding attachment is used. A machine of this type is automatic in the sense that it repeatedly performs all of the necessary operations, which include ejecting the finished work and presenting a new piece or length of stock to the tool. From the foregoing, it will be seen that the term "auto- matic" is a relative one as applied to machine tools generally. The early designs of lathes, after they had been equipped with self-feeding mechanisms, were automatic to the extent of feeding the turning tool. As automatic feeds became the rule rather than the exception, and as additional automatic features were incorporated in the designs of many machines, GENERAL FEATURES 3 the use of the term " automatic" was no longer justified in the case of a machine which simply had a feeding mechanism. According to present usage, the term "automatic" is generally applied to machine tools in which practically all of the move- ments are self-actuating, although, as previously mentioned, the extent of the automatic operation varies considerably on different machines which are classified as automatic types. When a machine is capable of automatically producing dupli- cate parts repeatedly, it is universally referred to as auto- matic, whereas, if it simply performs a complete cycle of machining operations, but requires the attention of an operator each time a part is finished, it may be 'considered automatic by some, and semi-automatic by others. In some cases, a machine of the latter class is termed " automatic," while one that is capable of continuous operation is known as "fully automatic." In American shop parlance, the term "automatic" is often used as a noun to indicate any kind of automatic turning machine, especially a screw machine or automatic chucking and turning machine of the turret lathe class. General Features of Automatic Screw Machines. Charac- teristic features of automatic screw machines in general are means for automatically locating successive tools in the cor- rect working position, the automatic changing of feeds and speeds to secure economical operation, and the presenting of new stock to the tools for a similar series of operations. These various movements, which are entirely automatic, are obtained principally from cams which are rotated at predetermined speeds and are so formed and set, relative to one another, that the parts of the machine which they control all operate at the proper time and at suitable feeds or speeds. There are two general methods of presenting new stock or raw material to the tools so that the machine can produce duplicate parts automatically. In most cases, the stock is in the form of a bar which is large enough in diameter to allow for making parts of the required size. This bar is held in the hollow rotating spindle of the machine and, as soon as the tools 4 CLASSIFICATION AND DEVELOPMENT have finished one part, the bar is automatically pushed forward far enough for making another piece. After the bar is fed forward, it is held firmly by a suitable chuck in the end of the spindle and the different tools advance in the proper order, perform their respective machining operations, and then recede. When the finished piece has been cut from the bar, the latter is again pushed forward against a stop which regulates the distance that it projects beyond the chuck, and the cycle of operations is repeated until the entire bar has been used and changed into the finished product. The attendant, who is able to care for quite a number of machines, then inserts a new bar. While most of the parts produced in automatic screw machines are made from bar stock, many castings and drop- forgings may also be finished in machines of this class. When each part is a separate unit, some auxiliary feeding mechanism must be employed for automatically inserting the rough pieces into the chuck, preparatory to the machining operations. These magazine feeding mechanisms or attachments are loaded or filled with the parts that require machining and are so de- signed and adjusted that a rough piece is transferred from the magazine to the spindle chuck, after the tools have com- pleted their work and the part finished previously has been ejected. These magazine feeding attachments vary in design, according to the shape of the work and the nature of the machining operation. Magazine attachments are used for that class of work which cannot be produced profitably from bar stock, either because of irregularity of shape or the amount of material which would have to be removed. Classification of Automatic Screw Machines. There are two general classes of automatic screw machines, known as single-spindle and multiple-spindle types, respectively. The single-spindle machines operate on one part at a time, as there is only one work-holding spindle. For instance, when operat- ing on a bar of stock, the tools perform whatever turning, drilling, reaming, counterboring, threading, or other operations may be necessary, and then the finished piece is cut off; hence, SCREW MACHINE DEVELOPMENT 5 the time required to complete a part on a single-spindle ma- chine is equal to the total time necessary for all of the separate operations, which includes the time for withdrawing the tools at the completion of the various cuts, indexing the turret which holds the tools, and presenting the succeeding tools to the work. The multiple-spindle machine is designed to operate on several parts at the same time. Thus, if a four-spindle machine is turning parts from bar stock, each spindle holds and rotates a bar which is operated upon by one or more tools, and the spindle carrier or head indexes or turns one-fourth revolu- tion as the tools at the four positions or stations recede after completing their work. With this arrangement, each bar is successively located in front of the different tools and a part is finished at each indexing. It is evident, therefore, that a multiple-spindle machine is practically several machines con- tained in one unit, and the total time required to complete a part is equal to the time necessary for the longest single operation plus the time for the idle movements. In some cases, the time may be reduced considerably by dividing the longest operation into two operations. For instance, when a comparatively long length needs to be turned, instead of using one box-tool, the cut is often divided between two tools held in the first and second positions. The drilling of a rather deep hole is frequently divided in the same way, by using two or three drills located in different positions. Development of Single-spindle Machine. The screw machine was developed to a state of practical usefulness principally by Christopher M. Spencer. With the intro- duction of the original Spencer automatic screw machine in the early eighties began the extensive use of " automatics" as an important factor in modern machine-shop practice. This machine was simply a small turret lathe or " screw ma- chine" fitted with a modified form of the Parkhurst wire or rod feed; but the various motions usually operated by hand were controlled instead from various cams on a single cam- shaft, extending under the machine for its whole length. 6 CLASSIFICATION AND DEVELOPMENT Changes in feed and length of cut were made by changes in simple strap cams. .The time taken for the idle movements was shortened by giving a quick movement to the camshaft, automatically changing to the slow feeding movement when the cutting tools approached the work. Machines of practi- cally the original design are still in successful use. The first automatic screw machine to depart from the Spencer type was the one built by the Brown & Sharpe Manu- facturing Co. This machine employs disk cams, which are usually special for the particular piece being made. Unlike the Spencer machine, these cams have a rotating motion at a uniform speed, all the idle movements being operated by intermittent clutch connections with a fast-running controll- ing shaft. The machine is noted for its accuracy and for the quickness of its motions and is familiar to all screw-machine specialists. As is the case with most of the modern machines, it may be fitted with various automatic attachments for milling, cross-milling, screw slotting, etc. The automatic field has been greatly extended by the de- velopment of the heavier class of automatic machines, such as the Gridley, Cleveland, and Chicago, which have made it possible to produce comparatively large work that formerly could only be done on an engine lathe or that type of turret lathe designed for handling bar stock. Development of Multiple-spindle Machine. While the machines previously referred to have led in widening . the field of the "automatic," there has been another line of development which has greatly increased production in those classes of work for which screw machines were first used. This is the multiple-spindle automatic screw machine which was originated by Reinhold-Hackewessell and E. C. Henn. The first successful design was built by the National Acme Mfg. Co. In this machine, the turret is dispensed with, and its place is taken by a tool-holder which feeds tools forward to operate on bars of stock held in four opposing work-spindles. It is a drum or carrier containing these spindles which " in- dexes/ 7 instead of the tool-holder or turret. After the tool- GENERAL APPLICATION 7 holder has concluded its working stroke and retired, the work -spindle carrier or head is revolved, bringing each bar of stock to the next tool in rotation. The final tool position pro- vides for a cut-off blade, and a complete piece is finished and cut off at each indexing. One or more forming slides also operate at the different spindle positions if necessary. With this type of machine, all the cutting tools are working on each feeding stroke, as each has a bar of stock presented to it, whereas, with a single-spindle machine, the various tools of the turret operate successively on a single bar of stock. Among other well-known designs of multiple-spindle machines may be mentioned the Davenport, Gridley, New Britain, and the Hayden machines. These various designs, which will be described later, each possess distinctive features and represent ingenious examples of modern machine-tool development. General Application of Automatic Screw Machines. Auto- matic screw machines are used for such a variety of operations that only a general outline of the work for which they are adapted can be given. As previously mentioned, machines of this class are designed primarily for producing parts from bars of stock, although by the addition of auxiliary attach- ments they may also be used for machining separate forgings or castings.- The work done on a screw machine usually involves such operations as turning, drilling, reaming, boring, recessing, counterboring, and threading. In order to avoid a secondary operation on another machine, attachments are also used which enable special operations to be performed. For instance, if a screw or pin requires a hole drilled through the head in a cross-wise direction, a cross-drilling attachment is used. There are also attachments for cutting the slots in screw-heads after the screws have been turned and threaded by the regular mechanism and tool equipment of the machine, and other ingenious attachments have been designed to in- crease the range of automatic screw machines and make it possible to completely finish parts on them in one series of operations. These attachments are separate units and are 8 CLASSIFICATION AND DEVELOPMENT applied to the machine in such a way that they operate in conjunction with the regular tools. The extent of the tool equipment and its cost naturally depends upon the nature of the work. For many operations, only standard tools, such as box- tools, reamers, dies, etc., are necessary. Frequently an additional special tool is needed, such as a forming tool for turning the head of a pin or screw to an irregular shape, and sometimes several special tools are necessary. The cost of the tool equipment for producing a certain part is often an important item. When a very large number of duplicate parts are required, expense for special tools is of less importance than when a relatively small number of pieces are to be made. In many cases, it is difficult to de- cide whether an automatic screw machine should be used, or some other machine, such as a semi-automatic turret lathe or a hand-operated turret lathe or screw machine. It is im- portant to consider the number of parts required and the rela- tion between the higher rate of production obtained with the automatic machine, the relative cost of tools for each machine, and the time necessary for adjusting or setting up the ma- chine. A general idea of the different points that should be considered in determining the conditions favorable to the use of automatic screw machines may be obtained by studying the various machines, tools, attachments, and operations re- ferred to in the following chapters. Advantages of Single- and Multiple-spindle Designs. - The difference in the rate of production between the single- and multiple-spindle types of screw machines varies considerably on different classes of work. When comparing the two types, there are two important points to be considered; i. The rela- tive rates of production for the general class of work required. 2. The degree of accuracy necessary in connection with the finished product. In general, multiple-spindle machines are greatly superior so far as rate of production is concerned, but as a general rule they are not capable of such extremely accu- rate results as well-designed and carefully constructed single- spindle machines. While well-built multiple-spindle machines GENERAL APPLICATION 9 will produce very accurate work, it is generally considered impracticable in a commercial machine to secure the same degree of accuracy as with a single-spindle design, assuming that each type of machine is constructed in accordance with approved methods. It is more difficult to secure accurate indexing with multiple-spindle machines than with the single- spindle types, because of the greater mechanical difficulties of constructing a machine having several spindles which are equally spaced and equi-distant from the axis of the spindle carrier. In order to overcome any slight inaccuracies which may exist, ingenious methods of locating the spindle carriers have been devised and the degree of accuracy obtainable on high-grade machines of multiple-spindle design, is sufficient for all except the most exacting work. Each type of machine has its own field, although it is impos- sible to draw a definite line which indicates just where one type is superior to the other. The rate of production is not always in favor of the multiple-spindle design. For instance, when turning small brass parts, etc., a very fast spindle speed is required to secure an efficient cutting speed, and a light single-spindle machine is especially adapted to fast speeds, whereas, with the multiple-spindle type, it is not practicable to operate the spindles so rapidly, because of the geared drive to each spindle; consequently, for a given rate of feed, the tools on a high-speed, single-spindle machine cut faster and also withdraw and index with great rapidity. With a mul- tiple-spindle machine, the indexing movements are somewhat slower because all of the work spindles, the spindle carrier, and the bars of stock must be indexed, and, owing to their combined weight, there is considerable inertia to overcome when the indexing movement is started and it is also necessary to arrest the movement of the spindle head without injurious shocks; hence a slower indexing movement is necessary. When turning brass or small steel parts, especially when there are no long operations, such as turning long surfaces or drilling deep holes, and the idle time represents a comparatively large percentage of the total time, the importance of rapid move- 10 CLASSIFICATION AND DEVELOPMENT ments is apparent, and while the single-spindle machine must index for locating each turret tool, whereas with the multiple- spindle machine a part is completed for each indexing move- ment, this handicap is overcome on some classes of work. When there are long turning or drilling operations, or in case considerable material must be removed by forming tools, the multiple-spindle design has a decided advantage as compared with the single-spindle type, because the tools all operate together and the time for the longest operation can be reduced one-half by using two tools simultaneously. The advantages of each type, as outlined in the foregoing, are subject to wide variations, owing to differences in the de- sign, the size of the machines, and the nature of the work. For instance, some multiple-spindle machines are designed especially for small work and index very rapidly, one well- known make requiring only one second for the indexing move- ment, during which time the chucks are opened, the stock fed forward against a stop, the chucks closed, and the feed-tube drawn back ready for the next feeding movement. The maxi- mum capacity of this machine is for ^-inch round stock. Mul- tiple-spindle machines of larger sizes require more time for indexing. The single-spindle type covers a much wider range of work as to size, some machines being adapted to the turning of small watch and clock parts, whereas others are capable of handling bars of stock 6 or 7 inches in diameter; in fact, one single-spindle machine (the Cleveland Automatic) has a maximum capacity of 7! inches. CHAPTER II SINGLE-SPINDLE AUTOMATIC SCREW MACHINES AUTOMATIC screw machines, in common with all machines of the self-acting type, are naturally more complicated than those types which require a certain amount of hand-manipula- tion, and, in order to understand the methods of adjusting and using such machines, it is essential to know just how the automatic action is obtained. While the automatic screw machines made by different manufacturers all differ in regard to details of design, the general principle upon which machines of the same class operate is practically the same in each case. The different methods of controlling the various movements and adjustments for the tools, however, differ considerably on some machines, and a study of these important features will prove of value to anyone desiring a knowledge of screw-machine con- struction and operation. In this chapter, representative types of single-spindle automatic screw machines are described. Other machines of the multiple-spindle design are referred to in the following chapter. Brown & Sharpe Automatic Screw Machines. The auto- matic screw machine shown in Fig. i is made by the Brown & Sharpe Mfg. Co. and is intended for comparatively small work. The bar of stock to be operated upon is inserted through the hollow spindle of the machine. This spindle is driven from an overhead countershaft by means of open and cross belts operating on the friction pulleys A and B. When one pulley is engaged by the clutch, a forward movement for turning operations is obtained, and a reverse movement for backing off a die when threading is secured when the other pulley is engaged. For ordinary operations, the necessary tools are held in the turret / and on front and rear cross-slides at E. ii 12 SINGLE-SPINDLE DESIGNS J L F BROWN & SHARPE SCREW MACHINE 13 There are six holes in the turret and all or part of these holes may contain tools, the number depending, of course, upon the extent of the operations. A stop for regulating the distance that the stock is fed through the spindle after each finished part is severed from the bar is held in the turret and, 4 in addition, such tools as a hollow mill, a box-tool, a threading die, etc. In case a forming operation is necessary, the forming tool is held on one cross-slide and the cutting-off tool on the other. All feeds and other movements of the machine, except the rotation of the spindle, are derived from the feed-shaft O 3 (Fig. 2) at the rear of the machine, which, in turn, is driven by a belt from an overhead countershaft operating on pulley C. All of the operations are timed or regulated from camshafts on the front and end of the bed. These shafts are driven from the constant-speed feed-shaft 3 at the rear, through a worm- wheel and change-gears H located at the end of the bed. By means of these change-gears, the duration of the cycle of operations, or the length of time required to make one piece, is positively regulated. The operations of feeding the stock, reversing the spindle, and indexing the turret are regulated by trip dogs or carriers on the camshaft D at the front of the machine, the adjustment of the dogs serving to accurately time the successive operations. These dogs operate levers which extend through the machine bed to the rear shaft Oa, where they connect with and operate positive clutches at the right time. The tripping of a lever by a dog engages the cor- responding clutch, thus causing gears or a face-cam to revolve with the feed-shaft 3 . In this way, motion is obtained for performing a certain operation, and then the clutch auto- matically releases. If more work is to be done than can.be per- formed by a single operation, such as feeding extra lengths of stock or passing empty holes in the turret, several dogs or a special dog can be used so that the same operation is performed several times in rapid succession. The turret-slide and cross-slides are fed to the work by the action of disk cams and levers, each slide having a separate cam or three cams in all. One, two, or sometimes three pieces SINGLE-SPINDLE DESIGNS BROWN & SHARPE SCREW MACHINE 15 of work are completed in one revolution of a cam so that the various movements of one of the slides, in making a particular piece, are laid out as curves around the cam; the curves for one piece include the whole circumference, whereas for two or three pieces they are repeated. Special cams are required for each job, and these must be laid out in accordance with the nature of the work, as described in Chapter VII. Stock-feeding and Chuck-operating Mechanism. The stock is automatically advanced through the spindle after successive parts have been formed and cut off in the machine shown in Fig. i, by means of a feed-tube extending through the spindle. This feed-tube has spring-feeding fingers that are located at the rear of the collet chuck. The tube may be withdrawn and the fingers readily changed for different sizes of stock. The motion for feeding the stock is derived from cam E 2 (Fig. i). This cam actuates a slide through a lever that engages a block that may be adjusted by crank N (Fig. 2) for varying the feeding movement. The feed-tube is connected to the slide by means of a latch that may be raised, thus allow- ing the feed to remain idle or the tube to be withdrawn. The opening and closing of the collet is controlled by another cam surface on cam E 2 . The action of this cam is controlled by dogs on drum K which serve to engage or disengage a clutch through which the cam is rotated. When the chuck is closed upon the stock, the feeding fingers are withdrawn preparatory to the next forward feeding movement. The feeding mecha- nism derives its motion from the rear shaft 3 (Fig. 2) through spur gearing at F 2 . Operation of the Cross-slides. The front and rear cross- slides are independent and may be used together or separately. They are operated by disk or plate cams C/ 2 and F 2 mounted on the front camshaft D, Fig. i. The front cross-slide is oper- ated by segment lever Wz, Fig. 3, the teeth of which mesh with rack F 2 . This rack is threaded on one end and has an adjust- ing nut A 3 which is used for changing the position of the cross- slide relative to the center of the spindle. The rear cross-slide is operated through a double lever or segment gear B 3) which i6 SINGLE-SPINDLE DESIGNS connects with a rack, as the illustration shows. The cross- slides are made to travel to exactly the same point by set-screws 3, which come into contact with stops Z) 3 . The cross-slide tools are circular in form and are attached to suitable holders by screw 1 3. Operation of the Turret-slide. The turret 7, Fig. i, which carries the end-working tools, is mounted in a vertical Mfahtnery Fig. 3. Partial Section of No. Machine showing Mechanism for Operating Cross-slides plane so that it rotates about a horizontal axis. This position allows the tools to work closely in between the cross-slide tools with a minimum of overhang, and the idle tools do not interfere with the cross-slide. The turret-slide is mounted directly on the machine bed and the turret is rotated or in- dexed to bring the different tools into the working position, by means of hardened roll C 4 (Fig. 4) attached to disk D 4 - This roll engages radial grooves in the disk E 4 . The disk D BROWN & SHARPE SCREW MACHINE is driven from the rear driving shaft through spur and helical gearing, and makes six revolutions for every revolution of the turret. The turret is locked in position by the hardened taper plug / 4 which is operated by latch L 4 , controlled by a cam MI ftl J -Jj'"-,i "" I ji| -i ' | [ I ^V -^ Cli----^f | nri__~|ipj'~ril I n LJJ J n\l REAR DRIVING SHAFT Machinery Fig. 4. Plan and Rear Elevation of Turret-slide and its Operating Mechanism on the end of shaft _V 4 . The slide G carrying the turret re- ceives its forward movement through a "lead cam" which transmits motion through the segment lever O 4 . The shaft carrying the lead cam is driven from the rear driving shaft through worm and spur gearing. The turret-slide is returned by a coil spring S 4 . The rapid return and advance of the turret-slide and the indexing of the turret are controlled in- l8 SINGLE-SPINDLE DESIGNS dependency of the lead cam by a crank TF 4 which is connected eccentrically to the turret revolving shaft F 4 . This crank indexes the turret while the roll on the bell crank lever O 4 is passing from the highest point of the lead cam to the starting point of the lobe for the next cut. Crank W \ is driven from the rear driving shaft by a positive clutch, the latter being operated by tripping levers and dogs on drum /, Fig. i. Automatic Spindle Speed Changes. The speed changes for the spindle are made by shifting a belt on cone-pulleys forming part of the overhead works. For each change so obtained on the two larger machines, two spindle speeds are available, one of which is fast and one slow. The change is made automatically and is controlled by an adjustable trip dog. This automatic change of speed is of especial value in threading, one speed being employed for turning and a slower speed for cutting the thread. Operation of the Deflector. In order to separate the chips and oil from the finished parts which are cut off from the bar, a deflector is used. This deflector is located on the end of a lever that is actuated by a cam-block mounted on the drum K, Fig. i. Before the finished part is severed, this cam-block causes the deflector to move under the chute of the machine so that, when the work falls, it strikes the deflector and enters a suitable receptacle, instead of falling into the pan containing the chips. Reversal of Spindle for Threading. The reversal of the spindle for backing off a die or removing a tap from a hole is obtained by means of a clutch mechanism, located between the two belt pulleys A and B, which revolve in opposite direc- tions. The clutch bodies, which are conical, are forced into conical seats in the pulleys by a sliding collar located between the clutch bodies on the spindle. This collar is operated by a lever and cam beneath the spindle. On the No. oo machine, the spindle is reversed by means of a spring plunger F, Fig. 2, and on the Nos. o and 2 machines, by a cam A 2 . The spring plunger F, when released, instantly engages the cone of the clutch with pulley A, thus rotating the spindle backward. CLEVELAND AUTOMATIC 20 SINGLE- SPINDLE DESIGNS To run forward, the clutch is shifted by the cam A 2 , to engage pulley B, which revolves in the opposite direction. This cam A 2 is actuated by clutch B 2 which is operated by a lever that is controlled by a dog held on drum L on the front camshaft. Several sets of trip dogs can be used on the drum or carrier for reversing the spindle, when more than one thread is desired on a piece. The carrier for controlling the reverse movement may be disconnected by pulling out a knob, thus allowing it to remain idle when work is to be done which does not require threading. The Cleveland Automatic Machine. The automatic screw machines which were originally designed for making small screws and later for miscellaneous small parts have led to the development of automatic machines capable of turning an endless variety of comparatively large and heavy parts. One of the Cleveland automatic machines is shown in Figs. 5 and 6. This particular machine will operate on bar stock 3! inches in diameter, and similar . designs are built in various sizes, one of which has a chuck capacity of yf inches. In addition to the full automatic type shown in Figs. 5 and 6, which is known as " Model A," the Cleveland automatic is also built in several other types. The "full automatic" machine is provided with a turret having five holes, on sizes from f to 2\ inches, inclusive, and six holes on the machines of greater capacities. The next type of machine is the plain automatic, known as "Model B." This machine has no turret, but is provided with one tool spindle which can be used for holding a box-tool, drill, or similar tools. The range of this machine can be greatly increased by the addition of simple attachments on the cross-slides and tool spindle. The Model C machine is of the full automatic type and is halfway between Models A and B. It is provided with only three holes in the turret and resembles Model B in construction. The type of machine known as " Model D " is similar to Model A, but is built to handle castings, forgings, etc., and is semi- automatic in its operation. The double-spindle, plain auto- matic is a modification of the plain machine and is provided CLEVELAND AUTOMATIC 21 22 SINGLE-SPINDLE DESIGNS with two opposing work-spindles located in a parallel line and with the chuck mechanism of both heads acting simultane- ously. This machine is particularly adapted for finishing both ends of a piece of work, thus obviating the necessity of a second operation to complete the part. Spindle Driving Mechanism. The work-spindle A of the machine shown in Figs. 5 and 6 is driven from the overhead countershaft by means of two pulleys, B and C, which trans- mit motion to the spindle through gearing. Between the pul- leys B and C there is a loose or idler pulley. The outer pulleys B and C may both be rotated in one direction, thus giving two speeds, or one may be given a reverse movement for threading operations. The shifting of the driving belt from one pulley to another is effected by a belt shifter V. The shifting device is operated by means of cam fingers 7i (see Fig. 8) which are carried on the rear shaft E and are adjustable. As the shaft rotates, these fingers alternately come into contact* with spring- operated plungers which are depressed and serve to withdraw a wedge from a slot in a plate located below the shifting device. When the wedge is withdrawn from one slot in the plate, the shifter is thrown so that the wedge engages the next slot, thus shifting the belt or belts, as the case may be. There are different combinations of these shifter arms for various types of belt drives. Chuck-operating Mechanism. The chuck FI, Fig. 7, is of the push type and is held in the cap GI screwed onto the nose of the work-spindle. It is operated by a sleeve HI that receives motion from the arm D (see also Fig. 9). A detail of this arm is shown in Fig. 10, which illustrates its adjustable features. This arm is provided with adjustable cams m t n, and o. The cam m is the chuck-opening cam, n the safety cam, and o the chuck-closing cam which is cast integral with the arm D. Cams m and n are on one casting and are adjustable on the arm D, being held in the desired position by three clamp- ing screws fitting in elongated slots. There are also additional tapped holes in the arm allowing for further adjustment. When smooth stock is being held in the chuck, the adjust- CLEVELAND AUTOMATIC CLEVELAND AUTOMATIC able cams m and n are set tightly up against cam o, thus giving a quick closing and opening action to the chuck and allow- ing a short space of time for feeding the stock. When rough bar stock is being handled, and for magazine work, it is neces- sary to keep the chuck open much longer; for this action the cams m and n are sepa- rated from cam o in order to allow additional time. The action of closing the chuck is as follows: As arm D rotates, cam m comes in contact with roll Mi, Fig. 7, held on the fulcrumed yoke Ni. This yoke carries two rolls that work in a cir- cular groove cut in sleeve Oi. As the cam forces this sleeve away from the chuck, the sleeve acts upon two fingers PI which bear against the Fi S- 10 - Adjustable Cam for Con- trolling Operation of Chuck rear end of the chuck- closing sleeve HI. As cam 0, Fig. 10, comes into action, it reverses the operation of yoke Oi and removes the pressure from the sleeve Hi, allowing the chuck to open, due to spring tension. Stock-feeding Mechanism. The bar stock is fed through the spindle by a spring finger Ji (Fig. 7) screwed into the front end of the tube KI, the rear end of which is provided with a grooved collar LI. Fitting in this grooved collar is a forked lever G which is carried on the rod RI (Fig. 6). The movement of forked lever G is controlled by a cam H, which contacts with a roll held on bracket U\ clamped to rod RI. Adjust- ment for length of feed is controlled by shifting the position of the bracket U\ along rod RI, and the timing is effected by shifting the cam H around the shaft E. An open-wound 26 SINGLE-SPINDLE DESIGNS coil spring serves to keep the forked arm G and its sliding bracket up against a stationary bracket when the rod R\ is not acted upon by the cam. For double feeding, a drum is provided carrying two cams, allowing for feeding the stock twice for every revolution of the camshaft. Turret and Turret-slide. The turret is of the drum type and is carried on shaft A 2 (Fig. n) that is parallel with the work-spindle. The turret on the 3j-inch machine accommo- dates six tools which are held by two clamping bolts each, in the holes in the front end of the turret, and are located con- centrically with the axis of the work-spindle. The turret / is moved forward for cutting and backward for withdrawing the tools, by a cam-drum K which is free to rotate on shaft A 2 and carries segment cams B 2 fastened to its periphery. These cams work against a roller which is held on a stud driven into a hole in the base of the machine. As the cam-drum is rotated by means of gearing, the engagement of the inclined cam grooves or surfaces with the fixed roller cause the drum and turret to move in the direction of their axes, the turret moving in a straight line or without rotation, except when indexing. Cast integral with drum K is a spur gear D 2 which rotates it. Gear D 2 engages pinion E 2 , beneath it, which, in turn, is ro- tated at different speeds for the cutting and idle movements of the machine by a mechanism to be described later. The turret is indexed upon its back stroke by means of a rod H 2 held adjustably by locking nuts to a spur gear forming part of the feeding mechanism. This rod comes into contact with hardened pins held in the rear face of the turret. Before the turret can be turned around, however, it is necessary to disengage 'a locking wedge from a slot in the circumference of the turret. This is done by means of a cam-block held on the flange of drum K. The indexing can be effected by hand by simply depressing a lever, which has the same action on the locking wedge as the cam-block held upon the drum K. The turret head is mounted on the bed of the machine and can be adjusted to suit various lengths of work and tools held in the turret. The turret is held to the base of the machine by means CLEVELAND AUTOMATIC 28 SINGLE-SPINDLE DESIGNS of bolts. A scale fastened to the base of the machine and a pointer on the turret-slide enable the operator to obtain the same setting of the turret head when setting up the machine for a part which has been machined previously. Operation of the Cross-slide. On the Cleveland auto- matic screw machine, as regularly equipped, the cross-slide for holding both the rear and front cutting tools consists of one casting, but a double cross-slide can be supplied, when desired. The cross-slide is actuated by means of a fulcrum lever T (Fig. n), which derives motion from cams K 3 on the drum U carried on the rear shaft E. The flange of this drum is numbered so that the position of the various cams can be recorded on a lay-out card to facilitate re-setting the work. The cross-slide is provided with an adjustable stop-screw so that accurately formed work can be obtained. It is also provided with adjustable gibs to compensate for wear. The position of the cross-slide relative to the axis of the spindle is controlled by regulating nuts on the connecting-rod fastened to the rear of the slide. Variable Feeding Mechanism. As the cam-drum K (Fig. n) is rotated, the turret is moved towards the spindle for bringing the tools into contact with the work, and then backward for withdrawing the tools. This cam-drum is ro- tated through gearing at a predetermined rate of speed which is controlled by a series of adjustable cams that automatically vary the rate of the turret feeding movement according to the nature of the work. Motion for this variable feeding mecha- nism is derived from an overhead countershaft by a belt operat- ing on pulley N, which is keyed to an extension of the friction disk L. When a fast movement is required, in order to reduce the non-cutting or idle period to a minimum, a sliding clutch is engaged with pulley N, so that the drive is direct to the worm gearing at the rear of the turret, which transmits motion to the cam-drum K through a spur gear, pinion E 2 and the gear D% forming part of the cam-drum. This clutch is oper- ated by means of levers that engage dogs F 2 which are adjust- ably mounted on the rear face of the regulating drum 3 . CLEVELAND AUTOMATIC 29 When the turret is to be moved at its slow or cutting speed for feeding the tools forward, the clutch is shifted in the oppo- site direction by dogs Vz so that it engages teeth on the extended hub of a pinion which forms the central member of a planetary gear mechanism. The drive from belt pulley N to the worm gearing at the rear of the cam-drum is then through friction disks L and M and a planetary reduction gearing which transmits motion to the worm-shaft and is Fig. 12. Detailed View of Automatic Feed-regulating Mechanism located adjacent to the worm-wheel, as the illustration shows. This change from fast to slow speed, or vice versa, can also be controlled by a handle at the front of the machine. The Feed-regulating Drum. One of the interesting features of the Cleveland machine is the regulating drum which is used for securing independent feeds for each tool in the turret and on the cross-slide. This regulation is secured by means of a series of adjustable cams mounted upon the periphery of the regulating drum 3 , Fig. u. By changing the position of these cams, any desired feed may be secured 30 SINGLE-SPINDLE DESIGNS for each tool. As each cam comes into contact with lever Q, the position of the roll between friction disks L and M is changed with reference to the center of the disks, so that the speed is either increased or decreased. The bell crank lever Q (Fig. 12) has a segment gear at its outer end the teeth of which mesh with the sliding sleeve R on the rod F s . This rod is held in a bracket attached to the machine. As sleeve R is moved up and down by the action of lever Q, the position of the roll 2 between the two friction disks is changed, thus varying the speed. Variations in the position of the friction roll are transmitted to the pointer of the indicator dial Gs, so that the positions of the different regulating cams for any given job can readily be duplicated, provided their re- spective positions, as shown by the indicator dial, have been properly recorded. With this arrangement, a wide range of feeds for the turret and cross-slide tools is easily obtained and the feed may also be varied after the machine has been set up for a given job, provided a higher rate is considered essential to economical production. Gridley Single-spindle Automatic. The Gridley single- spindle automatic shown in Fig. 13 (built by the Windsor Machine Co.) is designed for handling straight bars of stock up to and including i\ inches in diameter, and it will feed lengths through the chuck up to 13! inches. These machines are also made, at the present time, in two larger sizes for han- dling bars of stock 3! and 4! inches in diameter, respectively. The spindle A, through which the bar of stock is inserted, is rotated from a parallel shaft at the rear to which it is geared. This rear driving shaft may either be belt-driven or motor- driven. The various end-working tools required are attached to slides B on the turret. Forming tools may be held on slide C and a cutting-off tool on arm D. The movements of these tools and other parts of the machine requiring automatic operation are controlled by cams mounted on the cam-drums E and F. The Turret. The turret of the machine shown in Fig. 13 does not move axially, but it is indexed or rotated part of GRIDLEY AUTOMATIC 3 1 32 SINGLE-SPINDLE DESIGNS a revolution after each successive operation has been per- formed, in order to locate the various tools attached to it in the working position. The tool-slides B are given the neces- sary feeding movement. The axis of the turret is parallel with that of the spindle, but it is lower than the spindle, so that the tools attached to the different slides of the turret will be in alignment with the spindle when indexed to the upper position. This turret revolves in bearings located in both ends of the main frame or headstock of the machine. The turret is revolved by a worm which has an intermittent movement and engages a worm-wheel located between the turret bearings. The machine can be so adjusted that the turret stops only at the tool positions required and skips any of the regular locations, if it is not necessary to use all of the tool-slides. The turret is rigidly held in its different positions by a locking pin which engages steel plates set in the periphery of a locking disk attached to the turret. Tool-slides on Turret. The slides which hold the end- working tools are gibbed to the square end of the turret cast- ing that extends beyond the frame of the machine. These slides are moved toward and away from the chuck by suit- able cams attached to the cam-drum E. The longitudinal movement is transmitted from the feed cam-drum to whatever tool-slide is in the working position, by means of draw-bar G (Fig. 14) which extends through the center of the turret and has a roll for engaging the cam on one end and is con- nected to a tool-slide at the other. When a tool-slide comes around to the working position, a pin P, attached to the slide, engages a notch in a collar attached to shaft G. When the turret indexes, this pin moves out of the notch and the pin on the next successive tool-slide enters the notch. The tool-slides are provided with T-slots throughout their length, so that the tool-holders can be secured to them at any point, or several tools may be attached to the same slide, if necessary, one being back of the other. Between the tool- slides or at the corners of the turret, accessories to the tools GRIDLEY AUTOMATIC 33 may be applied, such as drill-supports, stops for self-opening dies, taper guides, etc., or a stop for the stock when all of the tool-slides are required for tools. This method of mounting the tools on slides enables each tool to be given a rigid support. Operation of Forming and Cutting-off Tools. The forming slide C at the front of the machine, and the cutting-off tool held by the swinging arm D at the rear, are operated inde- pendently of each other. As the back-rests in the turners held on the turret are so located as to take the thrust of the Machinery Fig. 14. Sectional View showing Method of Supporting Turret and Operating Tool-slides forming tool, turning and forming operations can be performed at the same time, or the turner may be used as a support for the work when the forming tool is in action. Arrangement of Cams. The camshaft carries the feed cam-drum E and the operating cam-drum F. The cam H on drum , through the medium of draw-bar G extending through the machine, imparts a forward feeding movement to the tool- slides; cam / controls the return movement. Three feed cams are regularly furnished with the machine. The inclina- tion of these cams vary so that they give fine, medium, and coarse feeds; they may readily be located anywhere on the 34 SINGLE-SPINDLE DESIGNS CHICAGO AUTOMATIC 35 cam-drum, as they are held in position by two cap-screws. The camshaft has a rapid and a slow movement. The cams for operating the high-speed lever K which controls the rapid and slow movements of the camshaft are held in a circular T-slot in the left-hand edge of the operating cam-drum F. A set of cams L, for operating the belt shippers, is also at- tached to this cam-drum. The dogs for operating the turret- revolving mechanism at the proper time are held in a circular T-slot extending around the right-hand edge of cam-drum F. The cams for operating the forming slide C and the cutting-off arm D are attached to disk M. The forming-slide cam is lo- cated on one side of the disk and the cutting-off cam on the other side. These cams are held in place by screws, so that they can readily be changed. The cams for opening and clos- ing the spindle chuck are located at N, and the movement for feeding the stock through the spindle is derived from cam 0. Application of Motor Drive. When the Gridley automatic is motor-driven, two variable-speed motors are employed, each having its own controller, resistance, etc. One motor drives the spindle while the other drives the feeding mecha- nism, so that the cutting speed and the feed are independently controlled. The feed or speed may be varied automatically as the controllers for each motor are operated by cams on the operating cam-drum. The Chicago Automatic Screw Machine. The single- spindle automatic screw machine shown in Fig. 15 (built by the Chicago Automatic Machine Co.) is driven by a single belt from the lineshafting direct to tight and loose pulleys at M on the rear shaft of the machine. The lever R controls the position of the belt. The shaft on which the pulleys are mounted drives the main drive shaft N through two change- gears, which are enclosed in the case on the left-hand end of the machine. The work-spindle is driven from this main drive shaft through gearing having a ratio of 5 to 8, and these gears are never changed. The main drive shaft extends the entire length of the machine and through gearing, drives the mecha- nism for rotating and indexing the turret, operating the cam- 36 SINGLE-SPINDLE DESIGNS shaft, and, through a separate spindle and gear, the threading mechanism. Chuck Feeding Mechanism. The spindle of the machine is provided with the usual spring chuck and friction feeding finger. This mechanism is operated by cams on drum A. Segment B pulls the feeding tube back and, when the chuck is opened by the segment C, the spring D forces the stock for- ward against the stop. The chuck is then closed by the regular type of chuck-closing fingers. In setting-up the machine on a new job, considerable saving in stock can be effected by pull- ing lever E up. This removes roll F from the path of the seg- ment and prevents the chuck from opening and the stock from feeding. This enables the operator to set-up all the tools on one piece without spoiling a large number of parts before the required size and shape is obtained. Turret Mechanism. The turret J derives its indexing movement from the main drive shaft N through a train of gears and a friction clutch, which is operated at the proper time by circular segments or cams attached to the rear side of index plate P. These segments control the engagement of the friction clutch when the turret has been withdrawn and, in this way, the turret is rotated far enough to locate the next successive tool opposite the work-spindle. In many cases, tools are not needed in some of the holes in the turret and these empty holes can be skipped in indexing, by attaching long circular segments to the side of the index plate. If only two tools were used, there should be two long circular segments on the index plate, whereas, if three tools were used, there should be two short segments and one long one, and so on. After the turret is approximately located by the indexing mechanism, it is accurately aligned by a guide which engages the notches in the index plate P when the turret is advanced to the working position. When setting-up the machine, the turret can readily be indexed by means of lever H which serves to engage the clutch at the rear of the machine. The Camshaft. The camshaft is driven from shaft N through a train of gears at the right-hand end of the machine, CHICAGO AUTOMATIC 37 these gears being changed in accordance with the speed re- quired as determined by the number of spindle revolutions necessary to complete a series of operations. There are fifty divisions around the circumference of the cam, marked by rows of tapped holes one inch apart, so that the circumference of the cam is 50 inches. In order to illustrate how the lengths of the cams for the different tools are determined, assume that a piece requires a milling operation for a length of one inch. With a feed of 0.005 inch, this will require about 200 revolu- tions (i -r- 0.005 = 200) and, in the same way, the number of spindle revolutions for the other operations is obtained. If the total number for a complete series of operations were, say, 1040, this number divided by 50 (number of divisions on the cam) equals approximately 21, which represents the num- ber of spindle revolutions for every inch on the cam circum- ference. By dividing the number of spindle revolutions for the milling operation, or 200 by 21, the result equals the length of the segment on the cam for this particular operation; thus 200 -T- 21 = 9! inches, approximately. As the cut is to be one inch long, the segment should have a lead or rise of about lyV inch. The lengths of other segments for different operations can be determined in the same way. The return segments for the turret are always the same, although their position may have to be changed for different operations. The Cross-slides. The cross-slides of the machine shown in Fig. 15 are operated independently by plates or cams at- tached to drum K. These cams impart motion to the cross- slides through fulcrumed levers which are connected at their lower ends by means of a spring L that keeps the rolls in con- tact with the cams. These cams for controlling the movements of the forming and cutting-off tools do not require much adjustment, although sometimes a longer or shorter cam is required. The cross-slides are provided with adjusting screws for setting the tools in the correct position relative to the work. Method of Cutting Threads. For threading operations, a central spindle is used, which is driven directly by gearing. 38 SINGLE-SPINDLE DESIGNS On the i^-inch machine, this gearing is so arranged that, for every 100 revolutions of the spindle, the tap or die will make 128 revolutions, so that 28 threads will be cut irrespective of the pitch of the thread for every 100 revolutions of the spindle. If the spindle makes 50 revolutions, 14 threads will be cut, or 7 threads for every 25 revolutions of the spindle. As the spindle always runs backwards, and since the threading die runs faster than the spindle, it is evident that the variation in speed is utilized for cutting the thread. Whenever a thread has been cut to the required length and the turret starts to withdraw the die, the driving pins of the die-holder are dis- engaged and then the die-holder is held stationary by the engagement of a clutch, thus backing the die off of the thread. Feeding Movements for Tools. The feeds recommended for ordinary work on this machine are as follows: When turning machine steel with box-tools, the feed may vary from 0.004 to o.oio inch for roughing, and, for finishing, from 0.002 to 0.006 inch per revolution of the work. For drills less than | inch in diameter, the feeds may vary from 0.002 to 0.006 inch, and, for drills over f inch in diameter, from 0.006 to 0.015 inch per revolution. For forming tools, the feeds may vary from 0.00025 to 0.004 inch, the amount depending upon the width of the forming tool and the diameter of the stock being formed. Cut ting-off tools may be given a feed of from 0.002 to 0.004 inch per revolution. When operating on brass stock, the feeds previously given may be doubled. CHAPTER III MULTIPLE-SPINDLE AUTOMATIC SCREW MACHINES THE multiple-spindle screw machine represents a develop- ment of the single-spindle type and was designed primarily to increase production, by grouping several work-spindles together so that separate bars of stock one in each spindle - could be operated upon simultaneously. With this ar- rangement, when there are several end-working tools, such as a box-tool, a drill, a reamer, and a threading die, all of these tools operate on different bars of stock as the turret moves forward, instead of indexing first one tool and then another to the working position, as is necessary when all the operations are performed successively upon the end of a single bar of stock. The advantage of the multiple-operation method, as previ- ously explained, is that the time required for producing a part is equivalent to the longest single machining operation plus the non-cutting period necessary for advancing the tools to the work, withdrawing them, and indexing the spindle carrier, whereas, with a single-spindle machine, the production time equals the total time for all of the operations plus the idle or non-cutting period. Acme Automatic Screw Machine. The National- Acme automatic multiple-spindle screw machine shown in Fig. i illustrates the general principle governing the construction and operation of screw machines of this class. The machine has four parallel work-spindles A t which are equally spaced and equidistant from the axis of the cylindrical head in which the spindles are mounted. Each spindle contains a bar of stock when the machine is in operation, and the bar, as it rotates with the spindle, is operated upon by tools held in an opposing tool-slide B and also upon cross- or side-working tool-slides C. A tool from the side and one from the end may 39 MULTIPLE-SPINDLE DESIGNS NATIONAL- ACME SCREW MACHINE 41 work together on each bar, and all of the tools engage the stock at practically the same time. When the tools are all withdrawn, the cylinder contain- ing the work-spindle is indexed or revolved far enough to locate each spindle opposite the next successive set of tools which perform additional operations. When each bar reaches the last tool or set of tools in the series, the completed part is severed from the bar, which is then automatically moved out- ward through the spindle far enough for turning another piece. With this arrangement, a part is finished each time the spindle head indexes one-quarter of a revolution. Order of Operations. With the machine illustrated in Fig. i, there are eight standard tool positions, four being from the side and four from the end, thus allowing eight inde- pendent tools to be used, if necessary. The stop which engages the feeding movement of the stock does not occupy a tool position. Assuming that eight operations were required, the sequence or order in which the various tools are presented to the work would be about as follows : After the preceding piece is cut off in the fourth position, a new length of stock is fed forward, the feeding movement occurring during the indexing from the fourth to the first position, or with the larger type of machine in the fourth position, as the indexing is being completed. The cams next bring forward one tool from the side (usually a forming tool) and also a tool from the end, which may be a box-tool, drill, or tool for facing, countersinking, etc. The bar is then in- dexed to the second position, where it may be operated upon by a shaving tool in the front top slide, or tools for light form- ing, knurling, or thread rolling; at the same time, tools in the main slide may be used for milling, drilling, reaming, countersinking, facing, etc. The bar is next indexed to the third position, or opposite the rear top slide, which may carry a knurling tool, a thread-rolling tool, or one for a forming or shaving operation. The end tool may drill, ream, counter- bore, tap a hole, or cut an external thread. In addition, at- tachments are frequently used in this third position for milling Fig. 2. Spindle-driving and Stock-feeding Mechanism Fig. 3. Main Tool-slide and End-working Tool-holding Spindles NATIONAL-ACME SCREW MACHINE 43 from the end, and for drilling from the side or milling from the side, etc. The use of these attachments is made possible be- cause the work-spindle can be stopped in this position. In the fourth position, opposite the rear horizontal slide, the end tools may countersink, counterbore, drill, etc., whereas the cross-slide may be used for finish-forming, after which the finished part is severed from the bar. The operations previously referred to merely indicate, in a general way, how the tool equipment may be used. The order of the operations and the tools used depend upon the conditions governing each case. For instance, knurling can be done in the first and fourth positions from the side, if neces- sary, or from any of the end positions. Threading can some- times be done in the second position. Moreover, threads can be rolled in the fourth position, if necessary, the order being varied according to the requirements of the work. Spindle-driving Mechanism. The four work-spindles of the machine shown in Fig. i are driven by gears meshing with a central gear on the driving shaft D which derives its motion from the belt pulley E and extends through the main tool-slide and spindle head to the central driving gear. These spindle gears are not attached directly to the spindles but are driven through friction clutches which permit each spindle to be stopped at the third position in case a threading opera- tion is necessary. The exact arrangement of the spindle- driving mechanism is shown more clearly in the detail view, Fig. 2. In this illustration, the shaft HI corresponds to the main driving shaft D in Fig. i. The spur gears /i, which are driven from the central shaft, are free to rotate on bronze bushings and are provided with taper projections or shoulders which form the internal member of a friction driving clutch. The other member of this driving clutch consists of a tapering cup KI, which is keyed to a sleeve that is keyed to the spindle. The cup is held into engagement with the friction gear I\ by coil springs L 3 . The way in which these friction clutches are utilized in connection with threading operations will be described later. 44 MULTIPLE-SPINDLE DESIGNS The Camshaft. There is only one camshaft on the machine illustrated in Fig. i, and this is under the bed and carries all of the operating cams for controlling the move- ments of the various slides, and also a segment gear for indexing the spindle head. This shaft carries the two main Machinery Fig. 4. End View of Machine showing Speed-changing Mechanism for Camshaft cam-drums F and G. Attached to drum F are the cams for operating the stock-feeding, chuck-closing, and opening mecha- nisms, and also the dogs for operating the friction clutches which engage or disengage the work-spindles from their driving gears. On drum G are cams for operating the main tool-slide, and, on some machines, a thread-starting mechanism. This camshaft makes four complete revolutions to one revolution of NATIONAL-ACME SCREW MACHINE 45 the spindle head, and a complete range of speeds is provided by means of change-gears. Camshaft Speed-changing Mechanism. The upper or main driving shaft D, Fig. i, which drives the four work- spindles of the machine, transmits motion to the camshaft beneath the bed through the mechanism illustrated in Fig. 4, which enables the camshaft to be rotated at a suitable speed. The pulley U$ (which corresponds to pulley E, Fig. i) is driven from a constant-speed countershaft. This pulley normally runs free on the driving shaft, but can be secured to it for driving direct when necessary. Attached to the inner hub of this belt pulley, there is a bevel gear V 5) which meshes with another bevel gear on the shaft W^ which transmits motion to the horizontal shaft 5 through additional bevel gearing. (On some of these machines, spiral gears are used instead of bevel gears.) From this point, motion is transmitted to the camshaft by means of change gearing, which is selected in accordance with the speed required. The sleeve A 6 of this clutch is keyed to the horizontal shaft 5, and sleeve B& passes through the bearing in the frame and forms a part of a sprocket and clutch at C&. The shaft F 5 is also continued through the frame and has a washer E$ keyed to its outer end. , The first gear of the four change-gears is keyed to this washer and meshes with a larger gear on the stud. The mo- tion is then transmitted through two other gears to a clutch of which the sprocket C 6 forms a part. Motion is further transmitted to the camshaft, when the tools are at work, by means of a chain which drives another sprocket that is connected to a worm-shaft. This worm-shaft, in turn, drives a worm-wheel which is mounted upon the right-hand end of the camshaft of the machine as shown in Fig. i. The sprocket on the worm-shaft may be disengaged from the shaft by means of a clutch controlled by a hand lever. The sprocket is pro- vided with a safety device in the form of two fiber collars which are kept into frictional contact by a nut. This nut is tightened sufficiently to drive the worm-shaft when the ma- 4 6 MULTIPLE-SPINDLE DESIGNS chine is operating under normal conditions, but, in case of unusual strain, slippage occurs, thus relieving the gearing and other parts of the machine. For the idle movements of the machine or those movements which occur when the tools are not in operation, as when feed- ing the stock, indexing the cylinder, and moving the tools to and from the work, the camshaft is driven at the "direct SHAFT Machinery Fig. 5. Gears used in Obtaining Changes of Spindle Speed speed" which is much faster than the regular cutting speed, in order to reduce the idle period to a minimum. This direct drive is obtained by shifting the sleeve A & to the left, so that motion is transmitted to the sprocket C 6 direct from shaft Y 5) instead of through the combination of change gearing. The change of speed from the direct to the cutting speed, and vice versa, is controlled automatically by dogs on a cam-drum located at the right-hand end of the camshaft. This cam NATIONAL-ACME SCREW MACHINE 47 transmits motion through suitable shafts and levers to the sliding member A 6 of the friction clutch. The method of determining the change-gears to use in any case is explained in Chapter V, which deals with the adjustment and setting-up of screw machines. Speed of Main Driving Shaft. The speed of the main driving shaft from which all other members of the machine are driven can be varied by means of the gearing shown in Fig. 5. The direct speed is obtained by first sliding the gears A and B out of contact with gear C on the shaft, and the gear D which is attached to the hub of the belt pulley U$, or by removing the gears A and B entirely. Then a sleeve that is keyed on the end of the main driving shaft is fastened to the belt pulley by screws. In order to change from the direct drive to the drive through the back-gears, the screws binding the sleeve to the pulley are removed and motion is transmitted through gears A, B, C, and Z>, which are selected in accordance with the speed required and as shown by a table accompanying the machine. Main Tool-slide. The main tool-slide B (Fig. i) carries the end-working tools and also the driving mechanism for the threading spindle, as well as the cams which control the move- ments of the two top slides C. The main slide is actuated by cams directly beneath it which engage a roll attached to the under side. These cams are set so as to bring the tools up to the work quickly, feed them while cutting, at a comparatively slow speed, and then withdraw the tools at a higher rate of speed. As the roll travels over these " fast-angle" cams, the speed of the camshaft is increased considerably, and then reduced to the cutting speed as soon as the tools are in the working position. A detail view of the main tool-slide is shown in Fig. 3, where it is represented by the reference letter M%. There are four tool spindles to correspond to the four work-spindles of the machine. The spindle Nz is in what is known as the "first" position; 2 , in the "second" position; P 2 , in the "third"; and Q 2 , in the " fourth" position. The tool spindles 48 MULTIPLE-SPINDLE DESIGNS N 2 and Q 2 are held stationary in the main tool-slide, whereas the spindles 2 and P 2 may be revolved. The spindle P 2 is the one used for threading operations, as will be described later. The spindle O 2 is rotated when it is necessary to drill a small hole in a comparatively large piece of work. Without this feature the speed of the work-spindle would have to be Fig. 6. Main Tool-slide removed, showing Arrangement of the Cross-slides on the "Acme" Multiple-spindle Automatic Screw Machine increased considerably in order to drill a small hole efficiently. This tool-spindle is also used for holding a threading tool, if necessary. Operation of the Cross-slides. The lower horizontal cross- slides shown at 5 and F& in the detailed view, Fig. 6, carry the forming and cutting-off tools and are moved toward and away from the work by levers, the lower ends of which are engaged by cams on the disk K, Fig. i. These two slides are NATIONAL-ACME SCREW MACHINE 49 mounted on auxiliary slides G$ and # 5 , which are adjustable along the bed of the machine, which adjustment permits chang- ing the positions of the forming and cutting-off tools relative to the work, without adjusting the tools in the tool-holders. The upper ends of the levers which operate these slides engage slots on the under sides of the slides, and the lower ends are provided with rollers which come into contact with the cam- shoes. On some of the Acme machines, these operating levers are drilled in two separate places for the pins upon which they swing. This feature makes it possible to form deeper and cut off larger diameters of stock, when the levers are pivoted in the lower holes, without using cams of greater throw. The forming slide E 5 is provided with a stop and an adjustable stop-screw, to check it at the end of the cam movement so that duplicate parts may be turned to the same diameter. The upper cross-slides P 5 and () 5 for operating in the second and third positions, respectively, are similar in construction to the lower slides, but are operated by strip cams which are attached to and receive their motion from the main tool- slide, as shown in Fig. 3. The angles of these strip cams are governed by the rate of feed desired and the lead of the cam operating the main tool-slide. The slide P& in Fig. 6 is equipped with a shaving tool, whereas the slide Q b has a knurling tool. Indexing Mechanism. The head in which the four spin- dles is mounted is indexed a quarter turn between the suc- cessive machining operations, by means of a segment gear H, Fig. i, which engages teeth at the rear end of the spindle head. This segment or fan gear, which is shown more clearly at J in Fig. 7, is mounted on the main camshaft M of the machine, which, as previously mentioned, makes four revolutions to one complete turn of the cylinder. Provision for accurate alignment of the spindles with the tools in the tool-slide is made by means of two plungers O and K. The plunger drops into position first and is brought into contact with the aligning screw N; then the other plunger K is forced in against a hardened steel taper plug. The bolt K is withdrawn by an arm P fulcrumed at O and operated by a dog R on the cam- MULTIPLE-SPINDLE DESIGNS shaft. This dog should engage fully with the end of the arm before the first tooth of the segment gear J comes into contact with the cylinder. In operation, as the bolt K is withdrawn, the first tooth in the segment gear J comes into contact with the cylinder, thus rotating it and, at the same time, forcing back the bolt O. Then, as the cylinder revolves around to the Machinery Fig. 7. View showing how the Cylinder is indexed and locked in Position next position, the bolt is forced into the cavity in front of the aligning screw N by a coil spring. As the arm drops off of the dog T, the bolt K is forced home by the coil spring V, thus drawing the cylinder back and seating the aligning screw ^V firmly on the flat part of the bolt 0. Operation of the Spindle Chuck. The opening and closing of each spindle chuck at the point where the stock must be NATIONAL-ACME SCREW MACHINE 51 moved forward is controlled by a cam Vi, on drum W\, Fig. 2, which actuates lever Ui connecting with whatever sleeve on the spindle is in the stock-feeding position. (The drum Wi and lever U\ correspond with drum F and lever I, Fig. i.) The spring chucks are of the push type and are forced forward for tightening, whenever a tapered collar TI is pushed back- ward by the lever U\. The tapered collars T\ actuate the steel sleeves Oi by means of the levers PI which are forced outward in the usual manner. In order to tighten the spring chucks on the bars of stock, hollow set-screws in the collar S\ should first be unscrewed and then the collars are turned to the right, which changes the fulcrum point of the chuck operat- ing levers. Feeding the Stock through the Spindle. The lever for operating the stock-feeding tube also derives its motion from a cam on the drum Wi t Fig. 2. This lever D 2 is pivoted at its lower end and connects with a cam on the drum by means of lever E 2 and rod F 2 . The length of the feeding movement is controlled by adjusting the stop G 2 on the rod F 2 , thus vary- ing the distance that the rod F 2 travels through lever D 2 before moving it. The stock is fed against a stop or gage, and, on the smaller machines, the feeding is done during the index- ing, the stop being located between the fourth and first tool positions. On the larger machines, a cam control brings the stop into the first position and withdraws it after the stock is fed against it and before the tools feed up to the work. The feed-tube B 2 is first withdrawn by lever D 2 , causing the feed finger A 2 to slide over the bar which is held tightly in a spring chuck NI. Cam lever U\ next releases the chuck, and feed- tube B 2 is pushed forward. As the forward movement begins, the feed finger A 2 grips the stock and forces the latter through the open chuck until it comes into contact with the gage or stop H 2 . Just before lever B 2 has reached the forward end of its stroke, and after the bar of stock has come into contact with the stop, the cam lever U\ closes the chuck, so that the bar of stock is securely held in its position preparatory to being operated upon by the cutting tool. The holder for stop H 2 52 MULTIPLE-SPINDLE DESIGNS can be adjusted along the hexagonal rod J 2 and the stop is moved into or out of alignment with the spindle by a cam L 2 which engages the dog or lever K 2 . Mechanism for Threading. When cutting a right-hand thread, the work-spindle is stopped in the third position opposite the threading spindle, which is revolved at the proper speed for the size and pitch of the thread and the metal being cut. When the thread is finished, the threading spindle is Fig. 8. Gears arranged to Drive the Right-hand Threading Mechanism at its Slowest Speed stopped and the work-spindle is again rotated, allowing the threaded piece to run the tool off freely. The die or tap is not forced onto the work, but is advanced by the pitch of the thread. The threading speed is entirely independent of the spindle speed for the other cutting operations. When starting to cut a thread, the die is given a positive start by means of a cam-controlled lever. Change of speed for the die spindle is obtained by sliding the driving gear into mesh with the direct driving gear on the spindle for the high speed, and into mesh with a compound driving gear for a slower speed. The work spindles are stopped one at a time as the cylinder indexes NATIONAL-ACME SCREW MACHINE 53 them to the third position, by the action of a cam on drum W\, Fig. 2, which disconnects the friction clutch KI that nor- mally engages the spindle-driving gear I t . When the friction clutch is disengaged, the driving gear runs freely while the spindle is locked stationary for the threading operation. The length of time that the work-spindle must be held stationary Fig. 9. View of the Main Tool-head, showing the Right-hand Threading Mechanism in the third position is determined by the duration of the threading or other special operation to be formed. Rotation of the Threading Spindle. The threading spindle is rotated from the main driving shaft HI, through the ar- rangement of gearing shown in Fig. 8. A slow and a fast speed may be obtained for each feed of the work-spindle, the slow- speed gearing being shown in place in Fig. 8. When a shoe at RS, Fig. 9, is in the groove S 3 (see Fig. 8) of the sliding gear, 54 MULTIPLE-SPINDLE DESIGNS the drive is transmitted through gears T 3 , / 3 , and F 3 to the gear W s on the threading spindle, rotating the latter at its slowest speed. When the shoe R$ is engaged with groove A 4 of the sliding gear, the drive is direct from this gear to gear W^ thus rotating the spindle at its fastest speed, which is used for threading brass or cutting very fine threads on soft steel. When it is desired to prevent the threading spindle from rotating, the shoe jR 3 is drawn up and gear C 3 slid out of en- gagement with the other gears. The threading spindle P 2 (Fig. 9) is driven by a block C 4 that engages an adjustable pin jE 4 . This pin may be adjusted out when the forward travel of the threading tool must be faster than the speed at which the main tool-slide is traveling. Mechanism for Starting Threading Die. When cutting a thread, the die or tap is not forced onto the work, but is advanced by the thread after being given a positive start by a cam-controlled mechanism so that a poor first thread will be avoided. Just as the threading operation begins, the cam- operated lever Nt, Fig. 9, causes the roller 7 4 to engage the swinging lever H, which, through the plunger G 4 , pushes the threading spindle forward. In this way, the threading tool is given a positive start; then the threading tool " leads" onto the work as far as the thread is to be cut. The main tool- slide then recedes, but the threading spindle P 2 is prevented from moving backward by the grip of the threading die or tap, so that the coil spring P 4 is compressed. As the tool- slide moves backward, the pawl () 4 engages ratchet R on the rear end of the threading spindle, thus preventing the latter from rotating, so that, as the work-spindle rotates, the thread- die is backed off of the work. The spring P 4 , which was com- pressed by the backward movement of the tool-slide, then returns the threading spindle to its normal position. Cutting a Left-hand Thread. When cutting a left-hand thread on the Acme machine, slight alterations are necessary on the threading spindle, and both spindles revolve, the die spindle rotating slowly and the stock spindle at the regular speed. As the work-spindle is rotated faster than the thread- DAVENPORT FIVE-SPINDLE MACHINE 55 ing spindle, there is a relative motion between the two spindles, the work-spindle gaining on the threading tool so that a thread can be cut. For backing off a die, the stock is stopped and the threading spindle continues to run, which removes the tool from the work. Use of Opening Dies. Long outside threads or those that are extremely coarse or fine can be cut to particular advan- tage by using an automatic or self-opening die-head. On the Acme machine, the die-head is revolved while cutting and is opened automatically and closed by cam movements while rotating. The mechanism for timing the automatic opening of the die and closing it, for the threading operation, is attached to the main tool-slide on the cut-off side of the machine. The die-head operates in the regular threading position. Davenport Automatic Screw Machine. The multiple- spindle automatic screw machine shown in Fig. 10 is built by the Davenport Machine Tool Co., New Bedford, Mass. This machine has five work-holding spindles and is so designed that each tool is controlled independently by a separate cam, and the travel of each tool may be varied without changing the cam which operates it. The five spindles are mounted in the spindle head A (Fig. n) and the five tool spindles are sup- ported by the frame B. In addition to the five tool spindles for holding end-working tools, there are two horizontal cross- slides K and L (Fig. 12) and two swinging arms M and N for operating forming and cutting-off tools. The mechanism for driving the work-spindle and actuating the tool spindles, and cross-slides at different rates of speed, as well as other impor- tant features of the machine, will be described. Method of Driving Spindles. The five work-spindles are driven from a belt pulley J (Fig. 13) at the rear of the machine, which transmits motion to them through change-gears selected in accordance with the speed required. These change-gears drive a large gear C, Fig. n, which has internal gear teeth that mesh with the smaller gears D mounted on the various spindles. This outer internal gear has a bearing on the hubs of the spindle gears at the pitch diameter, giving a free-running MULTIPLE-SPINDLE DESIGNS Fig. 10. Davenport Five-spindle Automatic Screw Machine rolling bearing. The change-gears provide for eight spindle speeds ranging from 600 to 1500 revolutions per minute. Operation of Tool Spindles. The end-working tools are mounted in sliding spindles, each of which is operated by a separate cam. These cams are mounted on the shaft E (Fig. 1 1), and actuate the levers F, there being one lever for each spindle. The connecting-rods G extending from each spindle to its operating lever are attached to adjustable blocks H on the DAVENPORT FIVE- SPINDLE MACHINE 57 ^^-^ 58 MULTIPLE-SPINDLE DESIGNS levers, and, by changing the position of these blocks, each tool is made to advance the same amount as the throw of the cam which operates it, or a less amount, down to one-half the throw of the cam. The face of each lever is graduated to indicate the movement of the tool relative to the cam throw. For instance, a cam for turning a maximum length of 2 inches has a rise or throw of 2 inches, but it is equally effective for turning a length of i inch, the reduction being obtained by simply setting the block on the cam lever to the 0.5 division. When the block is set at graduation i.o, the tool moves a dis- tance equal to the cam throw. The tool spindles may be ad- justed lengthwise for varying the operating position of each tool by a turnbuckle connection between the cam lever and the spindle. The curved surface on the lever provides that the tool in its forward position will be the same distance from the spindle regardless of where the block H is clamped to the lever. There are seventeen cams furnished with the machine and these cover the work ordinarily done on it. For large quantities of certain kinds of work, it is well to use special cams. Cross-slides and Swinging Arms. Each horizontal cross- slide and swinging arm is operated by a separate cam, two of which are mounted on the front camshaft O and two more on the rear camshaft P. Motion is transmitted to the arms M, N, and slides K, L, through levers and connecting links which have the same adjustment as the levers that actuate the end- working tools. These arms and slides provide for one cutting- off tool and three forming tools, where they are required, or more than one tool can be used for cutting off, the arrange- ment depending upon the nature of the work. Circular form- ing and cutting-off tools are generally used and are shown in position opposite four of the spindles. Each toolpost has a stop-screw for regulating the size of the work formed, the same as on a single-spindle machine, and, in addition, an adjusting screw or compensating stop, which will be described later. Driving Mechanism for Camshaft. The front and rear camshafts for the cross-slides and swinging arms, and the cam- DAVENPORT FIVE-SPINDLE MACHINE 59 shaft at the end of the machine for actuating the tool spindles, are all driven from a feed-shaft Q (Fig. 13) extending along the rear of the machine. This feed-shaft, in turn, is rotated from the main driving shaft through a friction clutch R that is con- trolled by a hand lever at the left-hand side of the machine in front. The friction clutch is held into engagement by a spring to allow it to slip in case of accident. The rear feed- shaft Q drives the shaft 5 (Fig. n) which extends across the Machinery Fig. 12. Cross-slides and Swinging Arms of Davenport Machine machine. This shaft has right and left-hand worms which mesh with worm-wheels T mounted on the front and. rear cross-slide camshafts. Bevel gears at the sides of these worm-wheels mesh with corresponding bevel gears on cam- shaft , and thus rotate the camshaft which imparts movement to the end-working tool spindles. The speed at which the three camshafts revolve is controlled by change-gears at U (Fig. 13) which enable the time in seconds that is required to make one piece to be varied from 3 to 20 seconds, increas- 6o MULTIPLE-SPINDLE DESIGNS ing by \ second up to 7 seconds, and then by i -second incre- ments up to 20 seconds, which is the maximum time allowed. Indexing the Spindle Head. The head containing the five spindles is indexed by a rod which carries two pawls and is operated at the right moment by a crank disk mounted on the indexing shaft that extends along the front of the machine. This indexing shaft derives its movement from the handwheel shaft (see Fig. 10) which is driven continuously when the feed driving clutch of the machine is engaged. An indexing clutch is disengaged except when the work-spindle head is to be indexed. When the cam for starting the index comes into con- tact with this clutch at each revolution of the shaft, the clutch is engaged and the shaft for indexing the head is rotated one complete revolution. The feed cams for feeding the tools are stationary during the indexing of the spindle head. Spindle Head Locking Mechanism. The spindle head is locked in position by a lever which has a notched shoe that successively engages locking blocks on the spindle head, as these are indexed in position. The locking lever is pulled out of engagement and also pushed back by a positive action. In addition to the locking lever, the spindle head is also clamped by a rod which is drawn downward by the action of a cam surface and serves to tighten the front bearing cap, thus holding the head rigidly while the tools are in operation. Stock Stop. The stock is fed through the spindles against a stop which is made of a part of the first turning or other end- working tool. The length that the cams feed the stock is controlled by a nut on the left-hand end of the shaft, and the stock stop is adjusted by a screw near the lower front sliding spindle. The bars of stock rotate inside of a wooden tube, instead of in gas pipes, so as to avoid excessive noise and marring the surface of the material. Compensating Stops. In order to insure that the tools on the swinging arms and cross-slides will be located accu- rately, with reference to the different spindles, the Davenport multiple-spindle machine is equipped with what are known as compensating stops. These stops consist of a series of pins V DAVENPORT FIVE-SPINDLE MACHINE 6l 62 MULTIPLE-SPINDLE DESIGNS (Fig. 12) which project from the periphery of a disk which is secured to the front end of the spindle head. There are four separate stops for each spindle; two are for the front cross- slide and swinging arm and there are two additional stops for the back cross-slide and rear arm, which are utilized when the spindle has been indexed around to the rear position. These pins or stops are engaged by additional stops upon the swing- ing arms and tool-slides and the adjustment of each stop is such that the cutting edges of the tools are accurately located relative to the axis of each spindle when the stops are in en- gagement. In this way, each tool is positively located, and any slight inaccuracy, due either to constructional defects or wear in the machine, is automatically compensated for, after the stops have been adjusted. Method of Cutting Threads. When cutting threads on the machine illustrated in Fig. 10, the work-spindles are not stopped or reversed. The spindle carrying the die or tap is revolved in the same direction as the work-spindle, but at a slower speed when running the die on, and at a faster speed for backing it off of the finished thread. The speed of a die or tap when cutting is about three-fourths of the spindle speed, so that the actual threading speed is one-fourth of the spindle speed in revolutions per minute, and, as the diameters that are threaded are usually quite small, the actual surface speed for cutting the threads is low enough to insure smooth threads and durability for the dies. When backing off a threading die or removing a tap from a hole, the threading spindle re- volves rapidly. The mechanism for driving the threading spindle is shown in Fig. 13. The long "threading shaft" W is driven from the belt pulley shaft at the rear, through change-gears, as shown. This long shaft carries the male part of two friction clutches which engage either of two friction clutch gears of different diameters. These clutch gears, in turn, transmit motion to the threading spindle at the different speeds required for running a die on or for backing it off of the work. Thus, when cutting a thread, the slow-speed gear is engaged; the clutch DAVENPORT FIVE-SPINDLE MACHINE 63 is shifted to engage the high-speed gear when the thread has been cut to the required length, by means of a cam which actuates the clutch through the lever X. In the illustration, the threading clutch is shown engaged for running a die off of right-hand threads. Work for which Camshaft Rotates Continuously. For ordinary operations, the camshafts for feeding the tools are stopped when the spindle head is indexed, as previously men- tioned. For some classes of work, however, it is preferable to arrange the machine so that the camshafts rotate continu- ously. For instance, many pieces can be made from brass rods, in 2, 23, or 3 seconds, and, for these rapid jobs, the ma- chine is equipped with special cams which do not stop revolv- ing when the head is indexed, thus saving a fraction of a second on each piece of work. In order to operate the machine in this way, the roll on the lever operated by cam F, Fig. n, is removed and attached to the outside of the lever for safe keeping. When this change is made, the feed clutches on the handwheel shaft are not disconnected during the indexing of the head; the cams for feeding the tools then revolve con- stantly and are so shaped that the tools remain in their back positions during the indexing of the head. The tools arrive at their working position before the crankshaft which indexes the head has entirely completed its revolution, thus effecting a saving in time. Speeds and Feeds Recommended. The following feeds and speeds are recommended for the Davenport multiple- spindle automatic: For brass work, the spindles should usually revolve at the fastest speed, which is 1500 revolutions per minute. When using high-speed steel tools and turning soft iron wire, the surface speed of the work should vary from about 90 to no feet per minute; for soft machine steel, from 80 to 100 feet per minute; for tool steel, from 20 to 30 feet per min- ute. Especially heavy cuts will require slower speeds than those listed. For turning ordinary screw stock, the surface speed is usually 100 feet per minute. These speeds are ordi- narily used in conjunction with fine feeds varying from 0.004 6 4 MULTIPLE-SPINDLE DESIGNS to o.oio inch for turning; from 0.0005 to 0.0015 mcn for forming and cutting off. Hayden Automatic Screw Machine. The five-spindle automatic screw machine shown in Fig. 14 (built by the Cin- cinnati Automatic Machine Co.) has incorporated in its de- sign several distinctive features. The five spindles, which Fig. 14. Hayden Five-spindle Automatic Screw Machine revolve in a forward direction, thus permitting the use of right-hand tools, such as drills, etc., are driven either from a constant-speed motor, or by a single belt pulley A, at the rear, which transmits motion to the spindles through a geared speed-changing mechanism, at B (Fig. 15) of the tumbler- gear design. The end-working tools, such as box-tools, drills, reamers, etc., are held in spindles which are operated inde- HAYDEN FIVE-SPINDLE MACHINE 66 MULTIPLE-SPINDLE DESIGNS pendently by cams that are a permanent part of the machine and are adjustable for varying the feed of each tool in accord- ance with its work. Four cross-slides are provided for holding either circular tools, rectangular forming tools, knurling tools, thread rolls, a cross-drilling attachment, or combinations tools. The cams for operating all the cross-slide and end- work- ing tools are held on slides and are actuated by a master cam which imparts to each slide a reciprocating motion. Spindle Chuck. The chucks or collets of the machine shown in Fig. 14 are of the draw-back type, but they are held in a stationary position endwise while the closing member is pushed forward over the chuck for tightening it upon the stock. When a chuck of the "push-out" type is closed, it grips the stock while moving forward, because the tightening of the chuck depends upon this forward motion. By designing the chuck-closing mechanism so that the outer chuck-closing member is pushed forward instead of the chuck, it is claimed that excessive strains on the mechanism, resulting from the movement of the stock after it is partially gripped by the chuck, are eliminated. The chucks are opened and closed and the stock fed forward by cams on the master cam-drum C at the end of the machine. Adjustment for feeding the stock to different lengths is made by a screw in the master drum. By the shifting of a lever, the machine can be made to run in the usual manner without feeding any stock or operating the chucks, which is convenient when setting up the machine or when testing the size turned by any tool after the cutters have been sharpened, etc. Operation of the Master Cam. The master cam-drum C, which imparts motion to the cross-slide and the tool spindles, has two speeds. This master cam-drum revolves at a uni- formly fast speed, for three-quarters or its circumference, this movement requiring one and one-half second. The re- maining one-fourth of the master cam-drum circumference is utilized in operating the cutting tools, and the speed of rota- tion is reduced in accordance with the nature of the machining operations, by means of a geared feed : box D at the front of the HAYDEN FIVE-SPINDLE MACHINE 6 7 machine. While the master cam is operating at the fast speed, the first action that occurs is the withdrawing of all tools, and, when these are back out of the way, the head which carries the work-spindles is unlocked and indexed. The Fig. 16. Adjustable Cams of Hayden Automatic chuck holding the stock from which a finished piece has been severed is opened and the stock fed against a stop, after which the chuck is closed; these movements occur simultaneously with the indexing and are followed by the locking of the 68 MULTIPLE-SPINDLE DESIGNS head and the bringing of all tools into position for starting another series of operations. At this point, the speed of the master cam is automatically reduced and continues to rotate at this slower speed until the tools have completed their work and are ready to be withdrawn again; therefore, it will be seen that the time required for finishing a part is equal to the time necessary for the cutting operations, plus a constant period of one and one-half second (three seconds on preceding design) while the master cam is rotating three-fourths of a revolution at the fast speed. Adjustable Cams. The cams for operating the cross- slides and the tool spindles of the machine shown in Fig. 14 are in the form of a slide or wedge having a hinge or swivel point at one end. The arrangement of these cams for the end- working tool spindles is shown by the detailed view, Fig. 16. The five cams E for the end-working tool spindles are carried by a slide F which is moved in a direction parallel with the tool spindles, by the master cam C at the opposite end of the machine. Each cam E transmits motion to the tool spindle which it controls, by means of vertical rods G, having rack teeth at their upper ends which engage pinions H that mesh with rack teeth on the tool spindles. The lower ends of these vertical rods G are equipped with rollers that bear against the cams E and, as the latter are moved by the master cam, each tool spindle is also moved longitudinally an amount depending upon the inclination of the particular cam E by means of which it is operated. The angular position of each cam is varied in accordance with the feed required by the tool, by adjusting screws /. With this arrangement, special cams are not required for each job, and the only cams furnished with the machine are those which form a permanent part of it. The four cross-slides are also operated by separate cams, the inclination of which may be varied for regulating the feeding movement of each cross-slide independently. These cams L (Fig. 14) also transmit motion to the cross-slides through vertical rods K having rack teeth at their upper ends which engage pinions meshing with racks attached to the HAYDEN FIVE-SPINDLE MACHINE 69 cross-slides. The cams L are carried by slides which receive their motion from the master cam-drum C. Cross-slide Stops. Each cross-slide has an adjusting screw and a separate stop on the outside of the revolving head. These stops are adjustable and provide means to compensate for any slight wear which may occur, although, after having once been correctly set, they should not require adjustment for a considerable period. Each slide is provided with a swivel to enable work to be formed tapering or for correcting a taper- ing cut. Each slide also has a screw for crosswise adjustment. Indexing and Locking Mechanism. The head is indexed by a crank and slot mechanism, insuring an easy starting and stopping movement, in order to avoid excessive vibration and jar. The locking pin for the spindle head is located at the bottom near the chucking end, and has one flat side and one angular side so that the latter pushes the head around until the flat side comes into contact with the locating block. The head may be unlocked when it is desired to index or revolve it by hand. Time Required for Making One Piece. As previously explained, the master cam-drum C, Figs. 14 and 15, controls the movements of all cutting tools and completes all of the cutting operations while it is turning one-fourth of a revolu- tion; therefore, the time required to make one piece depends upon the speed at which the master cam rotates during this one quarter revolution. This speed is regulated by the shift- ing of two tumbler gears located in the case D in front of the machine. By means of these gears, 20 different speeds may be obtained which give periods of time ranging from i\ to 36 seconds. A plate or table attached to the machine shows, opposite each unit of time and under the different spindle speeds available, the number of spindle revolutions during that particular period of time, which, of course, is equivalent to the number of revolutions available for each operation. After deciding the order of the operations and which opera- tion requires the greatest number of spindle revolutions (which may be found by dividing the length of the cut by the feed MULTIPLE-SPINDLE DESIGNS GRIDLEY FOUR-SPINDLE MACHINE 71 per revolution), the total number of revolutions per operation is obtained. Then referring to the plate or table, the nearest number of spindle revolutions is located in the column headed by the spindle speed which is suitable for the work to be pro- duced ; opposite this number will be found the time in seconds required for machining, and also letters indicating the respec- tive positions of the tumbler-gear levers. There are sixteen changes of spindle speeds obtained by shifting gears in the speed-box B at the rear. Thread Cutting Operations. The top spindle of the machine illustrated in Fig. 14 is usually used for thread cut- ting. If threading operations are not necessary, however, this spindle may be converted into a regular tool spindle or it may be used for high-speed drilling. When cutting a right-hand thread, the spindle which holds the die is revolved in the same direction as the work-spindle, but at three-fourths of the spindle speed, whatever that speed may be, so that the actual threading speed is equivalent to one-fourth of the spindle speed. At a fixed time, which is three-fourths of the total time required for making a part, the spindle is caused to stop instantly, and as the die continues to revolve, it is unscrewed from the work. When cutting a left-hand thread, the spindle that is in line with the die is stopped and the die revolves at one-fourth of the regular spindle speed. After the thread is cut, the spindle is rotated at full speed, thus backing the work out of the die. The mechanism for thread cutting is self- contained on the machine and the machine is readily changed for cutting left-hand threads. Gridley Multiple-spindle Automatic Screw Machine. The Gridley multiple-spindle automatic screw machines have four spindles, the ij- by 5^-inch size being shown in Fig. 17. These spindles are driven constantly in one direction from a driving shaft at the center of the spindle-carrying cylinder. This shaft is provided with a gear which meshes with a gear on each spindle and is driven through change-gears from a pulley A running at a constant speed. This pulley may be con- nected with an overhead countershaft or be driven from a motor. MULTIPLE-SPINDLE DESIGNS GRIDLEY FOUR-SPINDLE MACHINE 73 The four work-spindles are mounted in a spindle carrier which extends from one end of the machine to the other. This spindle carrier is given an indexing movement each time the tools have completed their work and have been withdrawn. In this way, each of the work-spindles is brought into align- ment with the various tools held on the tool-slide B, which is fed forward and quickly withdrawn by a cam. After each indexing of the spindle carrier, the tool-slide moves forward and each tool or set of tools performs the required operation. The tool-slide is then withdrawn and the spindle carrier in- dexed to locate each spindle into alignment with a different tool or set of tools. A finished piece is produced every time the tool-slide moves forward. A Geneva stop mechanism is employed for indexing the spindle-carrying cylinder. With this mechanism, the starting and stopping of the carrier are gradual, but the intermediate movement is rapid. Tool-slide. The tool-slide B is mounted upon an exten- sion D of the central part of the spindle-carrying cylinder. This extension is supported in a bearing at one end of the machine while the larger diameter which carries the spindles is supported at the other end, the tool-slide being mounted between the two bearings. With this arrangement, if either end of the cylinder becomes loose in its bearing, the align- ment between the spindles and' tool-slide would not be affected. The tools on the tool-slide are held in holders which are rigidly bolted to the slide instead of being held by shanks. Feeding Movement for the Tools. The feeding movement for the tool- slide which holds the end- working tools is derived from a cam on the cam-drum C, Fig. 18. The slides carrying the forming and cutting-off tools are operated by cams on the drum E. By means of a quick change-gear mechanism con- trolled by lever F, the feed may be varied at will, while main- taining a constant spindle speed. With this arrangement, the machine may be set up without considering the rate of feed, as the latter may be varied afterwards until it is as coarse as conditions will permit. The Idle Movements. After the tools have finished cut- 74 MULTIPLE-SPINDLE DESIGNS ting, the withdrawal of the tool-slide, the indexing of the spindle-carrying cylinder, and the movement of the tools for- ward again to the position for cutting are commonly known as the idle or non-productive movements. On the Gridley multiple-spindle machine, the time necessary for these idle movements is independent of the feed used when the tools are cutting. Camshaft and Cams. The main camshaft is parallel to the driving shaft and is driven from it by a worm on the spindle driving shaft, through a change-gear box, a worm- Fig. 19. Independent Stops for Each Spindle Position shaft, and a worm-gear mounted on the camshaft. This shaft carries the cams for feeding the tool-slide, for operat- ing the chuck- and stock-feeding mechanism, and also operates the mechanism for revolving the spindle carrier and drives the shaft upon which the forming and cutting-ofT cam-drum E (Fig. 1 8) is mounted. The long cam-drum H operates the mechanism for feeding the stock. The indexing arm /, for revolving the spindle carrier, carries a cam which withdraws the locking bolt and indexes the spindle carrier one-fourth of a revolution for each revolution of the camshaft. The cam- drum E which carries the cams for operating the cut-off and NEW BRITAIN SIX-SPINDLE MACHINE 75 7 6 MULTIPLE- SPINDLE DESIGNS forming tool-slides has its axis at right angles to the main cam- shaft and is driven through a pair of bevel gears. The large cam-drum C for feeding the tool-slide is provided with cams of three different leads, and cam lever K is set in one of three positions, depending upon the particular cam that is being used. Stops for Forming Tools. Independent stops for the form- ing tool are provided for each spindle position, so that the tool is moved up to the same position relative to the spindle each time a part is produced. The arrangement of these stops is shown by the detailed view, Fig. 19. The stop A, which is attached to the spindle carrier, is engaged by a stop B, passing through an arm that is fixed to the forming tool-slide. Method of Cutting Threads. When cutting threads on the Gridley multiple-spindle automatic, the die is held in a holder L (Fig. 18) which is carried by a slide. This slide is fed forward by a cam M which imparts motion to the slide through the bellcrank N and the connecting link shown, and the slide is returned by another cam on drum //. The die is rotated in the same direction as the spindle, but at a speed slightly less than the spindle speed while the thread is being cut; the die is then revolved at a higher rajte of speed, in order to run it off of the work. These two speeds are obtained by means of two gears on the spindle driving shaft which mesh with two loose gears and P on the threading shaft. For cutting a thread, the slow-speed gear is engaged by a clutch located between the two gears, and, as soon as the thread is completed, this clutch is shifted to the high-speed gear, thus backing off the die. The adjusting nut Q controls the point at which the die is reversed, and the cam for re-engaging the clutch is attached to a worm-wheel on the camshaft. Either right-hand or left-hand threads can be cut by trans- posing one connecting link and changing one cam. These machines, at the present time, are built in four sizes: namely, } by 4^ inches; ij by 5^ inches; if by 7 inches; and 2\ by 7 inches. New Britain Automatic Screw Machine. The New Britain automatic screw machine shown in Fig. 20 has six NEW BRITAIN SIX-SPINDLE MACHINE 77 78 MULTIPLE-SPINDLE DESIGNS spindles, so that nine operations can be performed simultane- ously on six pieces, by utilizing both the end-working and cross-slide tools. Fig. 22 shows the arrangement of the drive. The driving shaft is shown at the extreme right, and this shaft runs at constant speed. At the left-hand end of the driving shaft there is a gear A that transmits motion to the main shaft B through gear C. The main shaft passes through the tool-slide and spindle carrier, and at its extreme left-hand end ca-rries a gear D the function of which is to ro- tate the six spindles through gears E. The drive is carried from the main shaft to the camshaft through a small pinion F on the main shaft, that meshes with gear G on the feed-shaft. This feed-shaft carries a pinion H that meshes with an internal gear on the feed cam 7. Camshaft / is rotated through gears from the end of the feed-shaft, and these gears may be changed to secure any required speed for the camshaft. The drive to the indexing shaft is taken direct from the drive shaft to the index drive shaft K through spur gearing. The index shaft is in two sections; the forward section marked L and the rear section M. (See also Fig. 21.) The forward half rotates con- tinuously, but, at the time of indexing, a clutch connects it with the rear section M and the indexing is done through spur gearing and a Geneva motion that will be described later. Power is carried to the threading shaft N (see Figs. 21 and 22) through spur gearing direct from the main shaft. At the left- hand end of the threading shaft is a spur gear that is thrown into mesh with the driving gear on the threading spindle, for performing the threading operation. Spindle Construction. All of the spindle thrust is taken upon the ball thrust bearings Q (Fig. 23) that are set into the frame of the spindle carrier, and receive the thrust of the ro- tating spindles. The collet chucks, one of which is shown at R, are closed on the " push-in" principle, being forced into sleeves on the noses of the spindles. The usual mechanism for closing the chucks is used, there being fingers S that are oscillated and throw the chucks forward into the sleeves. These fingers are operated by clutches. The stock tubes T NEW BRITAIN SIX-SPINDLE MACHINE 79 are also of the usual type, the work being seized by the spring jaws on the chuck-end of the stock tubes. The stock tubes are advanced by a cam mechanism acting through the sleeve that may be seen on the extreme left-hand end of the stock tube. The main shaft of the machine is indicated at B, and transmits power to the spindles through gear D that meshes with gears E on the spindles. The spur gears W are for driv- ing the spindles when in operation for threading, the gear W being slidably keyed to the spindles. At all times, except when the spindles are in the threading position, these gears W are kept thrust into a taper seat in the gears E, and the spindles are driven by the gear D. This friction is maintained by fingers X that are operated by clutches and yokes. At the time of threading, the clutches are cam-operated so as to re- lease fingers X, and the friction drive between gears W and E is broken; thus at this time the spindles are not driven by the driving gear D, because the connection between gears E and W is broken. For threading, therefore, it is evident that gears W, operated by a special driving mechanism to be de- scribed later, are responsible for the rotation of the spindles. While the main shaft B passes through bronze bushings in the spindle carrier, none of the weight of the spindle carrier comes upon it, this weight being all taken on the spindle- carrier bearings at V. Six or more speeds are available for the spindles, and these are effected by change-gears that may be placed upon the right-hand ends of the feed-shaft and cam- shaft, as illustrated in Fig. 22. The Tool-slide. There are six tool-holding positions on the tool-slide P (Fig. 20) which is operated from cam-drum 7. Upon this drum are placed the cams that govern the opera- tion of the slide. These cams act through a stud on the lower part of the tool-slide. The cam-drum is kept free from back- lash by a hardened steel roll supported from the frame, that runs against the right-hand edge of the drum. As previously mentioned, the cam-drum is driven by an internal gear and pinion, shown at H in Fig. 22. A stud (Fig. 20), carries a bevel pinion that meshes with a corresponding bevel gear on 8o MULTIPLE-SPINDLE DESIGNS the feed-shaft which carries the small pinion H, so that the cam-drum may be turned by hand when setting-up the ma- chine. A hand lever on stud Q operates a clutch for disengaging the camshaft at any desired time, thus stopping the action of the tools. This clutch may also be thrown out from the rear of the machine. A laminated cam is made use of on the feed drum. This is a patented cam construction, in which the .THREADING CHANGE-GEARS Machinery Fig. 22. Diagram showing Arrangement of Driving Mechanism on New Britain Six-spindle Automatic cam strip is composed of three leaves, which permits of the adjusting of one cam to any length of work within the capacity of the machine. Indexing Mechanism. -- The indexing of the machine shown in Fig. 20 is done at constant speed, irrespective of the speed of the main shaft or camshaft and without regard to the length of the job on the machine. As has been explained, the index shaft is in two sections; the forward section L (Figs. 21 and 22) revolves continuously, and the rear section M revolves only at the time of indexing. A clutch connects the two sections of the indexing shaft; and, at each revo- NEW BRITAIN SIX-SPINDLE MACHINE 8l lution of the cam-drum, this clutch is tripped by the small edge-cam R, Fig. 22. When the clutch is tripped, and the rear index shaft is caused to turn, gear S turns gear T through exactly one-half revolution, because gear- S is just one-half the diameter of gear T. Diametrically opposite each other on the side of gear T are two studs that operate the Geneva gear U which may be more clearly shown in the front view, Fig. 20. This gear is supported, but not driven, by the camshaft. The operation of the stud in the slot in the Geneva gear turns it exactly one- sixth of a revolution, and as this gear U is in mesh with the W E O EjgWV. \ r-~. Machinery Fig. 23. Cross-sectional View of One of the Six Spindles of New Britain Automatic Screw Machine gear on the spindle carrier, which is of the same diameter, the spindle carrier is also turned one-sixth of a revolution. Just previous to the indexing, a cam and cam lever operated from the camshaft withdraw the locking bolt shown at V in Fig. 21. This is a wide heavy key that is normally kept in contact with the spindle carrier by spring pressure, engaging in one of the six slots equally spaced about the circumference of the spindle carrier. The cam releases the key, so that, when the spindle carrier has turned far enough to engage the locking bolt, it jumps into place and holds the spindle carrier until the time of next indexing. The Geneva motion is particularly adaptable to indexing mechanisms in that the starting motion is slow, gradually accelerating and then diminishing at the end of the motion. The Cross-slide. The cross or forming slides of the machine shown in Fig. 20 are three in number, operating on 82 MULTIPLE-SPINDLE DESIGNS the second, third, and sixth spindles. Provision has also been made for adding a cross-slide to the fifth spindle if the work to be performed requires it. Fig. 20 clearly illustrates the second and third spindle cross-slides which are operated by means of cam levers engaging plate cams on the camshaft /. The rear cross-slide may be readily seen in Fig. 21 and is used principally for cutting off. The stock-feeding and chuck- closing operations are performed from the cam-drum at the extreme end of the camshaft. This operates on the clutches that feed the stock and close the chuck on the spindle in the first or lowljj position, which is just above the top surface of the cam. The Threading Spindle. The threading shaft N is mounted at the left-hand end (as viewed in Fig. 21) in a float- ing bearing that permits the entire shaft to be oscillated, thus allowing the gear under the guard at Z on the opposite end to be thrown into or out of mesh with the spindle gear W, when actuated by lever Y that is guided by a cam on the cam- shaft. The operation of this threading shaft is as follows: Just before the spindle carrier is indexed, the threading shaft and its gear are thrown away from the spindle to give the spindle carrier a clear path for indexing. As soon as the lock- ing bolt has shot into place, a rise on the cam that governs lever Y carries this lever back into its inner position with the gear in mesh with the gear W on the spindle at the threading position. Simultaneously with this action, lever X is operated by the cam on the camshaft and operates the spindle clutch that releases the spindle driving gear E (see Fig. 23) from con- tact with the gear W that is now in mesh with the gear Z on the threading spindle. By this means the spindle is operated at the correct threading speed. Before the indexing takes place, the threading shaft is again swung away and gear Z is thrown out of mesh with the spindle gear. A brake lever located at the right of lever X (Fig. 21) is operated from the camshaft. The upper end of this lever is fitted with a fiber plug and its function is to bear against the spindle and retard rotation just before the threading-shaft NEW BRITAIN SIX-SPINDLE MACHINE 83 gear Z goes into mesh with the spindle gear. On the left- hand end of the threading spindle is a reversing shaft by means of which a left-hand rotation may be given the shaft when left- hand threads are to be cut. The threading die or tap-holder on the tool-slide is fitted with a pusher that presses against the rear of the holder to engage the threading die or tap on the work, after which it "leads" itself on. Spring fingers prevent the threading-die holder from turning when in action. This machine at the present time is built in four sizes; namely, f by 3! inches; i by 5 inches; if by 7 inches; and 2 by 9^ inches. CHAPTER IV AUTOMATIC SCREW MACHINE TOOL EQUIPMENT THE various cutting tools used on automatic screw machines for external and internal machining operations include form tools for accurately producing irregular shapes in duplicate, box-tools, hollow mills, shaving tools for light finishing cuts, recessing tools, drills, reamers, counterbores, centering tools, knurling tools, cutting-off tools, threading dies, taps, etc. There are also many special designs, some of which are neces- sary for making a given part on the screw machine, whereas others are used to obtain a higher rate of production than would be possible with regular or standard tool equipment. The most important tools, especially of the class that is adapted to general work, will be described. Most of these tools were designed for use on certain screw machines, although the same general types, in practically all cases, may be applied to screw machines made by other manufacturers, with such modifica- tions regarding size, etc., as may be necessary owing to varia- tions in the design of the machine. Circular Forming and Cutting-off Tools. When a part is to be produced on the automatic screw machine, the suc- cessive order of the operations and the kind and number of the cutting tools required should be decided upon before de- signing the cams, assuming that the machine is of the type requiring special cams for each job. The method of applying a forming tool varies somewhat according to the shape and proportions of the work. A simple application of a circular forming tool is illustrated by the diagram to the left in Fig. i. This tool A is attached to a holder which is mounted upon the cross-slide of the ma- chine; the cutting-off tool is located on the opposite side, as the illustration indicates. The stock is first fed out against 8 4 FORMING TOOLS the stop in the turret and then the forming tool A moves in, turning the body and the conical head; just as the tool A is finishing, the cut-off tool B moves in and severs the part from the bar. The body of this screw could be turned by a tool held in the turret, but, when using a machine of the Brown & Sharpe type, a tool held on the cross-slide is usually preferable, because the work can be done more rapidly. This method is recommended when the length of the work does not exceed i\ times the smallest diameter A of the part when finished; parts that are longer than this are too flexible to be turned by a cross-slide tool. Another example is shown to the right in Fig. i. In this Fig. 1. Application of Forming and Cutting-off Tools case, the forming tool C turns the part c and e. Then a die in the turret threads the end after which the tool D moves in and serves the finished piece from the bar of stock and, at the same time, forms the part d for the next screw. The stock is then fed out against the stop in the turret and the operation repeated. Methods of Applying Circular Forming Tools. When turning short screws on a Brown & Sharpe machine with circular forming and cutting-off tools, as indicated at A Fig. 2, if the time utilized by the tools will not permit revolv- ing the turret for locating the stock in position for the next successive feeding movement of the stock, two sets of tools, that is, two stops and two die-holders should be used in the 86 TOOL EQUIPMENT O _L FORMING TOOLS 87 turret. The method shown at B is not to be recommended, because the feeding of the stock varies to such an extent that the forming tool will break off the screw when the latter has been reduced to a diameter a by the forming tool, in case there is an excessive amount to face off of the end of the stock. As the turret would require to be indexed, in any case, to clear the arm of the slotting attachment, the screw end could be finished by a tool in the turret with little loss of time as compared with the method shown at B, although the latter may be employed when part a is large in diameter and the screw is short and stiff. When a box-tool or hollow mill follows the forming opera- tion, when turning a comparatively long screw or bolt as indi- cated at C, the forming tool should be beveled as at e % as this leaves a beveled shoulder on the work, so that, when the box- tool or hollow mill reaches the formed surface, it completely removes the superfluous material as at C\ without leaving the objectionable ring which would be produced if the face of the forming tool were square, as indicated by the diagrams C 2 and C 3 . This ring of metal c prevents the finishing box- tool or die from being fed up to the shoulder. The cutting-off tool should bevel the end of the stock as at d (diagram C), so that the box-tool will have a light cut until the back-rests have a good support. This beveled or pointed end also locates a hollow mill and equalizes the cutting action on the teeth. The method illustrated at D may sometimes be used to advantage when making shouldered screws or other pieces of similar form. This method, however, is not recommended when considerable accuracy is required, because a slight eccentricity in the spring collet would cause part / to be out of true with part g. For accurate work, the part g should be rough-turned with a cut-off tool and a light finishing cut taken with a box-tool held in the turret. The forming tool shown at DI is so shaped that it moves the burr from the screw-head. When applying circular forming tools, the gaging of the work should be carefully considered, because in some cases, when irregular shapes are to be formed, it may be possible to 88 TOOL EQUIPMENT use a forming tool which will greatly simplify the method of gaging the finished work. The piece shown at E in Fig. 2 will require a box-tool, a forming tool, and a cutting-off tool, but, when using the forming tool shown, it is simply neces- sary to measure the diameter and over-all length, and the latter does not require to be very accurate. Another method of producing the same part is shown at F; three tools are used as before, but the cutting-off tool finishes the work to length h, whereas the box-tool finishes the shoulder to length k. In this case, a more expensive gage will be necessary, and con- siderable extra time will be required for setting up the tools after grinding. It is generally necessary to provide means REAR SLIDE Machinery, N.Y. Fig. 3. Circular Forming Tools and Holders for removing the objectionable burr made by turning tools, as indicated at G. In order to remove these burrs, forming tools are frequently given beveled edges as indicated at Gi. Holder for Circular Forming and Cutting-off Tools. In order to prevent chattering, it is necessary to hold a forming tool rigidly. The Brown & Sharpe type of holder shown in Fig. 3 provides a rigid support for the tool and includes suit- able adjustment, provision for periphery clearance, as well as means for adjusting the tool at right angles to the work. The tool is firmly clamped against the face of the holder by means of a cap-screw b in the center and a clamping bolt which grips the rear side of the tool and prevents it from turning while cutting. FORMING TOOLS 8 9 Arrangement of Circular Tools. When applying circular tools to automatic screw machines, their arrangement has an important bearing on the results obtained. The various ways of arranging the circular tools, with relation to the rota- tion of the spindle, are shown at A, B, C, and D, in Fig. 4. These diagrams represent the view obtained when looking towards the chuck. The arrangement at A gives good results for long forming on brass, steel, or gun-screw iron, for the reason that tjie pressure of the cut on the front tool is down- ward; the support is more rigid than when the forming tool is turned upside down on the front slide, as shown at B; here Machinery, N.Y. Fig. 4. Different Arrangements of Circular Tools the stock, turning up towards the tool, has a tendency to lift the cross-slide, causing chattering; therefore, the arrangement shown at A is recommended when a high finish is desired. The arrangement at B works satisfactorily for short steel pieces which do not require a high finish; it allows the chips to drop clear of the work, and is especially advantageous when making screws, when the forming and cut-off tools oper- ate after the die, as no time is lost in reversing the spindle. The arrangement at C is recommended for heavy cutting on large' work, when both tools are used for forming the piece; a rigid support is then necessary for both tools and a good supply of oil is also required. The arrangement at D is objec- 90 TOOL EQUIPMENT tionable and should be avoided; it is used only when a left- hand thread is cut on the piece and when the cut-off tool is used on the front slide, leaving the heavy cutting to be per- formed from the rear slide. In all "cross-forming" work, it is essential that the spindle be kept in good condition, and that the collet or chuck have a parallel contact upon the bar which is being formed. Clearance for Circular Tools. In order to provide periph- ery clearance on circular tools, the center of the tool is lo- cated a certain amount above or below the center of the work, as shown in Fig. 4. On account of this offset of the cut- ting edge, the actual difference in the diameters of different surfaces of the forming tool does not exactly correspond with the same relative dimensions on the work. For instance, if a circular forming tool has two or more diameters, the dif- ference in the radii of the steps on the tool will not be exactly the same as the difference in the steps on the work. There is a difference of opinion regarding the question of side clearance for circular tools, some advocating considerable clearance, others only a slight amount, or no clearance at all. When tools heat up and "welding" occurs, this may not be due to the lack of clearance, but rather to the poor quality of cooling lubricant used. Side clearance is necessary in some cases, but tools made without clearance should be ground smooth on the sides and a good grade of lard oil used as a cutting lubricant. Tool-holders for Flat Forming Tools. Flat or straight forming tools are used on automatic screw machines instead of circular forming tools, in some cases, especially when the part to be formed is quite large and a very rigid tool is de- sirable. The toolpost shown at A in Fig. 5 is extensively used on the Cleveland automatic machine. The base a is bolted directly to the cross-slide and the top face of this base is beveled to an angle of about 15 degrees. The bevel wedge b has a tongue which fits into a corresponding groove in the base and the top face of the wedge has a tongue that fits into another groove in the flat forming tool c. The forming tool FORMING TOOLS is adjusted vertically by screw d, the head of which engages one of a series of slots in the wedge. The toolpost shown at B is used for holding light forming tools or for cutting-off tools that are not of the blade type. It consists principally of a Fig. 5. Two Types of Flat Forming Tool-holders Fig. 6. Open-side Forming Tool-holder and Standard Universal Cut-off Tool- holder for Cut-off Tools of the Blade Type clamping strap e, a base /, and a tapered wedge g, which is adjusted by screw h. The design of tool-holder shown at A in Fig. 6 is known as an open-side forming toolpost. It is used for holding forming tools having square shanks. The forming tool is clamped by set-screw b and is adjusted to the required height by wedge e and screw /. This type of toolpost is adapted to holding inex- pensive forming tools. The toolpost shown at B in Fig. 6 is known as a universal cutting-ojj tool-holder. The swinging Q2 TOOL EQUIPMENT tool-holder h is pivoted on bolt i t which also clamps the holder, ratchet, and post together. A threaded stud j supports the ratchet k and this ratchet gives adjustment to the tool-holder h. The blade type of cutting-off tool I is clamped in place by two bolts m. This tool-holder may be used on either the front or the rear of the cross-slide. As shown in the illustra- tion, it is set for the rear position. When it is to be used on the front of the cross-slide, the position of the tool-holder h may be reversed so that the blade is located below the center. Tools for Cutting Off Finished Parts. There are two general types of tools used on automatic screw machines for cutting off finished parts from a bar of stock; namely, the blade type and the circular type. The blade type consists of a narrow straight blade which is clamped in a suitable holder. Tools of this kind serve only to sever finished parts, whereas the circular type are, in many cases, so formed that, as the blade cuts off the finished piece, another cutting edge on the tool either bevels or rounds the end of the part being severed or performs some other operation, such as " point- ing" the bar of stock or reducing its diameter at the end, pre- paratory to making the next piece. The view to the right in Fig. i illustrates how a cutting-off tool is used to turn down the end of the next succeeding piece while cutting off the one that has just been finished. Other similar applications of circular cutting-off tools are shown in Fig. 2. The edge of a cutting-off tool is ground at an angle, so that it will sever the finished part completely by a cutting action. If the cutting edge were parallel with the axis of the work, the latter would break off, due to the pressure of the cut before the cutting edge reached the center, so that the end of the severed part would not be finished neatly, but, with the cutting edge at an angle, this does not occur. This angle a (see Fig. 2, Chapter VII) for different materials should be about as follows: For drill rod and tool steel, a = 10 degrees; for Nor- way iron and machine steel, a= 15 degrees; for gun screw iron, a = 18 degrees; for hard brass, a = 20 degrees; for soft brass and copper, a = 23 degrees. CUTTING-OFF TOOLS 93 The thickness of the blade of a cutting-off tool should be varied according to the diameter of the work, the angle of the cutting edge, and the hardness of the material to be operated upon. The thickness of the blade of an ordinary circular cutting-off tool which is not required to form part of the work may be determined by the following formula: r = D X cot a. X 0.14, in which T = thickness of blade in inches; D = diameter of stock in inches; a = angle between cutting edge and axis of work. When the cutting-off tool is also used for forming, the blade is shorter and the thickness may be about three-fourths of that ob- tained by the preceding formula. In any case, when a tapped hole passes through the work, the cut- ting-off blade should be wide enough to remove the por- tion cut by the chamfered end of the tap. Rake of Forming and Cutting-off Tools. For cutting brass, the top face of the cutting part of the tool is usually in the same plane as the axis of the work, although, in some cases, especially for soft brass, a negative rake of about 5 degrees is given the cutting edge. For cutting other materials, forming and cutting-off tools will operate more satisfactorily if given a positive rake. ^ The angle for drill rod and tool steel should vary from 8 to 10 degrees; for gun screw iron, 12 degrees; for machine steel, 15 degrees; for Norway iron, 18 degrees; for copper and aluminum, from 25 to 30 degrees. For cutting steel and iron, the cutting edge of the tool should be at the same height as the center of the work, whereas for cutting brass, bronze, copper, and aluminum, Fig. 7. Box-tool designed for General Work 94 TOOL EQUIPMENT better results are sometimes obtained by setting the cutting edge slightly above the center, although for such material as Tobin bronze, the cutting edge should be set the same as for steel. Box-tools. Box-tools are made in a great variety of designs and types which differ chiefly in regard to the number and arrangement of the cutters and the method of supporting the part being turned. Most of the types described in the following have been extensively Used. The box- tool shown in Fig. 7 carries two cutting tools. The tools rest on a pin d and are held by set-screws a and 6, and by two other set-screws, 012 i p TT1H Machinery, N.T. Fig. 8. Finishing Box-tool largely used for Steel Work not shown, which are on the under side of the box-tool. The support, which is of the V-type, is located at the back of the box-tool at an angle of 45 degrees with the vertical center- line, and is held by the set-screw c. This box-tool is used for general work, for turning both one and two diameters, as required. When one diameter is being turned, the cutter in the rear is pushed back. In Fig. 8 is shown a finishing box-tool which is used largely for steel work. In this box-tool, the turning tool is held in an adjustable block A which is adjusted up and down on the body of the holder by the set-screw B, and held to the body by the cap-screw C. A projection is formed on the body of the box-tool and a corresponding guiding groove is cut in the block. The turning tool is held by means of two set-screws BOX-TOOLS 95 D and the headless screws E. These latter are for adjusting the turning tool, in order to increase the clearance between the tool and the periphery of the work. The V-support is held in beveled grooves in the body of the holder, by two screws F which pass through the two parts of the body sepa- rated by a saw cut, thus binding them together. The cutting edge of the turning tool is located from o.oio to 0.012 inch in advance of the face of the supports. A hole is drilled through the shank of the box-tool for holding a pointing tool or other internal cutting tool, which is held with the set-screw G. Fig. 9. Box-tool of the Roller-support Type In Fig. 9 is shown a box-tool of the roller-support type, which is provided with a roller support for the front cutter and a V-support for the rear cutter. The supports A are held by pins in the two blocks B, which are adjusted in and out by the knurled-head screws C. The blocks B are held to the body of the box- tool by cap-screws which are tapped into them. A slot is cut in the body of the holder in which the bodies of the cap-screws slide, thus providing adjustment for turning different diameters. A simple type of shaving box-tool is shown at B in Fig. 10. This tool is provided with V-supports which are adjusted by 9 6 TOOL EQUIPMENT the collar-head screw e and are clamped in position by means of the clamp bolts /. The turning tool g is adjusted by a collar- head screw h and is held in position by a set-screw i. This tool Fig. 10. Roller Steadyrest Shaving and Roughing Box-tools is of very simple construction and is used where only one diameter is to be turned at a time. The roughing box-tool C, Fig. 10, is provided with roller supports, and the turning tool j is held in a square hole pro- vided in the stud k; this stud clamps the turning tool against the face of the box-tool holder. Adjustment for height is BOX-TOOLS 97 secured by means of the set-screw /. Two set-screws, one of which is shown at m, act as an adjustment for stud k. The box- tool shown at A in Fig. n holds three turning tools, and can also carry a centering tool or drill, which is held in the shank of the holder. The flat base a has two grooves 11. Multiple Turning Tool, Adjustable Hollow Mill, and Standard Three-tool Box-mill extending its full length, in one of which the three holders b for the cutting tools are held, and in the other two the brackets c for roller supports. This box-tool can be used for turning three different diameters at one setting and is used either for roughing or finishing cuts. The roller supports may be ad- justed to lead or follow the cutting tools by simply moving them along the slot in the holder. The brackets carrying the 98 TOOL EQUIPMENT supports can be placed in any desired position and the holders for the cutting tools can also be adjusted to suit the various diameters and lengths of shoulders on the work. An adjustable type of " hollow roughing mill" or box- tool is shown at B in Fig. u. This is supplied with two cutter heads, each containing four cutters d. The flat arm e of the box-tool has a spline cut the full length, and also a slot through which the studs of the cutter heads pass. The studs are made integral with the cutter heads and are clamped by nuts as shown. The four cutters in each head are adjusted by re- moving the head from the arm and placing it on a stand fitted with a plug gage of the same diameter as the work to be turned. This stand holds the cutter head in the correct relation to the plug gage, so that the tools can be brought into contact with the plug gage and then clamped. This tool which is adapted to rough turning cast iron is supplied with a hole in the shank for holding a centering tool or drill. The heads for the cutters are adjustable along the body of the holder. The box- tool shown at C in Fig. n is of the open- type con- struction and is supplied with one turning tool clamped to its face, the work being supported at this point by roller supports. The second tool, which is set at an angle and held down by a heel clamp, can be used for turning a second di- ameter; the work is supported opposite this tool by a V-support. Box-tools of Over-cut Type. The type of box-tool com- monly used on the "Acme" multiple-spindle automatic is known as the over-cut type; this usually carries two cutting tools as shown in Fig. 12. The front cutting tool is set "tan- gentially" to the work, while the rear cutter is radial in rela- tion to the center of the work. The front tool, when used for taking a finishing cut, is set about o.oio inch in advance of the supports and is ground a little high at the rear to provide for clearance. The roller supports c which are commonly used are shown dismantled at D and fastened to the holders at E. The support holders are held to the box-tool body by BOX-TOOLS 99 a cap-screw e and are backed up by large-headed screws /. The rear cutting tool h is held in a tool-holder which is retained in a V-groove in the body of the box-tool by a cap-screw k and is provided with an elongated slot for adjustment. The box- tool shown at H is known as a "round box- tool" because of the rounded shape of its body. It is provided with a solid support which is very rarely used except on small brass work. It is particularly suited for use in the "first" position when the forming cut overlaps the box-tool cut. This type Fig. 12. Group of Over-cut Box- tools used on the "Acme" Mul- tiple-spindle Automatic Screw Machines of box-tool is also provided with roller supports for general work. Spring-releasing Box-tool. The regular box-tool, when used for taking heavy roughing cuts, usually leaves a spiral mark on the work in backing off. This is due to the extreme point of the cutting tool becoming heated, and a certain amount of the cuttings sticking to it, thus forming a ragged edge, which produces an objectionable mark on the work when the tool is withdrawn. To overcome this difficulty, the National-Acme Mfg. Co. designed the "spring-releasing box- tool" illustrated in Fig. 13. In this design, the front cutting tool is removed from the work on the back stroke, and is thus 100 TOOL EQUIPMENT prevented from producing an objectionable mark. The front part of the body A is cut out as shown, and a block C is held to it by a bolt and nut. This block is provided with a tongue so that it is adjustable in a vertical direction on the face of the box-tool body. The tool-holder B is provided with an angular groove which fits over a corresponding tongue on the face of the block C. The tool-holder is held to block C by a shouldered screw E, the diameter of which is smaller than the elongated hole in the tool-holder, to provide for a slight movement. . Screw E is backed up by headless screw F to POSITION OF TOOL' WHEN CUTTING POSITION OF TOOL WHEN RELEASED Machinery Fig. 13. Spring-releasing Type of Box-tool prevent it from loosening when the tool-holder is moved back and forth on it. In the tool-holder B, there is a spiral spring H which acts on a plunger, the latter bearing against the body of the shoul- dered screw E. The action of this spring draws the tool- holder forward toward the center-line of the box-tool body, its movement being stopped by the headless screw G. The tool-holder B works on a tongue which is at an angle with the line X Y. When the front cutting edge of the tool strikes the work, it compresses the coil spring //, forcing the tool- and holder back until its movement is stopped by the shoul- dered screw E. Then when the main tool-slide stops advancing BOX-TOOLS IOI and begins to retreat, the pressure on the cutting tool is re- leased, allowing the spring to force the tool-holder up on the angular tongue and thus raise the tool from the work as shown by the diagrams at the lower part of the illustration. The block C carrying the tool-holder is adjusted vertically for turning different diameters by means of the collar-head screw /. The roller supports are held in holders / which are backed up by blocks K\ these blocks are held in place by a cap-screw Fig. 14. Turning Tool for Taper or Irregular Shapes M and drilled out to receive a headless screw L y the latter forming a heel on which the rear part of the block rests. As the diameter of the work increases, the screw M is released, allowing the roller-support holders / to drop back to bring the rolls to the proper position. Then the screw L is brought out until the block K is practically in a parallel position, when the screw M is tightened. Taper-turning Box-tool. The box-tool shown in Fig. 14, which is adapted to the turning of taper or irregular forms, is held by a shank in the turret of the machine and is supplied 102 TOOL EQUIPMENT with a bushing on the front end which. guides the work. The circular slide A carries the turning tool B and is fitted with a pin C which comes in contact with the adjustable guide D held on the cross-slide. When the turning operation is com- pleted, the cross-slide recedes, allowing a spring located inside the holder to move the slide A back to its original position. The guide D held on the holder E which is attached to the cross-slide can be made of any shape, so that any irregular form as well as tapered work can be secured. This guide is Fig. 15. Taper-turning Tool fulcrumed on a pin in the bracket and is supported and adjusted by two set-screws. This tool is used on the Cleveland automatics. A taper- turning tool made by the Brown & Sharpe Mfg. Co., and one that is recommended for accurate work, is shown in Fig. 15. When in operation, a block or plate, which can be set at any angle desired, presses on the point of screw a, which forces the holders carrying the supports and turning tool out from the center. The screw a is tapped into sleeve b and moves the latter in the direction of the arrow. Now as the sleeve b is forced in, it pulls on the band spring c, which is attached to the circular block d, thus turning the latter around in the direction of the arrow. The spring is fastened in a slot cut in the circular block d. The circular block d has eccentric projections e formed on it, which fit in slots cut in the tool- holder / and support-holders g. As the sleeve b is forced in, BOX-TOOLS I0 3 it carries the spring c forward, thus rotating the circular block d in the direction of the arrow and forcing the holders carry- ing the supports and turning tools out from the center. In the end view shown at A, the turning-tool and support- holders are shown in the position they occupy before screw a engages the operating block. The supports and turning tool can be adjusted independently of each other by the set- Machinery Fig. 16. Various Methods of Applying Box-tool Cutters to the Work screws h, and are held by the screws i. After the turret drops back, disconnecting the screw a from the block, the turning tool and supports are returned to their former position by means of the coil springy (shown at B). The spring j presses against a pin k (shown at C) which is riveted to a plate /; this plate is held to the shank of the holder by a pin fitting in a slot. Plate / is held up against the outer casing of the holder by the nut w, screwed onto the shank of the holder. 104 TOOL EQUIPMENT Methods of Applying Box-tool Cutters. Box-tool cutters are applied to the work either radially as shown at A, Fig. 16, or tangentially as illustrated at B and C. The radial position for the cutter is more commonly used for brass work, whereas the tangential cutter is used for all classes of steel work, and also for brass work in some cases. The cutting edge of a radial cutter is set above the horizontal center-line of the work an amount that is usually about 0.02 times the diameter which is being turned. This is the preferable method of applying the turning tool for taking roughing cuts on brass rods. If the stock is rough or of irregular shape, the cutter should precede the support an amount varying from o.oio to 0.020 inch, but, if the bar is cylindrical and has a finished surface, the sup- port, when taking roughing cuts, should precede the turning tool, as shown by the dotted lines at A . The tangential cutter shown at B is set to take a roughing cut from a bar having a comparatively rough surface. The tangential cutter shown at C is set for taking a finishing cut in steel. The cutting edge is located back of the center of the work an amount equal to o.io of the diameter d, being turned. For cutting brass, the tangential cutter is set in line with the center, or, in some cases, slightly in advance of the center. A method of applying two turning tools for roughing down steel work is shown at D, and at E three turning tools used for the same purpose. For taking roughing cuts on brass, where considerable material is to be removed, a hollow mill is generally used, but the method shown at D can sometimes be employed to advantage. At E no supports are used, as the tools support the stock. These tools can either be set radially as shown, and a slight amount in advance of each other, or tangentially and at varying heights, so as to distribute the cuts equally among the tools. For taking roughing cuts on steel, it is preferable to set the cutters tangentially to the work. At F is shown a method of applying two tangential turning tools for turning down two diameters on a piece of work. This method is used when the distance a is not much greater iff -4*1 I 1 1 ' b 106 TOOL EQUIPMENT than from J to f inch. For a larger dimension a, it is generally advisable to use two separate box-tools, provided there is sufficient room in the turret. When turning tools are used in this manner, the thickness b of the first tool should be such that the second tool, when set tightly against the first one, will turn the shoulder to the desired length. To illustrate, assume that a = 0.375 i ncn J = 10 degrees; then b = a X cos j8 = 0.375 X 0.9848 = 0.369 inch. When two turning tools are used in this manner, they should be ground on all sur- faces and should also be made a good fit in the square or oblong hole cut in the body of the holder to receive them. Holding and Adjusting Box-tool Cutters. At A in Fig. 17 is shown a method which is commonly used for holding a box- tool cutter for brass work. A square hole is cut in the body of the holder to receive the cutter, the latter being held by a set-screw a. The cutter is adjusted for different diameters by the collar-head set-screw b which bears against the rear end of the tool. By cutting a slot in the turning tool to fit the collar on the screw, this screw may be used for adjusting the tool both in and out. The method shown at B for holding the turning tool is used particularly for brass work. The turning tool is held in the block c by two set-screws d, the block being adjustable along the body of the holder. The block c has a projecting shank which passes through the body of the holder and is fastened to it by means of the nut and washer shown. This method of holding the tool is very convenient for certain classes of work, especially when different diameters are re- quired, as it is possible to have one or more blocks for holding the turning tools. A method of adjusting and holding a tangential cutter is shown at C. The cutter is set at an angle from the face of the box-tool, and is held in the body of the holder by two set- screws e and /. The tool rests on a small block /i, thus allow- ing it to be adjusted for turning different diameters, the two set-screws being used in connection with this block for adjusting. BOX-TOOLS 107 A method of holding the turning tool somewhat similar to that just described is shown at D. The tool rests on the body of a screw g instead of on a block. These two methods of adjusting the tool can only be used for certain classes of work. A method which allows of more adjustment is shown at E. The tool is adjusted and held by three set-screws, thus allow- ing it to be adjusted for various diameters, with the face of the tool held in a place parallel to the horizontal center-line. The methods shown at C, D, and E are used principally for roughing box- tools. At F is shown the method of adjusting the turning-tool holder which is usually applied to finishing box-tools. The tool is held in a block h, which is adjusted up and down on the body of "the holder by means of set-screw i\ the block is held, when in the desired position, by cap-screw/. This block has a groove in it which fits on a tongue formed on the box-tool body, thus holding the tool-holder rigidly. At G is shown a method similar to that just described, but the turning tool is held in the holder in a manner similar to that shown at C. By this means, the cutter may be set at a slight angle from the horizontal center-line, thus giving it more clearance, as is sometimes necessary, especially when cutting steel. A slight adjustment of the tool, independently of the tool-holder, is also possible. With the design shown at H and 7, a micrometer screw is used for setting the box-tool cutter to the correct diameter. This micrometer screw k has two shoulders and is screwed into the body of the holder, the body of the screw being made a good fit in the block shown in detail at /. A 4o-pitch thread is cut on this screw, so that for one revolution of the screw the turning tool is moved a distance equal to 0.025 inch. The block is held to the body of the holder in the same manner as that shown at F and G. A good method of holding two or more turning tools for roughing is shown at /, the holder being made with the desired number of projecting lugs or tool-holders m. The tool is held in a stud n, which has a square hole cut in it to receive the tool. This hole is cut at an angle with the face, so that the tool io8 TOOL EQUIPMENT is set at the desired angle. Two set-screws o are used to pre- vent the tool from turning under the pressure of the cut, and also to permit of a slight adjustment of the tool. This method of holding a turning tool is used mostly for roughing work. Box-tool Work Supports. The type of support to use and the method of applying it are governed largely by the follow- ing conditions: Shape of the stock, whether round or other- wise; character of the cut, whether taper or otherwise; na- ture of the material, whether soft or hard; number of different diameters to be turned; length of the work being turned; Machinery, N.Y. Fig. 18. Methods of Applying Box-tool Supports to the Work clearance allowable between the face of the circular form tool and the box-tool. At A in Fig. 18 is shown a box-tool support used in rough- ing box-tools. This support surrounds the work and precedes the turning tool. It is used mainly for turning down cylindrical work in which the finished diameter is to be concentric with the part which is not finished, that is, which has not had a cut taken from it. Where the work being turned projects more than five times its diameter from the chuck, and is of large diameter, it is not advisable to use a bushing support, unless the stock is reduced by the circular cut-off tool, in order to weaken it somewhat. At B is shown a support which is sometimes used for finish- BOX-TOOLS 109 ing box-tools. One objection to the design is that as it does not surround the work, a bar of larger radius than the sup- porting surface is deflected to one side, thus producing work which is not straight, but slightly tapered. The support shown at C is commonly called a U V- support," and has a two-point bearing on the work. The thrust from the tool is against both supports. As a rule, this support should not precede the cutting tool, for the reason that, if the work is not cylindrical in shape, the irregularities of the bar will be reproduced on the work that is turned. This V-support can be used for brass, steel, and similar materials, and gives satisfactory results when it does not precede the turning tool. In turning cast iron or aluminum, difficulty is sometimes encountered in producing a finished surface on the work. This is usually due to fine chips or dust becoming wedged in between the supports and the work, thus causing an abrasive action which roughens the work. It is, therefore, advisable when turning aluminum or cast iron, to use roller supports. One method of applying the roller supports is shown at D. These rollers should be hardened and ground, and it is usually preferable to lap them also, so that they are very smooth. This support is also used when turning machine steel, and is made to bear rather hard against the work, which gives it a burnished appearance. Another support which is sometimes used for cast iron is shown at E. This gives a two-point bear- ing, and allows the tool to be set radially to the work. This support, however, is not as good as the roller type. At F is shown a method of supporting the work when apply- ing two turning tools to it. This method is used principally for roughing down steel work and also when it is necessary to rough down the work from a large to a small diameter in the least possible time. As a rule, supports for box-tools should be made from high-carbon steel, left glass-hard, and given a very smooth finish, which is one of the chief requirements of a box-tool support. Holding and Adjusting Box-tool Supports. Various methods of holding and adjusting box-tool supports are shown no TOOL EQUIPMENT in Fig. 19. At A is shown a common method of holding a bushing support. The support shown at B is tongued to the holder and is adjustable in an axial direction. At C is shown one method of holding a V-support. A rectangular hole is cut in the body of the holder in which the supports fit. When in position, the supports are held by the set-screw b. This method of holding a V-support is commonly used for both roughing and finishing box-tools, when one cutting tool is H Machinery Fig. 19. Methods of Holding and Adjusting Box-tool Supports applied to the work, and sometimes when two cutting tools are used so close together that it is only necessary to support the work at one place. At D is shown a method of holding a V-support when it is necessary to apply more than one sup- port to the work, as when turning down to more than one diameter at a time. This support is held in a movable block c, which is adjusted along the body of the holder. These last two methods are principally for box-tools used for turning brass or a similar class of materials, in which the cutter is set radially to the work. At E is shown a common method of BOX-TOOLS III applying the V-support to a box-tool used for cutting steel. This method is used when the cutting tool is set tangentially. The methods shown at C, D, and E are limited in their scope, to a certain extent, owing to the fact that they cannot be used in conjunction with a circular form tool when it is necessary to have the box-tool work closer to the forming tool than the thickness of the web e. For this class of work, the design shown at F is commonly used. This support is beveled and set in a beveled slot cut in the front end of the box-tool body. The body of the holder is split and screws bind the two parts together. At G is shown a method of applying roller supports. These roller supports are held in two movable members, / and g, which, in turn, are fastened to the body of the holder by the clamping screw h. As the clamping screw h would not be sufficient to hold these roller-support holders against the pressure of the cut, they are held in the correct position by large-headed screws i, which are screwed into the body of the holder. At H is shown another method of applying roller supports. In this case, the supports are held on two sliding holders, j and k, which slide in grooves cut in the box- tool body. They are adjusted in and out to the required diameter, and are held by the clamping screws. There are numerous other methods of holding roller supports, but they are all of a somewhat similar character to those already shown. Natu- rally, there are various conditions which govern the method of applying these supports. The methods of holding supports, previously described, are those generally used in standard box-tools, and do not include those used for special conditions. Design H is preferable usually to the one shown at G. Cutting Angles for Box-tool Cutters. It is not sufficient to hold a box-tool cutter rigidly and support the work well, to obtain good results, but it is also necessary to have sufficient clearance, and the correct cutting angle on the tool. The tool must have sufficient clearance and rake, so as to remove the material with the least possible resistance and power. The manner in which the tool is applied to the work, and the ma- 112 TOOL EQUIPMENT terial on which it operates govern the cutting angle on the tool. Generally, in automatic screw machine practice, the cutter is set radially for turning brass and, when held in this way, the cutting angles are approximately as illustrated in Fig. 20. Tool A is for roughing and tool B for finishing, the cutting face of the latter being ground parallel for a short distance y equal to approximately one-fifth of the diameter being turned. For steel turning, the cutter should be set tangentially to the work as shown at C and D. The end of tool C should be ground to approximately the following angles: Cutting Angles for Machine Steel Cutting Angles for Tool Steel a =10 degrees; a = 8 degrees; 6 = 10 degrees; b = 8 degrees; c=8 to 10 degrees; c. = 8 to 10 degrees; d= 70 to 72 degrees. d=?2 to 74 degrees. The form of tool shown at C is commonly used for roughing cuts, but will, not produce an absolutely square shoulder. For finishing cuts, the tool is ground as shown at D, which produces a square shoulder. The cutting angles for tool D are as follows: Cutting Angles for Machine Steel Cutting Angles for Tool Steel e =from 10 to 12 degrees; e =from 8 to 10 degrees; / =from 15 to 1 8 degrees; / = from 8 to 10 degrees; g = from 60 to 65 degrees. g = from 70 to 74 degrees. While the cutting face on the tool shown at D is straight, it is usually advisable, especially when cutting machine steel and Norway iron, to give more "lip" to the tool, as shown by the dotted line h. The cutting edge of a radial cutter for rough- turning brass rod is set above the horizontal center line of the work, an amount equal to about 0.02 times the diameter being turned. If the stock is rough or of irregular shape, the cutter should precede the support by an amount equal to from o.oio to 0.020 inch, but, when the bar is cylindrical and has a fin- ished surface, the support for roughing cuts should precede the tool. The face of a tangent cutter should be set back a distance x (see Fig. 20 D) equal to about one-eighth the diameter being turned, for tool steel, and one-tenth the diameter, for machine HOLLOW MILLS steel. Sometimes, it is also advisable, especially when cutting machine steel, to elevate the tool from the horizontal an angle of from i to 2 degrees, to increase the clearance. Size of Steel for Box-tool Cutters. For special conditions, the tool is sometimes made of rectangular section, but ordi- J 1 t V Eig. 20. Different Methods of Applying Box-tool Cutters in Automatic Screw Machine Practice narily square stock is used. The square sections recommended for box-tool cutters are as follows: Largest diameter of work, in inches: 5 f \ f i Square section of tool, in inches: T \ \ T \ f T \ Roller Steadyrest. A simple steadyrest of the roller- support type is shown at A in Fig. 10. The roller supports a are held in slides b which are adjusted by means of screws c. The slides are then clamped in the desired position by means of the clamp bolts d. This steadyrest may be used to support the end of a bar when using exceptionally wide forming tools, when knurling, or for centering the end of the stock by insert- ing a suitable tool in the shank. Hollow Mills. For roughing cuts, especially in brass, a hollow mill gives satisfactory results. A form which is com- TOOL EQUIPMENT monly used in connection with automatic screw machine work is shown in Fig. 21, which includes the angles of the cutting edges for turning various materials. The hole in the center of the hollow mill should have a taper of from f to yV inch per foot to provide clearance. The cutting edge of a mill to be used on steel should be set about one-tenth of the diameter ahead of the center, whereas, if the mill is to be used on brass, the cutting edge should be on the center-line. Hollow mills of the inserted-blade type are also used to some extent on ./TAPER X'TOJJ"PER FOOT /FLAT Machinery Angle as Shown by Illustration Angles of Cutting Edges, in Degrees, for Different Materials Brass Rod Machine Steel Tool Steel 10 3 Fig. 21. Hollow Mill and Angles of Cutting Edges automatic screw machines, although they are more extensively employed on screw machines of the hand type. Centering and Facing Tools. When drilling holes which are less than 7% inch in diameter, it is always advisable, es- pecially when the hole passes through the work, to use a start- ing or centering tool. At A in Fig. 22 is shown a centering tool which is used for brass work, and at B, one which is used for steel and soft iron. This latter tool is similar to the or- dinary twist drill, except that the flutes are shorter. A worn- out twist drill is sometimes used for this purpose, with the CENTERING AND FACING TOOLS point ground thin, as shown at a, which reduces the pressure and allows the drill to start easier. This tool also makes a better center than would a drill with a thicker point. The included angle of the cutting edges on a centering tool should be less than the drill which is to follow. If this is not the case, the point of the drill will start- to cut before the body of the drill is properly supported; consequently, an imperfect center will be formed. If an imperfect center has been formed, the drill will run out, as shown at C. It is practically impossible for a drill to start concentric with the center of the work when a small teat, as shown, has been left by the centering tool, unless the latter has a more acute angle 90TO 100 90 TO 100 'ACE OF DRILL HOLDER Fig. 22. Centering Tools Starting the Drill Concentric than the drill to follow, when there is no difficulty (see diagram D). The included angle of the point for centering tools varies from 90 to 100 degrees; 90 degrees should be used, preferably, for brass, and 100 degrees for steel. The included angle of the point of the drill varies from 118 to 120 degrees, 118 degrees being generally used. At A in Fig. 23 is shown a common form of centering- tool holder. This tool holder has been found very successful for general conditions when the work has been gaged to length by a stop, thus obviating the" necessity of using a facing tool. It is provided with a split bushing a, or is made without the bushing, the hole for the centering tool simply passing through the body and the shank, and being of the same diameter as the centering tool. At B is shown a combination centering n6 TOOL EQUIPMENT and facing tool. This tool is used when the stop for gaging the work to length has been dispensed with, the tool b being used for facing the work to the required length. At C is shown a combination centering and facing tool with a supporting bushing c, which is held in the body of the tool by two head- less screws d. The centering tool is held in a split bushing by 1 1 1 1 1 1 Fig. 23. Centering and Facing Tools set-screw k. The turning or facing tool e is adjusted to cut the required diameter by set-screw / and headless screws g, the block h acting as a fulcrum. This holder is used when the work has been turned before centering, and it is also found con- venient for centering long and slender work. Drills and Drilling. For general work, commercial drills of the two-fluted type are used exclusively on the Brown & DRILL-HOLDERS Sharpe automatic screw machines for drilling cylindrical holes. The spiral fluted drill is used for drilling machine steel, Norway iron, etc., and also for shallow holes in brass; but, when deep holes are to be drilled in brass, a straight-fluted drill should be used in preference to a spiral drill, as it breaks up the chips, allowing them to be removed with greater ease. The shape of the cutting edge of the drill affects the shape of the chips produced and also the amount of power required [F = 4* -4 3 Fig. 24. Various Types of Drill-holders to force the drill into the work. If the included angle of the point is about 118 degrees, and if the point is ground thin, it will produce a long, curling chip, and will not require much power for drilling. When drilling, if the edges of the drill burn, it is an indication that the surface speed is too high; if the drill chips, the feed is too great; and if the drill splits at the point, that the proper clearance has not been given at the cutting edges. For shallow holes, the best results are obtained by giving a rotary motion to the work and a feeding motion to the drill, but, when drilling deep holes, the drill and the work should both be given a rotary motion. This helps to clear the chips from the hole and also allow oil to penetrate to the cutting Ii8 TOOL EQUIPMENT point of the drill. When drilling deep holes, the drill should not penetrate into the work more than i\ times the diameter of the drill before being withdrawn. For drilling deep holes in tool and machine steel, the spiral-fluted drill is generally used with good results, but, for drilling deep holes in brass, the straight-fluted drill gives better satisfaction, as it does not produce a long, curling chip, which is generally objectionable. Drill-holders. There are various types of drill-holders used in the automatic screw machine. The alignment of the turret holes with the spindle is usually very accurate and it is not necessary to have a floating holder for holding a drill. At A in Fig. 24 is shown a common form of drill-holder. It is flattened on the sides to take up as little space as possible when working in conjunction with the cross-slide tools. A plain bushing as shown at a is used. At B is shown a more expensive holder which is sometimes used for holding reamers and counterbores for operating on a piece which has previ- ously been drilled concentric. The bushing part of the holder is shown at b. At C is shown a holder somewhat similar to that shown at , but, instead of the shank and drill-holder being in one piece, a separate bushing is used. For ordinary work, the holder shown at A is recommended. High-speed Drill-holder. A high-speed drill-holder that can be used on the larger sizes of machines for increasing the speed of small drills in the turret is shown in Fig. 25. The re- volving spindle a is mounted in two bronze bearings with the driving gear b shown at B. The thrust is taken on the ball bearing c shown at C. The drill chuck d is of the spring collet type. The shank e is ground to fit the tool hole in the turret and the rear end of this shank is a reservoir for oil which lu- bricates all the bearings in the holder. Sufficient oil should be put in at the point / to completely fill the reservoir. For holding small reamers, the spindle a is especially constructed to receive a floating type of reamer -holder instead of the drill- holder shown. This holder is driven by a shaft running through the turret shaft and a small pulley belted to the overhead works. COUNTERBORING TOOLS 119 Counterboring Tools. Trouble is often experienced in using counterbores on automatic machines. This is probably due to the fact that counterbores are used which are not adapted for the work on which they operate. Generally speaking, there are several reasons for the unsuccessful work- ing of counterbores, some of which may be summed up as follows: i. Too many cutting edges, not allowing enough chip space and also not providing for sufficient lubrication. Fig. 25. High-speed Drill-holder 2. Too much cutting surface in contact with the work. 3. Insufficient clearance on the periphery of the teeth. 4. Im- proper location of the cutting edges relative to the center. 5. Improper method of holding the counterbore. 6. Improper grinding of the cutting edges. 7. Too weak a cross-section. 8. The use of a feed and speed in excess of what the tool will stand. For work in automatic machines, where the counterbore cannot be withdrawn when it plugs up with chips and seizes in the work, the tool should not have more than three cutting I2O TOOL EQUIPMENT teeth. The periphery of the teeth should be backed off eccen- trically, and the body of the counterbore should taper towards the back. The amount of taper generally varies from 0.020 to 0.040 inch per foot. The relation of the cutting edge to the center has an important bearing on the efficiency of the TAPER FROM ~ TO INCH PER FOOT 32 TO W\ OT U B FROM 5 TO 10 D FROM 10 TO 15 BACKED OFF HELICALLY Fig. 26. Three-fluted Drill Various Types of Counterbores tool. For deep counterboring, where the difference between the diameter of the teat and the body of the counterbore is great, the cutting edge should never be located ahead of the center; often, if it is located a little behind the center, better results are obtained; but this rule is only general, as the ma- terial to a considerable extent governs the location of the cutting edges. It is advisable to have the cutting edge ahead COUNTERBORING TOOLS 121 of the center, when the counterbore is to be used as a facing tool or for counterboring brass, provided it is not required to enter the work to a depth greater than its diameter. For general work, the cutting edges should be radial. Straight flutes are suitable for either brass or steel, but for steel it is better to have the teeth cut spirally, the spiral being sufficient to give a rake of from 10 to 15 degrees. If the difference be- tween the diameter of the pilot and the body of the counter- bore is not very great, and if the counterbore must extend into the work to a depth greater than its diameter, the cutting edge should be back of the center, that is, to the rear of the radial line parallel to the cutting face. When the counter- bore has to remove considerable material or enter the work to a depth greater than its diameter, it is generally advisable to rough out the hole to the diameter of the body of the coun- terbore with a three-fluted drill, such as shown at A, Fig. 26. Then the counterbore is used only for squaring up the shoulder at the bottom of the hole. This method is especially advisable when counterboring machine or tool steel. At B is shown a counterbore which can sometimes be used to advantage on brass work, but which is not recommended for steel. At C is shown another counterbore for brass work, which has three cutting edges, and at D is shown a counter- bore for steel work, having its teeth cut spirally. Teeth cut on a spiral which will produce a rake angle of from 10 to 15 degrees are generally found suitable for machine or tool steel. Counterbores of the type shown at C and D should have in- serted leaders or teats to facilitate resharpening. At E is shown a counterbore which is recommended for work having complicated shapes, or requiring to have two or more di- ameters finished with the same tool. This tool is backed off helically as shown, thus allowing it to be ground and still retain its initial shape and size. The counterbores described are for making pieces which permit using a pilot on the counterbore. The ordinary method used in producing holes which bottom is to use flat drills and combination counterbores and facing tools. 122 TOOL EQUIPMENT Flat Drills and Combination Counterbores. At A in Fig. 27 is shown a flat drill which is used for roughing out a hole having one diameter, and at B is shown the counterbore or facing tool which is used for squaring it up. The cutting edge a on the tool should be set about one-tenth times the diameter Machinery.N.Y. Fig. 27. Flat Drills and Combination Counterbores ahead of the center, and the thickness of the blade b should be about one-eighth of the diameter. At C is shown a flat drill or counterbore for producing a hole having two diameters, and at D is shown the combination counterbore and facing tool for squaring it up. This counterbore is adjustable, the part a being adjusted with relation to part b by means of the headless screw c } thus governing the distance between the COUNTERBORING TOOLS 123 shoulders, the headless screw d being used to prevent the part a from rotating. These counterbores can be used for either brass or steel work, but for steel work it is preferable to use a spiral-fluted drill for roughing out the hole, instead of a flat drill, as the material can be removed with greater ease and rapidity. Holders for Counterbores. For counterbores having leaders or pilots, a rigid holder should not be used, as the Fig. 28. Method of Holding Counterbores for Various Conditions leader will follow the hole previously drilled or reamed, and if the counterbore is not allowed to float, it will produce poor work, and a broken tool will sometimes be the result. At A in Fig. 28 is shown a floating holder which will be found very serviceable. The sleeve or shank a is made to fit the turret and is bored out from ^V to yV inch larger in diameter than the shank of the holder b. The holder b is kept from turning by the driving pin c, which is made a driving fit in the part b and a loose fit in the part a. The hole in the part a should be about sV inch in diameter larger than the pin c. The two headless screws d are used for adjusting the counterbore so that it will enter easily into the drilled hole. They also help to keep the holder b from turning. It is good practice, when 124 TOOL EQUIPMENT possible, to chamfer the hole so that the leader will enter easily. The counterbore is held by the split bushing e and set-screw/. If this holder is properly made and set it will be found to give good results for general work. Fig. 29. Adjustable Counterboring, Boring and Recessing Toolholders At B is shown a holder for holding the flat counterbore shown. The holder is made adjustable so that the tool can be set concentric with the center of the work. After adjusting, the part a is held tightly against the part b by the cap-screws c. The counterbore is held in the part a by set-screw d. This REAMERS 125 holder is also found very serviceable for holding a counter- bore when the hole to be counterbored penetrates into the work to a distance greater than its diameter and a chucking drill has been used to rough it out. A counterbore holder of the adjustable type is shown at A in Fig. 29. The front holder or plate a is bolted firmly to the shank b, and is adjusted by means of four set-screws c, only two of which are shown. This holder is made adjustable in order to set the cutting tool perfectly concentric with the hole in the work. Adjustable Tool-holders for Boring and Recessing Tools. - The tool-holder shown at B, Fig. 29, is used for a boring tool. The front part of this tool-holder is adjustable by means of two set-screws d, which work through the shank of the clamping bolt e and in this way secure the desired adjustment to set the boring tool concentric or to the correct diameter. The recessing tool shown at C has a shank /, to which is f ul- crumed a holder g on a stud h. This tool is operated by means of a cam i held in an arm j that is clamped to the cross-slide of the machine. Cam i comes in contact with the pin k on the holder and operates it after the tool has advanced into the hole in the work. A stud in the sliding part of this holder is spring-controlled and contacts with the screw k, which acts as a stop for setting the cutting tool in a concentric position for entering the hole in the work. Reamers for Screw Machine Work. When reaming holes in automatic screw machines, it is advisable not to leave any more material to be removed by the reamer than is absolutely necessary. For general work, the following allowances will give good results for reamers ranging in diameter from f to f inch. For reamers over f inch in diameter, a drill $-% inch less in diameter is generally used; this would leave from 0.012 to 0.015 inch to remove, as the drill will cut slightly larger than its nominal size. Diameter of reamer, in inches i & i T\ f Diameter of hole before reaming 0.120 0.182 0.242 0.302 0.368 Reamers are generally made slightly tapering towards the 126 TOOL EQUIPMENT back; a taper varying from 0.002 to 0.005 mc ^ P er foot is generally used, and a less taper should be used for brass than steel, as brass work, especially thin tubing, contracts and expands more readily than steel, so that, if a perfect hole is desired, the reamer should be tapered but slightly. For ream- ing machine steel, a rose reamer is generally used, as it has been found satisfactory for producing straight and perfect ADJUST TO BRING REAMER CONCENTRIC WITH HOLE IN WORK Fig. 30. Methods of Holding Reamers holes. This reamer tapers towards the back and is not re- lieved on the periphery of the cutting edges, the end of the reamer only being backed off. The cutting edges of reamers are generally cut on the center (radial) for steel, but, for brass work, they are sometimes cut slightly ahead of the center, which produces a scraping action, and makes a smooth cut. For brass, the cutting edges of the reamer should be parallel REAMERS I2 7 with the axis, but for machine steel the reamer gives better results when the flutes are helical, making about one turn in 12 inches. For reaming tapered holes, a reamer having ser- rated flutes gives the best results, and, when the taper is steep (included angle greater than 30 degrees), the finishing reamer should be preceded by a stepped counterbore. Reamer Holders. The method of holding a reamer when applying it to the work governs to a considerable extent the quality of the hole produced. When reaming a deep hole, if the reamer is held rigidly, it will nearly always produce a Fig 31. Swing Tool used for External Cutting hole which will be tapered and large in diameter. At A in Fig. 30 is shown a floating holder which is sometimes used. This holder is cheaply made, but is not recommended for automatic screw machine work, although it can sometimes be used to advantage on the hand screw machine. One of the disadvantages of this reamer holder is that the reamer drops down as shown at a, if much clearance is allowed be- tween the diameter of the reamer shank and the diameter of the hole, thus preventing the reamer from entering easily into the work, which generally results in a broken reamer. At B is shown a more efficient holder, especially for deep- hole reaming. The reamer is guided at the rear by a cone- pointed screw b, and is kept from rotating and is guided at the same time by the two cone-pointed screws c. By means of these screws, the reamer can be set so that it will enter the 128 TOOL EQUIPMENT drilled hole easily, and at the same time be allowed to adjust itself to correspond to the eccentricity of the hole in the work. The small hole d is drilled through the shank of the reamer, allowing the cone-pointed screws to enter. This holder will be found very satisfactory for holding reamers when it is not necessary to remove an excessive amount of material. At C is shown a floating holder which is used for reaming shallow holes. The reamer is held rigidly by a split bushing and set-screw /. The reamer is set concentric with the hole \ Machinery, N. Y. Fig. 32. Raising Block used for Operating Swing Tools on Brown & Sharpe Machines in the work by loosening the cap-screws g and then locating it in the hole by the bevel or rounded corners on the end of the reamer. Swing Tools for Turning. Swing tools are so named be- cause the cutting tool is held in a swinging holder as shown in Fig. 31, which illustrates one of the designs used on Brown & Sharpe automatic screw machines. This tool is held in the turret of the machine and the swinging member is operated by a raising block equipped with either an adjustable or fixed SWING TOOLS 129 guide plate, which comes into contact with the screw seen at the end of the swinging arm. This raising block (Fig. 32) is held under the toolpost of the front cross-slide and it has a guide plate E that can be set at an angle with the spindle for generating taper surfaces. The exact shape of this plate de- pends upon the nature of the operation and the shape required on the work. The arm D which carries the guide plate can be adjusted in and out and is held in position by screws d. The screw / serves to adjust guide plate E which is locked in position by screw g. The swing tool is used for straight, taper, or irregular Fig. 33. Shaving Tool used on the "Acme" Multiple-spindle Automatic Screw Machine, and Examples of Work turning, where box-tools or circular forming tools are not applicable, as when turning long, slender work of irregular shape or when turning behind shoulders. The work is often roughed out with this tool and finished with a shaving tool. The swing tool is also used for cutting-off finished parts when both cross-slide tools are used for forming operations. The shank is arranged to hold a back-rest for supporting small flexible work. This back-rest or support is inserted in the hole in the shank of the tool and the V-shaped supports are usually set in advance of the tool. Recessing Swing Tools. When it is necessary to chamfer inside of a hole, or to enlarge the central part of a hole so that 130 TOOL EQUIPMENT a bearing surface will be left at the ends only, this may be done on the automatic screw machine by the use of a swing tool. The design used on the Brown & Sharpe machine for internal chamfering and recessing is similar in principle to the one shown in Fig. 3 1 , which is intended for .external work, except that the swinging arm is arranged for holding the shank of boring or recessing tools. The guide plate which controls the movement of the swinging arm is shaped to suit the work. A recessing or chamfering operation should always precede a reaming operation, so that all burrs formed by the recessing tool will be removed by the reamer. OOL IS ASSEMBLED FOR SECOND POSITION TO ASSEMBLE FOR THIRD POSITION TURN BASE UPSIDE DOWN Machinery Fig. 34. Shaving Tool-holder with Roller Support Shaving Tools for Screw Machines. When forming work of irregular shape or contour, in the automatic screw ma- chine, it is common practice to use a shaving tool which oper- ates tangentially to the work and takes a light finishing cut. Shaving tools are used to follow circular forming tools for producing a smooth, accurately finished surface, and they are also used to completely form the work without any previous roughing operation. The amount removed by the shaving tool varies somewhat with the size of the work. When taking shaving cuts on small parts, from 0.003 to 0.005 inch might be removed, while for larger parts the allowance is often greater. A design of shaving tool which is used on the Acme SHAVING TOOLS 131 multiple-spindle automatic is shown in Fig. 33. This tool is used in the second or third side positions and removes 0.002 or 0.003 inch of stock left by the forming tool. The blades H and G of this tool are made in pairs. One blade is used as a rest and does no cutting, whereas the other one has a cutting edge. The holder H is adjusted by means of a screw for lo- cating the two parts H and G the required distance apart. The supporting blade is slightly longer than the shaving tool, so that it comes into contact with the work slightly in advance of the tool. The support and the shaving blade are not exactly parallel, the blade being inclined one-half degree to provide a slight clearance. Another design of Acme shaving tool which has proved very effective on wide and difficult cuts is shown in Fig. 34. This tool is similar in its general construction to the design shown in Fig. 33, except that it is equipped with a roller type of support. The cutting edge of the shaving tool should be exactly in line with the axis of the supporting roller. The shaving blades and supports are made from Jessop's tool steel. For cutting brass, Jessop's high-speed steel has been found to give better results. When the support and shaving tool have an irregular form, the surfaces should be smoothly finished before the tool is hardened and then all the surfaces are lapped by the work running between them. The tools illustrated in Figs. 33 and 34 are only recommended for taking light finishing cuts. The allowance for shaving depends to some extent upon the nature of the work and the kind of tools used prior to the shaving operation. The allow- ances for various diameters of stock should be about as follows : Amount to Remove Diameter in Inches in Inches iV to i 0.0015 ^ to \ O.OOlS to | 0.0020 f to f 0.0023 | tO 1 1 0.0026 1^ to Ij O.OO28 i j to 1 1 0.0030 l| tO 2\ 0.0032 132 TOOL EQUIPMENT Fig. 35 shows a type of shaving tool and tool-holder which does not have a support for the work. This type of tool is employed when the work is so rigid that a support is unneces- sary. When a shaving tool is not preceded by a forming tool, and if the work is long in proportion to its diameter, it is advisable to grind the end of the shaving tools so that a shear- ing cut will be taken in each way from the heaviest part of the cut, in order to remove the material more easily. In other words, the end of the tool is beveled each way from the part that will take the heaviest cut, so that a point is formed which first comes into contact with the work. The angles for the cutting point of the tool, as indicated by the detailed views to the right in Fig. 35, should be about as follows: For brass Machinery Fig. 35. Shaving Tool and Holder for Long Work rods, A equals 20 degrees; for machine steel, 30 degrees; for tool steel, 40 degrees. For brass rods, B equals 30 degrees; for machine steel, 40 degrees; for tool steel, 50 degrees. For brass rods, C equals 10 degrees; for machine steel, 15 degrees; for tool steel, 15 degrees. Of course, these angles may vary more or less without appreciably affecting the action of the tool. Dies for Screw Machine Work. The common form of spring screw threading die equipped with a clamping ring for making slight diameter adjustments has been used exten- sively on automatic screw machines. For ordinary use, the adjustable spring dies are often recommended, because they can readily be ground and adjusted for size and are considered economical. There are two methods of making the spring screw threading dies. One is to use a hob tap which is from DIES FOR SCREW MACHINES 133 0.005 to 0.015 inch larger than the standard size of the thread in order to provide clearance, and then close in the ends of the dies by the adjusting ring or clamp. A preferable method is to tap out the die from the rear with a taper hob tap, leaving the front end of the die about 0.002 inch oversize. The hob tap should have a taper varying from T \ to J inch per foot. The round split dies or " button dies," as they are commonly called, are also extensively used. While a round or button die cannot be resharpened readily like a spring die, its initial cost is considerably less, so that it can be discarded when dull. The button dies, owing to their shape, are not distorted as much as the spring screw dies when hardening, and they can be held more rigidly in the holder. The cutting edges on spring screw dies should be radial for brass and about one-tenth the di- ameter ahead of the center for Norway iron, machine steel, etc. The cutting edges of button dies can be ahead of the center about one-tenth of the diameter. Holders for Threading Dies. There are many different designs of die-holders for use on automatic screw machines. Many of these die-holders are applicable to different makes of machines, while others are designed more especially for a given type. The Brown & Sharpe Mfg. Co. makes two general styles of die- and tap-holders, which are known as the non- releasing type and the releasing type. The non-releasing type is so arranged that the die is free to move axially a limited distance. The releasing type is so designed that, when the turret stops feeding forward, a slight additional forward move- ment on the part of the die causes the driving members of the die-holder to disengage so that the die spins around with the work until the spindle reverses; the die then starts to rotate backwards with the spindle and work, but this backward motion is automatically stopped by the die-holder, so that, as the die is held stationary, it is unscrewed as the spindle continues to revolve. The non-releasing type of tap- and die-holder is used on a very large percentage of the work done on Brown & Sharpe automatic screw machines; in fact, the releasing type is gen- 134 TOOL EQUIPMENT erally used in order to eliminate the use of a threading lobe that is too pointed. For instance, some lobes which are de- veloped for the non-releasing type of holder have a thin sharp point, but by using the releasing type a certain amount of dwell can be allowed at the top of the lobe which is some- times desirable simply for strengthening the lobe. The non- releasing type will enable threads to be cut to as uniform a distance from the shoulder as the releasing type. Releasing Die-holder. A releasing type of die-holder for button dies is shown in Fig. 36. When the die-holder or spindle a draws out from the body 6, the driving pins c Fig. 36. Releasing Die-holder are also withdrawn, so that the ends of these pins are flush or even with the plate m. When the machine spindle is re- versed, the spindle a revolves with the work and the ball e is thrown out of the deep part of the pocket in which it nor- mally rests, as shown at B, into the position shown at C. This outward movement of the ball locks the die-holder, thus allowing the die to be backed off of the work as the spindle continues to revolve in a reverse direction. When the ball e is placed in the pocket /, the die-holder may be used for cut- DIES FOR SCREW MACHINES 135 ting a right-hand thread, whereas, when the ball is in pocket g, the die-holder may be used for left-hand threads. Another design of releasing die-holder, which is a product of the Cleveland Automatic Machine Co., is shown in Fig. 37. This is known as the " Silent" die-holder because it is so de- signed that the driving members do not strike against each other after disengagement at the forward end of the turret travel. The holder has a sleeve which is gripped in the turret and a stem which fits inside of this sleeve. In the driving mechanism, there are two pieces A, of the same shape, which are held in position by screws B. The driving pins E, which Machinery Fig. 37. Sectional View of Cleveland Releasing Die-holder come in contact with parts A when threading, are plain pins having heads which are somewhat larger than the body and flattened on the sides. Parts A and E are held in their cor- rect positions by a weak, piano-wire coiled spring 7, which is just strong enough to keep the two large members of the die- holder together. After the turret has advanced to the end of its travel, and the driving points A and E are disengaged, the small springs G swing parts A , which are pivoted on screws B, back so that their angular ends are nearly in a straight posi- tion, or in a plane at right angles to the axis of the holder. By this movement, the ends of driving pins E and parts A clear one another, regardless of how long the turret remains in the advanced position, thereby eliminating any pounding and damaging of the parts which carry the die or tap forward. The pieces C have no duty to perform when the die-holder is on the threading operation, but, when the spindle reverses, TOOL EQUIPMENT parts C drop into the slots H and hold the die-holder rigid while the turret recedes. These pieces are constantly held in their position, whether in the slots or otherwise, by springs K. The slots H, into which pieces C fit, are milled on a fairly large diameter, and this part of the mechanism is designed to last indefinitely. When changing the die-holder for cutting left-hand threads, the screws B are removed and the parts A are turned over so that the straight driving side is in the opposite direction in both cases. The screws / and F are also removed so that Machinery Fig. 38. Telescopic or Combination Die- and Tap-holder pieces C can be turned around to reverse the position of the driving sides. The small screws F fit into slots E and simply hold the pieces C in their proper position. Telescopic Die- and Tap-holder. A telescopic or combi- nation die- and tap-holder, designed for use on the "Acme automatics," is shown in Fig. 38. With this die-holder, two threading operations may be completed at the same time; that is, two dies of different diameters can be used, or a die and tap as required, the tap being held in the rear part of the holder. This special tool consists of a shank A in which a button die B is held by the cone-pointed screw shown. When a tap is to be used, the button die is replaced by a bushing for holding DIES FOR SCREW MACHINES the tap. The front part C of the holder, which carries the lead- ing button die, is a sliding fit on a key in member A. To en- able the cutting of two threads of different pitch, the front member C is restrained by two coil springs D, which allow it to lead out in advance of the other part of the die-holder, and as the shank A is held in the die spindle, which also is spring- controlled as regards the leading out of the spindle, it is evi- dent that the lead of the two members is controlled by the pitch of the thread in the dies. A stop-screw E is provided for locating the holder C in its backward position, so that the two Fig. 39. Self -opening Die Attachment on Acme Machines dies will always be in the same relation to each other when starting to cut. Clearance cuts are provided in both members to facilitate the removal of chips. Self-opening Die Operating Attachment. Fig. 39 shows a self-opening die applied to an Acme multiple-spindle auto- matic. This type of die is recommended for cutting long threads of accurate pitch. The working mechanism of the die-holder is enclosed within the body which carries the cam-operating blocks. The chasers have closing and adjusting cams milled on their outer ends that bear against the cam-operating blocks. The adjustment of the chasers is controlled by a fine-pitch screw, the amount of adjustment being indicated by microme- 138 TOOL EQUIPMENT ter graduations. This die is operated by an arm / which en- gages a groove in the outer body of the die-holder and shifts it axially relative to the inner member which holds the chasers, thus causing the latter to move inward or outward, accord- ing to the direction of movement. Fig. 39 shows the attach- ment in the position it occupies when the die is to be opened after cutting the thread. The die is rotated by the threading spindle in the usual manner. A shoe 7, similar in shape to shoe 7, is connected to the rear end of the threading spindle, and is held on a spindle K which is retained in the bracket L attached to the end-working tool-slide. In operation, as the end- working tool-slide advances the chasers in the die come in contact with the work and start to cut the thread. When the pitch of the thread is greater than the forward advance of the tool-slide, the spring M is com- pressed as the threading spindle is withdrawn; this action carries forward the two arms 7 and / at the same speed. When the die chasers have advanced on the work to the required distance, the sleeve N comes into contact with adjustable stop held in bracket P. This bracket is provided with an adjusting screw and is attached to the casing enclosing the cylinder. As the die continues to cut, the outer body A of the die-holder is held back by arm 7 and the chasers advance until they come out of contact with the cam-operating blocks, allowing the head to spring open; then, as the end- working tool-slide moves back, the lever Q strikes the rear dog R and pulls the chaser head back into the casing and closes the die, ready for cutting the next thread. Taps for Automatic Screw Machines. When tapping holes in the automatic screw machine, there is tendency for the chips to clog back of the cutting edges, thus subjecting the tap to excessive torsional strains at the moment its movement is reversed relative to the work for backing it out of the hole. In order to prevent the breaking of taps, the flutes should be relatively large in order to provide ample space for the chips, the lands being made just strong enough to resist the cutting pressure. The flutes may be milled with an 85-degree double- TAPS FOR SCREW MACHINES 139 angle cutter having an inclination of 55 degrees on one side and 30 degrees on the other. Screw machine taps in all sizes smaller than i inch in diameter should have four flutes, and for larger diameters, six flutes. The width of the lands for different diameters should be about as follows: Diameter, J inch, land width, y^ inch; diameter, f inch, land width, -/2 inch; diameter, \ inch, land width, f inch; diameter, J inch, land width, A inch; diameter, i inch, land width, J inch. Ordinarily the thread is relieved only on the top of the chamfered end. If the straight part or body of the tap is relieved, the chips are liable to wedge in between the tops of the threads on the lands of the tap and the thread in the hole, ,GRIND GROOVE AFTER HARDENING Fig. 40. A Tap Suitable for Norway Iron and Machine Steel which might result in either breaking the tap, owing to the excessive torsional strain, or in damaging the thread in the hole. The chamfered end of screw machine taps is usually very short, because the tap, in most cases, is required to cut threads close to the bottom of a hole. The amount of chamfer required on taps for various pitches is as follows: From 14 to 24 threads 2\ threads. From 26 to 32 threads 3 threads. From 36 to 48 threads 4 threads. From 56 to 80 threads 5 threads. In regard to the diameter of the shank, manufacturers making a specialty of these taps recommend that the shank diameter be made to correspond with the outside diameter of a spring screw die for cutting the same size of thread as the tap is intended for, so that the same holder may be used for both the tap and the die. If a tap is to be used for cutting triple 140 TOOL EQUIPMENT or quadruple threads, the flutes should be helical so that they will be at right angles to the teeth and form square cutting edges. While an ordinary machine tap may be used for tapping brass in the screw machine, it does not give satisfactory results when tapping such material as Norway iron, machine steel, etc. The tap shown in Fig. 40 has proved satisfactory for materials of the kind mentioned. The end of this tap is ground at an angle of about 55 degrees and is slightly cupped out at the center and backed off as indicated in the end view. The tap should be slightly tapered towards the back for clearance. A groove is ground the entire length of the threaded part after the tap has been hardened. This groove allows the oil to reach the point of the tap and also provides clearance for the chips. When made from Stubb's imported drill rod and carefully hardened, this tap can be worked at a cutting speed of from 35 to 40 feet per minute. Some taps intended especially for threading copper have an odd number of flutes which are cut spirally. The Echols patent tap, made by the Pratt & Whitney Co., has proved effective for cutting clean threads in copper and tough ma- terials, such as gun-metal, etc. This style of tap has an odd number of flutes and each alternate tooth is omitted, the arrangement being such that each tooth is followed by a blank space on the following land, which, in turn, is followed by a tooth on the next successive land. Knurling Tools. The tools used for knurling the edges of screw-heads, etc., in automatic screw machines, are held either on the cross-slide or in the turret, their position de- pending upon the location of the surface to be knurled or the arrangement of the other tool equipment. There are three general methods of presenting knurls to the work. When the knurling tool is attached to the cross-slide, it may be forced against the work either radially or tangentially and, when the knurling tool is held in the turret, two knurls move along the surface of the work on opposite sides and parallel with its axis. KNURLING TOOLS 141 A cross-slide type of knurl-holder is shown in Fig. 41. The knurl operates on the top side of the work as the cross-slide moves laterally; as this movement is continued, the circular cutting-off tool back of the knurl severs the finished part, and then the cross-slide and knurl return to the starting posi- tion. The knurl-holder is held to the outer face A of the rear cross-slide tool-holder, by means of screw B, which also holds the circular cutting-off tool. The distance C from the knurl to the cutting-off tool may be changed in accordance with Fig. 41. Rear Cross-slide Knurl-holder the location of the knurled surface relative to the end of the work. This design of knurl-holder can only be used on a tool- holder which carries the cutting-off tool, because the finished piece must be severed from the bar before the knurl can return to the starting position. Universal Cross-slide Knurling Tool. Another design of cross-slide knurling tool is shown in Fig. 42. This design is more complicated and expensive than the one previously described, but it can be appli-ed to a wider range of work and may be used in conjunction with either circular forming or cutting-off tools on the front cross-slide. The knurl is held in arm F, which is pivoted to lever C, and this lever is mounted on a pin upon which it has a certain amount of adjustment for locating the knurl relative to the work in a lengthwise 142 TOOL EQUIPMENT direction. The nuts M on the stud shown serve to hold arm C and also provide adjustment for raising or lowering arm F in accordance with the diameter of the part to be knurled. As the knurl passes over the stock on the outward movement of the cross-slide, the nuts H bear against the face B of the L K Fig. 42. Universal Cross-slide Knurl-holder lug shown, and spring K is compressed; when the knurl has cleared the work and the pressure on the spring is released, nut J is forced against the opposite side of the lug and arm F swings outward, so that the knurl clears the work on the return movement. Turret Knurling Tools. Knurling tools which are held in the turret and move parallel with the work usually have KNURLING TOOLS 143 two knurls which engage the work on opposite sides. The design that is used on the Brown & Sharpe machines is shown in Fig. 43. The knurls have teeth which are parallel to the axis so that they may by used for either straight or cross- knurling. Each knurl-holder A may be set to the different angular position required, by means of the graduations on the lugs B in which the knurl-holders are inserted. These lugs are clamped by nuts C and are adjustable in the main holder F for varying' the distance between the knurls, in accordance Fig. 43. Brown & Sharpe Adjustable Turret Knurl-holder with the diameter of the surface to be knurled. This adjust- ment is effected by screws D which are locked by screws E. Opening and Closing Type of Knurl-holder. It is some- times necessary to use a turret tool for knurling a diameter which is either of the same size or smaller than a preceding part of the work. For knurling operations of this kind, a special knurl-holder is required which is so designed that the knurls will move inward to the working position at a prede- termined point and then open automatically after the required length has been knurled. Double Knurl-holder for Cross-slides. The double ad- justable knurl-holder shown in Fig. 44 was designed primarily for use on the Acme multiple-spindle machines. It is usually 144 TOOL EQUIPMENT held on a top working tool-slide. The shank A is slotted at the end to receive a swinging member B which is pivoted on screw C. The lower knurl is retained in holder B and the upper knurl in an adjustable holder D, which is held in position by cap-screw E which is backed up by screw F. The movement of part B is controlled by the stop-screw G against which the holder is held by a bevel pin H and coil spring /. This con- struction gives a certain amount of flexibility, thus making it unnecessary to set the holder accurately relative to the work, as it is self-adjusting. The Teeth of Knurls. The teeth of knurls may be either Machinery Fig. 44. Double Knurl-holder of the Adjustable Type for Use on Top- or Side-working Tool-slides straight or parallel with the axis, or they may be at an angle with the axis. Knurls having straight teeth are presented to the work so that these teeth are parallel with the axis of the work when straight knurling, similar to the milled edge of a coin, is desired. By applying two knurls of this type to opposite sides of the work and inclining them to the axis of the work, a cross or diamond knurling is obtained. A similar form of knurling may also be obtained by using a pair of knurls which have right- and left-hand helical teeth and mount- ing the knurls in their holders so that their axes are parallel with the axis of the work. Knurls also differ in regard to their form, some being cylindrical for operating upon plain cylin- KNURLING TOOLS 145 drical surfaces, whereas others are made concave to conform to the convex head of a screw or other part that requires knurling. Straight Knurls. Straight knurls or those having teeth which are parallel with the axis are generally cut in the milling machine by the use of a cutter of the desired angle. It is im- portant to select a suitable angle for the teeth for knurling different materials. A " blunt knurl" will work better on soft materials than one with teeth of a more acute angle. The following included angles for the teeth have been found satis- factory for the materials specified: Brass and hard copper 90 degrees. Gun screw iron 80 degrees. Norway iron and machine steel 70 degrees. Drill rod and tool steel 60 degrees. When laying out a set of cams for knurling operations, it is necessary to know the depth of the tooth in the knurl. If d = depth of tooth in knurl; p = circular pitch of knurl; a included tooth angle of knurl; then, for all practical pur- poses, the depth may be calculated as follows: When, a = gp degrees, d = -, a = 80 degrees, d = - x tan 50 degrees, 2 a = 70 degrees, d = - x tan 55 degrees, 2 a = 60 degrees, d = - x tan 60 degrees. 2 Concave Knurls. The radius of a concave knurl should not be the same as the radius of the piece to be knurled. If the knurl and the work are the same radius, the material compressed by the knurl will be forced down on the shoulder D and spoil the appearance, of the work. A design of concave knurl is shown in Fig. 45, and all the important dimensions are designated by letters. To find these dimensions, the pitch of the knurl required must be known, and also, approximately, 146 TOOL EQUIPMENT the throat diameter B. This diameter must suit the knurl- holder used, and be such that the circumference contains an even number of teeth with the required pitch. When these dimensions have been decided upon, all the other unknown factors can be found by the following formula : Let R = radius of piece to be knurled; r = radius of concave part of knurl; C = radius of cutter or hob for cutting the teeth in the knurl; B = diameter over concave part of knurl (throat diameter); A = outside diameter of knurl; d = depth of tooth in knurl; P = pitch of knurl (number of teeth per inch circumference) ; p = circular pitch of knurl; then, r = R + \&\ C = r + d', A = B + 2r (3 d + o.oio inch). As the depth of the tooth is usually very slight, the throat diameter B will be accurate enough for all practical purposes for calculating the pitch, and it Fig. 45. Concave Knurl j s not nec essary to take into consideration the pitch circle. For example, assume that the pitch of a knurl is 32, that the throat diameter B is 0.5561 inch, that the radius R of the piece to be knurled is JQ inch, and that the angle of the teeth is 90 degrees; find the dimen- sions of the knurl. Using the notation given: />=- = = 0.03125 inch; d = 0.0156 inch; i . 0.0156 Y = 0.0703 inch; C = 0.0703 + 0.0156 = 0.0859 inch; A = 0.5561 + 0.1406 - (0.0468 + o.oio) = 0.6399 inch. Spiral Knurls. When a knurl has spiral or helical teeth, the number of teeth around the circumference may be deter- mined as follows: Divide the normal pitch of the teeth or the shortest distance between adjacent rows of teeth by the cosine of the angle between the teeth and axis of the knurl, KNURLING TOOLS 147 thus obtaining the pitch of the teeth as measured circum- ferentially; the circumference of the knurl is then divided by this circumferential pitch to obtain the number of teeth in the knurl. To illustrate, if the normal circular pitch is 0.0455 inch, and if the angle between the teeth and the axis of the knurl equals 30 degrees, the circumferential pitch will equal 0.0455 ~=~ cos 3 degrees = 0.0525. The circumference divided by 0.0525 inch will equal the number of teeth around the circumference of the knurl. To find the lead of the helix or spiral, multiply the circum- ference of the knurl by the cotangent of the angle between the axis of the knurl and the teeth. If the circumference equals 2.362 inches, and the circular pitch is 0.0525 inch/ the number of teeth equals 2.362-7- 0.0525 = 45 teeth. If the angle be- tween the teeth and the axis of the knurl is 30 degrees, the lead of the tooth groove or spiral equals 2.362 X cot 30 degrees =4.09 inches, which represents the lead for which the milling machine would be geared when cutting the knurl teeth. CHAPTER V ADJUSTING OR SETTING-UP AUTOMATIC SCREW MACHINES THE automatic screw machine, like automatic machine tools in general, requires first a set of cutting tools that is suitable for the particular work to be produced and, in addition, a certain amount of adjustment, so that the movements of the different tools will occur in the required order or sequence. As the tool movements are ordinarily controlled by cams, setting-up or adjusting a screw machine involves setting the cams as well as the tools and whatever additional parts of the machine must operate in accordance with the nature of the work. On some automatic screw machines, the cams are previously laid out and milled to the exact contour or shape necessary for moving the tools the required amount and at a suitable rate of feed; these cams, which are special for each job, are then placed on the machine in such positions that the tools which they control act at the right time, as determined by the successive order of the operations. Other types of screw machines are so designed that special cams for each job are not needed, because the machine can be adjusted for varying the feeding movements and the time at which the different tools operate. The following general information on screw machine adjustment applies to several well-known designs and indicates what changes are necessary for adapting these machines to the production of different parts. Setting-up the Brown & Sharpe Machine. The cams which control the movements of the Brown & Sharpe machine are made special for each job, and the laying out of these cams is often referred to as " camming the machine." The outline of each cam is plotted on paper in advance, and this work can be facilitated by the application of a cam templet for lay- 148 ADJUSTMENT OF BROWN & SHARPE MACHINE 149 ing out the rise and drop on the cam lobes for various speeds. In connection with this work, it is necessary to consider the speed at which the spindle is to be operated; the best method of producing the piece; and the feeds for the various opera- tions. In order to avoid confusion, the actual methods of designing cams have been treated separately in Chapter VII. After the machine is equipped with the proper cams for operating the turret-slide and the cross-slides, setting-up the machine is a comparatively simple operation. The selection of the right feeds and speeds for the work is done in advance in connection with the laying out of the cams. In addition to making the adjustments common to hand-operated machines, it is simply necessary to put on the three cams which control the movements of the two cross-slides and the turret-slide, respectively, select the specified change-gears, and set the adjustable dogs which control the time of indexing, feeding of stock, etc., to trip at the proper time. The cams are defi- nitely located by pins. If the record of speeds, change-gears used, and name of the part for which the cams were designed, are stamped upon the side of one of the cams, it is an easy matter to duplicate the work for which the cams were designed, at any future time, by simply equipping the machine with the same cams and gears previously used. When arranging and adjusting the tools, the most simple tools should, generally, be set first. As a rule, these are the circular form and cut-off tools which are held on the cross- .slides. Before any of the tools are set, however, the collet and feed finger should be changed for the size of work required, the proper change-gears put on, and the driving belt placed on the required step. After the feed finger and spring collet have been put in place, the stock is inserted and pushed out far enough so that it can be faced off with the circular cut-off tool. Setting Circular Form and Cut-off Tools. The cut-off tool is then clamped to the toolpost and set with its cutting edge as close as possible to the height of the center of the work. The spindle is rotated and the end of the stock faced off, SETTING-UP SCREW MACHINES using lever K 2 , Fig. i, to operate the cross-side. The illus- tration shows an operator setting the cutting edge of a circu- lar form tool to the height of the center of the work by means of the adjusting nut L%. Care should be taken in setting the circular form and cut-off tools, so that they will form the work parallel and cut it off with a square face. This is accom- plished by means of the adjusting screws a in the rear of the toolpost, which can be adjusted when nut K$ is slackened slightly. Fig. 1. Operator setting a Circular Form Tool In setting the tool on the front cross-slide, the cutting edge should never be below the center of the work, but should be set preferably above or at the height of the center. The cutting edge of the tool on the rear cross-slide should be set just the reverse in reference to the center of the work, when the latter is running forward. When the work is running backward, the position of the cutting edges of the tools on the front and rear cross-slide should be reversed from that for the forward ADJUSTMENT OF BROWN & SHARPE MACHINE 151 rotation of the work. If the cutting edges of the circular tools are not set in the positions described, the work, when rotat- ing, has a tendency to pull them around, thus increasing the diameter of the work, and causing chattering. When the circular form, tool is used for finishing the work to an exact diameter, the set-screw C 3 should always be set so that it will come in contact with the stop Z} 3 , when the work is turned to the desired diameter. In setting this stop, it should be so adjusted that it will put a slight strain on the cross- Mathinerj/ Fig. 2. Simple Method for Setting a Stock Stop slide operating lever. The resulting action keeps the roll in close contact with the cam, and thus assures the parts formed being of the same diameter. When the circular form tool wears slightly, the set-screw C$ can be adjusted back a slight amount, and the strain which has been set up in the lever will allow the tool to turn the work to the desired diameter. The cross-slide is adjusted back and forth to bring the cross- slide tools in contact with the work by means of split nut A, which is locked by means of a screw. Gib Q 5 should be adjusted so that there will be no unnecessary side play of the cross- slide in the bed. 152 SETTING-UP SCREW MACHINES Setting the Stop. When the circular cut-off tool has been set correctly, the chuck is opened by lifting the tripping lever, and the stock is fed out the desired length by hand ; this length can be. easily measured off by the method shown in Fig. 2. A flexible scale, the length of which depends upon the size of the machine, is placed in an empty hole in the turret and brought up against the inside face of the circular cut-off tool. The cut-off tool is now brought up against the work by means of the handle operating the cross-slide. It is then an easy mat- ter to set the stock to the desired length. When this has been done, the chuck is closed and the turret swung around so that the stop comes in line with the stock. When the stop is in this position, the roll should be on the quick rise of the lead cam so that, by rotating the cam, the roll will rise up onto the lobe, thus forcing the stop back into the turret the required amount, where it can be locked with the lock-screw provided for that purpose. When it is necessary to have the length of the piece to within a limit of o.oio inch or less, the stop A gives considerable trouble, because the only, way in which it can be set is by tapping it in or out, which is a rather difficult matter. A stop which gives better results is shown at B. The parts a, b, and c are made from machine steel and casehardened. The body a is drilled and tapped for a screw the diameter of which is made in accordance with the size of the machine in which the stop is to be used : For the No. oo, d = T 5 ^ inch; for the No. o, d = f inch; and for the No. 2, d = ^ inch. For the No. oo machine, the number of threads per inch of the screw should be thirty-two, which means that one revolu- tion would give an adjustment of 0.031 inch. For the other machines, the screw should have twenty threads per inch. The stop proper, b, is made of hexagonal stock to fit the stand- ard wrenches supplied with the machines. The nut c is made .__ ORILL^ 1 "\ -GAGE h DRILL HOLDER. Machinery Fig. 3. Gage for Setting a Drill ADJUSTMENT OF BROWN & SHARPE MACHINE 153 of the same shape and from the same size of stock as b. By having the stop hexagonal, as shown, it is an easy matter to set it within 0.005 inch, by means of the faces on stop b, as the relation of these faces to the nut can be noted, provided the latter is held with a wrench while part b is rotated. Setting a Hollow Mill or Box-tool. In setting a box-tool, the bar should project out of the spring collet only far enough for the machining operation, as otherwise the work will not Fig. 4. Method of Operating Machine by Hand when Making Adjustments be held rigidly, and will spring away from the cutting tool. The cutting tool is first set to turn the work to within about 0.0005 or o.coi inch of the finished diameter; then the sup- ports are forced up tightly into contact with the work and clamped. It will be found that, when the stock is fed out to the desired length, the supports bearing against the work tightly, the tool turns it slightly smaller in diameter. The box- tool cutter is brought in contact with the work by means of the handle K^ Fig. i, on the No. oo machine, and by the lever R 5 on the Nos. o and 2 machines, as shown in Fig. 7. These 154 SETTING-UP SCREW MACHINES levers should always be removed before engaging the driving clutch. Setting Centering Tools and Drills. When the drill used is less than f inch in diameter, and is to pass entirely through the work, a centering or spotting drill should always be used. The centering tool should be ground and set so that it will not leave a teat in the work. It should also have an included angle less than that used on the drill. To set the centering tool, the holder carrying the tool is placed in the turret, the latter swung down, the spindle stopped, and the centering tool brought in contact with the work. The lead cam is then rotated by handwheel V&, Fig. 4, until the roll rises up on to the starting point of the lobe for feeding the centering tool into the work. The holder is tapped back into the turret, so that the point of the tool just clears the end of the work; then the holder is clamped in the turret. If, upon trial, it is found that the centering tool does not project in to the required distance, it is a simple matter to bring it out. The procedure given for setting the centering tool also applies to setting a drill. It is advisable to have a number of ground drills on hand, and to use a gage for setting the drills, as shown in Fig. 3. This gage is made from sheet steel about iV inch thick. The dimension A is made equal to the distance that the drill is required to extend out of the holder. If there is more than one drill in the turret, which would be necessary when a deep hole is to be produced, a gage of this kind should be made for setting each drill. These gages should be marked according to the position that the drill for which they are used takes in relation to the other drills; that is, "ist," "2nd," etc., and kept in the same box as the other tools used on the job. If this precaution is taken, no time will be lost in setting a drill, because the machine need not be stopped. Setting Counterbores and Reamers. A counterbore .pro- vided with a leader should always be held in a floating holder. Before setting the counterbore, the hole should be drilled; then the procedure for setting centering tools should be followed, ADJUSTMENT OF BROWN & SHARPE MACHINE 155 except that the leader is inserted, bringing the face of the counterbore in contact with the end of the work. Reamers which are to produce deep holes should be held in floating holders. Setting Dies and Taps. Before a die or tap and its holder are placed in the turret, the dogs should be set in posi- tion to reverse the spindle in the correct relation to the thread- ing lobe on the lead cam. The two parts of clutch M (see Fig. i, Chapter II) should first be engaged, so that the shaft carrying the disk on which the dogs are located will be rotated in step with the other driving mechanism of the machine. Then FACE OF WE X Machinery Fig. 5. Turret-slide Operating Mechanism on Brown & Sharpe Machine the shifter is pulled over and the main spindle started. The lead cam is now rotated by means of handwheel F 5 , Fig. 4, the operator also pressing his thumb against the turret-slide and bearing on the turret base. While rotating the handwheel F 5 , notice when the spindle reverses; and by keeping the thumb in contact with the turret-slide one can tell when the roll drops over the highest point of the lobe on the cam. When the spindle reverses at the same instant that the roll drops 156 SETTING-UP SCREW MACHINES REAR CROSS- SLIDE c -SQUARE over the highest point of the lobe on the cam, the dog is set in the desired position. This is illustrated graphically, for setting a die, in Fig. 5. 'A button die, held in a holder, is shown in position ready to start on the work. The face of the die should be set the distance A from the end of the work. This distance varies from tV to -3^ inch, depending upon the pitch of the thread and the length of the threaded portion. The detail view to the right shows the cam roll set just back of the highest point of the lobe; when the roll is at this point, the spindle should reverse. After the first setting, if it is found that the die does not travel onto the work far enough, the holder is brought further out of the turret. The same procedure is followed in setting a tap, except that it should be set more carefully, only going into the work a slight dis- tance when starting, and the holder moved out of the turret until the desired depth is reached. It is sometimes found necessary, after setting the tripping dogs, to adjust them slightly, especially when using the drawout type of die or tap-holder. The turret should not be indexed until the die or tap is clear of the work. Setting Swing Tools and Taper-turning Tools. Swing tools are used for both internal and external cutting, and are operated under three different conditions: i. The cutting tool is fed into the work from the cross-slide alone. 2. The cutting tool is fed longitudinally by the turret. 3. The cutting tool is fed inward by the cross-slide and longitudinally by the turret. For the first condition, the raising block need not be Machinery Fig. 6. Use of a Square for Setting Raising Block ADJUSTMENT OF BROWN & SHARPE MACHINE 157 set in any particular relation to the axis of the spindle. When straight turning is to be produced under the second condition, the face of the raising block should be set parallel with the axis of the spindle. For the third condition, when the work is to be turned taper, the face of the raising block should be set at an angle with the axis of the spindle. In Fig. 6 is shown a simple method of setting the face of the raising block parallel with the axis of the spindle. An ordinary adjustable square is held against the face of the rear cross- slide, and screw A is adjusted until the block is set correctly, Fig. 7. Testing Position of Raising Block by means of Dial Indicator after which screw B is tightened. This method can be used when it is not necessary to have the raising block set exactly parallel with the axis of the spindle. A better and more accurate method is shown in Fig. 7. Here a dial test indicator B is 1 used. A split bushing is inserted in one of the holes in the turret, and a bent rod with the indi- cator is held in it. The finger of the indicator is brought to bear against the face of the raising block C, and the turret is traversed by handle R$ on the Nos. o and 2 machines, and by using handle K^ Fig. i, on the No. oo machine, inserting it in the turret traversing lever. While the turret is being trav- ersed back and forth, the movement of the needle on the dial is noted, and the screw A adjusted until no movement is transmitted to the needle. 158 SETTING-UP SCREW MACHINES The setting of the raising block for operating a taper turn- ing tool or a swing tool for taper turning is generally done by the cut-and-try method, the first time the tools are set up. Most operators, when setting up a job for the second time, use what is called a " set piece" to set the tools by. This is a piece of work which has been made correctly to size, but which is not entirely cut off, as shown at C in Fig. 6. It is gripped in the collet, and the turning tool as well as the circular form and cut-off tools are set to it. General Method of Setting-up Screw Machine. To illus- trate the method followed in setting-up a Brown & Sharpe automatic screw machine, let it be assumed that a set of cams as illustrated in Fig. 8 have been designed and made for pro- ducing a button-head screw on the No. oo machine. These cams, together with the special and standard tools which are numbered, are turned over to the operator. He also receives a drawing similar to that shown in Fig. 8. Assume that the machine has been set up for another piece of work, so that it is necessary to dismantle it. The operator first removes all the tools from the turret and the cams from the front and rear end shafts. He also removes the spring collet by removing the cap, and the feed- tube by lifting the latch; then he unscrews the feed finger, which is threaded left-hand. The change- gears are now removed, leaving the machine dismantled ready for the new job. To proceed, the operator first inserts the spring collet, puts on the cap, and then screws the new feeding finger into the feed-tube, and inserts the latter into the spindle. He then puts the stock into the feed-tube, and places a suitable pipe in the stand in which the stock is to revolve. This pipe should be central with the feed-tubes, thus reducing the wear in the hole of the latter. The belts are now placed on their proper cones to give the desired spindle speeds. All belts should be without rivets, and preferably should be laced with wire, as this gives a smoother running belt. All the bearings should be oiled with good machinery oil, and also the friction clutch. The latter should be oiled at least twice a day. ADJUSTMENT OF BROWN & SHARPS MACHINE 159 160 SETTING-UP SCREW MACHINES After the belts have been placed on the proper cones, the collet, feed finger, etc., having been inserted, the change- gears should be put in place. The handwheel is next put or for operating the machine by hand. Before putting on the cams, set the collet so that it has the proper grip on the stock ; then open the collet again and push the stock out far enough to be faced off by the cut-off tool. After closing the collet, start the spindle and set the cross-slide circular form and cut- off tools at the height of the center of the work, and in their proper relation to each other. Next put on the front and rear cross-slide cams, and if the job requires a threading operation, as in this case, the shaft with the drum carrying the tripping dogs for reversing the spindle should be connected with the front camshaft. Next, set in the cross-slides by adjusting nuts A 3 , Fig. i, so that the circular form and cut-off tools travel in to the re- quired distance. Place the hollow mill in the turret, set it correctly, and also set the tripping dog so as to revolve the turret. Put the box-tool in the turret, set it, and also set the dog for indexing the turret. The die is then set as previously described, and all the tripping dogs are set to index the turret completely around. After all the tools have been set in their proper relation, make a piece, except threading, by turning the handwheel; at the threading operations, drop down the die so that it does not pass onto the work. Gage the piece thus made; if it is correctly to size, and the tripping dogs for reversing the spindle and the die have been properly set, throw the feed clutch by means of handle P (Fig. i, Chapter II) and start the machine. When the bar is all used up, the chuck should be opened by tripping the lever, and the turret revolved by withdrawing the locking pin, so that it will not interfere with the short piece left in the chuck, which should be driven out for the inser- tion of a new bar. To insert the new bar, turn the handwheel sufficiently to bring the shoulder of the feed-tube against the end of the spindle, and push out the bar just far enough so that its front end can be faced off with the cut-off tool. Now ADJUSTMENT OF CLEVELAND MACHINE 161 turn the turret back into position and start the machine by throwing in the clutch. The ends of the rods of stock should be ground to remove the burrs, thus insuring their entering and feeding freely and evenly through the feed- tube. The work should always be tested after the insertion of a new bar of stock. If the parts made are short or thin, the tools will become dull much more quickly; consequently, the work should be tested more frequently in that case, so that any errors may be corrected as soon as possible. Adjusting the Cleveland Automatic Machine. The setting- up of a Cleveland automatic screw machine is principally a Fig. 9. Turret-slide of Cleveland Automatic, which is Adjusted Along the Bed to Suit the Various Lengths of Work and Turret Tools matter of adjusting the cams on the cross-slide drum, as well as the cams controlling the variable tool feed and the stock feed. Assuming that all the tools and other equipment that have been used on previous jobs have been removed, the first step is to insert the chuck. The hood on the nose, of the spindle is first removed by a spanner wrench, and the chuck is then in- serted, care being taken to remove all chips and heavy oil which would retard its action. When the chuck is of the pad type, it is only necessary to remove the pads and replace them by those suited to the size of the stock that is to be handled. After putting the chuck in place, the feed-tube is then taken out and the desired size of shell or pads inserted. After 1 62 SETTING-UP SCREW MACHINES putting the chuck and feed-tube in place, the chuck is then closed by hand and the cross-slide tools are placed in their ap- proximate positions, allowing about f inch clearance between the front face of the chuck and the inner face of the cutting-off or forming tools. Adjusting the Turret Head. Following the insertion of the chuck and feed-shell, the next move is to adjust the turret head A (Fig. 9) along the bed to accommodate the length of work to be turned. This adjustment is made by turning screw B. The turret should be advanced to full stroke, that is, to its extreme forward position, by means of shaft C oper- ated by the same crank handle that adjusts screw B, and the turret tool having the greatest body length should be used in determining the position of the turret head on the bed. In making this adjustment, the clamping screws which fasten the turret head to the bed should be released; one of these screws is shown at D and the other is at the front end of the turret head underneath the bed. These should be securely tightened when the turret head is in the desired position. Setting the Turret Tools. Turning our attention now to the turret, the first tool to be set is the gage stop. This is used for gaging the stock to the correct length and should be set in relation to the cut-off tool. The proper procedure is to measure from the outside face of the cut-off tool to the front face of the gage stop, when the turret is advanced to its ex- treme forward position. All the other tools are then placed in the turret in their proper holes. In setting the turret tools, the exact length required for the job is secured by measuring from the face of the gage stop to the cutting tool, or from the outer face of the cut-off tool to the front edge of the cut- ting tool, with the turret advanced to its extreme forward position, as before. No attention is given to the final setting of the cutters in a box-tool, until all the tools have been set in their proper relative positions. Adjusting Cross-slide Operating Cams. The cams for operating the cross-slide are of curved segment form and are held on a drum F shown in Fig. 10. The procedure in setting ADJUSTMENT OF CLEVELAND MACHINE 163 these cams is to first advance the turret E to its full outward stroke and then bring the cross-slide by hand to the approxi- mate position that the forming tool will occupy when it has finished taking a cut. The bellcrank lever G is then moved until the roll touches the flange of the cam drum, and a mark is made with a lead pencil, indicating the position of the roll on the surface of the drum. Then the machine is operated again by hand, rotating the drum about one-half turn, and the high point of the forming cam H is placed so that it coin- Fig. 10. Cams on Cross-slide operating Drum, which are moved around to the Required Position and Clamped by Cap-screws cides with the circumference of the circle previously outlined. The cam for operating the cut-off tool is located in the same manner, and is generally the last to be set. The relief cams / (only one of which is shown) that draw the cross-slide to a central position, after the forming and cut-off tools have finished their operations, are next adjusted. The cap-screws fastening these cams to the drum F are re- leased, and the cams are shifted around so that the high points contact with the roll and hold the slide in the central position, after which the cams are clamped, to the drum. 164 SETTING-UP SCREW MACHINES The cross-slide connecting-rod which controls the exact posi- tion of the cross-slide is adjusted as required by the move- ment of the forming and cutting-off tools. Two adjusting nuts provided with individual locking nuts are located on this connecting-rod, and these are adjusted back and forth in rela- tion to the central pin in the bellcrank lever G, in order to carry the slide to its exact position. After making this adjust- ment of the cross-slide, the machine should be turned one Fig. 11. Adjustment of Belt-shifter Dogs for Controlling Speed and Direction of Spindle Rotation complete cycle by hand, in order to insure the operator that each tool has been properly placed. Making the Speed Changes. The next point that requires attention is the correct spindle speed to use. This is governed largely by the material that is to be operated upon, and to some extent by the tools that are to perform the operations. Fig. ii illustrates the method of adjusting the belt-shifter dogs to obtain the different spindle speeds required to suit the tools that have been placed in position. When a job is to be threaded ADJUSTMENT OF CLEVELAND MACHINE 165 with a spring or button die, or a tap is to be used, it is neces- sary to set the reversing dogs to reverse the spindle exactly at the time when the turret is at the full forward position. In order to make this adjustment without danger of injuring the tap or die, the bar stock should be removed from the spindle, the turret advanced by hand to the extreme forward position, and the belt-shifter dog set to reverse the spindle at this point; then the turret is backed up by hand and the power feed is thrown in, care being taken to observe whether Fig. 12. Adjustment of Compression Collar Nut for Varying the Gripping Pressure of the Chuck on the Bar the spindle reverses just as the turret starts on its backward motion. If the spindle reverses a little too soon or a little too late, the belt-shifter dog is adjusted slightly to correct the time of reverse. When it is seen that the spindle reverses exactly at the moment the turret starts on its backward stroke, the adjustment is correct, and the bar stock may then be replaced in the machine and the threading die will cut correctly. No adjustment of this kind is necessary when self- opening dies or collapsible taps are used, because, when the thread is finished, the chasers clear the work, and it is not necessary to reverse the spindle. There are several different 1 66 SETTING-UP SCREW MACHINES combinations and arrangements of spindle drives possible on the Cleveland automatics. Chucking and Feeding Adjustments. Assuming now that the tools have been set in approximately correct positions, the next step is to place the bar of stock in the spindle of the machine and adjust the chuck to its proper grip on the work. This is accomplished by means of an adjusting nut A shown Fig. 13. Method of Regulating the Length of the Stock-feeding Movement in Fig. 12, which is located at the rear end of the spindle. In this illustration, the operator is shown turning the ad- justing nut with the spanner wrench.* Before adjusting this nut, it is necessary to release the binding nut B until compres- sion nut A is released. Adjusting nut A is turned until the chuck has sufficient grip on the work to prevent it from being shifted by the action of the turning tools. When it is desired to tighten the grip of the chuck, the adjusting nut A is turned ADJUSTMENT OF CLEVELAND MACHINE I6 7 toward the right; turning it toward the left loosens the grip of the chuck. This direction is taken with the operator facing the spindle and standing at the end of the machine. When the correct adjustment of the chuck on the work is obtained, the binding nut B is tightened to lock the adjusting nut. The next step is to set the stock-feeding mechanism so that Fig. 14. Setting the Shifter Pins on the Regulating Drum so that the Feeding Movements and the High-speed Movements occur at the Proper Time the bar will be fed out to the correct distance. Fig. 13 shows the method of making this adjustment, which is secured by shifting the position of the stock feed-rod head A along the shaft so that cam H will engage with the roll B at a point that will feed the stock out to the desired length. The last J-inch movement of the stock feed-rod should take place after the chuck is opened. This will give time for the spring chuck to open fully before the stock starts to feed to the gage 1 68 SETTING-UP SCREW MACHINES stop. The stock-feeding mechanism should be set to feed about % inch more than the job requires, and the gage stop in the turret will force the stock back to the desired length just as the chuck is closing on the bar. Setting the Feed-shifting Pins. The feed on the Cleve- land automatic is changed from the slow to the fast speed through a sliding clutch. This is secured by means of shifter pins A and B (Fig. 14) which are held in T-slots in the rear face of the regulating drum. In setting these feed shifter pins, each tool in the turret is advanced by hand, so that it is brought to within about 3*2 mcn f where it should start to cut. Then the feed shifter pin B is moved around in the T-slot of the regu- lating drum and set to shift the clutch to the slow speed at this point. In the case of a tap or die, the tool should be brought to a position J inch from the face of the work. The feed shifter pins A in the outer T-slot of the regulating drum control the fast or idle movements of the machine, and should be set to shift the clutch into the fast speed at the completion of each tooling cut, whereas the pins B in the inner T-slot control the shifting of the clutch to the slow speed and are set to move the clutch at the point previously described. Adjustment of Feed-regulating Drum. One of the impor- tant features of the Cleveland automatic is the regulating drum, which is used for securing separate feeds for each tool in the turret and on the cross-slide, the feed per revolution of the spindle being controlled by segment cams which can be adjusted while the machine is in operation. Fig. 15 shows the setting or adjusting of the feed regulating cams 7. These cams are attached to the flange of the regulating drum by means of two cap-screws. The flange of the drum is slotted to allow adjustment of the cams. By shifting the position of the cams, any desired feed can be secured for each individual tool. Moving them toward the outer edges decreases the feed, and in the opposite direction increases the feed. The edges of cams /, through the medium of a bellcrank lever, guide the position of roll / automatically up and down between the friction disks K which drive the turret drum and camshaft. ADJUSTMENT OF CLEVELAND MACHINE 169 This makes it possible to increase or decrease the tool feed as required, to suit the material being cut and the type of tools performing the operations. The position of the pointer on indicator L determines the location of the feed regulating cams when setting up a job for the second time. The indicator is held on an arm moving up and down on a post; this arm receives its motion from the bellcrank lever which, in turn, is operated by the cams on the Fig. 15. Adjustment of the Regulating Drum Segment Cams to give the Required Rate of Feed for the Turret and Cross-slide Tools regulating drum. The position of the pointer is recorded on a record sheet which should be filled out before changing to other work, and used as a guide when setting up the same job again. This record sheet shows the position of all adjust- able cams and gives all the necessary tooling data. In addition to the adjustments previously mentioned, there are positive stops for the front and rear of the cross-slide which need to be set and which make extreme accuracy easily obtainable. These stops are in the center of the slide and control the exact posi- tion of the tools. 170 SETTING-UP SCREW MACHINES Adjustment of Acme Multiple-spindle Machine. To make clear the methods followed in setting-up and operating the " Acme " automatic multiple-spindle screw machine, a representative piece will be taken as an example, and the various steps to be followed in setting-up and operating the machine for producing this piece will be dealt with in detail. While there are many questions that will arise in setting-up the machine for producing various parts, where actual experi- ence in work of a similar character would in many cases elimi- nate the necessity of experiment, if the operator has a general idea of the various working mechanisms of the machine and their relation to each other, he will experience little difficulty in adjusting the machine for average work. Assuming that the machine has been set up on a piece of work, the first thing that the operator does is to dismantle those parts, tools, gears, cams, etc., which have to be changed for every new job, leaving any cams or tools in position that can be used on the new piece. As a rule, the spring chucks and feed chucks are removed first and are replaced by those of the proper size and shape. Then the tools in the main tool-slide and the side- and top- working tool-slides are removed. When a straight blade cut-off tool is used in the cut-off tool-slide, it generally can be used for more than one job, so that in many cases this tool need not be removed. The cams on the main drum, and also the cams for operating the side-working tool- slides, are now removed and replaced by cams which will give the required amount of travel. The back-gears for rotating the end-working tools and the threading spindle are next removed and replaced by gears that will give the proper speeds ' for the work in hand. If it is necessary for the operator to proceed without instruc- tions, he must first decide on the best method of applying the tools before he begins to set up the machine. As this is frequently the case, it may be advisable to give a short de- scription of some of the points which have to be taken into con- sideration when deciding on the best method of tooling the machine for producing any certain part. ADJUSTMENT OF ACME MACHINE Deciding on the Method of Tooling. The four spindles of the Acme automatic multiple-spindle screw machine may tend to confuse a new operator, and to give him the impression that a clear understanding of the method of tooling is more difficult to obtain than when using a single-spindle machine. The chief reason for this is that all the tools are used at once; ORDER OF OPERATIONS FIRST" POSITION I "SECOND" POSITION* "THIRD" POSITION "FOURTH" POSITION PIECE TO MAKE 16 P. MACHINE STEEL Machinery Fig. 16. Successive Operations for Producing a Hexagon-head Cap- screw on a Multiple-spindle Machine however, this fact frequently makes it possible to rearrange the tools considerably on repeating a set-up, and what might have been considered the best method of tooling a certain piece when it was first made may prove inferior to the new 172 SETTING-UP SCREW MACHINES method. This possibility of improving upon the method of tooling sometimes changes the order of operations to such an extent as to entirely change the method of manufacture. As an illustration, assume that it is necessary to produce the cap-screw shown in Fig. 16, which is to be made from cold- rolled hexagon steel, {J inch in " diameter" across the flats. As this is just an ordinary cap-screw, the body need not be shaved, but can be produced accurately enough for all prac- tical purposes, by dividing the cuts on the body between two box-tools, which are held in the end-working tool-slide. The operation at A, which takes place in the "first" position, is performed with a circular form tool and box-tool. The circular form tool forms the head and "necks" or grooves the piece, whereas the box-tool, held in the "first" position tool spindle, turns one-half the length of the body. In choos- ing the lead cam for the forward travel of the main tool-slide, a one-inch cam is sufficient, owing to the fact that the two box-tools are working on different bars at the same time. The second box-tool cutter is set one inch further out from the face of the main tool-slide than the first box-tool cutter, in order to complete the turning on the body of the cap-screw. Calculating the Production per Hour. As all of the end- working tools come up to the work at the same time, it follows that in most cases all four tools from the end would be at work on different bars at the same time. In this case, the screw only requires the use of three end-working tools two box-tools and a die although a pointing tool could be used if neces- sary to make the point on the screw after it is threaded. By considering the operations on this cap-screw, it will be found that the longest operation is that necessary to turn one-half the length of the body; then to find the production per hour, it is first necessary to determine the speed at which it is best to run the work. As a rule, ordinary cold-drawn stock can be worked at from 65 to 75 surface feet per minute for forming tools or box- tools. In this case, select 75 surface feet as a suitable speed; then, assuming that the bar is round and of a diameter equal to the distance across the flats, it will be ADJUSTMENT OF ACME MACHINE 173 found that a spindle speed of 420 revolutions per minute will be about right. The table of spindle speeds accompanying the No. 53 machine shows that 445 is the closest number ob- tainable. As the speed will not be increased excessively, the back-gears for this higher speed may be used. The next step is to find the number of revolutions of the spindle required for the box-tool to travel one inch along the work, at a certain feed per revolution. The body diameter of this cap-screw is f inch, while the diameter across the corners is 0.794 inch, giving a depth of cut of 0.209, or approximately 3*2 inch. If a feed of 0.004 mcn P er revolution is selected and 0.040 inch allowed for the tool to approach the work, it will be found that it will take 260 revolutions of the spindle for the box-tool to travel the distance required. There are several methods followed in obtaining the pro- duction of the Acme automatic screw machine, one method being based on the assumed output per hour, which can be obtained by the following formula: RX 60 r in which P = assumed product in pieces per hour; R = revolutions per minute of work-spindle; r revolutions of spindle required to complete the longest single operation. Inserting the values previously obtained in this formula: P = - = 103 (approximately). 260 In assuming this product, the time required to feed the stock, index the cylinder, etc., was not considered, and, in- stead of calculating the actual time required for these idle movements, an approximation is made. Referring to the change-gear table for the machine that is to be used, it will be found that the next closest production to 103 is 98.5; then, by reducing the production to 98.5 pieces per hour, allow suf- ficient time to take care of the idle movements of the machine. Another method is to calculate the time required for the 174 SETTING-UP SCREW MACHINES longest single operation in the manner just described, and then determine definitely the actual time required to feed the stock, index the cylinder, etc. This is added to the time required for the longest single operation, the sum giving the exact time required to produce one piece. This method, while considerably longer than the other, has the advantage of working on a definite basis and may be clearly understood by those not entirely familiar with the construction and opera- tion of this machine. Spring Chucks and Stock Support. Assuming that the machine has been dismantled and is to be arranged for the operation shown in Fig. 16, the first thing to consider is the insertion of the proper spring chucks and feed chucks for feeding and holding the bars. A round chuck should never be used for holding either square or hexagon stock, but a chuck of the same shape as the work should always be used. After' the feed chuck and spring chuck have been put in place, the bars of stock are inserted in the spindles, the chucks being opened and the bars pushed through, so that they ex- tend far enough out of the chucks to allow for cutting off the finished parts. As a rule, it is good practice to put the bars of stock into pipes for guiding them, before the machine is started. In putting the stock-supporting reel in place, when the bars are already in the spindles of the machine, the reel is simply slid back over the rear bracket until it passes the end of the bars, and is then pushed forward again, the bars passing into the pipes. A satisfactory method is to leave the reel in place and push the rods through the pipes into the spindles, then slide the reel back slightly to facilitate chucking, and replace it again in the running brackets before starting the machine. When the stock is small in diameter, the ends pro- jecting from the rear end of the machine should be guided by the pipes of the reel, as this prevents damage to both the machine and the operator, due to a slight twist in the bars which causes them to rotate eccentrically and buckle. Selecting and Changing the Back-gears. After the stock has been inserted in the machine, and the chucks closed on it ADJUSTMENT OF ACME MACHINE 175 by cranking the machine, the next step is to obtain the desired spindle speed. This is secured by removing the back-gears shown in Fig. 5, Chapter III, and replacing them with the gears which will give the proper speed for the work in hand. For the operation shown in Fig. 16, a spindle speed of 445 revolutions per minute has been selected. Referring to the spindle-speed table for the No. 53 machine, it will be found that the gears should go on as follows: A 52; B 46; C 26; D 32. In putting on the back-gears, see that they do not mesh too closely. Selecting the Lead and Forming Cams. A feature of the Acme automatic screw machine which should be borne in mind is that the lead cam, located on the drum for governing the forward advance of the main tool-slide, is not adjustable, but is bolted to the drum. Now, for different work, these cam strips which are all of the same length, but have different rises, are put on the drum G (Fig. i, Chapter III) and clamped by cap-screws. For making the cap-screw shown in Fig. 16, it is necessary that the main tool-slide travel forward approxi- mately one inch, so that in this case a lead cam having a rise of one inch in its length is selected. To determine this rise, measure both the narrow and wide ends of the cam strip, and the difference between these two dimensions will be the lead of the cam. To select the forming cam for operating the forming tool, measure the distance between the largest and smallest diameters of the work formed by it, and divide the result by 2. In this case, it will be found that the forming cam should have a rise of -32 inch. All forming cams are plainly marked on the end with the rise for which they were laid out. It is not always possible to select a forming cam which will give the rise to within a few thousandths of an inch of that required, but this does not make much difference, as the longest single opera- tion governs the time required to make one piece, and all the other operations are completed in that time. In this example, as is usually the case, the forming is one of the shorter opera- tions and, therefore, it does not matter if the forming tool 176 SETTING-UP SCREW MACHINES moves a little farther than is actually required, provided its inward movement is arrested at the proper point. To select the cut-off cam, measure the diameter of the piece to be cut off and at the same time make allowance for the angle on the point of the cut-off tool, so that it will pass the center of the work. For cutting off the cap-screw shown in Fig. 1 6, a |-inch cut-off cam, which actually has a rise on the cam of j inch for cutting through a bar ^ inch in diam- eter, should be selected. The cut-off cams are all marked on the end to correspond with the diameter of the piece to be cut off. Placing the Cams in Position. In placing the lead cam on the drum, when the operations performed from the main tool- slide are of a heavy nature, a backing-up strip should be fitted into the groove in the drum, behind the lead cam, so as to resist the thrust of the cutting tools. A starting strip should also be put on just in front of the point where the lead cam strip starts to bring the tool-slide up to the work, and a take- back cam wide enough to draw the end-working tool-slide back sufficiently to clear the work when the cylinder is indexing should next be put in place. This starting strip is adjusted even with the starting or narrow end of the lead cam, and is used to bring the tools up quickly to the work. When the roller is working on the " fast-angle " cams, the camshaft is rotated at an increased speed, so that all the movements when the tools are not cutting are a great deal more rapid than the cut- ting movements. This is done to reduce the idle time and is accomplished through the medium of the clutch mechanism described in Chapter III. In placing the cut-off cam in position, it should be put on the disk opposite the one on which the forming cam is held, and the take-back cam is also put on the same disk and at- tached by screws. There are two sets of holes in the disk for the cut-off cam, and the position of this cam on the disk de- pends upon whether the " fourth " end tool position is in use or not. The disk for the forming cam has only one set of holes, so that it is impossible to adjust it. ADJUSTMENT OF ACME MACHINE 177 Setting the Circular Forming and Cutting-off Tools. The circular forming tool A, Fig. 17, is held to an oblong-shaped tool-holder B by a stud and nut. This holder is held in the slot in the forming slide by a strap. For locating the cutting edge of the forming tool in the proper relation to the work, a tool setting gage C is used. This is held by the operator against Fig. 17. Setting the Cutting Edge of a Circular Forming Tool to the Proper Height with a Tool-setting Gage the bottom face of the forming tool holder, and the nut for holding the forming tool to the holder is then tightened. The holder is then placed in its proper position in the slot in the tool-slide and clamped. To bring the forming tool into its correct relation to the work, the machine is cranked or turned by hand until the roll is just over the starting angle on the forming cam; then the screw in the back of the slide is adjusted until the forming tool just clears the work. 178 SETTING-UP SCREW MACHINES The adjusting screw on the slide in which the forming tool is held should be set to stop the slide just as the cam lever clears the highest point of the cam. Usually it is good prac- tice to put a slight tension on this lever (by adjusting the screw a little farther in than necessary), so that, when the extreme knife edge of the tool is removed, thus making the work larger in diameter, a slight outward turn of the adjusting screw will bring the work back to the required diameter. The next step is to set the cut-off tool. This tool, when of the blade type, is set so that its top cutting edge is on a line with the center of the work. It should also be set in a horizontal position relative to the forming tool, by adjust- ing the screw in the slide, which is provided for that purpose. After the form and cut-off tools have been set in approxi- mately the correct relation to each other, the next step is to set the form tool so that it will turn the work to the required diameter. To do this, " crank the machine" or turn the camshaft by applying a hand crank to the worm-shaft, until the wedge is disengaged from the wedge fingers; then push the rod through the chuck until its end passes the outside edge of the circular form tool. Continue cranking until the rod is chucked and the roll on the lever operating the forming slide is on the starting point of the cam rise. The form tool can now be adjusted inward, the machine started, and a cut taken. It is good practice to adjust the form tool to give the required diameter, before going further. It is necessary to set the cut-off tool to remove the formed ends during the adjust- ment of the forming tool. After one piece has been cut off, it can easily be seen whether the cut-off tool has been set in the proper relation to the center of the stock. Setting the Box-tools. Assuming that the forming and cut-off tools have been properly set, place the box-tool in the "first" position tool spindle. Then open the chuck and feed out the stock. When the work is long or of small diameter, it is good practice, in setting the box-tool, to feed the stock out only a short distance from the face of the chuck, to pre- vent springing or bending of the bar while adjusting the tool. ADJUSTMENT OF ACME MACHINE 179 In setting the box-tool, release the rollers and set the front turning tool to turn from 0.005 to 0.007 mcn smaller than the proper diameter, after which adjust the rollers until they come into light contact with the piece to be turned. Then by ad- justing the front cutting tool upward slightly, the tool and rollers will come into the proper relation with each other. In Fig. 18. Setting the "First" Position Box-tool to turn to the Required Distance on the Work many cases, a slight additional adjustment of the box-tool cutter is necessary after the machine has been started and the power feed is used. Several methods are in common use for setting the box-tool to turn to the desired distance. One of these is to crank the machine until the roll just starts on the rise of the lead cam; then to operate the screw A, Fig. 18, in the tool spindle, until the box-tool cutter B just touches the work which it will be l8o SETTING-UP SCREW MACHINES assumed has been fed out to the required length. After adjust- ing in this manner, tighten the screw holding the box-tool in position in the tool-holder. After the "first" position box-tool has been set in position in proper relation to the work, the power feed may be thrown in to index the cylinder by oper- ating the starting clutch lever at the front of the machine. This will bring the rod just operated upon into the " second" position. Now adjust the gage stop and set the feed stop on the lever operating the feeding mechanism, so that the stock will be fed to the length of the piece to be made, being sure to ascertain beforehand that the feed-tube is withdrawn sufficiently to insure the end of the rod coming in contact with the gage stop. When the stop has been properly set, the stock fed the proper distance, and the cam roll-holders set so as to give ample clearance for all tools, crank the machine until the cam roll beneath the main tool-slide is in contact with the start of the rise on the lead cam. After having set the " first" position box- tool, again crank the machine until the forming tool and " first" position box- tool have completed their operations and another indexing of the cylinder is about to take place. After this indexing has proceeded about halfway, place the "second" position box- tool back far enough to clear the stock during the indexing operation. Continue cranking until the cam roll is in contact with the cam, as before; then adjust the "second" position box-tool so that it will "pick up" or continue the cut at the position where the "first" position box-tool finished, and at the same time, set the rest and front cutting tool to the diameter formed by the "first" position box- tool. To bring the box-tool out so as to turn up the correct length, an ordi- nary scale C, as shown in Fig. 18, is sometimes used. Some operators prefer the "scale method" of setting the end- working tools, instead of working from the end of the bar. When the screw is to be pointed, a pointing tool can be held in the "first" position box- tool, or, if the " fourth" posi- tion tool spindle is not used, a pointing tool can be used from this position. Assuming, in this case, that the pointing tool ADJUSTMENT OF ACME MACHINE i8l is in the " first " position box- tool and that the gage stop, forming tool, box- tools, etc., have been properly set, release the set-screw which holds the pointing tool. Then crank the machine until the tool-slide travels forward the required dis- tance, and adjust the pointing tool out until it will remove the desired amount of metal from the end of the screw. Selecting Change-gears. After all the tools previously mentioned have been set in their proper positions, several pieces are made from the bars, the machine being operated by power feed. Then change-gears are selected to give the desired rate of production. As a rule, in setting up an Acme automatic screw machine, the gears which have been decided upon to give the desired production are not put on until all the tools have been properly set and the various parts of the machine work in the proper relation to each other. Most operators set-up the machine on a "slow" set of gears, and, after the machine has been set correctly, put on the gears which will give the desired production. This change-gear mechanism was described in connection with Fig. 4, Chapter III. For the piece chosen as an example (see Fig. 16), it was decided that a production of 98.5 pieces per hour would be suitable. Referring to a table of change-gears, it will be found that the first gear on the shaft should have 36 teeth; the second gear on the shaft, 82 teeth; the first gear on the stud, 74 teeth; and the second gear on the stud, 28 teeth. After these gears have been put in their proper positions, the next step is to set the threading spindle. Setting the 'Threading Spindle. On the Acme multiple- spindle automatic screw machine, the work-spindle is held stationary while a right-hand thread is being cut, and the die- spindle carrying the threading tool is rotated. When backing off the die or tap from the work, the threading spindle is held stationary and the work-spindle is rotated. The manner in which this is accomplished was explained in connection with the description of the threading mechanism in Chapter III. In setting the tools for threading, before starting the ma- chine, see that the clearance between the ratchet and pawl 182 SETTING-UP SCREW MACHINES extension is anywhere from yg- to -g- inch, when the pin block on the holder and the pin in the spindle are placed end to end (after the pin has been adjusted). It is very important that this precaution be taken, as a " hang up " between these two points might occur, resulting in the stripping of the teeth in the gears driving the holder, should this adjustment not be made properly. For this example, the front face of the die should be set almost in line with the cutting tool held in the box- tool in the " first" tool position, when the die-spindle is as far back as the tool-slide will let it go. The lead cam does not advance the threading tool at the required rate of feed, as determined by the thread, but pro- vision is made so that the die follows the lead of the thread. It is, therefore, unnecessary to take the lead cam into considera- tion, as far as the feeding of the die-spindle is concerned. The die pins which actuate the die-holder for driving the threading die should be set so as to carry the die up far enough after the end of the travel of the lead cam has been reached, before allowing the die to rotate freely. In this case, the lead cam only travels approximately one inch, while the travel of the die is ij inch, so that it will be necessary to set out the die pins. After all the tools have been properly adjusted and are working satisfactorily, set the cam dogs which shift the clutch to the direct drive, so that they operate at the proper time in relation to the cutting tools and the indexing of the cylinder. As a general rule, the clutch should be shifted to the direct drive when the die or tap is just free from the thread and the rolls have cleared the cutting-off and forming cams. The clutch again shifts to the gear drive just before the tools begin to operate. Calculating Speed of Work-spindles. The speed of the work-spindles obtainable by direct drive and through the back gearing may be obtained from tables, but it might be pos- sible, in some cases, to secure more satisfactory speeds with gears having a different number of teeth than those given in the table. The calculations used in obtaining the proper gears to use for different speeds will be explained. The work- spindles are rotated from the main drive shaft through gear- ADJUSTMENT OF ACME MACHINE 183 ing, the gears on the main shaft driving the spindles through a friction gear that can be disconnected from the spindle when it is necessary to stop its rotation for performing operations such as threading, cross-drilling, milling, etc. As there are only two gears involved in this calculation, the method of obtaining the speeds of the spindle is simple and can be obtained from the following formula : rXN K = - , n in which R = revolutions per minute of work-spindles; r = revolutions per minute of top or main drive shaft; N = number of teeth in gear on top or main drive shaft; n = number of teeth in friction gear. For example, on the No. 54 machine, R = - - = 373 45 revolutions per minute, approximately. In the calculations to follow, particular reference will be made to the Nos. 54 and 55 machines, as these two sizes meet general commercial requirements. Calculating Speeds of Threading and " Second Position " Tool Spindles. A notable feature of the Acme multiple- spindle automatic screw machine is that, for threading, the work is stopped and the die is rotated, but, in backing off, the reverse is the case. In order to fulfill these requirements, it is necessary to gear up the threading spindle to the main drive or top shaft. Two speeds for each speed of the top or main drive shaft are possible by shifting the gearing, one speed being obtained by driving direct through the sliding gear on the main drive shaft to the gear on the threading spindle, and the other by driving through an intermediate and a compound gear. The following formula is used for obtaining the speed of the spindle when driven direct : 7? ~r~' in which RI = revolutions per minute of threading spindle (direct drive) ; r = revolutions per minute of top or main drive shaft; 1 84 SETTING-UP SCREW MACHINES ^Vi = number of teeth in sliding gear on top or main drive shaft; t = number of teeth in gear on threading spindle (also called direct gear). As an example, assume that the speed of the top or main drive shaft is 480 revolutions per minute, then : 480 X 26 RI = - - =227 revolutions per minute, approximately. 55 The formula for obtaining the speed of the threading spindle, when driven through the intermediate and compound gear, is as follows : r X Ni X T KZ = - , iX / in which Rz = revolutions per minute, of threading spindle (gear-driven) ; r = revolutions per minute, of top or main drive shaft ; NI = number of teeth in sliding gear on main drive shaft ; T = number of teeth in pinion gear ; n\ = number of teeth in back-gear ; / = number of teeth in gear on threading spindle (also called direct gear). The "second position" tool spindle which can be used for threading, if necessary, and which in many cases is used for driving small drills at their proper peripheral speeds, is also rotated from the top or main drive shaft through gears. The speed of this spindle can be obtained by the following formula : rX N, *3=~, in which Ra = revolutions per minute of "second position" tool spindle ; r = revolutions per minute of top or main drive shaft ; Ni = number of teeth in sliding gear on main drive shaft ; T\ = number of teeth in gear on "second position " tool spindle. Assume that the speed of the main drive shaft is 480 revolu- tions per minute, then : 480 X 26 36 = 346 revolutions per minute, approximately. 1 86 SETtlNG-TJP SCREW MACHINES Main Camshaft Computations. The main camshaft on the Acme automatic carries all the cams for operating the vari- ous slides, spindle-stopping mechanism, etc., and also the fan gear for indexing the cylinder. As shown in Fig. 19, which is a developed plan view of the camshaft with the drums and cams on it, it will be seen that one revolution of this camshaft completes one cycle of the machine; that is, one revolution of the camshaft would mean the completion of one piece, or four revolutions the complete indexing of the cylinder. The rotation of the camshaft is not connected directly with the rotation of the work-spindles, but indirectly the cams on it govern the rate of travel of the tools on either the top- or side- working tool-slides, and also the end-working slide. It is, therefore, necessary to determine for each job the relation be- tween the speed of the spindle and the speed of the camshaft in order to determine the production per hour, minutes, or seconds. The camshaft is driven from the main drive pulley through bevel gearing and a Johnson clutch. The clutch forms the connection between the direct drive and gear drive to the camshaft, so that it is possible to rotate the camshaft at a much higher speed for the idle movements than the speed at which it is operating when the tools are cutting. The speed of the camshaft, when driven direct, may be obtained from a table, accompanying the machine, giving the number of pieces produced per hour, as this number will represent the number of revolutions the camshaft makes in one hour. For example, the camshaft on the Nos. 54 and 55 machines has a speed of 576 revolutions per hour. Dividing 576 by 60, the camshaft will be found to make 9.6 revolutions per minute or 0.16 revo- lution per second. As there are 360 degrees in a circle, and as any point on the cam drum makes 0.16 revolution per sec- ond, the number of degrees passed through in this time equals o.i 6 X 360 = 57.6 degrees, approximately. Now, if it takes one second for the camshaft to rotate through a space of 57.6 degrees, the time required to complete the idle movements can easily be found, when the number of degrees taken up by 1 88 SETTING-UP SCREW MACHINES the idle or non-productive movements are obtained. By refer- ring to Fig. 20, in which the various drums and cams have been laid out in their respective positions, and at the point in their rotation at which the machine is indexing, it will be seen that the non-productive movements come in between the time that the lead cam A starts to operate and finishes. This applies when the longest single operation is performed by the end- working tools or from the forming slide. Where the longest operation is performed from the cutting-off slide, the idle time is less because there are thirty more degrees taken up on pro- ductive work. It is safe to assume that, on 75 per cent of the jobs set up on this machine, the longest operation is performed from the end-working tool-slide; hence, the calculations can be based on the number of degrees of drum surface between the starting and finishing points of the cam. This is found to be 360 220 = 140 degrees. When the longest single opera- tion is performed from the cut-off tool-slide, the idle move- ments occupy no degrees of the drum circumference. Time required for Idle Movements of Machine. The idle movements of the machine are those required for advanc- ing and withdrawing the tools to and from the work and indexing the cylinder. The stock is fed out and the chuck closed while the cylinder is indexing on the smaller machines and in the "first position" on the larger machines, but, in all cases, as can be seen from a study of Fig. 20, the idle move- ments more than compensate for the time required to feed out the stock. The three main idle or non-productive move- ments of the machine should be considered in calculating the actual time required for producing a given part. These movements are all confined to the space between B and C on the circumference of the cam drum. As all the non-productive movements take place while the camshaft is being driven at its highest speed direct through the clutch and not through the change gearing it is necessary to determine what part of the cam circumference these movements occupy and also the speed at which the drum is being rotated when driven direct. ADJUSTMENT OF DAVENPORT MACHINE 189 As previously determined, the idle movements or the space on the cam circumference from B to C equals 140 degrees, and, on the Nos. 54 and 55 machines, the camshaft, when driven direct, is rotated at a speed of 0.16 revolution per second. If it takes one second for the camshaft to rotate through a space of 57.6 degrees, it will require 140 - 57.6, or 2.43 seconds, approximately, for the idle movements. This time, if added to the time required for the longest single operation, will give the actual time required to complete one piece. Setting-up the Davenport Automatic. The method of setting-up and adjusting the Davenport multiple-spindle au- tomatic screw machine illustrated in Fig. 10, Chapter III, will be explained by considering the method of procedure for making a J-inch machine screw. The successive order of the operations and the tools to be used should first be determined. In this case, the order of operations is indicated by the dia- grams A to E, inclusive (Fig. 21) and the finished product is shown at F. The principal operation is that of rough-turning the body of the screw, and, in order to reduce the time per piece, two box- tools are used as indicated at A and B. The tool in the first spindle turns one-half of the required length, and then the remaining half is rough- turned by the other box-tool in the second spindle. When the first box- tool is at work, a forming tool on the cross-slide cuts away the metal on both sides of the screw-head, as the illustration indicates. The finishing cut is taken by a single box- tool in the third spindle (diagram C) ; this tool is given twice the feed of the roughing box-tools, so that the finishing cut will be completed in the same length of time required for the two roughing cuts. A die is next used to cut the thread, as indicated at Z>, and then the finished screw is severed from the bar of stock by the cutting-off tool, as shown at E. The end or point of the stock is also rounded by the cutting-off tool, preparatory to making the next successive screw. Speed for Work-spindles. The machine is geared so that the work-spindles will revolve at whatever speed is considered essential to economical production. For ordinary screw stock, SETTING-UP SCREW MACHINES a surface speed of about 100 feet per minute is considered a fair average for this machine. The material, in this case, is -j^-inch hexagonal steel (a special size for a J-inch screw), so that the surface speed may be based upon a diameter of y 7 6 Machinery Fig. 21. Examples of Work done on Davenport Five-spindle Automatic inch. By referring to the table of spindle speeds and corre- sponding change-gears to use, it will be found that the spindle speed should be 840 revolutions per minute, which speed is obtained by equipping the machine with a driving gear having 28 teeth and a driven gear having 36 teeth. This speed of 840 ADJUSTMENT OF DAVENPORT MACHINE 191 revolutions per minute will give a surface speed of approxi- mately 100 feet per minute. Number of Revolutions for Each Operation. The next step is to determine the number of revolutions the spindles make for each of the operations. The number of revolutions which the spindles make for any given operation depends upon the feed of the tool per revolution and the length of the part to be turned ; therefore, it is necessary to first decide what feeds are to be used. For rough-turning, the feed usually varies from 0.004 to o.oio inch per revolution of the spindles and, in this case, it will be assumed that a feed of 0.0075 mcn * s to be used for roughing and twice that amount, or 0.015 m ch) for the finishing cut, so that the box-tool which takes this finishing cut will traverse i-jf inch or over the entire body of the screw, while each of the roughing tools is feeding f f inch or one-half the length of the screw body. By dividing the length of the turned surface by the feed per revolution, it will be found that approximately 121 revolutions are necessary, (1.8 1 2 -f- 0.015) = I2I > nearly. Adding two revolutions to allow for a little clearance, for indexing, between the ends of the tools and the stock, gives a total of 123 revolutions of the spindles. After having determined the number of revolutions of the spindles for the longest operation, the machine is equipped with change-gears at U, Fig. 13, Chapter III, as indicated by a table accompanying the machine. Under the heading " Revo- lutions per Minute of Spindles" and in the column headed "840" (which represents the selected speed of spindles and revolutions per minute) will be found the figure 123 represent- ing the number of spindle revolutions required for the forward feeding movement of the tools. Opposite 123, the necessary change-gears are listed and also the rate of production. These gears transmit motion to the camshafts. In this case, the gear on the driving shaft has 20 teeth and the gear on the driven shaft, 44 teeth. The time in seconds required to make one piece, which includes the time for withdrawing the tools and indexing, is 1 2 seconds per piece. 192 SETTING-UP SCREW MACHINES Selection of Cams. Seventeen cams are furnished with the Davenport multiple-spindle automatic machine. Six of these cams are intended for turning operations, two for point- ing the ends of the stock, four for threading operations, and five for forming and cutting-off operations. The rise or throw of the cams varies ; for instance, among the cams used for turning, there is one having a rise of ^ inch (used for center- ing and facing operations) ; another having a rise of ^ inch ; two others, a i-inch rise, and two additional cams, a 2 -inch rise. If the travel required for the tool differs from the rise or throw of the cam, the motion of the tool is varied by changing the position of the link connecting the cam lever with the tool spindle, as previously explained in Chaper III. When setting- up a machine, cams are selected for each operation which are nearest to the required size as to rise, but which have a rise, in every case, that is equal to or greater than the travel re- quired for the tool. When these cams have been placed in position, the adjustable blocks at the upper ends of the cam levers are set so that each tool will travel the exact distance required on the work. After making these adjustments, the feed for most of the tools will be finer than those first selected, but, as the time for making a screw is governed by the longest operation, an increase in the number of revolutions that the spindles make during some of the shorter cuts simply means that these tools will, in most cases, leave a finer finish and will last longer, owing to the feed reduction. Adjustments for Threading Operation. The rise of the cam to use for operating the threading die spindle and the position of the link-block on the cam lever are shown by a table. This table shows what the rise of the cam should be for a given number of threads per inch, and also the position of the link-block on the cam lever. The figures denoting the cam rise and the graduation on the cam lever are listed under the required number of threads per inch to be cut, and oppo- site the number of turns which the work-spindle makes while a part is being machined. When the cam-lever block is cor- rectly set, the die-holder will follow up the thread, although ADJUSTMENT OF DAVENPORT MACHINE 193 the clutch pins of the die-holder permit a slight axial move- ment, so that the die is free to follow the lead of the thread. When the die is running off of the thread, the spindle carrying the die-holder is moved in the opposite direction by the cam, and the die-holder is provided with a ratchet which catches on the first revolution after the threading clutch is shifted from the low-speed gear to the high-speed gear. No adjustment of the cam which controls the clutch of the threading spindle is required for any pitch, as the clutch is always shifted just after the die-cam has reached the highest point. Record of Operations. It is good practice, preparatory to setting-up the machine for producing a new part, to lay out the operations as shown in Fig. 21, and then record the order of the operations, the tools used, etc., so that the machine can readily be adjusted or set-up for reproducing the same part. Such data are also useful for comparative purposes, when estimating on other work which is similar in size and shape. The data recorded on page 194 apply to the operations shown by the diagrams A to E, Fig. 21. As will be seen, a standard box-tool set to turn to 0.265 inches in diameter is used for the first roughing cut. This tool is actuated by a cam having a rise of one inch. As the tool is to turn one-half of the length of the screw body, or f f inch, the block of the cam lever is set to the 0.9 division, thus reducing the amount that the tool travels. For the forming operation, which is performed by a tool in the cross-slide at the same spindle posi- tion, a -fz-inch cam is used, and, as the feeding movement of the tool is only % inch, the cam-lever block is set at the 0.8 di- vision. In a similar manner, the data for the other turning tools is recorded. Ordinarily, it is easier to make all the neces- sary calculations beforehand and then adjust the machine accordingly, than to attempt to set the machine as each cal- culation is made. Turning a Trial Piece. After the machine has been equipped with the necessary cams, chucks, etc., it is cus- tomary to put a single bar of stock in one spindle and adjust each tool, as the head is indexed to the different positions, SETTING-UP SCREW MACHINES so that all the tools have the correct movement in a length- wise direction. These adjustments are made by means of the turnbuckles G which are shown in Fig. n, Chapter III. After all of the tools in the end-working spindles, as well as those on the cross-slides and swinging arms, in case it is necessary to use the latter, are adjusted to approximately the correct posi- tion, the five bars of stock should be inserted in the machine spindles and the final adjustments made. Order of Operations and General Data for Producing Screw shown at F, Fig. 21 Operations Tools Used Size of Cams, Inch Feed of Tool, Inch Feed per Revolution Effective Revolutions Location of Block Turn to 0.265 Standard Box I H 0.0075 I2 3 0. 9 Form to 0.265 Forming * ft O.OO08 123 0.8 Turn to 0.268 Standard Box I II 0.0075 123 0.9 Turn to 0.250 Standard Box 2 ill 0.015 123 0.9 Thread Die and Holder i| it 123 0.86 Cut-off Cut-off A 0.174 0.0015 I2 3 0.8 Surface speed, 100 feet per minute; spindle speed, 840 R.P.M.; gears, 28-36; seconds per piece, 12; feed gears, 20-44. Regulation of Stock-feeding Movement. The stock is always fed against a stop which forms a part of the box-tool or other tool in the first spindle or " position A" and the length to which the stock is fed out of the chuck is regulated by a screw at the rear end of that tool spindle. This screw is tapped into the spindle carrier, and the head of the screw engages a latch on the tool spindle and prevents the spindle from moving back farther than is necessary for the length of stock required. When it is desired to draw the tool spindle farther back, this latch attached to the rear end of the spindle is lifted. The turnbuckle for this spindle is adjusted for the position of the cutting tool independently of the stop-screw ADJUSTMENT OF DAVENPORT MACHINE 195 just referred to. The nut at the extreme left-hand end of the crankshaft should be adjusted to feed the stock about | inch farther than is represented by the length of the finished piece, to insure a firm contact of the stock against the stop. Use of Thread Spindle for Other Operations. When the work does not require a threading operation and it is desired to use some other kind of tool in the threading spindle, one of the change-gears which rotates the threading-spindle driving shaft can be removed, and a square-head set-screw engaged with a tooth space of the intermediate gear through which the threading clutch gears are rotated. By locking the inter- mediate gear in this way, the clutch gear teeth will act as keys and prevent the threading spindle from turning around, but permit it to slide freely, so that it can be used for holding an end-working tool the same as any of the other spindles. Independent Feeding Movement. An example of work done on the Davenport multiple-spindle automatic machine is shown by the series of diagrams G to K, inclusive, in Fig. 21, which illustrate the advantages of a separate feed for each of the turret and cross-slide tools. The operations for the first spindle position are performed by a forming tool on the cross- slide and an end-facing tool. The tool-slide advances o.oio inch for facing the end accurately and smoothly, and the form- ing tool rough- turns the work, leaving about o.oio inch on the diameter and width of the groove for finishing. The next suc- cessive operation is indicated at H. The tool-slide advances 0.040 inch for centering the work, and it has a long dwell at the end of ^ the feeding movement, thus insuring an accurate center. A forming tool also turns the part to the required diameter and the groove to the finished width. A stop-screw on the toolpost comes against a compensating stop for each spindle, to insure uniformity of diameters. At the next spindle position indicated at /, the tool-slide advances jfa i ncn f r drilling the hole. This drill is revolved rapidly by a drilling attachment driven by a round belt from the countershaft, so that the actual cutting speed is the speed of the work plus the speed of the drill spindle. The tool-slide next advances -jV 196 SETTING-UP SCREW MACHINES inch for finish-turning a shoulder as at / ; this shoulder must be very accurate and it was roughed out by the cutting-off tool at the time that it severed the previously finished part. For the final operation shown at K, the tool-slide advances f inch for reaming the hole. As but little metal is removed, the feed is rapid. When the operation is completed, the reamer is quickly withdrawn and the cutting-off tool, which has been at work in the meantime, severs the piece which drops from the bar. CHAPTER VI ATTACHMENTS FOR AUTOMATIC SCREW MACHINES THE variety of work for which an automatic screw machine is applicable may be greatly increased by the addition of auxiliary attachments. Some of these attachments are de- signed to do work which could not be done with the ordinary tool equipment, thus enabling the machine to complete a series of operations and produce finished parts without a second operation upon another machine. Other attachments are designed for automatically feeding separate parts, such as castings or forgings, to the machine or for transferring pieces requiring a second operation to an attachment operating in conjunction with the machine. While screw machines made by different manufacturers are often equipped with attach- ments for doing the same class of work, these attachments usually vary considerably in their design, as they are con- structed for application to a certain type of machine. Some of the more common attachments will be described. Screw Slotting Attachments. The screw slotting attach- ment is used for milling a screw-driver slot across the head of a screw, after the latter has been turned and threaded by the regular mechanism of the machine. One of these attachments is shown applied to a Brown & Sharpe machine in Fig. i. This attachment is designed to take screws as they are cut off by the machine and to slot them automatically, thus elimi- nating a second operation in another machine and completing the screw in practically the same time that would be required to finish it without the slotting operation. The saw which does the slotting is mounted on a slide and is driven by a round belt from the overhead works. The arm F which transfers the screw from the machine spindle to the saw is actuated by a cam K through a lever connecting with rockshaft C. The 197 i 9 8 ATTACHMENTS screws are held in a bushing carried in a " floating holder" located at the end of the transfer arm F. This transfer arm is swung down so that the bushing is in line with the work in the main spindle, and the bushing engages the work before it is severed from the bar of stock. After the screw is cut off, FACE OF CHUCK Fig. 1. Front Elevation and Plan of Screw-slotting Attachment for Brown & Sharpe Screw Machine the arm swings up to the position shown in the illustration. The rockshaft C is then fed longitudinally towards the slotting saw by means of the advancing cam / which imparts motion through lever E. When the slot in the screw-head has been cut and arm F drops back, the screw is removed from the bush- ing by the ejector K\, which is simply a piece of sheet steel fastened to the attachment. The transfer arm F is accurately SLOTTING ATTACHMENTS 199 located with reference to the spindle by set-screw E\, which engages block F\, whereas the set-screw G\ and block HI control the position of the arm with reference to the saw. Slotting and Slabbing Attachment. The attachment shown in position on the Cleveland automatic screw machine in Fig. 2 is used for slotting the heads of screws, slabbing operations, and similar work. The operation is done while the turret tool is working, so that no time is lost. The opera- tion on a screw is as follows : After the part has been finished, and is ready to be cut off, the turret advances carrying the Fig. 2. Slotting and Slabbing Attachment on Cleveland Automatic screw-slotting conveyor A which takes hold of the screw as it is severed from the bar. The stock is then fed forward and the turret tools begin on the next piece ; at the same time, the conveyor A, carrying the screw that has just been cut off, brings the head into contact with the slotting saw B. By the time the turret tool has finished its cut, the saw has also completed its operation. The finished part is ejected from the conveyor by means of a pin C, upon the backward stroke of the turret. The slotting arm D carrying the saw B is a slight distance back from the face of the chuck hood, so that it clears all the turret tools, except when the conveyor A, carrying the screw, comes into line with it. 200 ATTACHMENTS The saw spindle is driven by a belt from the countershaft. The drum which carries the chuck opening and closing cams has, in addition, another cam which operates the slotting arm D. This cam moves the saw toward the turret when the conveyor A, held in the turret, advances with the part to be slotted. The slotting arm is returned to its original or neutral position by the coil spring shown, after the roll on arm D comes out of contact with the operating cam. To fit up this attachment for slabbing operations, two slab- bing cutters are mounted on the saw spindle in the same Fig. 3. Index Drilling Attachment on a Brown & Sharpe Automatic Screw Machine manner as the slotting saw B, and the same movement takes place as in slotting. It is also possible by means of a special slotting arm D to cut a groove or slot of any shape or depth lengthwise of a piece by raising the center of the saw spindle, so that the work will pass under the milling cutter or saw. Index Drilling Attachment. The Brown & Sharpe index drilling attachment shown in Fig. 3 is designed to drill radial holes in such work as binding posts, capstan screws, studs, bushings, and similar pieces, which are made in the automatic screw machines. An adjustable swinging arm takes the pieces as they are severed from the bar and transfers them to the spindle of the drilling attachment where they are securely held DRILLING ATTACHMENTS 2OI in a spring chuck for drilling. The movements of the arm and mechanism that control the indexing, the operation of the spring chuck, and the movement of the drill are all governed by cams located on an auxiliary camshaft. The chain and sprocket drive for rotating this camshaft is shown encased at the left of the illustration. The drill spindle B is driven by a small round belt from the overhead works, which operates around the idler pulleys M. The drill spindle is operated by cam C, through lever D. The motion for indexing the work-spindle of the attachment is obtained from cam F. This indexing Fig. 4. Cross-drilling Attachment held on Cut-off Tool-slide of Acme Multiple-spindle Automatic movement makes it possible to drill several accurately-spaced holes through the head of a screw or other part. One piece is drilled by the attachment while another is being made by the regular mechanism of the machine. Cross-drilling Attachment. When only a single hole is to be drilled cross-wise through the work, what is known as a cross-drilling attachment may be used. This is simpler in con- struction than the index drilling attachment (shown in Fig. 3) and is mounted on the cross-slide when applied to a Brown & Sharpe machine. The spindle is driven by a small belt from the overhead works, and the feeding movement for the drill 2O2 ATTACHMENTS is derived from the cross-slide itself. Before cross-drilling, it is necessary to stop the spindle and hold it rigidly. On Brown & Sharpe machines, a spindle brake is used. One of the standard cross-drilling attachments used on the Acme multiple-spindle machine is shown in Fig. 4. This con- sists of a cast-iron frame A which is bolted to the top face of the cut-off tool-slide and works in the third position, where the work-spindle can be stopped. The cross-drilling and thread- ing operations can usually be performed at the same time. The drive for this attachment is by a flat belt from a special Fig. 5. Acme Cross-drilling Attachment with Accelerating Movement overhead countershaft running on the pulley B, which is fastened to the spindle C that carries the drill. This attach- ment, by a slight modification in its construction, can be driven by gears and a universal- joint shaft from the main tool-slide. Cross-drilling Attachment with Accelerating Movement. Another Acme cross-drilling attachment, but one having an accelerating movement for increasing the travel of the drill, is shown in Fig. 5. The attachment A is similar in construc- tion to that shown in Fig. 4, except that it is mounted on two slides B and C. Slide C is fastened to the top face of the cut-off tool-slide, and slide B fits over the former and is furnished with a gib to provide for adjustment. This enables the drilling DRILLING ATTACHMENTS 203 attachment to be moved longitudinally along the base, facili- tating adjustments for the drilling of holes at different distances from the face of the chuck. Attachment A is operated by a lever D which is fulcrumed to the lower slide C. A block E provided with hardened adjustable stops F is fastened to the base in which the cut-off tool-slide works. This block, by means of its adjustable points, stops the lower Machinery Fig. 6. Cross-drilling Attachment with Opposite Spindles portion of lever D, so that, instead of following the movement of the cut-off tool-slide when it is fed in, it transmits a move- ment to the lower arm of the lever and thus accelerates the travel of the drill-holder. The ratio between the arms of lever D is if to i, thus making it possible to drill a hole clear through a piece. The regular travel of the cross-slide is only equal to a little over one-half the diameter of the bar, so that, when it is necessary to drill a hole entirely through the work, 204 ATTACHMENTS this attachment with accelerated movements can be used to very good advantage. Cross-drilling Attachment with Opposite Spindles. The Acme cross-drilling attachment shown in Fig. 6 is provided with opposite spindles and is adapted for drilling cross holes, and, in addition, counterboring or countersinking from both sides. It can also be used for drilling parallel holes of the same or different diameters at a given distance from each other and from the face of the chuck. The holes can either be drilled entirely through the work or to any distance desired. When necessary, the attachment can be provided with an Fig. 7. Brown & Sharpe Automatic Screw Machine equipped with Turret Drilling Attachment accelerating device for increasing its travel. The second or auxiliary spindle of this attachment is driven by spur or bevel gears from the regular drill spindle. When driven by spur gears, the drive is through gear A, shaft B, and gears C and D. Gear D is keyed to the spindle in which the counter- sink E (or drill) is held. The bracket F carrying the auxiliary mechanism is bolted to the front side of the regular attach- ment used for cross-drilling. In operation, as the cylinder indexes, the stock comes between the spindles of the attachment, and the machine is so cammed that the cut-off tool-slide feeds forward, drills the first hole, and then pulls back far enough to bring the drill BURRING ATTACHMENT 205 held in the opposite spindle into contact with the work. The slide then feeds forward again to an intermediate position, before the next indexing operation. Turret Drilling Attachment. The turret drilling attach- ment shown applied to a Brown & Sharpe machine in Fig. 7 is used to increase the speed of a drill relative to the work, without running the work-spindle faster. This is accomplished by rotating the drill in the opposite direction to the stock. This attachment is often used when making small studs and Fig. 8. Rear View of the Burring Attachment applied to Brown & Sharpe Automatic Screw Machine a variety of work requiring the use of one or more small drills which must be run at a much higher speed than is required for any other tool, in order to obtain an economical cutting speed. The attachment is driven from the overhead works by a belt C which rotates a spindle located at right angles to the spindle of the machine. This spindle, in turn, drives the drill spindles by means of bevel gears G. The illustration shows the turret equipped with two drill spindles A and B. The number may be varied to suit the work. Burring Attachment. The burring attachment shown in Fig. 8 applied to a Brown & Sharpe machine carries a single tool for removing burrs or for performing light operations, such 2o6 ATTACHMENTS as drilling, counterboring, or facing on the cut-off ends of pieces before they leave the screw machine. The attach- ment has a work-spindle C which is driven from the overhead works by a small belt. The cutting tool is held in this spindle. A chuck encased at M attached to a swinging arm picks up the piece of work as it is severed from the bar and conveys it first to a device that clamps it securely in the chuck and then to the tool in the spindle of the attachment. The movements of the arm are controlled by two cams located on the end of the camshaft. The small collet chuck located inside of part M Fig. 9. Tap and Die Revolving Attachment is opened by the engagement of a small pin which comes into contact with a stationary rod P. The work is then ejected from the chuck by means of a small plunger which engages finger R when the transfer arm drops back preparatory to receiving another piece. Tap and Die Revolving Attachment. When a series of operations requires no other slow movement except the reduc- tion of speed for a threading operation, the tap and die revolv- ing attachment shown in Fig. 9 is used in connection with Brown & Sharpe machines. This attachment provides means for reducing the speed of the tap and die relative to the work, when threading, and of increasing the speed when removing a REAMING ATTACHMENT 207 tap or die from the threaded part, without altering the speed of the work-spindle. This is effected by revolving the tap or die in the same direction as the spindle, but at a slower speed, the combination of the two speeds giving the desired result. The attachment is driven by a belt B from the countershaft through pulley C and bevel gears D. The spring E acts in the same manner as the spring in an ordinary draw-out die or tap-holder. Accelerated Reaming Attachment. For reaming holes which exceed in depth the travel of the end- working tool- MacMncry Fig. 10. Accelerated Reaming Attachment slide, the accelerated reaming attachment shown in Fig. 10 is used on the Acme multiple-spindle machine. This attach- ment is held in the " fourth" end position in the tool-slide, and consists of the regular cast-iron collet A which fits in the hole in the tool-slide. The reamer holder C is a sliding fit in the steel bushing B, and is furnished with a loose cap D in which the reamer is held by the set-screw shown. The cap D is held to the holder C by two shoulder-head screws, the bodies of which are -5% inch smaller in diameter than the holes in the cap, thus allowing the cap to " float" a slight amount. A stud E screwed into the shank of the holder C and working 208 ATTACHMENTS in an elongated slot in the bushing and collet projects through from the under side of the collet and works in an elongated slot in the lever F. This lever is fulcrumed on a screw which is located in either holes G or H, depending upon the excess amount of travel required, and it serves to accelerate the travel of the reamer. In order to increase the travel, the screw is placed in hole H, and, to reduce the travel, the lever is moved back so that the screw would take the G position. The bracket / in which the lever is fulcrumed is fastened Fig. 11. Acme Cross-drilling and Milling Attachment with Spindles located at Right Angles to collet A and advances with the end- working tool-slide. The rear end of lever F is provided with two hardened screws rounded on the heads, which come in contact with the dogs J and K when the device is in operation. These dogs are ad- justable on the bracket L, fastened to the gib If, which, in turn, is held to the bed of the machine. In operation, as the end-working tool-slide advances, the round-headed screw in the front face of the lever comes in contact with dog /, and, as the tool-slide continues to advance, this dog acts upon the fulcrumed lever, drawing out the reamer holder and accelerat- MILLING ATTACHMENTS 209 ing its movement. The position of dog / on the bracket, and also the location of the screw in holes G or H, determines the amount of excess movement given to the reamer. When the tool-slide drops back, dog K returns the reamer holder by means of lever F to its "back" position. Drilling and Milling Attachment. A two-spindle drilling and milling attachment in which the spindles are located at right angles to each other is shown .in Fig. n applied to an Acme machine. This attachment is used for drilling a cross hole and milling a flat on the work. The casting C which carries the spindles A and B is fastened to the top face of the cut-off tool-slide, and > carries a pulley D which is driven through a flat belt from a special overhead countershaft. Pulley D is keyed to the top horizontal shaft and drives the vertical mill- ing spindle through bevel gears E. On the rear end of the top horizontal shaft is a spur gear F which, through the inter- mediate gear G, drives the spur gear H fastened to the drilling spindle A. This attachment is adjustable longitudinally on the base 7, the latter being fastened to the top face of the cut-off tool-slide. The attachment can be provided with an accelerating movement, if desired. Vertical-spindle Milling Attachments. Fig. 12 illustrates an Acme vertical-spindle slab milling attachment, designed for carrying two face-milling cutters A and B. These cutters are held on the vertical spindle C and are separated by a spac- ing washer of the required thickness. The attachment is held on the top face of the cut-off tool-slide, and is arranged for milling two flats on a cold-rolled steel piece, which is turned out at the rate of fifty-three pieces per hour. The vertical spindle C is driven by bevel gears (enclosed in the guard D) and the pulley E, the latter being belted to a special counter- shaft. It is possible to drive this attachment without employ- ing a special countershaft, by connecting it directly through a telescopic knuckle-joint shaft to the gears driving the thread- ing spindle. Another vertical-spindle slabbing attachment somewhat similar in construction to that just described is shown in 2IO ATTACHMENTS Fig. 13. In this case, however, two end-milling cutters A and B are used. The spindles carrying the end-mills are driven from a special countershaft belted to pulley C. This pulley Fig. 12. Acme Slab Milling Attachment Fig. 13. Acme Slab Milling Attachment equipped with Two End-mills is keyed to the shaft D which drives the vertical shaft E through bevel gears enclosed in guard F. On opposite ends of shaft E are held gears G and H, which mesh with gears on the vertical milling spindles. This attachment is fastened MILLING ATTACHMENTS 211 to the top face of the cut-off tool-slide and is operated as previously described. End-milling or Slotting Attachment. Fig. 14 illustrates an Acme end-milling or slotting attachment which is held in the third position and driven by gears. The bevel gear A receives power from the regular gears that are provided for Fig. 14. Acme Slotting or Milling Attachment held in Third Posi- tion and Driven from Gears in Second Position Tool-spindle driving the tools held in the second position tool-spindle. The cutter is adjusted for depth by means of a special device on the rear end of the main tool-slide. This attachment is held rigidly, being tied to both second and third position tool-spindles. The work-spindle in the second position is stopped when the end-milling or slotting attachment is at work. Independent Cutting-off Attachment. The attachment shown in Fig. 15 is used on Cleveland automatics for cutting 212 ATTACHMENTS off the work when the tools on the rear and front of the cross- slide are used for forming operations. This attachment con- sists primarily of a swinging arm A mounted on a stud which is attached to the spindle head of the machine. The cutting-off blade is mounted in a holder B, at the forward end of the swinging arm A ; the holder B is fulcrumed on a bolt C which is provided with a locking nut on the opposite side for clamp- Fig. 15. Independent Cut-off Attachment on Cleveland Automatic ing the tool-holder in the desired position. The proper setting of the cutting-off blade is secured by means of the set-screws D which operate against a pin driven into the arm. To make this adjustment, it is necessary to release the nut on the clamping bolt C. This attachment is operated by the cam G held on the camshaft F, the cam being adjustably mounted on the disk H, as illustrated. This cam contacts with a roll held in arm A and gives it the required move- ment at the desired time. The roll is carried on an eccen- tric stud for fine adjustment of the cutting-off blade. The SPECIAL ATTACHMENTS 213 blade is clamped in the holder by two clamping bolts as illus- trated. Attachment for Forming Squares and Hexagons. An attachment for automatic screw machines is shown in Fig. 16 which is used for cutting flat surfaces, such as squares and hexagons or other polygons, on work produced from a bar, directly in place, so as to save a second handling of the work after leaving the automatic machine. The attachment, as designed, is particularly intended to be applied to a four- spindle automatic screw machine, and provisions are included Machinery Fig. 16. Attachment for Milling Squares and Hexagons while Work is Revolving for Other Machining Operations for driving a milling cutter of special design, by means' of which flat surfaces are. cut, and also for feeding this cutter past the revolving work. It should be understood that the work revolves while the flat surfaces are cut. The attachment shown in the illustration is arranged for cutting a hexagon on the end of one of the bars in the machine, the cutting tool being the cutter A , provided with three teeth. This cutter is placed on a supplementary slide, mounted on the work-carrying head of the machine, and is fed by means of a leverage system adjustable to suit the requirements. When the device is in operation, the work and the cutter re- volve in the same direction in relation to' their axes, so that at the cutting point the directions of the surfaces which are 214 ATTACHMENTS in contact are opposite, but the cutter is geared to revolve at twice the speed of the work to be provided with the hexagon, and, as the cutter has three cutting points and revolves very rapidly, it produces a polygon with six equal sides when it has traversed the full width of the flat. If the cutter had only two points, a square would be produced. If a cutter having only one point were used, the gearing being the same, two flats only would be produced, and the remaining portion of the circular surface would remain curved. It is clear that I I FORMING TOOL CROSS- Machinery Fig. 17. Arrangement of Worm Robbing Attachment on Automatic Screw Machine the same results can be obtained by gearing of other ratios than 2 to i, provided the number of teeth in the cutter is se- lected to suit the ratio of revolutions. The sectional view shows how the drive is transmitted to the cutter from the main drive of the machine. When any devices are applied to automatic machines which in a certain sense belong outside of the original field of the machine, it is very important to take into consideration whether these devices require a stoppage of the regular func- tions of the machine, and thereby rob the machine itself SPECIAL ATTACHMENTS 215 of the efficiency of which it is capable, or whether these extra devices perform their work simultaneously with the per- formance of certain of the legitimate functions of the tool. In the former case, it is often doubtful whether the intro- duction of such devices is economical. Stopping an auto- matic machine for such operations as screw slotting, milling, etc., which prevent the continuous working of the machine, is sometimes questionable economy. On the other hand, if the devices are so designed that operations, which of neces- sity must be performed on the machine, can still be carried on while the device performs its own functions, then the introduction of such devices is of distinct advantage. With the device just described, the work is provided with its flat surfaces while it still continues its rotary motion, thus per- mitting other cutting tools to perform their functions without interference. Fig. 18. Worm to be Hobbed, and the Hob Attachment for Robbing Worm and Spiral Gears. An at- tachment applied to a National-Acme automatic screw machine for bobbing worm and spiral gears from blanks formed from bar stock is shown in Fig. 17. The design of the worm is such that it could not be handled by a circular hob fed longitu- dinally ; therefore, a drop feed is used. By calculation, it was found that forty teeth would give a hob of the diameter that would clear the two high points on the worm blank, marked A and B in Fig. 18, and this number of teeth on the 216 ATTACHMENTS hob determines the entire gearing of the attachment. The worm being of the single- threaded type, and the hob used to produce it having forty teeth, it follows that the worm must make forty revolutions to one revolution of the hob. Now the chucking spindle holding the worm blank must make forty revolutions to one revolution of the hob, which is driven by an extra shaft geared to the center spindle of the machine at the back or pulley end. Having the ratio between the speed of the chucking spindle and the center spindle, which in this case is 29 to 36, the shaft B in Fig. 17 must revolve at the same speed as the chucking spindle. The 40 to i reduction is ob- tained through the worm on this shaft and the worm-wheel on the hob spindle. In Fig. 17, D shows the worm-wheel and C the worm keyed on the shaft B. On the No. 53 machine fitted up for this job, a 29-tooth pinion on the center spindle drives a 3 6- tooth gear on each chucking spindle. There- fore, a 29-tooth pinion is keyed on the center spindle on the back end of the machine and drives a 3 6- tooth gear on the shaft B with any idler between that conveniently meshes with the two gears. This attachment is so designed that the hob starts hobbing the worm as soon as the forming tool begins ^to form the blank. Since the worm C and the worm-wheel D drive the hob at the required speed, and as their relative positions cannot be changed without altering the speed of the hob, it is evident that the center of the worm C must be the center about which the hob spindle oscillates. The worm can drive the worm- wheel D keyed on the hob spindle at the same speed in any position of the hob. The hob spindle is carried in bearings on an independent plate H which swings back and forth about the center of C, on the surface of the casting I that is bolted down on the screw-machine head. A cam E is mounted on the forming tool cross-slide to raise and lower the hob. An Machinery Fig. 19. Detail of the Feed Cam SPECIAL ATTACHMENTS 217 arm on the casting H has a roll F that fits in the cam E, and thus the raising of roll F by cam E lowers the hob, and vice versa. Fig. 19 shows the cam E more clearly. From B to A, the cam lets the hob drop quickly down to the surface of the worm, and this drop occurs when the cross-slide of the ma- chine moves in quickly until the forming tool starts to cut. This action of the cross-slide reduces the time required to feed in by sliding in quickly to the point where the forming tool begins to cut. The tool then has more time to feed in and do the forming at a slower feed, thus producing a more perfectly finished blank. For this reason, the cross-slide was selected to feed the hob on this attachment, and obtain the same action for the feed of the hob as for the feed of the form- ing tool. When the roller F has passed up the sharp incline By the cross-slide is just beginning to feed in slowly and the hob is just touching the blank ; then the roller starts up the incline A at a slow speed, thus feeding the hob down into the blank to the required depth at a very slow feed. No spring or weight is required to lift the hob out of the hobbed worm, as the cam C performs this function by lifting the hob high enough to clear the chucking spindle of the machine, which carries the hobbed worm, allowing it to swing around a quarter of a revolution to its next position for the drilling operation. Not being certain of the accuracy of the scaled dimensions of positions of the parts of the machine and the outside diameter of the worm being subject to a change, the cam E (Fig. 17) was made adjustable. By sliding it in or out by means of the screw /, various diameters of a o.oQS-inch lead single- threaded worm may be hobbed, providing that the variation does not amount to enough to change the spiral angle sufficiently to interfere with the angle of the teeth cut in the hob. However, considerable variation in the diameter of the worms to be hobbed can be taken care of. The face of the hob being flat and tangent to the worm, there is considerable clearance between the sides of the teeth on the hob and the sides of the threads on the worm in back of the cutting surface of the 218 ATTACHMENTS hob. This clearance increases as the curvature of the worm is farther from the toothed face of the hob. This is evident, in that the teeth become narrower at the top, and the space between becomes wider. The hob spindle is made adjustable to compensate for the re-grinding of the hob. By loosening the nuts on the back end of the spindle from the steel thrust Fig. 20. Tilting Magazine Attachment collar, the clearance may be taken up by tightening the lock- nut on the hob end, thus pulling the spindle forward. To make the generating hob, another hob is required to cut the teeth, this hob being similar to the one used in hobbing a worm-wheel. In fact, the relation between these two hobs is the same as between a worm and worm-wheel. This hob for producing the teeth in the generating hob used on the fixture is made to the same dimensions as the worm to be hobbed. It is thus evident that the generating hob will repro- duce a worm of the same form of thread as that of the hob that MAGAZINE ATTACHMENTS 2I 9 produced the teeth in it. There is, however, a slight exception in this case, in that the hob takes a drop cut in the worm blank, thereby leaving a curve on the threaded length of worm with a radius equal to half the diameter of the hob in other words, producing a worm somewhat of the Hindley form. No ad- vantage in this shape of worm is gained, however, as the worm- wheel driven by the worm is much smaller in diameter than the generating hob. Fig. 21. Vertical Hopper Magazine Magazine Feeding Attachments. Magazines for han- dling work to be chucked automatically have developed along many lines, and a great number of ingenious devices have been designed which are adapted to the various shapes and kinds of work that are operated upon in automatic machines. The attachments shown in Figs. 20 to 23, inclusive, have been de- signed for the Cleveland automatics. What is known as a " tilting magazine attachment" is shown in Fig. 20. This attachment is designed for handling castings, drop-forgings, 22O ATTACHMENTS and other parts requiring a second operation. The magazine A is filled from the top, the parts being placed one upon the other. In the illustration, the magazine is shown tilted down- ward, so that the conveyor B is in a position to advance and secure one of these pieces. After a part is removed from the magazine by the conveyor, the magazine tilts upward about shaft C, so that it is out of the way of the turret tools ; the conveyor is then brought into line with chuck D into which the Fig. 22. Rotary Magazine Attachment part is deposited. The tools in the turret and those on the cross- slide then proceed to machine the part held in the chuck. (No tools are shown in this particular illustration.) The maga- zine frame is provided with adjustable strips and bushings to accommodate parts of different size. The finished pieces are automatically removed by an ejector inside of the machine spindle. Vertical Magazines. A vertical hopper magazine for feed- ing studs into the rear end of the spindle of a Cleveland auto- matic machine is shown in Fig. 21. This might be called a MAGAZINE ATTACHMENTS 221 "reservoir magazine," as it has a widened upper portion for carrying a large number of parts. The work feeds by gravity into bushing A, and it is forced into the spindle by means of a push-rod B, which is operated from the cam-drum at the rear of the magazine. There is an agitator, which, by means Fig. 23. Front View of Rotary Tilting Magazine of a cam-and-lever mechanism, oscillates the agitator shaft C which insures feeding the work from the hopper. The magazine holds from 300 to 1500 pieces, the number depending upon the diameter, and the entire frame is adjustable to suit any length within its capacity. Rotary Magazine Attachment. The rotary attachment shown in Fig. 22 is intended for irregular-shaped parts which 222 ATTACHMENTS cannot be fed through a tilting magazine. The pieces are placed by hand in the bushing C of the magazine. The illus- tration shows a piece of work A which has been removed from one of the bushings C when the turret was in its forward posi- tion; this part will be placed in the chuck when the turret is indexed so as to bring the turret into alignment with the spindle. The magazine is indexed by a dog on the camshaft B at the rear, this indexing movement occurring before the conveyor is in position to take another casting from the maga- zine ; the latter is locked in position by a spring plunger after indexing. The work is removed from the chuck by an ejector after being finished. Rotary Tilting Magazine. The rotary type of tilting maga- zine, shown in Fig. 23, is used for second-operation work. The magazine tilts to the working position, as shown in the illus- tration, and, after the piece has been removed, it rises to clear the turret tools. In this respect, it is similar to the tilting magazine shown in Fig. 20, but differs from this design in that the parts to be machined are placed in the bushings A which are mounted in the links B. This arrangement permits of handling a greater variety of irregular shaped parts than was possible with the original form of magazine, where the parts were laid one upon the other and guided by parallel bars. The chain composed of the links B is indexed by means of the lower pair of sprocket wheels C, one of which is pro- vided with a series of pins that engage an index pawl not shown in the illustration. This pawl rotates the sprockets upon the downward tilt of the magazine and brings each link B in line with the conveyor D in the turret hole ; upon the upward tilt, the pawl drops down and engages the pin follow- ing the one that has acted upon it. The sprocket shaft E rests in the saddle F on the main supporting arm G, which serves as a stop and also maintains the required alignment while the conveyor is removing the part to be machined. The adjustable stop H mounted on the main supporting arm prevents the conveyor straining the magazine while removing the work from the bushing. MAGAZINE ATTACHMENTS 223 The operation shown in Fig. 23 is the machining of cast- iron bushings having a collar or shoulder at one end. In this case, the part that is gripped in the chuck is cut off by the in- dependent cutting-off attachment /. Occasionally, when the magazine is used for some odd-shaped piece that has surface enough to grip in the chuck, it is necessary to employ a simple form of latch held by a spring to keep the piece from falling out. This statement applies only to second-operation work and is referred to in order to show that the magazine may be employed for practically any shaped piece upon which a second operation must be performed. Aside from the tools required for different jobs, the only special equipment necessary is bushings of the required size. CHAPTER VII DESIGNING SCREW MACHINE CAMS WHEN an automatic screw machine is equipped with special cams for controlling the movements of the various tools and parts of the machine requiring a change of action, whenever a different class of work is to be produced, the designing of these cams constitutes an important part of screw machine practice. As the preceding descriptions of different screw machines indicate, some types do not require special cams for producing different parts, but are so arranged that the necessary changes of feed for the tools, etc., are obtained either by adjustable cams forming a permanent part of the machine or by adjust- ments which vary the motion of cams that are a part of the regular equipment. When a machine is designed to use special cams, the advantages aimed at are the securing of the ideal conditions as to rates of feed for each operation, and the minimum time for idle movements; such cams enable the machine to duplicate readily the same part at any future time, the cams being marked and preserved for this purpose. /The following description of the general method of procedure in designing cams applies especially to the Brown & Sharpe auto- matic screw machines, although a study of the principles involved will prove of value in connection with the design of cams for screw machines made by other manufacturers. On the Brown & Sharpe automatic screw machines, three cams constitute a set. What is known as the "front-slide cam" operates the front cross-slide, the " back-slide cam" operates the back cross-slide, and the "lead cam" controls the movement of the turret slide. The motion for feeding the stock, revolving the turret, and reversing the spindle is taken from a rear driving shaft which runs at a constant speed. This shaft, through suitable change-gears, rotates the shafts upon 224 GENERAL PROCEDURE 225 which the cross-slide and turret operating cams are mounted, at a speed suitable for the work to be performed. The dura- tion of the cycle of operations or the length of time required to make one piece is positively regulated by means of these change-gears. When designing cams, it is well to bear these essential points in mind. Effect of Cutting Speed on Cam Design. Before the cams are laid out, it is necessary to decide what types of tools are to be used and the successive order of the operations. Then the cutting speed for the material to be operated upon should be determined in order to ascertain the speed of the spindle. The tool movement that will be necessary in a given time in order to secure a certain rate of feed per revolution must also be determined. The rise of each cam lobe is then proportioned according to the number of revolutions which the spindle and work make while the tool controlled by that particular cam is taking its cut. When turning parts from iron or steel, the formed tools will withstand a much higher speed than a tap or die, which should be taken advantage of in order to operate the machine as economically as possible. It is common practice to run the spindle backwards at a comparatively fast speed for the form- ing and cutting-off operations, and forward at a somewhat slower speed for thread cutting and other operations which can be performed to advantage at slower speeds; however, if the machine is to be used for a variety of work, or if hollow mills or box-tools are used principally, the correct speed for a die or tap can be obtained by means of an attachment which serves to revolve the die or tap in the same direction as the spindle, but at one-half the spindle speed. This tap and die revolving attachment is of especial value where the work requires no other slow movement except that for threading. General Method of Designing Cams. As the rise of each cam lobe is proportioned according to the number of revolutions made by the spindle while that part of the cam is in use, the relation between the spindle revolutions and the various opera- tions is first determined. The total number of revolutions 226 CAM DESIGN required to complete one piece is found by adding together the number of revolutions for each cut, the number for each indexing of the turret, for feeding the stock, etc. ; an approxi- mate number of revolutions may also be added for clear- ance. In determining the number of revolutions for each operation, it is necessary to decide what the feed should be in each case. Assuming, for instance, that a feed of 0.006 inch per revolution would be about right for rough turning, and that there is a length of 0.630 inch to turn, this operation would require about 105 revolutions of the spindle. If one-half second were necessary for indexing the turret, and the spindle speed is about noo revolutions per minute, approximately 9 revolutions of the spindle would be required for indexing ; in actual practice, probably 12 or 13 revolutions would be allowed. In the same way, the number of revolutions for the finishing cut and also for the succeeding operations would be deter- mined, the number required for indexing being added between each operation. The time required for the complete operation is next de- termined by dividing the total number of revolutions by the number of revolutions which the spindle makes per second. Thus, if the estimated number of revolutions for machining the work is 406, and the spindle makes 18 revolutions per sec- ond, the time for completing the piece will equal 406 -*- 18 = 23 seconds, approximately. When the number of seconds for completing the work has been obtained, the revolutions re- quired for each operation are converted into hundredths of the cam circumference, and the different lobes on the cam are proportioned according to the number of revolutions for each operation. If the spindle revolves 18 times per second, and 23 seconds are required to make one piece, it will revolve 414 times for each part produced, which agrees closely with the approximate estimate ; therefore, if the spindle revolves 414 times for machining each part, or for one revolution of the camshaft, each y^-0- of the cam periphery represents 414 -r- 100 = 4.14 revolutions of the spindle. If 105 revolutions are required GENERAL PROCEDURE 227 for rough-turning, that portion of the cam for operating the turret, when the rough-turning tool is in position, will extend over 105-^4.14= 26 spaces, approximately, or -ffo of the circumference of the cam. This part of the cam circumference is then laid out so that it will impart the required movement to the tool. In this way, the operation of the turret-slide and the cross- slides can be worked out in conjunction with one another, and the proper feeds for each operation can be determined in advance. One, two, or sometimes three pieces of work are completed in one revolution of the cam, so that the various movements of one of the slides in making a particular piece are laid out as curves around the cam; these curves either occupy the whole circumference or are repeated once or twice, according to the number of pieces produced per revolu- tion. Laying Out Cams for a Screw. The method of laying out cams on the No. oo Brown & Sharpe automatic screw machine, for producing the screw shown in Fig. i, will be described. These screws are to be made from ^--inch soft machinery steel stock. The tools used and the successive order of operations are as follows: i. Rough- turn the body of the screw with a hollow mill. 2. Finish- turn the body of the screw with a box- tool. 3. Cut a thread on the end of the screw. 4. Cut off the finished screw and at the same time shave under the head and remove the burr with a forming tool. For roughing cuts, a properly constructed hollow mill is recommended. Such a tool will cut easier if the cutting edges are inclined so that they form a slightly conical shoulder rather than one which is square. For finishing, the best results are usually obtained with a box- tool. Such a tool also has the ad- vantage of a wide range of sizes and it can be equipped with two or more cutters for turning different diameters. Speed of the Spindle. The number of revolutions of the spindle required for the various operations will necessarily depend upon the kind of work to be done and the amount of stock to be removed. In this case, two spindle speeds will 228 CAM DESIGN be employed in order to use a comparatively high speed for some of the operations. By referring to the spindle speed chart accompanying the No. oo machine, it will be found that a speed of 927 revolutions per minute with the spindle running forward and 1273 revolutions with the spindle running back- ward may be used to advantage for producing the screw shown in Fig. i. The slower speed gives a surface speed of 30 feet per minute for cutting the thread and a surface speed of 53 feet per minute at the outside of the stock ; 1273 revolu- tions per minute gives a surface speed at the outside of the J-*- i.^^1 -IS jiii'mlilD^ ^ . JtL = .o|g 48 THREADS / PER INCH / TURRET / Yi K DIE-HOLDER / >i rm !/ TURRET / ] i n / | ^ i f i , 1 H j ' ~jj ! 1 [\_i I -*~* \1 \ \ K 8TOP-\i > h\ HOLLOW MILL >( ^ i \ V Fig. 1. Diagram illustrating Relation between Tool Lengths and Travel of Turret stock of 73 feet per minute; therefore, the machine will be arranged so that the rough-turning, finish-turning, and thread cutting are done at the slower speed, and backing off the die, cutting off the finished screw, feeding the stock, etc., at the higher speed. Spindle Revolutions for Turning. When different spindle speeds are used for the forward and backward directions of rotation, the total number of revolutions for producing the part should be based on the higher speed. In order to deter- mine the total number of revolutions, it will be necessary to find out how many spindle revolutions are required for each GENERAL PROCEDURE 229 operation, which, in the case of cutting tools, depends upon the amount they feed per revolution. As the turning is to be done at a comparatively slow speed, the feed may be rather coarse, o.oio inch being selected for roughing and o.on inch for finishing. Rough- turning a length of 0.625 mcn pl us o.oio inch for clearance, and with a feed of o.oio inch per revolu- tion, will require about 63 revolutions (0.635 -f- o.oio = 63). The finishing cut with an advance movement of 0.635 mcn at o.on inch per revolution, plus a dwell equivalent to three revolutions at the end of the cut for finishing the shoulder, will require about 61 revolutions. It will be assumed that both the roughing and the finishing cuts are to be taken in 62 revolutions. Number of Revolutions for Thread Cutting. To find the number of revolutions for cutting the thread, determine the number of threads on the end of the screw by multiplying the number of threads per inch by the threaded length ; thus 48X0.25= 12. Adding, say, two revolutions for clearance, 14 revolutions will be required for cutting the thread and 14 revolutions for backing the die off of the threaded end. Revolutions for Cutting off Finished Screw. In deter- mining the number of revolutions for cutting off the finished screw, the question of feed is again involved. Cutting-off tools can be fed from 0.0012 to 0.0017 inch per revolution, but the feed should be reduced towards the latter part of the cut. Forming tools can be fed from 0.0002 to o.ooi inch, the amount largely depending upon the width of the formed part. It will be assumed that the feed in this case is to be 0.0015 mcn - Now the total movement of the cutting-off tool equals the radius of stock, or eV inch + 0.005 i ncn f r clearance + dimension x (see Fig. 2), which depends upon angle a of the cutting edge. The reason for inclining the cutting edge is to sever the finished part without leaving a teat or rough spot in the center of the screw-head, such as would usually be left by a tool having a cutting edge parallel with the axis of the work. The dimen- sion x equals the width y of the blade multiplied by the tangent of angle a. Fifteen degrees has been proved to be a suitable 230 CAM DESIGN angle for tools used on steel and iron, whereas, for brass or bronze, a somewhat greater angle, varying from about 20 to 25 degrees, gives better results. Assuming that the cutting-off tool is 0.035 mcn wide and the angle of the cutting edge is 15 degrees, then x equals o.oio inch. Therefore, the total movement of the tool equals g 7 ^, or 0.1093 + 0.005 + o.oio = 0.125 inch approximately. The spindle revolutions required equal 0.125 -5- 0.0015 = 83 revolutions, approximately. (This number will be reduced to 81 revolutions in this particular case, for reasons to be explained later.) While the stock is being cut off, a forming tool can shave under the head and Fig. 2. Inclined Edge of Cutting-off Tool remove the burr, so that additional spindle revolutions are not required for this part of the work. Revolutions while Indexing Turret. On the No. oo Brown & Sharpe automatic screw machine, the time required for indexing the turret is one-half second. With a spindle speed of 927 revolutions per minute, there will be about 15.5 revolutions per second, or approximately 8 revolutions during the one-half second, for indexing. It is usually advisable to add from two to four revolutions to the actual number required for indexing the turret and feeding the stock; therefore, 10 revolutions should be allowed for indexing at the slower speed. Spindle Revolutions based on Fast Speeds. As previously mentioned, when there is a variation between the forward and backward spindle speeds, the number of revolutions for each operation which is considered in designing a cam is based GENERAL PROCEDURE 231 upon the fast speed. In Table I, the various operations for producing the screw shown in Fig. i, and the corresponding number of spindle revolutions in each case, are listed in the successive order. The column headed " Spindle Revolutions for Each Operation" shows the actual number of spindle revo- lutions for making one screw; the next column shows what the spindle revolutions would be if the spindle ran at 1273 revolutions per minute continually. On all operations for Table I. Revolutions of Machine Spindle and Hundred ths of Cam Circumference for Different Operations Successive Order of Operations Spindle Revolutions for Each Operation Spindle Revolutions Based on 1273 R. P. M. Hundredths of Cam Circumference E Index turret and reverse spindle . . Rough-turn with hollow mill Index turret 10 62 10 14 84 14. 4 25 A =r>i Finish-turn with box-tool 62 84 2C Index turret IO 14. A :n > Run threading die on 14. 2O 6 Run threading die off 14 14 4 S^ Cut-off with back tool 81 81 24. !* fl fO 3 r-* Shave under head and remove burr with form tool and index turret three times while cutting off Feed stock to stop 14. 14 4 Total number of revolutions for making one screw 277* 57Qf IOO * Actual number of revolutions for making one screw. t Number of revolutions required if spindle speed were 1273 R. P. M. con- tinually. which the slower speed of 927 revolutions per minute is em- ployed, the spindle revolutions based on the higher speed of 1273 revolutions per minute are used in proportioning the cam. For instance, 62 revolutions per minute are actually required for rough-turning with the hollow mill, but the hundredths of cam circumference used for this operation is based on 84 revolutions at the fast speed. The relation 232 CAM DESIGN between the spindle revolutions at the fast speed and the actual number at the slower speed corresponds to the relation between the spindle speeds; thus, 1273 X 62 927 : 1273 : : 62 : x ; x = = 85 revolutions. 927 The reason why 84 revolutions are listed in Table I instead of 85, and the reason for similar modifications will now be explained. Modification of Spindle Revolutions to suit Change-gears. After the number of spindle revolutions for each operation have been determined and they have been added together to obtain the total number, the next thing to consider is the relation between this total number and the numbers that can be obtained with the different combinations of change-gears accompanying the machine. As the total number of revolu- tions for producing a part does not always equal the number obtained with the change-gears, it is necessary to modify the revolutions for the different operations in order to obtain an exact number for which the change-gears are suited. In this case, the revolutions listed in Table I were changed slightly in order to obtain the total of 339, because Table II shows that this is the number for which the machine should be geared. For instance, instead of allowing 85 revolutions for rough- turning and finish-turning, 84 revolutions were allowed ; the number of revolutions for cutting off was also reduced from 83 to 81, so that a total of 339 was obtained. The effect of these changes on the action of the tools is, of course, very slight, the effect being to change the feeding movement of the tool somewhat. As will be seen by referring to Table II, the number 339 is found in the column headed by the spindle speed of 1273 revolutions per minute, and, opposite 339 at the left-hand side of the table, the change-gears to use are listed. In this case, there should be a 3o-tooth gear on the driving shaft and a 48- tooth gear on the worm-shaft. As 339 repre- sents the total number of revolutions at the fast spindle speed required to make one piece, 339 -f- 21.2 (the number of revo- GENERAL PROCEDURE Table II. Change-gears and Data for Laying Out Cams, No. oo Brown & Sharpe Automatic Screw Machine 233 | ttl 5 D ^ Q "*ft tSTSH I ir 31 Till . f*} T. "i ^r H UJ _ r *& g r> D I SH LU- L mi 1 o O cT * ^^ uio 9g - (-tO*~ ,>" fc s 2* s - Cf\ * s- ?S &:, QD oo = 2 = QO2 o i CO UJ X U- UJ ONEV VAYOr. LY BE \ \ U CQ & U$ cJ> * o-x is OX 5 g2 *? < HI $ 1?, ** s 4 4 5 VO ri A o 2 "4 *"J 8' tg HI < 8 H 5 P 8 z O o C Is _J r^ 00 * ^ to GO- jj 9 760 20 I800 I600 2O 40 3 < 140 164 192 225 264 309 362 424 4 )7 583 6! 53 800 21 1714 1500 20 42 3 ? 147 172 202 236 277 324 380 446 5 22 612 7 i? 840 22 I63JS 1450 20 44 3 154 180 211 247 290 340 399 467 5 M 641 7 51 880 23 1400 20 46 3 l_ z6i 189 221 259 34 355 417 488 5 72 670 7 i5 920 24 1500 1350 20 g 3 168 197 230 270 317 371 435 509 5 # 699 8 19 960 2 5 1440 1300 20 5 3 2; 175 205 240 281 330 386 453 530 6 22 728 8 S3 1000 26 1384 1250 20 5 2 3 o 182 21.1 250 292 343 402 471 552 6 47 757 81 <7 1040 27 1333 1200 20 54 3 189 221 259 304 356 417 4*9 5V3 6 7 1 T 8 ? 9 22 1080 ?8 1285 1150 20 3 3 190 230 269 315 370 433 507 594 6 ^6 816 9 # 1120 29 1241 1100 20 58 3 1 203 23^ 2 7 8 326 _383 448 525 OI 5. 7 21 845. 9< ? 1 1 60 30 1200 1050 20 60 3 o 210 246 288 337 396 463 543 636 7 *6 874 10 24 1200 32 1125 1000 30 30 48 60 3 > 224 262 307 360 422 494 580 679 7 36 932 I0< ? 2 1280 34 1050 95 20 44 5 U 60 3 UJ 238 279 326 3*3 449 525 616 721 8 *b 99 II 31 1360 36 1000 900 30 30 54 60 3 252 295 346 405 475 55b 652 704 8 95 1049 12 29 J440 3 8 947 850 20 30 38 60 3 266 312 365 428 502 587 688 806 s to 1107 12 97 1520 40 900 800 20 30 40 60 3 280 328 384 450 528 618 724 8 4 9 9 ^ 1165 13 35 1600 42 857 775 20 30 42 60 3 ft 294 344 403 473 554 649 761 891 10 45 1224 14 J4 1680 44 818 725 20 30 44 60 3 CD 308 361 422 495 58i 680 797 934 IO 94 1282 15 32 1760 46 782 700 20 30 46 60 3 322 377 442 518 607 711 833 976 11 44 1340 15 70 1840 48 750 20 3 48 60 3 3 336 394 461 540 634 742 870 1018 II *4 1398 16 ^8 1920 50 720 6,-fo 20 30 50 60 3 Z 410 480 503 660 723 906 1061 12 43 1457 17 7 2OOO 5 2 692 620 20 30 60 426 499 585 686 803 942 1103 12 93 17 /5 2080 54 666 600 20 30 60 3 178 443 5i8 608 713 834 1146 13 43 1573 18 3 2100 642 575 20 30 60 3 392 459 630 739 86-i 1015 1188 13 93 1631 IV u 224O 58 620 550 2O 3 60 3 406 476 557 653 766 896 1051 1231 14 42 1690 19 io 2320 60 600 525 30 21 54 7 3 420 492 576 675 792 927 1087 1273 14 y* 1748 20 [8 2400 J>3_ 57' 500 3 2O 54 70 3 441 517 60^ 709 832 973 1141 1337 15 J7 1835 21 V 2520 70 450 20 20 40 3 1400 574 672 788 924 1082 1268 1485 17 41 2039 2 3 *) 2800 77 467 420 20 20 44 70 3 539 631 739 866 1016 1190 1395 1634 19 15 2243 26 28 3080 84 428 385 20 20 48 70 3 S88 806 945 1109 I2q8 1522 1782 20 89 2447 2 ^7 3360 " W 355 70 7 3 746 874] 1024 I2OI I4O6 1649 1931 22 h 1 26si 31 06 3640 The number of hundredths given is always sufficient for feeding stock, but it is usually best to add i-ioo for revolving the turret lutions per second) = 16, which is the number of seconds required to make a piece. Proportioning the Cam Circumference. If the spindle revolves 339 times while making one screw or for one revolu- tion of the camshaft, each y-J -Q of the cam periphery represents 234 CAM DESIGN 339-7-100=3.39 revolutions of the spindle. Then, if 14 revolutions are required for indexing, the part of the cam cir- cumference controlling this indexing movement will extend over 14 -5- 3.39 = approximately 4 spaces, each representing a hundredth of the cam circumference. Similarly, if 84 revo- lutions are required for rough-turning, the cam circumference needed for this operation will equal 84 -f- 3.39 = 25 hundredths, approximately. In this way, the cam surface is divided in proportion to the number of spindle revolutions necessary Fig. 3. Templet used for Laying Out Automatic Screw Machine Cams for each operation, and it is advisable to list the results as shown in the column at the right-hand side of Table I. The Cam Blanks. The cam blanks used on the Brown & Sharpe machines are made from solid disks of mild cold-rolled steel. The blanks for lead cams are 4! inches in diameter for throws less than one inch, and 5 inches in diameter for throws over one inch. The blanks for the cross-slide cams are 4! inches in diameter. Each cam has a hole J inch in diameter and ^f inch from the center, which is used for locating the cam GENERAL PROCEDURE 235 on its shaft. This hole also serves as a zero point from which all the divisions are started when laying out the cam. Laying Out the Cam. Laying out a cam involves, first, dividing the circumference into spaces which are proportional to the number of spindle revolutions for each operation, and, second, in giving each cam division or lobe a curvature, which will impart the required motion to the cutting tool controlled by each division. In order to readily locate these lobes or 68\ Fig. 4. Cam for Controlling Movements of Turret-slide divisions, the cam circle is divided into one hundred equal parts, and, after having determined the hundredths of cam circumference needed for each operation, the division points are marked off accordingly. For locating these division points, a bristol-board templet of the same diameter as the cam blank and divided into one hundred equal spaces, as shown in Fig. 3, will make it unnecessary to space each cam circle separately. The holes in the templet correspond to those in the cam blank and facilitate setting the templet in the correct position. 236 CAM DESIGN Laying Out the Lead Cam. The lead cam for producing the screw shown in Fig. i is illustrated in Fig. 4. When laying out this lead cam, begin at a point on its circumference oppo- site, the J-inch hole, the zero line being established at this point. The cam should be laid out to use, as nearly as possible, the entire circumference. That part of the lead cam which is not used is cut down to a radius r of if inch. The contour of the lead cam or the shape of its outline is governed by three factors: i. The circumferential space to be allowed; 2. The movement to be imparted to the cam lever and tool ; 3. The distance that the tool projects from the front side of the turret. On the No. oo Brown & Sharpe machine, when the roll on the lever of the lead cam is at the highest part of the cam, the distance from the front side of the turret to the chuck is if inch, and the maximum distance between the chuck and turret is 3 inches, the two positions being indi- cated in Fig. i by the dotted arcs. In many cases, the tool projects so far from the turret that- the cam lobe controlling its movement must be laid out so that it does not extend out- ward to the full diameter of the cam blank. In other words, the cam lobe is so located with relation to the center of the cam that the tool in the turret will operate at the required distance from the chuck. To determine the radial distance of a cam lobe from the center of the blank, locate on a center-line the nearest and farthest positions of the turret with relation to the spindle chuck, as shown in Fig. i, and also the location of the part to be produced. Then measure the distance from the outward cutting edge of the turning tool (in this case, a hollow mill for the roughing cut), when the tool is pushed back in the turret against its shoulder. After adding about | inch to this dimen- sion to allow for clearance and adjustment of the tool, lay off the dimension from the point where the tool ends its cut, towards the line representing the forward turret position. As shown in the illustration, the dimension marked "Hollow Mill" extends about inch beyond the face of the turret when the latter is in its extreme forward position ; therefore, the LAYING OUT LEAD CAM 237 cam lobe for. opera ting this tool should be laid out so that its highest point is at least | inch from the full diameter of the cam blank. Cam Lobe for Roughing Cut. In producing the screw shown in Fig. i, the stock is first fed against a stop in the turret and then the latter is indexed. This indexing, as previ- ously determined and recorded in Table I, requires 4 hun- dredths of the cam circumference; beginning then with a zero line passing through the J-inch pin-hole in the cam blank and using the templet shown in Fig. 3, four spaces or hundred ths are laid out on the circumference; a radial line marked 4 should then be drawn through this point. As 25 hundred ths of the cam circumference is required for the roughing cut, another radial line is drawn 29 hundredths from the zero line. The spiral cam lobe for the roughing cut is then laid off be- tween these two lines, the curve starting on radial line 4 and ending on line 29. Now it was found by means of Fig. i that, owing to the length of the hollow mill and its holder, the high- est part of this cam lobe should not extend to the outer edge of the cam blank closer than f inch; therefore, the starting point of the curve at a is a radial distance in from the edge of the blank, equal to the travel of the tool plus f inch. As the tool is to have a uniform feeding movement, the cam lobe is laid off in the form of a spiral, or so that it has a uniform rise from the cam center. The way in which this curve is obtained is indicated by the illustration. The space between the radial lines 4 and 29 is divided into several equal divisions by additional radial lines. A corresponding number of equally- spaced divisions are then laid off on line 0.635, representing the rise of the cam, by means of circular arcs. The points of intersection between the inner arc and the first radial line, the next successive arc and the second radial line, etc., lie along the cam curve, which is drawn through these points. Withdrawal of Turret for Indexing. With the No. oo machine, one-half second is required for the indexing move- ment and, as previously determined, 4 hundredths of the cam circumference should be employed; therefore, a radial line 238 CAM DESIGN 4 hundredths from line 29 is located and marked 33, which repre- sents the number of hundredths from the zero position. The inclination of the "line of drop" b depends upon the speed at which the cam is to rotate. In this case, 16 seconds are required to make one screw, so that the cam makes one com- plete turn in that length of time. On this machine, if a part is produced within from 6 to 35 seconds, the line of drop may be tangent to the one-inch hole in the center of the cam blank. Cams which rotate faster require an easier line of drop or one which is not so abrupt, while cams which revolve at a compara- tively slow speed, as, for instance, those for a period of 35 seconds or over, may have a line of drop which is radial. Templets such as are shown in Fig. 7 are convenient to use for constructing both the rise and drop on cams. These templets have several lobes representing the rise and drop for different cam speeds which are plainly stamped on the templet. After drawing a line b (Fig. 4) tangent to the one-inch hole, describe an arc equal to the radius of the cam roll. This arc should be tangent with line b and located radially so that it connects with the starting point of the next cam curve. Cam Lobe for the Finishing Cut. A box-tool is to be used for the finishing cut, which does not project from the turret as far as the hollow mill, so that the cam lobe in this case may extend to the outer edge of the cam blank. As 25 hundredths of the cam circumference are required, radial line 58 is drawn (33 + 25 = 58). The feeding movement of the tool occurs be- tween lines 33 and 57 and then there is a dwell of i hundredth, which allows the tool to remain stationary for a moment at the end of its cut, in order to finish the shoulder or under side of the screw-head. The curve for this part of the cam lobe begins at a point 0.635 mcn m fr m the e dg e f the cam blank on line 33, as this dimension represents the advanced movement of the tool. The curve between lines 33 and 57 is laid out the same as for the cam lobe between lines 4 and 29. Cam Lobe for Threading. The drop for allowing the turret to withdraw preparatory to indexing is laid off between lines 58 and 62, the same as previously described for the drop LAYING OUT LEAD CAM 239 between lines 29 and 33, and then the cam lobe for controlling the movements of the threading die is constructed. This lobe is given a rise which is slightly less than the travel of the die, so that the latter will be free to follow the pitch of the thread. In order to allow this freedom of movement, the die- holder is so constructed that the die is prevented from rotating with the work, but is free to move in the direction of its axis. The actual rise of the threading lobe or cam equals the number of spindle revolutions required for threading, divided by the number of threads per inch, minus from 10 to 15 per cent (depending upon the pitch of the thread) to allow the turret to lag behind the die slightly. In this case, there are 48 threads per inch and 14 spindle revolutions are needed for the opera- tion, two being allowed for clearance ; therefore, the rise not allowing for a reduction equals 14 -f- 48 = 0.292 inch. This rise is next reduced, say, 15 per cent or to 0.250 inch, and the lobe is laid out between radial lines 62 and 68, as 6 hundredths are required for running the die onto the work. The thread- ing lobe is then given a drop of 0.250 inch, covering 4 hundredths more of the cam circumference. The exact method of laying out the curve of a threading lobe will be described later. The radial position of this threading lobe must also be de- termined so that the die movement will be in the required position relative to the work. The height of the threading lobe may be determined by the same method previously described in connection with Fig. i for the hollow mill. The distance that the face of the die-holder projects beyond the turret is measured and, after allowing a slight amount for clearance, this distance is laid off on the center-line from the point where the thread ends, as indicated by the dimension marked " Die-holder." If the die-holder projects ij inch from the turret and -$ inch is allowed for clearance, the dimension x, or f inch, will represent the radial distance from the outer edge of the cam blank to the top of the threading lobe. Unused Part of Lead Cam. After the threading operation is completed (see Table I), the cutting-off and forming tools come into action and the turret is not required until the fin- 240 CAM DESIGN ished part has been severed and the stock is fed forward against the stop in the turret for producing a new piece. That part of the lead cam which is not used should be reduced to a radius r of ij inch. This concentric part of the cam is connected with the radial lines 72 and 96 by a suitable drop and rise. While the lead lever is passing thi$ reduced part of the cam surface, and the cross-slide tools are at work, the turret is indexed three times, thus skipping the two holes which do not Fig. 5.. Rear Cross-slide Cam contain tools and bringing the stock stop around into align- ment with the spindle. Lobe for Stock Stop. The lobe for the stock stop is lo- cated between the lines 96 and o, since 4 hundredths of the cam circumference are required, as shown by Table I. This lobe is a "dwell," which means that it is concentric and holds the turret stationary while the lead lever is passing over it. The height of this lobe is determined by measuring the dis- tance that the stock stop projects from the turret, and laying off this distance as indicated by the line marked "Stop" in Fig. i. If the stop projects iiV inch and dimension y is f LAYING OUT BACK-SLIDE CAM 2 4 I inch, then the concentric surface of the cam lobe should be | inch in from the outer edge of the blank, as shown in Fig. 4. After laying out an arc between the zero line and radial line 4, having a radius equal to the radius of the cam roll, the lay-out of the cam is completed. As the lead lever is passing the space between lines o and 4, the turret is indexed to bring the hollow mill into position for rough-turning the next piece, and, at the same time, the spindle rotation is reversed and Fig. 6. Front Cross-slide Cam reduced to the slower speed used for the turning and thread- cutting operations. Laying Out the Back-slide Cam. The back-slide cam, or the one for operating the rear cross-slide, is illustrated in Fig. 5. As shown by Table I, the total movement of the cutting- off tool equals 0.125 inch, which equals the rise of the cam lobe between the radial lines 72 and 96. The cutting-off tool starts at line 72 or as soon as the die has been backed off of the work, as indicated by line 72 of the lead cam (see Fig. 4). The quick rise a of the back-slide cam is given a radius of ij inch, drawn from a center one-half inch from the outside, 242 CAM DESIGN whereas the drop line b is tangent to the one-inch hole in the center. These two lines a and b are connected to the concen- tric part of the cam by curves having a radius of J inch which corresponds to the radius of the cam-lever roll. As previously explained, the quick rise and the drop varies for different speeds and may be laid out directly from a templet similar to the one shown in Fig. 7, which is used on the Nos. oo and ooG Brown & Sharpe automatic screw machines. The back- slide cam lobe ends at line 96, 24 hundredths of the cir- Fig. 7. Templet for Rise and Drop of Cams used on Nos. 00 and OOG Brown & Sharpe Automatic Screw Machines cumference being utilized in connection with the cutting-off operation. The 4 hundredths remaining between lines 96 and o represent the time allowed for feeding the stock. That part of the front- and back-slide cams which is not used is laid out to a radius r of ij inch. Laying Out the Front-slide Cam. While the cutting-off tool is at work, a forming tool is used to shave under the head of the screw and remove the slight burr left by the cutting-off tool. The movement required for the forming tool is equal to the difference between the radius of the screw-head and the radius of the body, plus, say, 0.005 inch for clearance, giving a total movement of 0.036 inch. Assuming that the feed of LAYING OUT FRONT-SLIDE CAM 243 92 X \ A the tool is to be 0.0013 inch, the required number of spindle revolutions will equal 0.036 -f- 0.0013 =27.7. As each one hundredth of the cam circumference is equivalent to 3.39 spindle revolutions, 8 hundredths of the front-slide cam cir- cumference is utilized (27.7 -r- 3.39 = 8, approximately). The quick rise a (Fig. 6) and the drop b are laid off as previously described in connection with the back-slide cam. The forming tool begins work at line 72, which corresponds with the point at which the cutting-off tool comes into action, these two tools operating simultaneously. After the forming tool has been moved inward 0.036 inch, it is allowed a dwell of one hundredth of the cam circumference, so that the tool can remove the burr caused by the cutting-off tool when starting in. The re- mainder of the cam is made to a radius of ij inch, since this part is not used. Developing Cam Lobe for Threading Operation. When cutting a thread on the Brown & Sharpe automatic screw machines, the die is started on the work by the threading lobe on the lead cam which actuates the turret-slide, and then the die movement is governed by the lead of the thread, the turret traveling at a slightly slower rate. If the cam were laid out to positively control the movement of the threading die, unsatisfactory results would be obtained, as the die would be crowded at times, owing to the fact that the spindle speed and the speed of the driving shaft are not constantly in exactly the same ratio ; therefore, the cam lobe is laid out so that it gives the die a positive start when cutting the first two threads, Machinery, N. 7. Fig. 8. Method of Constructing Thread Lobe on Lead Cam 244 CAM DESIGN and then the cam is relieved so that the turret-slide lags be- hind slightly. Before the thread lobe can be constructed, the length of the threaded portion, the number of threads per inch, and the total number of revolutions of the spindle for completing one piece must be determined. The rise on the cam may then be found by the following formulas : From 14 to 24 threads per inch, r = (R -f- p) X 0.85 From 28 to 48 threads per inch, r = (R -r- p) X 0.88 From 56 to 80 threads per inch, r = (R -f- p) X 0.90 in which, R = revolutions required for threading ; * p = number of threads per inch ; r = rise on cam. The accompanying tables, "Spindle Revolutions and Cam Rise for Threading," give the spindle revolutions for thread- ing various lengths and pitches, and the corresponding rise for the cam lobe. To illustrate the use of these tables, suppose that a cam is to be laid out for threading the screw shown at A, Fig. 8, on a No. oo Brown & Sharpe automatic screw machine. Assume that the spindle speed is to be 2400 revolu- tions per minute ; the number of revolutions to complete one piece, 400 ; time required to make one piece, 10 seconds ; length of the threaded portion, | inch; pitch of the thread, ^2 inch, or 32 threads per inch. By referring to Table III, under "32 threads per inch" and opposite "f " (length of threaded portion) the number of revolutions required is found to be 15 and the rise of the cam lobe, 0.413 inch. To construct the lobe, convert the revolutions . into hun- dredths ofccam surface, or 15 -f- 400 = 0.0375, or 3! hundredths. Then draw the cam circle B, as shown in Fig. 8, and lay off on this circle 3! hundredths to advance on the screw and 3! hundredths to withdraw. Locate the top of the lobe an amount C below the outer cam circle B as required. Bisect the rise at E, and, with OE as a radius and a, 6, and c as centers, draw arcs intersecting each other at d and e. With d as a Table III. Spindle Revolutions and Cam Rise for Threading Length of Threaded Portion Number of Threads per Inch 64 56 48 40 | 36 | 32 30 28 24 20 | 18 16 First Line: Revolutions of Spindle for Threading Second Line: Rise on Cam for Threading 6.50 6. 50| 4.50 4.50 4.00 4.00| 4.00 4.00 3* 0.091 0.1040 082 0.099 0.098 0.1100.117 0.126 8 50 8 00 6.00 5.50 5.50 5.00 5.00 5.00 3.00 A 0.120 0.129 0.110 0.121 0.134 0.138 0.147 0.157 0.106 10.50 10.00 7.50 7.00 6.50 6.00 6.00 5.50 4.00 3.50 A 0.148 0.161 0.137 0.154 0.159 0.165 0.176 0.173 0.142 0.149 i 12.50 11.50 9.00 8.00 7.00 7.00 7.00 6.50 4.50 4.00 3.50 3.50 t 0.176 0.185 0.165 0.176 0.171 0.193 0.205 0.204 0.159 0.170 0.165 0.186 e 14.50 13.50 10.50 9.50 8.50 8.00 7.50 7.50 5.50 4.50 4.00 4.00 /I 0.204 0.217 0.192 0.209 0.208 0.220 0.220 0.236 0.195 0.191 0.189 0.212 16.50 15.00 12.00 10.50 10.00 9.00 8.50 8.50 6.00 5.50 5.00 4.50 A 0.232 0.241 0.2200.231 0.244 0.248 0.249 0.267 0.213 0.234 0.236 0.239 7 18.50 17.00 13.5012.00 11.00 10.00 9.50 9.00 7.00 6.00 5.50 5.00 32 0.260 0.273 0.247 0.264 0.269 0.275 0.279 0.283 0.248 0.255 0.260 0.266 1 20.50 18.50 15.00 13.00 12.00 11.00 10.50 10.00 7.50 6.50 6.00 5.50 \ 0.288 0.297 0.275 0.286 0.293 0.303 0.308 0.314 0.266 0.276 0.283 0.292 9 22.50 20.50 16.50 14.50 13.00 12.00 11.50 11.00 8.50 7.00 6.50 6.00 A 0.316 0.329 0.302 0.319 0.318 0.330 0.337 0.346 0.301 0.298 0.307 0.319 5 24.50 22.00 18.0015.50 14.50 13.00 12.50 12.00 9.00 8.00 7.00 6.50 TS 0.345 0.354 0.3400.341 0.354 0.358 0.367 0.377 0.319 0.340 0.330 0.345 1 1 26.50 24.00 19.50 ! 17.00 15.50 14.00 13.50 12.50 10.00 8.50 7.50 7.00 71 0.373 0.386 0.3570.374 0.379 0.385 0.396 0.393 0.354 0.361 0.354 0.372 28.50 25.50 21.0018.00 16.50 15.00 14.50 13.50 10.50 9.00 8.50 7.50 0.401 0.410 0.3850.396 0.403 0.413 0.425 0.424 0.372 0.383 0.401 0.398 U" 30.50 27.50 22.5019.50 17.50 16.00 15.00 14.50 11.50 9.50 9.00 8.00 0.429 0.442 0.4120.429 0.428 0.440 0.440 0.456 0.407 0.404 0.425 0.425 7 32.50 29.00 24.0020.50 19.00 17.00 16.00 15.50 12.00 10.50 9.50 8.50 iV 0.457 0.466 0.440 0.451 0.464 0.468 0.469 0.487 0.425 0.446 0.448 0.451 1 5 34.50 31.00 25.50 22.00 20.00 18.00 17.00 16.00 13.00 11.00 10.50 9.00 if 0.484 0.498 0.477 0.484 0.489 0.495 0.499 0.503 0.460 0.468 0.496 0.478 i 36.50 32.50 27.00 23.00 21.00 19.00 18.00 17.00 13.50 11.50 10.50 9.50 s 0.513 0.522 0.495 0.506 0.513 0.523 0.528 0.534 0.478 0.489 0.496 0.504 i 7 38.50 34.50 28.50 24.50 22.00 20.00 19.00 18.00 14.50 12.00 11.00 10.00 si 0.541 0.554 0.522 0.539 0.538 0.550 0.557 0.566 0.514 0.510 0.519 0.531 9 40.50 36.00 30.00 25.50 23.50 21.00 20.00 19.00 15.00 13.00 11.50 10.50 T* 0.570 0.579 0.550 0.561 0.574 0.578 0.587 0.597 0.531 0.553 0.543 0.558 1 9 42.50 38.00 31.50 27.00 24.50 22.00 21.00 19.50 16.00 13.50 12.00 11.00 H 0.598 0.611 0.577 0.594 0.599 0.605 0.616 0.613 0.567 0.574 0.566 0.584 44.50 39.50 33.00 28.00 25.50 23.00 22.00 20.50 16.50 14:00 13.00 11.50 0.626 0.635 0.605 0.616 0.623 0.633 0.645 0.644 0.584 0.595 0.614 0.611 21 46.50 41.50 34.50 29.50 26.50 24.00 23.00 21.50 17.50 14.50 13.50 12.00 If 0.654 0.667 0.622 0.649 0.648 0.660 0.675 0.676 0.620 0.616 0.637 0.637 48.50 43.00 36.00 30.50 28.00 25.00 23.50 22.50 18.00 15.50 14.00 12.50 0.682 0.691 0.660 0.671 0.684 0.688 0.689 0.707 0.638 0.659 0.661 0.664 50.50 45.00 37.50 32.00 29.00 26.00 24.50 23.00 19.00 16.00 14.50 13.00 ' 0.710 0.723 0.677 0.704 0.709 0.715 0.719 0.723 C.673 0.680 0.684 0.690 52.50 46.50 39.00 : 33.00 30.00 27.00 25.50 24.00 19.50 16.50 15.00 13.50 0.738 0.747 0.715 ( 0.726 0.733 0.743 0.748 0.754 0.691 0.701 0.708 0.717 Table IV. Spindle Revolution and Cam Rise for Threading Length of Threaded Portion Number of Threads per Inch 64 56 48 40 36 32 3 28 24 20 18 | 16 First Line: Revolutions of Spindle for Threading Second Line: Rise on Cam for Threading H 54.50 0.767 48.50 0.779 40.50 0.742 34.50 0.759 31.00 0.758 28.00 0.770 26.50 0.777 25.00 0.786 20.50 0.726 17.00 0.723 15.50 0.732 14.00 0.743 11 56.50 0.795 50.00 0.804 42.00 0.770 35.50 0.781 32.50 0.794 29.00 0.798 27.50 0.807 26.00 0.817 21.00 0.744 18.00 0.765 16.00 0.755 14.50 0.770 tt 58.50 0.823 52.00 0.836 43.50 0.797 37.00 0.814 33.50 0.819 30.00 0.825 28.50 0.836 26.50 0.833 22.00 0.779 18.50 0.786 16.50 0.779 15.00 0.797 t j 60.50 0.851 53.50 0.860 45.00 0.825 38.00 0.836 34.50 0.843 31.00 0.853 29.50 0.865 27.50 0.864 22.50 0.797 19.00 0.808 17.50 0.826 15.50 0.823 If 62.50 0.879 55.50 0.892 46.50 0.842 39.50 0.869 35.50 0.868 32.00 0.880 30.00 0.880 28.50 0.895 23.50 0.832 19.50 0.829 18.00 0.850 16.00 0.850 H 64.50 0.907 57.00 0.916 48.00 0.880 40.50 0.891 37.00 0.904 33.00 0.908 31.00 0.909 29.50 0.927 24.00 0.850 20.50 0.871 18.50 0.873 16.50 0.876 H 66.50 0.935 59.00 0.948 49.50 0.907 42.00 0.924 38.00 0.929 34.00 0.935 32.00 0.939 30.00 0.943 25.00 0.885 21.00 0.893 19.00 0.897 17.00 0.903 i 68.50 0.963 60.50 0.972 51.00 0.918 43.00 0.946 39.00 0.953 35.00 0.963 33.00 0.968 31.00 0.974 25.50 0.903 21.50 0.914 19.50 0.920 17.50 0.929 iA H 72.50 1.019 76.50 1.076 64.00 1.028 67.50 1.084 54.00 0.990 57.00 1.045 45.50 1.001 48.00 1.056 41.50 1.013 43.50 1.061 37.00 1.018 39.00 1.073 35.00 1.026 37.00 1.084 32.00 1.005 34.50 1.083 27.00 0.956 28.50 1.009 23.00 0.978 24.00 1.020 20.50 0.968 22.00 1.038 18.50 0.982 19.50 1.035 1A 80.50 1.126 71.00 1.141 60.00 1.100 50.50 1.111 46.00 1.122 41.00 1.128 38.50 1.128 36.50 1.146 30.00 1.062 25.50 1.084 23.00 1.086 20.50 1.089 li 84.50 1.188 74.50 1.197 63.00 1.155 53.00 1.166 48.00 1.171 43.00 1.183 40.50 1.187 38.00 1.193 31.50 1.115 26.50 1.126 24.00 1.133 21.50 1.142 1 T 6 * 88.50 1.244 78.00 1.253 66.00 1.210 55.50 1.221 50.50 1.232 45.00 1.238 42.50 1.245 40.00 1.256 33.00 1.168 28.00 1.190 25.00 1.180 22.50 1.195 H 92.50 1.301 81.50 1.310 69.00 1.265 58.00 1.276 52.50 1.281 47.00 1.293 44.50 1.304 41.50 1.303 34.50 1.211 29.00 1.233 26.50 1.251 23.50 1.248 1A 96.50 1.357 85.00 1.366 72.00 1.320 60.50 1.331 55.00 1.342 49.00 1.348 46.00 1.348 43.50 1.366 36.00 1.274 30.50 1.296 27.50 1.298 24.50 1.301 H 100.5 1.413 88.50 1.422 75.00 1.375 63.00 1.386 57.00 1.391 51.00 1.403 48.00 1.406 45.00 1.413 37.50 1.328 31.50 1.339 28.50 1.345 25.50 1.354 1A 11 Hi 104.5 1.469 92.00 1.478 95.50 1.535 99.00 1.591 78.00 1.430 81.00 1.485 84.00 1.540 65.50 1.441 68.00 1.496 70.50 1.551 59.50 1.452 61.50 1.501 64.00 1.562 53.00 1.458 55.00 1.513 57.00 1.568 50.00 1.465 52.00 1.524 53.50 1.568 47.00 1.476 48.50 1.523 50.50 1.586 39.00 1.381 40.50 1.434 42.00 1.487 33.00 1.403 34.00 1.445 35.50 1.509 29.50 1.392 31.00 1.463 32.00 1.510 26.50 1.407 27.50 1.460 28.50 1.513 U 102.5 1.647 87.00 1.595 73.00 1.606 66.00 1.610 59.00 1.623 55.50 1.626 52.00 1.633 43.50 1.540 36.50 1.551 33.00 1.558 29.50 1.566 HI U 106.0 1.703 90.00 1.650 93.00 1.705 75.50 1.661 78.00 1.716 68.50 1.671 70.50 1.720 61.00 1.678 63.00 1.733 57.50 1.685 59.50 1.743 54.00 1.696 55.50 1.743 45.00 1.593 46.50 1.646 38.00 1.615 39.00 1.658 34.00 1.605 35.50 1.676 30.50 1.620 31.50 1.673 l 2 96.00 1.760 99.00 1.815 80.50 1.771 83.00 1.826 73.00 1.781 75.00 1.830 65.00 1.788 67.00 1.843 61.00 1.787 63.00 1.846 57.50 1.806 59.00 1.853 48.00 1.700 49.50 1.752 40.50 1.721 41.50 1.764 36.50 1.723 37.50 1.770 32.50 1.726 33.50 1.779 ALLOWANCE FOR TOOL CLEARANCE 247 center and radius OE, join points b and a ; with e as a center and radius OE, join points c and a. This gives the shape of the thread lobe. For convenience in cutting, when a Brown & Sharpe circu- lar milling attachment is available, the cam surface used for threading is divided into minutes. Then, to obtain the lead (or the number of minutes traversed for each y oW-hich rise) divide the number of minutes contained in the portion of the lobe used, by the rise. For example, 0.810 -r- 0.413 = 1.96, or 2 minutes, approximately. Allowance for Tool Clearance. In laying out a set of cams, it is sometimes found necessary to make allowance FACE OF DIE HOLDER CUT-OFF TOOL-\ JL J^TOOL POST V FORM TOOL V X FACE OF DIE HOLDER MacMnery,N.Y. Fig. 9. Diagram illustrating Method of Finding Clearance for Die-holder for one tool to clear another, the amount of clearance neces- sary being determined by the diameter or width of tool used in the turret and the position of the cross-slide tools relative to the work. When determining the amount of clearance necessary, the rise and drop on the lead cam is disregarded and the rises and drops on the front-slide and back-slide cams are taken into consideration. To determine the rise and drop to use, make a rough lay-out of the various operations to be performed and also ascertain the approximate number of revolutions to complete one piece. The revolutions are then converted into seconds. Assume that it is required to make a brass screw as shown in Fig. 9. This screw is to be made from J-inch round brass rod, on the No. oo Brown & 248 CAM DESIGN Sharpe automatic screw machine, using a spindle speed of 2400 revolutions per minute backward and forward. Assume that it is required to find the amount of clearance necessary for the die-holder to pass the circular form and cut-off tools. Draw in the form tool in position on the screw as shown to the left, and also an outline of the toolpost. Then lay out the die- holder in position to start on the screw, as shown by the dotted Machinery, N.Y. Fig. 10. Method of Determining Clearance on Cross-slide Cams lines. If a releasing die-holder is used, take the diameter over the heads of the screws in the holder, but, if a "draw-out" type is used, the diameter of the cap is taken. In this case, assume that a releasing die-holder is to be used. The die- holder cannot advance on the screw until the form tool drops back a distance B, but, as B is the actual distance, it will be necessary to add an extra amount to insure that the die-holder can advance without coming in contact with the circular form ALLOWANCE FOR TOOL CLEARANCE 249 tool. The extra amount of clearance necessary varies with the type of tool used. The following dimensions give the approximate amounts that should be added to the actual clearance for the type of tools specified : Extra Amount Type of Tool of Clearance, Inch Drill-holders from | to -fa Box-tools (with V-supports) from f to Box-tools (with supporting bushing) from -^ to T \ Button-die holders (draw-out type) from T \ to T \ Button-die holders (releasing type) from | to 5 To find the amount necessary for clearance, make a diagram as shown in Fig. 10, laying out the drop on the front cam as shown. Then add, say, J inch to dimension B and measure down from the point where the lobe finishes, scribing an; arc of a circle through the point thus located, as shown. Then with a radius equal to the radius of the cam roll, describe a circle touching the arc drawn and the drop on the cam. Join the center of the roll with the center of the cam circle by a straight line. The clearance is then measured off in hundred ths, as shown by dimension H. The starting point of the lobe on the lead cam for threading, will be at the hundredth line D, and the intervening space between the lines D and E will be the amount necessary for clearance. When the cutting-off operation follows the threading opera- tion, it will also be necessary to allow for clearance. To find the amount of clearance necessary for the die-holder to clear the circular cut-off tool, proceed as follows : Make a lay-out as shown to the right in Fig. 9, measure the distance C, add J inch to C, and lay off this dimension from the starting point A of the rear cam as shown in Fig. 10, drawing an arc of a circle as before. Then draw a circle the diameter of which is equal to the diameter of the roll, touching the arc drawn and the rise on the cam, and measure off the clearance H as previously explained. The thread lobe would finish at the hundredth line F and the cut-off tool start at the line A. Clearance should also be allowed between the dropping back of the cut-off tool and the feeding of the stock. To find the 25 CAM DESIGN amount of clearance necessary add J inch to the largest radius of the stock used, and proceed as previously explained. Use of Cam-lever Templets. Cam-lever templets similar to those shown in Fig. n are used for laying out cams when very close timing is required, as, for instance, when a tool is operated by the combined action of the cross-slide and the turret-slide. When templets are used, the center A is pivoted at the center of the cam drawing, by inserting a pin or other pointed instrument through the small hole provided for that CENTER OF FULCRUM OF CROSS-SLIDE CAM LEVER CAM LEVER TEMPLETS FOR NO3. 1 &.2. B. &S. AUTO. S. CAM LEVER TEMPLETS ^T CAM LEVER TEMPLETS FOR NO.O.B.4S.AUTO.S.M. A FOR NO. 00. B. 4S. AUTO. S. M. Fig. 11. Nos. 00, 0, 1, and 2, Brown & Sharpe Automatic Screw Machine Cam-lever Templets for Finding the Starting and Finishing Points of the Lobes for the Cross-slide and Lead Cams purpose. The main body B of the templet can then be rotated in any desired direction, so that the two templet arms, repre- senting the cross-slide cam lever and the lead cam lever which operates the turret, can be set in whatever position relative to each other may be required. These cam-lever templets are made from sheet celluloid and are transparent, so that marks on the drawing can easily be seen. The use of a cam-lever templet will be illustrated by considering the method of find- ing the starting and finishing points on the lobes of the cross- slide and lead cams for a chamfering operation. There are two methods used in laying out a set of cams when it is necessary to obtain clearances or definite starting CAM-LEVER TEMPLETS 251 points for the lead and cross-slide cam lobes. The first one is to obtain a rough estimate of the total number of revolutions required to complete one piece, after which the revolutions are transferred into hundredths of cam circumference, and the location of the lobes laid out on the cam circles. Then the "rises" and " drops" are constructed and the amount of clear- ance obtained by the cam-lever templets. This method usually requires considerable experience in this line of work. Another method is to first find the rise on the cross-slide cam for chamfering. Then draw a diagram as shown in Fig. 12. CENTER OF FULCRUM OF CROSS^SLIDE LEVER Fig. 12. Diagram for Finding the Starting and Finishing Points of the Lobes of the Cross-slide and Lead Cams for Chamfering Operations First draw circles L and S, representing the largest diameter of the lead cam and the largest diameter of the cross-slide cam, respectively; then draw another circle H a distance R inside of the circle S, as shown, the dimension R being the rise on the cross-slide cam. In chamfering operations, the tool should move longitudinally the proper distance into the work before the cross-slide cam starts to operate. Therefore, the lead- cam roll should be on the highest point of the lobe before the cam on the cross-slide, used for feeding in the tool, touches the tool-holder. In order to accomplish this result, proceed as follows. Draw a circle G, as shown in Fig. 12, which has a radius an amount R -f- D -f- yV smaller than that of circle S. 252 CAM DESIGN The value of D is equal to the distance that the point of the tool extends in from the face of the work when in position for chamfering. The $ inch added to D allows for clearance. After these circles have been drawn, the starting and finishing points of the lobes can be found. The cam-lever templet is now placed in position, and the lead-cam roll is located so that its circumference touches the lobe on the lead cam and its center coincides with the line A indicating the completion of the lead-cam rise. Then the cross-slide lever is swung down so that the circumference of the roll touches the circle G as shown, and, with a sharp pencil, a line is scribed around the circumference of the roll, which will determine the quick rise of the cam. The compasses are then set to the desired radius for the quick rise of the cam, which is described so that it will cut the circle #, representing the start of the rise on the cross-slide cam, and also be tangent to the line which has been previously marked by scribing around the cross-slide lever roll. Where the quick rise of the cam and the circle H meet will be the starting point of the rise on the cross-slide cam, indicated by the line J3, as shown. When the starting points have been found, the next thing is to obtain the finishing points of the lobe. The lead cam should hold the tool in position until the cross-slide cam has dropped back an amount equal to the distance which it has fed the tool into the work. A line F is drawn at any con- venient position for the finishing point of the lead cam, and the cam-lever templet is then brought into position so that the roll of the lead lever touches the circle and the center coin- cides with the line F as shown. The cross-slide roll is then swung down until its circumference touches the circle H and a line is scribed around the circumference of the roll. Where this line intersects, the circle representing the largest diameter of the cam will be the finishing point of the lobe, provided the distance R is not greater than the radius of the roll. If distance R is greater than this radius, the line representing the drop should be constructed tangent to the roll circumference, and where the line representing the drop intersects the outside CAM-LEVER TEMPLETS 253 circle will be the finishing point of the lobe, as indicated by line C. The space from E to C represents from one to two revolutions for dwell on the cross-slide cam. The advantage of this method is that the amount of clearance between the starting and finishing points of the lead and cross-slide cams is known in hundredths of the cam circle circumference before the cams are laid out, thus facilitating the operation of laying out the cams. Laying Out Cams for Recessing. In Fig. 13 a method is shown for finding the starting and finishing points on the CENTER OF FULCRUM OF LEAD LEVER Fig. 13. Diagram for Finding the Starting and Finishing Points on the Lobes of the Cross-slide and Lead Cams for Recessing Operations lobes of the cross-slide and lead cams for recessing. To deter- mine these points, the cam-lever templets are used. The starting point, indicated by line A, and the circle represent- ing the dwell on the lead cam are first laid out. A circle is then drawn, the radius of which is a distance K greater than the circle representing the dwell on the lead cam. (Distance K is equal to the length of the recessing cut.) Before begin- ning to lay out the cam, a maximum cam diameter should be decided upon which will suit the length of the tool-holder used in the turret. A circle passing through the starting point of the rise of the cross-slide cam, as well as a circle representing the dwell on the cross-slide cam, should also be drawn, the 254 CAM DESIGN difference in radii between these two circles being the rise R. Now the cam-lever templets are placed in position on the drawing, and the lead roll brought down so that it touches the lead cam, its center coinciding with line A. A circle M is next drawn, having a radius L + yV mcn l ess than that of the circle passing through the starting point of the rise of the cross- slide cam. L equals the distance from the outer face of the work to the inner edge of the recessing tool when the latter is in the starting position. The cross-slide roll is then swung down until its circumference touches the circle M, as shown, and a line is drawn around the circumference of the roll. The kl E H H h~ c i I FULCRUM OF RECESSING HOLDER/ POINT OF APPLICATION OF CAM Machinery, N. y. Fig. 14. Diagram for Finding Rise on Cross-slide Cam for Recessing and Chamfering Operations quick rise line of the cam is then constructed tangent to the roll, and where this line intersects the circle previously drawn, which determines the beginning of the slow feeding-in rise of the cross-slide cam, is the starting point of the slower rise of the cross-slide cam, as shown at B. The line C, which repre- sents the finishing point of the rise on the cross-slide cam for feeding the tool inward, is then laid off and the cross-slide roll swung into position. The lead roll is then swung down until it touches the circle representing the dwell on the lead cam. The starting point of the rise on the lead cam, located on line Dj is slightly in advance of the finishing point on the cross- slide cam. The finishing points of the lobes are next located. Any line, as Gj is taken at a convenient location, and the cam-lever CAM FOR RECESSING AND CHAMFERING 255 templets are then used. The lead roll is first brought into position as shown, and then the cross-slide roll is swung down from the outside diameter of the cam a distance equal to R, and the drop laid off as before mentioned in regard to cham- fering operations. The finishing point of the cross-slide lobe would then be on the line E. The space from C to E on the cross-slide cam would be for dwell, while the space from D to G on the lead cam would be the rise. The space from F to G is for dwell on the lead cam, which represents about one or two revolutions. Rise on Cross-slide Cam for Recessing and Chamfering. When using a swing tool for recessing, the rise on the cam should be greater than the distance which the tool is fed into the work. To illustrate the method of finding the rise on the cam, refer to Fig. 14, where A = distance from center of fulcrum to center of the recessing tool; B = distance from center of fulcrum to point of application of cam or center of screw at end of swinging member; C = diameter of recessing tool ; D = diameter of drilled hole in the work ; E = diameter of recessed hole ; E-C r = travel of recessing tool = ; R = rise on the cam. Then R:r::B:A. As a practical example, let r equal 0.040 inch; B, i\ inches; A, i| inch; then 0.040 X 2j . R = - = 0.080 inch. if Cam Rise for Drilling. There are three general conditions which govern the amount of rise required for drilling: i. When the drill does not pass through the work and a center- ing tool is not used. 2. When the drill does not pass through the work and a centering tool is used. 3. When the drill passes through the work and a centering tool is used. There is also another condition, viz., when the drill passes through the work 256 CAM DESIGN and a centering tool is not used; but, as this is not a com- mendable method, it is not here considered. The rise on the cam for drilling, as governed by the previous conditions, is as follows : 1. R = g + e+ o.oio inch; 2. R = g a + o.oio inch ; 3. R= h + k a+ o.oio inch ; 1C "TO DEPENDING ON DEPTH OF HOLE AND \J DIAMETER OF DRILL Fig. 15. Method of Laying Out Cams for Deep-hole Drilling where R = rise on cam for drilling ; g = depth of hole to be drilled ; e = length of point on the drill ; h = overall length of the work ; k = thickness of the cut-off tool ; a = distance from the face of the work to a place in the centered end where the outer edges of the drill begin to cut. The values of a for centering tools having 90- and 100- degree-point angles are as follows : For 90 degrees, a = (d c) X 0.5 inch ; For 100 degrees, a = (d c) X 0.43 inch ; where d = diameter of centering hole ; c diameter of drill. CAM FOR DEEP-HOLE DRILLING 257 Designing Cams for Deep-hole Drilling. When drilling deep holes, the drill should be withdrawn clear of the drilled hole, after penetrating to a depth not exceeding two and one- half times the drill diameter, so that the chips can be removed from the flutes and the drill cooled and lubricated. To ac- complish this, the lead cam is laid out as shown in Fig. 15. To explain the method used for laying out the cam, assume that a hole f inch in diameter and f inch long is to be drilled in a piece of brass rod. This will require three lobes on the cam, as it will be necessary to drop the drill back twice in producing the hole. The rises for the various lobes can be found with the aid of the following formulas : Rise on first lobe = i\ X D + 0.005 ^ ncn J Rise on second lobe = 2| X D + 0.003 inch ; Rise on third lobe = 2 X D + 0.003 inch ; where D = diameter of drill in inches. The amount for each successive rise should be decreased in about the same proportion, and the feed on the drill should also be decreased slightly for each additional lobe when cutting machine and tool steel ; but, when cutting brass, the feed can generally be uniform for each lobe. The rise on the various lobes would then be as follows : Rise on first lobe = 2f X J + 0.005 = -349 inch ; Rise on second lobe = 2 X J + 0.003 = 0.300 inch ; Rise on third lobe =2 X f + 0.003 = 0.253 inch. The depth to which the drill can be fed into the work before withdrawing can sometimes be increased, especially when a turret drilling attachment is used and the drill is greater than J inch in diameter. The space on the cam surface necessary for dropping the drill back is generally equal to the space necessary for revolving the turret. It is, therefore, advisable to use more than one drill when there is a sufficient number of empty holes in the turret, as it will not be necessary to resharpen the drills so frequently, and they will also be kept cooler. CHAPTER VIII OPERATIONS ON SINGLE- AND MULTIPLE-SPINDLE SCREW MACHINES THE operations ordinarily performed in automatic screw machines involve plain cylindrical turning, taper turning, forming of irregular surfaces, drilling, counterboring, reaming, cutting annular grooves or recesses in holes, thread cutting, and knurling. The number and kind of cutting tools used on the machines depend, of course, upon the nature of the work ; that is, its size and the form and location of the surfaces which must be acted upon by the tools. The turning of simple parts, such as ordinary screws, pins, etc., from a bar of stock can be done by using the regular tool equipment commonly em- ployed on all screw machines, whereas more difficult work might necessitate the use of special tools and, in some cases, attachments for extending the range of the machine. Before a machine of this type is equipped for a machining operation, it is essential to consider the best method of arranging the various tools, as well as the different types of tools available, so that the successive operations may be performed to the best advantage as to economy of production and the degree of finish and accuracy required. To what extent standard tools may be used should also be determined, and whether or not special tool equipment will increase the rate of production sufficiently to warrant their expense. A general idea of the tool equipment used for different opera- tions and also the classes of work for which automatic screw machines are used may be obtained by studying the examples described in this chapter. Some of these examples illustrate the use of comparatively simple tool equipment, whereas others represent operations for which special tools and ingenious at- tachments are required. 258 POINTING END OF WORK 2 59 Before reducing the diameter of the work by means of a box-tool or other external cutting tool of a similar type, it is necessary to chamfer the end of the work to permit starting the box-tool cutter on a light cut, until the supports are in position to steady the work. Pointing or chamfering the end of the work also facilitates the setting of a hollow mill concen- tric with the work. One method of pointing the end of the work is shown at A in Fig. i. The circular cut-off tool has an angular projection on its face next to the chuck, which points the bar before it URCULAR CUT-OFF TOOL at 3 fe ,CIRCULAR FORM TOOL J Fig. 1. Methods of Preparing Work for Turning is fed out for the next piece. This method is generally used when the work is not very long, and when it runs practically true. When it is necessary to cut a thread on a piece, the beveled end of the bar is made small enough to facilitate the starting of the die. It is sometimes impossible to point the bar with the cut-off tool, and, in this case, the bar is usually pointed by a combination centering and pointing tool as shown at B. This tool can be used when the bar does not project more than three and one-half times its diameter from the face of the chuck, and also when the bar is unfinished or of irregular shape. The tool a is used for centering the work, thus preparing it for drilling a hole, and the tool b is used for pointing the end of the bar. 260 SCREW MACHINE PRACTICE Another condition is shown at C. Here the form tool pre- cedes the box-tool, " necking" the bar at a. If the face b of the circular tool were left square and not chamfered, as shown, a thin ring would break off before all the material had been removed, as illustrated at Ca, Fig. 2, Chapter IV. Turning Concentric with Unturned Surface. When it is necessary to turn down a portion of a long cylindrical piece of cold-drawn steel or other material which has a finished surface, and have the part turned concentric with that which has not been reduced, it is usually good practice to weaken the bar with the circular cut-off tool as shown at D, Fig. i. For this class of work, a supporting bushing held in the box- tool should precede the turning tool, so that the part turned will be concentric with the finished body of the work. Before turning, the bar is pointed with the circular cut-off tool as shown at A. The diameter a of the neck should be small enough to allow the bar to be straightened with the box-tool support, so that it will run true. In the majority of cases, the neck a may be made from 0.3 to 0.5 times 5, but the length c of the work, the depth of the chip removed, and the feed used, will govern largely the diameter of the neck. The material being turned will also affect this diameter slightly, but in most cases this latter condition can be disregarded. Rods which have short bends in them should not be used, as it will be found impos- sible to produce a good surface on the part which is turned. The spring collet should also run perfectly true, if good results are to be expected. Examples of Forming Operations. According to a common rule, two and one-half times the smallest diameter of the work is the maximum width advised for forming ; that is, the width of the form tool cutter a for forming the screw at A in Fig. 2 should not exceed two and one-half times the diameter of the threaded body b. This means that, when a piece is too long to form, it must be reduced by an end- working tool, such as a hollow mill or a box-tool. This rule, however, is subject to variations. By actual test FORMING OPERATIONS 261 it has been found that screws and other parts made from machine and tool steel can be formed with a form tool the width of which is four times the smallest diameter of the part to be formed. This does not mean a piece of the shape shown at B in Fig. 2, where the smallest diameter c is on the end of Fig. 2. Examples of Forming Tool Operations the piece, but it applies to pieces similar to those shown at A, C, and D, where the smallest diameter of the work is next to the spindle. Again, it would be very easy to form with a tool of a width equal to four times the smallest diameter, if that diameter were not very small. Two examples of this ,-CIRCULAR FORM ^ TOOL CIRCULAR CUT-OFF ^-CIRCULAR FORM TOOL CIRCULAR CUT-OFF^ Machinery. N. Y. Fig. 3. Method of Applying the Circular Forming and Cutting-off Tools class of forming are given, and can safely be used as a guide for doing work of a similar character. The first test was the forming of a f -inch piece of screw stock with a tool ~IQ inch wide, down to ^ inch in diameter. In this case, the width is four times the smallest diameter. This test was performed on a No. 2 Brown & Sharpe automatic 262 SCREW MACHINE PRACTICE screw machine and the surface speed of the stock averaged about from 80 to 85 feet per minute, with a feed of o.ooi inch per revolution. This forming was successfully done without any of the pieces breaking off. The second test was made on a piece of |-inch iron wire, which was formed to a diameter of -IQ inch, the form tool in this case being i inch wide. This test was made on a |-inch Cleveland automatic screw machine. The maximum surface speed of the stock was 90 feet per min- ute and it was calculated as nearly as possible that the chip averaged from 0.0004 to 0.0008 inch thick. Therefore, the use of a hollow mill or box-tool can sometimes be avoided and circular form and cut-off tools used instead. The two methods of forming the piece shown at A and B in Fig. 3 on the No. 2 Brown & Sharpe automatic screw machine, and the following order of operations, show clearly the advantage that the form- ing method has over the box-tool or hollow-mill method of turning. With the method shown at A, two roughing box- tools are used for reducing the diameter of the stem 6, and, as the stem was also required to be smooth, a finishing box-tool was used, as can be seen in the following order of operations. The feed also had to be fine, to avoid a large teat, as the cut-off tool forming such a round head would cause the piece to break off before it had been entirely cut off. Revo- Hun- Order of Operations lutions dredths Feed stock to stop 29 2 Revolve turret 29 2 First roughing box-tool o.soo-inch rise at o.oos-inch feed. . 100 8 Revolve turret 29 2 Second roughing box-tool o.5oo-inch rise at o.oo5-inch feed 100 8 Revolve turret 29 2 Finishing box-tool o^oo-inch rise at o.oo5-inch feed 100 8 Revolve turret ^ 29 2 Form o.5io-inch rise at o.ooi5-inch feed 340 29 Cut-off o.332-inch rise at o.ooo9-inch feed 383 33 Revolve turret twice while cutting off (58) (5) Total number of revolutions to make one piece 1168 100 The spindle speed used was 549 revolutions per minute, so that the time to make one piece was 135 seconds, gross product in ten hours, 266 pieces. The new method of making this piece is shown at B in Fig. 3. The form tool travels the same dis- FORMING OPERATIONS 263 tance as when using the method shown at A, but a much finer feed is employed on account of the greater width of the form tool. No time is lost, however, as one piece is being cut off at the same time that another piece is being formed. It might be well to mention that no trouble was experienced by feeding Fig. 4. Cams for Making the Piece shown in Fig. 3 by the Method shown at B the stem out against the stop ; that is, the stem b did not bend or become distorted in any way. By comparing the following order of operations with those previously given, it will be noticed that there is considerable increase in production, and also that the work is handled more expeditiously. Revo- Order of Operations lutions Feed stock to stop 16 Cut-off 0.33 2-inch rise at o.oooy-inch feed 503 Form 0.5 lo-inch rise at o.ooi-inch feed (503) Revolve turret five times (go) Total number of revolutions to make one piece 519 Hun- dredths 3 97 (97) 264 SCREW MACHINE PRACTICE The speed of the spindle was 519 revolutions per minute, giving a maximum surface speed of 84 feet per minute. The time required to make one piece was 60 seconds, giving a gross product of 600 pieces in ten hours. This is a considerable increase as compared with the 266 pieces obtained by the method shown at A, and the gain is not made by " hogging" out the work, because the feeds are finer and the work is better. The cams used for the operation shown at B in Fig. 3 are shown in Fig. 4. The cut-off and form cams start at o hun- dredths and finish at 97 hundredths on the cam circle. The 'Machinery Fig. 5. Piece to be Made Arrangement of the Circular Tools form cam is shown by the dotted lines and the cut-off by long dashes ; and the lead cam by a full line. Another piece on which the production was increased con- siderably is shown at E in Fig. 2. This is a thumb-screw made from i -inch machine steel on a f-inch Cleveland automatic screw machine, which had been changed to take i-inch stock. This piece was first made on a Cleveland automatic having a single-acting cross-slide, that is, the front and back tools were mounted on the same slide and could not be operated inde- pendently. The order of operations for making this screw by this method is as follows : Order of Operations Feed stock to stop Form Knurl from turret Thread on and off Cut-off Total number of revolutions to make one piece . Revo- lutions 30 275 IOO 40 300 745 Sec- onds 6 55 20 8 60 149 RECESSING 265 This order of operations gave a gross product of 240 pieces in ten hours. To increase the production of this piece, it was transferred to a Cleveland machine which had a double inde- pendent cross-slide, thus enabling the cut-off and form tool to be operated at the same time. A cross-slide knurling tool was also used on the cross-slide, obviating the necessity of putting it in the turret. The order of operations for this piece is as follows, and it can be seen that a considerable increase was the result of this change. Revo- Sec- Order of Operations lutions onds Feed stock to stop 30 6 Cut-off 300 60 Knurl, attached to cut-off tool Form, while cutting off (275) (55) Thread on and off 40 8_ Total number of revolutions to make one piece 370 74 The gross product by this method was 486 pieces in ten hours, or over twice that of the previous method. A Recessing Operation. The piece shown in Fig. 5 gave considerable trouble before it was made successfully on the automatic screw machine. This piece was made from machine steel | inch in diameter, in a No. o Brown & Sharpe automatic screw machine. In considering the speed, it was found that for forming the stock could run at about 80 feet per minute, and at 30 feet per minute for thread cutting. Therefore, the spindle speeds required are 611 and 603 revolutions per minute, respectively, but, by referring to the table, it will be found that the nearest spindle speed is 663 revolutions per minute. The recessing is performed with a Brown & Sharpe standard swing tool, which is the tool usually selected for this class of work. The recessing cutter is first fed at right angles to the spindle by the cross-slide, after which it is fed forward by the turret. The feeds given in the following were found to be sufficiently light, and the tools stood up well without continual sharpening. The method of setting the circular tools on the machine is shown to the right in Fig. 5. The circular form tool A is lo- cated on the back-slide, and the cut-off tool B, on the front- 266 SCREW MACHINE PRACTICE slide. The form tool operates while the hole is being drilled; this is practicable, because the smallest diameter to be formed is 0.245 inch, while the diameter of the drilled hole is 0.161 inch. The surface speed of the drill is only 28 feet per minute, as the machine spindle cannot be run faster on account of threading. Some operators prefer a high-speed drilling attach- ment for this kind of work. The order of operations for making this piece is as follows : Revo- Hun- Order of Operations lutions dredths Feed stock to stop 13 3 Form o.i 28-inch rise at o.ooi-inch feed (128) (29) Revolve turret 13 3 Center o.ogo-inch rise at o.oo5-inch feed 18 4 Revolve the turret 13 3 Drill o.5i2-inch rise at o.oo4-inch feed 128 '29 Revolve the turret 13 * 3 Recess o.o5o-inch rise at o.oo28-inch with rear cross-slide . . 18 4 Recess from turret o.25o-inch rise at o.oo5i-inch feed. ... 49 n Drop back rear cross-slide 9 2 Revolve turret 13 3 Thread in 9 2 Thread out 9 2 Cut-off o.274-inch rise at o.oo2-inch feed 137 31 Revolve turret twice (26) (6) Total number of revolutions to make one piece 442 100 With this lay-out, a piece is made every 40 seconds, which means a gross production of 900 pieces in ten hours. The cams for this piece are shown in Fig. 6 and consist as usual of the lead, front-slide, and back-slide cams. It will be noticed that the rear-slide cam has a lobe of from 45 to 60 on the cam circle. The use of this portion is as follows : At 45 the recess- ing tool is brought into place by the lead cam, the rear-slide cam moves forward 0.050 inch, feeding the recessing tool in to take the depth of chip required. Then at from 49 to 60 the form cam has a dwell while the recessing tool moves for- ward; the allowance from 60 to 62 is made to withdraw the back slide before withdrawing the swing tool. Drilling and Counterboring from Cross-slide. Hand screw machine operations are frequently performed on work partly made in the automatic machines, because in order to complete the work in the automatic machine it would require seven tools, which exceeds the number of holes in the turret of a DRILLING AND COUNTERBORING 267 Brown & Sharpe automatic screw machine. At A, in Fig. 7, is shown a piece of work knurled on one end, which was made in a No. 2 Brown & Sharpe automatic screw machine. Unless a combination counterbore is used, the list of turret tools required will be a stop, center, drill, reamer, two counterbores, and a knurl. The method used in holding the extra counterbore is shown CUT OFF 0.274 FRONT. REAR Machinery Fig. 6. Cams used in Making the Piece shown in Fig. 5 at A in Fig. 8. The counterbore is held in a holder placed on the cross-slide, and when the counterbore is in line with the hole in the work it is fed forward by means of the stop in the turret coming against the rear end a of the counterbore. The counterbore is made a good sliding fit in the hole in the boss, and is prevented from turning by the headless screw b. A pin driven into the shank of the counterbore and a helical spring assist in keeping the counterbore in the "back" position. 268 SCREW MACHINE PRACTICE The order of operations for producing the piece shown at A in Fig. 7 is as follows : Revo- Hun- Order of Operations lutions dredths Clearance 19.6 2 Feed stock to stop 19.6 2 Revolve turret 19.6 2 Center o.i 25-inch rise at o.oo63-inch feed 19.6 2 Revolve turret 29.4 3 Drill o.5oo-inch rise at o.oo56-inch feed 88.2 9 Revolve turret 29.4 3 Ream o.5oo-inch rise at o.oo72-inch feed 137.2 14 Revolve turret 29.4 3 Counterbore o.iso-inch rise at o.ooi4-inch feed 107.8 n Revolve turret 29.4 3 Knurl on o.3oo-inch rise at o.oio2-inch feed 29.4 3 Knurl off o.3OO-inch rise at o.oi 53-inch feed 19.6 2 Revolve turret 29.4 3 Advance front slide and dwell 88.2 9 Counterbore from cross-slide o.i 25-inch rise at 0.002 i-inch feed (58.8) (6) Clearance (19.6) (2) Cut-off o.477-inch rise at o.ooi67-inch feed 284.2 ^9 Total 980.0 100 The cams for producing the piece shown at A in Fig. 7 are shown in Fig. 9, where the various functions of the lobes are clearly indicated. The most interesting lobe on this set of cams is the lobe on the cross-slide cam from 63 to 71, which brings the special Counterbore shown at A in Fig. 8 in line with the hole in the work. The stop in the turret used for feeding in this counterbore, and which is also used for gaging the stock to length, is operated by the lobe from 63 to 69 on the lead cam. It will be noticed that this lobe is much lower than the lobe from 2 to 4 gaging the stock to length, the reason being that the counterbore projects much further from the chuck than does the stock when fed out. Another simple method of holding an extra tool on the cross- slide is illustrated at B in Fig. 8. Here the holder is made so that it will take either a drill or a counterbore, which is held in it by means of a headless screw. The tool is rotated by means of the grooved pulley c, which is fastened to the spindle d as shown. This pulley is driven from the overhead works by a round belt, which is left sufficiently slack to allow the front cross-slide to advance to a position in line with the work. DRILLING AND COUNTERBORING 269 The drill is fed forward by a stop held in the turret, and is withdrawn by the coil spring e. Other operations performed with drills and counterbores held on the cross-slide are shown in Fig. 7 at Bj C, D, and E, 0.30 u_ Machinery Fig. 7. Samples of Work operated on by Counterbores and Drills held on the Cross-slide respectively. At C is shown a piece made with an eccentric hole. This is easily produced by means of a drill held in a holder fastened to the cross-slide. It is necessary to lock the spindle when the hole is being drilled. A drill-holder similar WASHER \ 1? p _0 - 7~~~ e ^ -J Machinery Fig. 8. Holders for Carrying Drills and Counterbores on the Cross-slide in construction to that shown at B in Fig. 8 is used. The piece shown at C is made with holes having different degrees of eccentricity; otherwise the pieces made with an eccentric hole are of the same size and shape. It is interesting to com- pare this method of drilling with the old method, which con- 270 SCREW MACHINE PRACTICE sisted in holding the stock in an eccentric chuck or in drilling each piece in a drill jig. The method last mentioned is ex- pensive, and the eccentric chuck method is very destructive to the cut-off tools, owing to the pounding of the stock against the cutting edge. At B is shown how wrench slots were produced in a special nut. The holes were first drilled, after which the shank was 11 CAM OUTLINES 59 LEAD FRON REAR Machinery Fig. 9. Cams used in Producing the Piece shown at A in Fig. 7 turned down by means of a box-tool, leaving only one-half of the drilled holes in each side. To produce this piece, the cross-slide cam moves the drill and holder forward part way, then dwells while the first hole is being drilled, by means of a stop in the turret forcing the drill into the work. After the first hole is drilled, the cam advances into position for the second hole, when the same operation is repeated. At D is shown a washer provided with two holes which were also drilled MAKING WATCH PARTS 271 in this manner. At E is shown a piece which requires a differ- ent movement. The lead cam is not used at all, and the groove a is cut by a special tool held on the cross-slide. After the machine spindle is locked in position by means of the brake, this tool starts at one side and is fed across by the cross-slide cam. These special operations give little trouble, especially on brass work, the material from which the parts described were made. Making Watch Parts in the Screw Machine. Watch- making by automatic machinery is essentially an American development. Previous to the inauguration of the industry Machinery Fig. 10. Blank for Watch Pinion made by Forming from Tool- steel Stock Fig. 11. Blank for Watch Wheel Staff made by Turning from Tool-steel Stock in Waltham, Mass., Switzerland held the lead in the manufac- ture of watches on a large scale. The hand processes there followed are the result of long experience and careful study, and the work is highly organized so far as the division of labor is concerned, separate workmen specializing on single opera- tions, which they repeat day after day. Swiss watches are not handmade in the sense in which we apply that term to custom-made footwear, for instance. Lathes, presses, gear- and pinion-cutters, and other power-operated machines are used in the various operations required. These tools have, however, been largely operated by hand in the same way that ordinary engine lathes are operated, as distinguished from the mechanically-controlled movements of the automatic gear- cutter or screw machine. In American watchmaking practice the automatic principle has been developed to an extent that is little short of mar- 272 SCREW MACHINE PRACTICE velous, the parts not only having complicated operations performed on them in single machines, but even being trans- ferred from one machine to another automatically, through a long series of operations. The various manufacturers of watches FEED STOCK OF TURRET IN BACKWARD POSITION 1ST OPERATION POINT WITH POINTING TOOL- IK FLOATING HOLDER 2ND OPERATION FORM WITH FRONT AND BACK SLIDE TOOLS SUPPORT WHILE FORMING ' WITH TELESCOPIC SUPPORT 'IN TURRET 3RD OPERATION CUT OFF WITH ANGULAR CUTTING-OFF TOOL Machinery Fig. 12. Tools used and Order of Operations followed in Making the Pinion Blank shown in Fig. 10 in this country have, as a rule, each developed their own machinery, although the automatic screw machines made by the Brown & Sharpe Mfg. Co. have been invading this highly specialized field of watchmaking. These machines have also met with considerable favor in the Swiss watchmaking field, committed though it is by years of precedent to the use of MAKING WATCH PARTS 273 the hand-operated machine. The particular work for which this tool has been applied is in the turning of the larger pinion blanks and staffs (the slender shafts or spindles on which gears and pinions are mounted). These parts have to be made with a high degree of accuracy, both as to their dimensions and as to their concentricity, or the trueness with which they run on centers. Tools and Operations for Making a Pinion Blank. The part shown in Fig. 10 is one of the larger pinion blanks used in a Swiss watch. In making it by the old-fashioned methods, a blank is cut off and formed at each end with the cone points shown, which are supported in female centers in the lathe, where successive cuts are taken to bring it to the required dimensions, the same as would be done for much larger work in the engine lathe. This operation is practically duplicated in the automatic screw machine, so far as turning on centers is concerned. The order of operations and the tools used for each of them may be followed from Fig. 12. The first operation is the feed- ing of the stock. No stop is used for the stock to feed against, the feeding mechanism being accurate enough to always leave a few thousandths of stock for the first operation, which is that of pointing the end of the bar to form the outer cone- shaped pivot point of the work. This is done by a tool mounted in a "floating" holder, which may be firmly clamped in the proper position for forming an accurately pointed pivot each time the machine is set up. With this tool, the accurate align- ment of the turret with the axis of the spindle is not abso- lutely necessary; in fact, no alignment accurate enough for this purpose could be permanently maintained. This piece of work is short and stiff enough so that it can be turned en- tirely by circular forming tools mounted in the cross-slide. These forming tools are shown at work in the second operation in Fig. 12. The one in the front cross-slide turns the two diameters forward of the largest diameter on the work, while the rear cross-slide turns the two diameters on the other side of the collar, and rough-turns the protecting end of the stock 274 SCREW MACHINE PRACTICE WORK for the cone point of the next part to be made. While these operations are in progress, the outer end of the work is sup- ported in a delicate female center, in a spring plunger held in the turret. It was stated that this part is practically turned on centers. The significance of this statement will be under- stood by studying the second operation, and the succeeding or third operation. Since the outer end of the work is sup- ported by the center while the forming is in progress, the di- ameters thus turned must be true with that center. In the third operation, the center at the other end of the work is formed. The forming of this center is shown in Fig. 13. The blade follows a diagonal line of travel, so that the center is turned to the right angle. Face a is beveled so that it clears the work entirely, and the point is quite sharp. The cutting action is thus entirely on the face of the stock, and the work is not subject to any pressure whatsoever, but remains attached to the stock until the tool has progressed so far that it separates and falls off by its own weight, leaving the point so sharp as to be for all practical purposes a perfect one. The outside diameter of the piece is left stock size. This large diameter has the pinion teeth cut in it and runs true enough for all practical purposes. Cone-point Turning and Cutting-off Tool. The construc- tion of the point turning tool is shown in Fig. 14. The cutting- off blade B is held in a slot in tool-slide C and rests on adjust- ing screw D and pin E. It is clamped in position by screw F. By adjusting screw D, the blade is rocked about pivot E to bring the point higher or lower as may be required to accu- rately center it with the axis of the work. Slide C is gibbed to a dovetail guide on slide carrier G. This member is pivoted LINE OF TRAVEL OF THE TOOL Machinery Fig. 13. The Cone Point Turning and Cutting-off Operation MAKING WATCH PARTS 275 to the body of the tool H about the axis of bolt /, and is clamped by screw K in the proper location to guide the slide C in form- ing the desired angle for the pivot of the work. Tool-slide C has attached to it a rack which meshes with the 32-pitch pinion L, pivoted to the under side of G. Pinion L meshes with a similar pinion M , pivoted in a hole in the body SECTION ON LINE X-X ADJUSTMENT OF BLADE IN TOOL-HOLDER TOP VIEW WITH TOOL-HOLDER REMOVED FRONT VIEW WITH TOOL-HOLDER REMOVED SIDE ELEVATION WITH TOOL-HOLDER REMOVED Machinery Fig. 14. Construction of Cone Point Turning and Cutting-off Tool of the tool about the center of bolt /, so that the correct rela- tions between them are preserved whatever the angular ad- justment of G on H. Pinion M is lengthened and at its lower extremity meshes with rack teeth cut in the side of plunger N. This is best seen in the section on line xx. This plunger, as may be seen in the side elevation, has at its front end a projection extending upward bearing against a plunger in a hole above it, which is pressed outward by a spring. By this means, N is normally kept at the outer end of its movement, being limited in this direction by the seating of screw P in the recess 276 SCREW MACHINE PRACTICE I FACE OF TURRET IN BACKWARD POSITION 1ST OPERATION POINT WfTH BOX POINTING TOOL 2ND OPERATION TURN LARGE SHOULDER A USING SWING TOOL WITH TELESCOPIC SUPPORT 3RD OPERATION TURN INTERMEDIATE SHOULDER B TOOL USED IS A DUPLICATE OF TOOL USED FOR 2ND OPERATION 4TH OPERATION TURN SMALL DIAMETER C TOOL USED IS A DUPLICATE OF TOOL USED FOR 2ND OPERATION 6TH OPERATION FORM WITH BACK SLIDE TOOL FORM WITH FRONT SLIDE TOOL SUPPORT WHILE FORMING WITH TELESCOPIC SUPPORT IN TURRET 6TH OPERATION CUT OFF WITH ANGULAR CUTTING OFF TOOL Machinery MAKING WATCH PARTS 277 provided for it in the body H of the tool. In this position, the tool-slide is withdrawn so that the blade clears the work. The front end of N is provided with knurled screw Q and lock-nut R. These are so located as to be in line with a pusher or raising plate attached to the front cross-slide of the machine, when the turret has brought the tool to the proper position for cutting off. The cutting off is effected by the movement of the cross-slide. The pusher bears on screw Q, presses plunger N inward, revolving pinions M arid L, which, in turn, acting on the rack attached to the tool-slide, move cutter B inward, severing the work from the bar and forming the pivot point, as shown in Fig. 13. The length of the inward travel of the tool is adjusted by screw Q and lock-nut R. The swiveling adjustment of the pusher plate is not needed for this job. Cams for Making Pinion Blank. At A, B, and C in Fig. 1 6 are shown the cams by which the feeding movements of the machine are effected for performing the operations shown in Fig. 12. As is well known, the Brown & Sharpe automatic screw machine has a front and a back cross-slide and a turret- slide, each controlled by its own separate plate cam. In Fig. 1 6 the various radial lines are figured to show their distance from the starting point o, in hundred ths of a circle. The various acting surfaces of the cams are marked to indicate the operations performed by them. The material used for this pinion blank is tool steel. The spindle revolves 1320 revolutions per minute, giving a surface speed to the work of about 58 feet per minute, which is suitable for the material used with the heavy flow of oil directed on the cutting edges of the tools. It takes 770 revolutions to make a piece, so that each hundredth of a revolution of the cam represents 7.7 revolutions of the spindle. Knowing this, the various feeds can be readily figured out. On the back-slide cam, which takes the wider of the two forming cuts, a finer finishing feed is used between positions 60 and 72^ than for the first portion of the forming between 20 and 60. This is done to produce the finer finish which the finer feed gives. It will also be noticed that in all forming operations, such as those performed by the 278 SCREW MACHINE PRACTICE MAKING WATCH PARTS 279 two cross-slides, and by the turret-slide in pointing the work in the first operation, the cams are provided with " dwells," or resting places where the periphery of the cam is, for a short space, a portion of the circumference of a circle, so that the slide is allowed to rest at this point while the chip runs out. This produces a smooth final finish. The net production is 900 per day, allowing time for sharpening tools, etc. Tools and Operations for Making a Watch Staff. The part shown in Fig. n has to be handled somewhat differently from the one just considered. It is much longer and more slender, and cannot be formed by cross-slide tools. The order of operations is indicated in Fig. 15. The stock, having been fed to length, is pointed by the turret tool shown in the first operation. In this tool the stock is supported by a bushing while the end is being pointed, the work being too slender to support itself, as in Fig. 12. In the second operation, shoulder A is turned. This is done by a swing tool. The pointed end is supported in a female center, a turning cut is taken over the shoulder of the finished diameter required, the cutting blade is released so that it is not dragged over the work on the return, and then the turret is revolved for the next opera- tion. Operations 3 and 4 are also performed by the same kind of a tool and in the same way, shoulders B and C being each finished in turn. It will be noticed that the smallest diameter is finished last. If shoulder C were turned first to its finished size, it would not be stiff enough to support the succeeding cuts A and B, with assurance that they would be true with the cone-pointed end. In the fifth operation, the work is supported in a female center while formed tools in the front and rear cross-slides square up the shoulders already turned, and remove the burrs caused by the turning tools. The front cross-slide tool forms the small diameter to the left of the collar and squares up the sides of the collar itself. As will be seen from a study of the cams D, E, and F, Fig. 16, the front cross-slide tool does not begin to cut until the one in the rear has completed its work. The stock is too slender to permit of too much work being done 280 SCREW MACHINE PRACTICE on it at once. In the sixth operation, the same angular cutting- off tool as shown in Fig. 14 is used for severing the work from the bar and forming the cone point at the same time. It will be seen that in the operations just described, as in the previous case, the various diameters will be as concentric with the pointed centers of the work as if they had been turned on them. Machinery Fig. 17. Swing Tool used for Operations on Part Shown in Fig. 15 Operation of the Swing Tool. The swing tool used in Operations 3, 4, and 5 in Fig. 15 is shown in Fig. 17. To the body T of the device is pivoted (about stud U) the tool-holder V, carrying blade W, which is adjusted vertically and clamped by the square-headed screws shown. In a hole drilled into the body of the tool is contained a plunger Z pressed outward by a spring. The opening of this hole is closed by a screw, as shown. A pin X driven into the side of tool-holder V pro- jects through a side hole into T, and bears on the face of plunger Z. By this means, the spring keeps V swung outward, the movement being limited by the bearing of Z on the head- less set-screw. Abutment screw F, in part V, is in position to bear against the pusher or raising plate carried by the cross- slide. In turning shoulders A, B, and C (Fig. 15), the movements MISCELLANEOUS EXAMPLES 281 of the front cross-slide and turret-slide cams are so arranged that the swing tool is brought up to the work ; the cross-slide is next moved in to set the tool W to the diameter desired, as determined by the adjustment of screw F; then the swing tool is fed forward the proper distance for the shoulder. The front cross-slide is next withdrawn, allowing tool W to swing outward under the influence of the spring and plunger Z. The turret-slide then retreats, drawing the blade out of the way without allowing it to drag on the work. The swivel adjustment on the raising plate allows either straight or taper turning to be done, as required. The Cam Equipment. The cams, shown at D, E, and F in Fig. 1 6, for making the part shown in Fig. n appear to be somewhat complicated, but the operations may be easily followed. The various lobes of the three cams are marked for the operations for which they are intended. The abbrevia- tion "I. T." means "index turret," and the term " dwell" indicates a concentric portion of the cam, where the slides are at rest. In making this piece, the spindle revolves at 2400 revolutions per minute. The stock is 0.063 inch in di- ameter, which gives a surface speed of about 40 feet per min- ute. The material is tool steel. The net production for these pieces was 1500 per day. The total revolutions to make one piece is 840, so that each hundredth on the periphery of the cams represents 8.4 revolutions. Examples of Work on Cleveland Automatic. The suc- cessive operations for produqing the parts shown in Fig. 18, on the Cleveland automatic, will be described. The special chrome-nickel steel sleeve shown at A requires drilling, form- ing, recessing, and tapping. A 3^-inch model A machine with a No. 4 spindle drive is used. As shown in Fig. 19, the operations are in the following order : 1. Gage the stock to length by a gage stop A in the first hole in the turret. 2. Index the turret and rough-turn the large diameter with cutter a, using an overhanging turning attachment B, and at the same time drill a large hole full depth, using a drill 282 SCREW MACHINE PRACTICE and split holder C in the second hole in the turret; time of operations, 3 minutes 35 seconds. 3. Index the turret and finish- turn the large diameter with the second cutter b held in a turning attachment, and at the same time counterbore a large hole, using a counterbore and holder D held in the third hole in the turret. As no tools are in the way on the front side, forming tools E and F can be brought into operation to face the end and to form the rear fftf A CHROME NICKE'L STEEL Machinery C.R. STEEL Fig. 18. Examples of Work done on Cleveland Automatic diameters, using flat forming tools and a toolpost, and an open-side toolpost on the front of the cross-slide. The time for these operations is 4 minutes 30 seconds. 4. Index the turret and drill a small hole, using a drill and splif holder G in the fourth hole in the turret. Time of opera- tion is 2 minutes 15 seconds. 5. Index the turret, recess, using a recessing tool and holder H in the fifth hole in the turret. The operating cam for effecting a movement of the recessing tool is held on the front of the cross-slide. Time of operation is i minute 25 seconds. 6. Index the turret and bring the tap-holder I and tap held MISCELLANEOUS EXAMPLES 3RD FINISH TURN, COUNTERBORE, 6TH AND 7TH TAP AND CUT-OFF Fig. 19. Tool Equipment and Operations for Making a Chrome-nickel Steel Sleeve on a " Model A" Cleveland Automatic 284 SCREW MACHINE PRACTICE in the sixth hole into operation. The time for threading this piece is i minute 45 seconds. 7. Cut off, using the cut-off blade / held in a universal cut-off toolpost on the rear of the cross-slide. Time for opera- tion is i minute 30 seconds. The total time for the entire operations enumerated, includ- ing the idle motions of the machine, is 15 minutes. When the tools have been set in their proper relation to each other, and the feed-regulating cams have been so adjusted as to give the proper feeds for the various tools, the position of the various cams is noted and recorded on a chart. All the tools used are also recorded on this chart, so that the machine can easily and quickly be equipped and adjusted for reproducing this same part, if necessary, at any future time. Another comparatively simple piece of work to produce on the Cleveland automatic is shown at B in Fig. 18. The successive operations are shown in Fig. 20, the machine being a 3^-inch Model A, using the No. i drive : 1. Feed the stock to stop A, which is held in the first hole in the turret. 2. Index the turret and drill a hole full depth, using a drill- holder B in the second hole in the turret. Time for operation, 50 seconds. 3. Index the turret and finish- turn the outside diameter with an overhanging turning attachment D, carrying two cutting tools tool a for roughing and tool b for finish-turning. At the same time, counterbore the hole, using a counterbore held in holder E in the third hole in the turret, and form and face with tools F and G which are held on the front part of the cross-slide, using a post with flat cutters and spacing blocks to locate them the correct distance apart. Time for the opera- tion, 3 minutes 55 seconds. 4. Index the turret and finish-turn with the second cutter b in an overhanging turning attachment D, and ream the hole, using a reamer and floating holder H carried in the fourth hole in the turret. The time for these two operations is 18 seconds. MISCELLANEOUS EXAMPLES 1ST GAGE STOCK TO LENGTH 2ND DRILL HOLE B V n_A 3RD FINISH TURN, COUNTERBORE LARGE HOLE, FORM AND FACE 4TH AND STH FINISH TURN, REAM AND CUT-OFF Machinery Fig. 20. Tools for Making a Clutch Case on a "Model A" 3^-inch Cleveland Automatic 5. Index the turret and cut off with a universal cut-off, tool blade / and post held on the rear of the cross-slide. Time, 32 seconds. The total time, including the idle motions for chucking, 286 SCREW MACHINE PRACTICE advancing, and withdrawing the turret and indexing, is 5 minutes 35 seconds. The arrangement of the forming and cutting-ofT tools is shown in Fig. 23. All the data obtained from the setting-up of this job are recorded on the operation sheet, as well as any particular features necessary to turn out this job more effectively. All the tools and attachments are noted under the various headings on the sheet, as well as the size of the pulleys, number of pins in the regulating drum, and other points regarding the proper setting-up of the machine. In producing the twin gear blank shown at C in Fig. 18, the greatest amount of work is done from the cross-slide. The drilling depth is considerable, so that the best way to lay out this job would be to use two drills, one going in part way and the other the remainder of the distance. The operations on a 3|-inch Model A machine with a No. i drive are as follows : 1. Gage the stock to length by a stop A (Fig. 21) held in the first hole in the turret. 2. Index the turret and turn part way with a tool a in an overhanging turning attachment B carrying two turning tools, and drill part way, using a high-speed drill held in holder C in the second hole in the turret. Time for the two operations, 40 seconds. 3. Index the turret and finish- turn, using the second cutter b in an overhanging turning attachment B, and drill full depth, using a high-speed drill-holder D held in the third hole in the turret. At the same time, advance tools E and F held on the front of the cross-slide and start forming the rear diameters. Also take a cut on the front face, using tool F and an open-side toolpost on the front of the cross-slide. Time for operations, i minute 55 seconds. 4. Index the turret and ream a hole, using a reamer held in a high-speed drill-holder G in the fourth hole in the turret. The use of two drills on a hole of this depth avoids the necessity of using a boring tool, and the reamer in this case can be held in a rigid instead of a floating holder. At the same time that the hole is being reamed, three cutting blades H, held on the rear of the cross-slide and separated by flat spacing blocks, MISCELLANEOUS EXAMPLES 287 Fig. 21. Successive Operations for Producing the Twin Gear Blank Shown at C in Fig. 18 are brought into action. The grooving blade nearest the chuck is made considerably wider than the requirements of the work demand, and is used for roughing the front end of the next piece. Time for operations, 3 minutes 40 seconds. 288 SCREW MACHINE PRACTICE 2ND TURN SMALL END-BOX-MILL Machinery Fig. 22. Operations for Producing the Stanchion Bolt shown at D in Fig. 18 5. Index the turret, and counterbore with a tool held in holder I in the fifth hole in the turret. Time for operation, i minute. 6. Cut off with blade /, using an independent cut-off attachment shown in Fig. 24, and index the turret twice. Time for operation, 35 seconds. Total time, 7 minutes 50 seconds. This is an example where there was considerable forming to be done from the cross-slide, which could not be handled MISCELLANEOUS EXAMPLES 289 efficiently with only one set of tools, that is, using only one end of the cross-slide for forming tools; consequently, both ends of the cross-slide, as shown in Fig. 24, are utilized and the work is then cut off by the independent cut-off attachment shown. For the operation of this attachment a special cam disk A is held on the rear shaft carrying a cam B. This is adjustably mounted in the T-slot groove cut in the side of the disk and can be set in any desired position. This cam comes in contact with a roll carried in the rear end of the fulcrumed arm of the attachment, raising it up and consequently depress- ing the front end and advancing the cutting-off tool toward the center of the work. The stanchion bolt D, Fig. 18, brings up a point in the operation of the Cleveland automatic that is worthy of special attention; that is, the handling of long forming operations, especially on steel parts. This can be done much more effi- ciently by means of a long flat forming tool than by a circular forming tool. There are two reasons for this: i. The flat forming tool gives much better side clearance than the cir- cular tool. 2. The flat forming tool can be held much more rigidly and heavier cuts can be taken with it. It is also much cheaper to make. The only other point of interest about this job is the use of a self-opening die-holder. The use of this type of die reduces the time necessary for threading, as the die does not need to be backed off, but is opened as soon as the thread is completed, and the turret can be drawn back on the fast speed. Referring to Fig. 22, it will be seen that the operations are done in the following order, a 2 f -inch Model A machine equipped with a No. i spindle drive being used : 1. Gage the stock to length with a gage stop A held in the first hole in the turret. 2. Index the turret and turn down the stem with a box- tool B held in the second hole in the turret. Time for this operation, i minute 30 seconds. 3. Index the turret and form an irregular shape, using a flat forming tool C held on the front of the cross-slide ; support 2 go SCREW MACHINE PRACTICE the work at the same time with a roller steadyrest D held in the third hole in the turret, and engaging the stem of the work. Time for this operation is 3 minutes 20 seconds. 4. Index the turret and thread, using a self-opening die- head E in the fifth hole in the turret. Time for operation is 35 seconds. 5. Cut off, using a circular cut-off tool F held on the rear of the cross-slide. Time, 45 seconds. The total time, including all the idle movements, is 6 minutes 15 seconds. The arrangement of the tools held on the cross- slide is clearly indicated in Fig. 25. The flat forming tool C is mounted on a wedge A for vertical adjustment. The form- ing tool is held down by the cap-screws and the wedge is ad- justed by a set-screw D. Another set-screw E backs up the forming tool, supporting it much more rigidly. The cut-off tool is held on the rear forming slide and is turned upside down so that the spindle need not be reversed, the cutting off being done with the stock running in the forward direction. Operations on Acme Multiple-spindle Machine. The successive order of the operations in producing a long set- screw in an Acme multiple-spindle automatic is shown in Fig. 26. This set-screw is made from a square wrought-iron bar. The threaded portion is 5! inches long, the length over- all, 63; | inches. The longest single operation consists in turning down the body diameter to the required size. The spindle speed at which to rotate the work should first be determined. Taking the diameter of the stock across the flats as the basis of our calculations, and deciding on a surface speed of 100 feet per minute, it will be found that the desired spindle speed should be 611 revolutions per minute. The nearest available spindle speed, in this case, is 635 revolutions per minute, which gives a surface speed of about 104 surface feet per minute. The next step is to determine the number of revolutions necessary for the box-tool to travel up half the length of the screw 2 1 inches. With a feed of 0.0045 inch per revolu- tion of the work, the number of revolutions required to make this cut is about 640. As the spindle makes 635 revolutions USE OF MULTIPLE-SPINDLE TYPE 2QI Machinery Fig. 23. Diagram showing Arrangement of Cross-slide Tools for Forming and Cutting off Piece shown at B in Fig. 18 Machinery Fig. 24. Arrangement of Cross-slide Tools for the Forming and Cutting-off Operations on the Part shown at C in Fig. 18 Machinery Fig. 25. Arrangement of Cross-slide Forming and Cutting-off Tools used in Connection with Operations shown in Fig. 22 292 SCREW MACHINE PRACTICE per minute, the time, in seconds, to turn half the body is 60 640 ~ X ~ ~ = 60.47 seconds. Adding to this the time for the 635 i idle movements of the machine gives 60.47 + 2.4 = 62.87, or, approximately, 63 seconds. This gives a product of 57 pieces per hour, but, upon referring to the table of change-gears, it will be found that gears to give this product are not ob- tainable. Therefore, it is necessary to either increase the product to 59 and increase the feed of the tools accordingly, or else decrease the product to 51 pieces per hour with a cor- responding decrease in feed. The tool equipment used in making this set-screw is illus- trated in Fig. 27. The operations start in the first position, where the first box-tool A comes into position, turns up half the length of the body 2| inches and points the end of the screw. At the same time that the box-tool is in operation on the work, the form tool comes in from the side and turns down the neck also rough-forming the top of the head. As the cylinder is indexed into the second position, the second box-tool B comes into operation and finish-turns the body. The cylinder is again indexed to the third position, where a self- opening die C cuts the thread. After threading, the cylinder is again indexed and the piece cut off with a straight-blade cut-off tool D. These various operations have been described separately, but in actual performance all tools are at work on different bars at the same time. Making Knurled Thumb-nuts. The knurled thumb-nut shown at A in Fig. 29 represents an example in which the forming is the longest single operation, and is the time to make one piece. This knurled nut is made from a 2 -inch bar of round brass rod in a No. 56 Acme multiple-spindle automatic screw machine. The first step in determining the time to make this piece is to obtain the correct speed at which to rotate the work. Rod brass can be worked at from 150 to 200 surface feet per minute, and, by calculation, it will be found that a spindle speed of 290 revolutions per minute will give 150 feet surface speed. The next step is to determine the proper feed at which USE OF MULTIPLE-SPINDLE TYPE 293 to operate the form tool. Now the conditions under which this thumb-nut is made are ideal, as far as a heavy feed is con- cerned, so that the form tool can easily be operated at 0.005 inch per revolution. By dividing the travel of the form tool or 0.635 inch (allowing o.oio inch to approach the work) ~~~L FORM, TURN WITH BOX-TOOL U" . J '"I. ? HALF WAY AND POINT FINISH TURN WITH BOX-TOOL THREAD 1ST POSITION 2ND POSITION SRD POSITION 4TH POSITION CUT-OFF Fig. 26. Successive Operations for Making a Long Square-headed Set-screw by 0.005, it will be found that it will require 127 revolutions of the spindle to complete the forming operation. As this is a case where the longest single operation is per- formed from the form tool-slide, it will be necessary to calcu- late the time required in seconds to complete the idle move- ments of the machine. This is found to be 4.6 seconds. (For information regarding the method of calculating the time for 294 SCREW MACHINE PRACTICE idle movements, see Chapter V.) Then the time in seconds to complete the forming operation equals 26.27 seconds. Add- ing the time for the idle movements will give 26.27 + 4.6 = 30.87 seconds. Assume that it takes 30 seconds to make one piece ; then the rate of production will be 120 per hour. The nearest production to this for which change-gears are obtainable is 122 pieces; and, by using the change-gears to obtain this production, the feed of the tools is increased slightly, which, in this case, could be done with satisfactory results. In making this thumb-nut, the rough-forming is done in the first position and the hole drilled to the proper depth with drill A (see Fig. 28). In the second position, the head of the nut is knurled with knurl B, and the hole counterbored to a square bottom, both operations being done by tools held in the end- working tool-slide. The hole is tapped with tap C and the head beveled and grooved in the third position, the grooving being done with a shaving tool D. In the fourth position, the completed nut is cut off from the bar with cut-off tool E. Making a Part Requiring Cross-drilling. The brass knob shown at B in Fig. 29 is a difficult piece on which to determine the longest operation at a glance. It is evident, however, that the drilling of the large hole in the end will not require much time, so that the longest operation lies between the forming and cross-drilling cuts. The depth of form cut is 0.195 inch and, with a feed of 0.002 inch per revolution, it will require 98 revolutions of the spindle to complete this operation. The cross-drilling attachment is held on the cut-off tool- slide, as shown in Fig. 30, and its travel is governed by the feed given to the cut-off tool. As the cross-hole is deeper than half the diameter of the stock to be severed by the cut-off tool, it is necessary to use an accelerating cross-drilling attach- ment. This will increase the rate of travel of the attachment in relation to the cut-off tool-slide in a ratio of if to i. The travel of the cross-drill is equal to the depth of the hole ^ inch plus the length of point on the drill and the height of Fig. 27. Tool Equipment for Producing the Set-screw shown in Fig. 26 on Acme Multiple-spindle Automatic Screw Machine Fig. 28. Tool Equipment for Producing a Brass Thumb-nut 296 SCREW MACHINE PRACTICE the arc removed from the ball by drilling a hole in it. This is equal to 0.750 inch. With a feed for the cut-off tool of 0.003 inch per revolution, the feed of the drill in relation to the rotation of the spindle is 0.003 X 1.75 = 0.0052 inch. Then the number of revolu- tions of the spindle equivalent to the time required to drill the cross-hole is 143. If this work is done on an Acme No. 54 machine and the speed is 520 revolutions per minute, it will require 16.5 seconds to drill the cross-hole. Adding the time for the idle movements i .88 gives a product of one piece in 18.38 seconds, or 195 pieces per hour. Upon referring to the table, it will be found that the nearest production to this for which gears are provided is 190 pieces. Operation Requiring Use of Milling Attachment. The cold-rolled steel bushing shown in Fig. 31 has " flats" milled on the flange by means of an attachment similar to the one shown in Fig. 13, Chapter VI, which is mounted on the cross- slide. The end-milling cutters are brought in at the same time as the cut-off tool and work in the " third" position, the cut-off tool severing the completed piece from the bar in the "fourth" position. (Instead of using two end-milling cutters from the side, this operation might be done as well with a pair of saws working from the end.) It is evident from a close study of this piece, the operations for which are shown in Fig. 32, that the longest single cut lies between the milling and form- ing operations. Taking the forming cut first, it will be found that the distance the forming tool must travel is IQ inch. No allowance need be made for the tool to approach the work, as the diameter is finished by a shaving tool. The length of the forming tool is about ij inch, and the smallest diameter, i inch, so that the feed should not exceed 0.002 inch. This rate of feed will require 93 revolutions. As the slab milling attachment is carried on the top face of the cut-off tool-slide, it can easily be seen that the feed given to the milling cutters will be governed by the feed used for cutting off. As the distance that the milling cutters must travel is greatly in excess of the travel of the cut-off tool, an accelerating device is used USE OF MULTIPLE-SPINDLE TYPE 297 Machinery Fig. 29. (A) Successive Operations on Brass Thumb-nut. (B) Operations on Brass Knob on the milling attachment. This increases the travel of the milling slide over the travel of the cut-off slide in a ratio of if to i. With a feed for the cut-off tool of 0.0025 i ncri P er revolution, the feed or rate of advance of the milling cutters in relation 298 SCREW MACHINE PRACTICE to the revolutions of the spindle will be 0.0025 X 1.75 = 0.0043 inch. Then dividing this amount into the travel of the slide (j| plus the radius of the milling cutters, which are J inch in diameter, plus 0.020 inch for clearance) gives 1.082 inch travel. This is equivalent to 247 revolutions of the spindle. This piece can be most economically produced on a No. 54 machine, and, with a surface speed of about 95 feet per minute, Fig. 30. Example of Cross-drilling on the "Acme : Automatic Screw Machine Multiple-spindle a spindle speed of 260 revolutions per minute is obtained. The time required to complete the milling operation was found to be equivalent to 247 revolutions of the spindle, or 57 seconds. Adding the time for the idle movements (1.88 second) gives approximately 59 seconds to complete one piece, which is equivalent to a product of 61 pieces per hour. The nearest gears to the product required are those for 58.5 pieces; thus the rate of production would be decreased to this amount. USE OF MULTIPLE-SPINDLE TYPE 299 Division of Cuts between Two Tools. The threaded bushing shown at A, Fig. 33, is made from cold-rolled steel bar, 2 1% inches in diameter. The forming cut is rather heavy, so that the production on this piece can be considerably in- creased by dividing the forming cut between two forming tools. The first forming tool is used for breaking down only while the second forming tool is used to finish the piece to the desired shape. The greatest reduction in diameter on this piece is yf mcn j making a rough-forming travel of 0.440 inch necessary. Now the finish-forming tool has to travel prac- L COLD-ROLLED STEEL Fig. 31. Bushing that is made as indicated in Fig 32 tically the same distance as the rough-forming tool, but, while it does not remove as much material, it is operated by the same slide as the roughing tool; hence, both roughing and finishing cuts consume the same amount of time and are the longest operations. Turning now to the drilling operation, it will be found that a hole yf inch in diameter and 2\ inches deep has to be drilled. This can be divided between two drills, as shown at the first and second spindle positions, so that the travel of the main tool- slide for drilling will be i| + A inch, or a total of 1.406 inch. The drills can be operated successfully in this material at a feed of o.oio inch per revolution, so that 140 revolutions will be required to complete the drilling operation. Figuring on a feed of 0.0015 inch for the rough-forming operation, and a rise of 0.445 inch (0.005 mcn being allowed to approach the work), it requires 296 revolutions of the spindle. 300 SCREW MACHINE PRACTICE The tool equipment used for making the piece shown in Fig. 33 is shown* in Fig. 34. The first forming tool A is held in the regular tool-holder, working in the first position, while the second or finish-forming tool B is held in a special holder, attached to the top face of the forming slide. This holder is provided with an overhanging arm in which a set-screw C is located, to enable the forming tool to be held rigidly in place. In making a double tool-holder of the type illustrated, it is essential that it be rigidly clamped to the tool-slide and have 1ST OSITION \ STRADDLE MILL SHAVE, FINISH-DRILL LARGE HOLE AND FACE \ REAM AND CUT OFF Machinery Fig. 32. Successive Operations on Steel Bushing shown in Fig. 31 as much bearing surface as is consistent with the space avail- able. As a general rule, it is advisable, when a holder is of the built-up type, to have the stock rotating toward the form tool instead of away from it. This enables a much heavier cut to be taken without chatter, as the thrust is directed against the tool-slide instead of from it, the latter action tending to lift the tool. In this case, however, the holder is supported by the top bracket, thus overcoming the tendency of the tool to rise. This job also presents another interesting feature in the double or telescopic die-holder D. This die-holder, which is described in Chapter IV (see Fig. 38), can be used for cutting USE OF MULTIPLE-SPINDLE TYPE 301 FINISH-FORM AND FINISH-DRILL CUT DOUBLE THREAD ROUGH-FORM AND DRILL LARGE HOLE HALF WAY FINISH-FORM AND FINISH-DRILL LARGE HOLE DRILL SMALL HOLE, SHAVE ALL OVER AND FACE Machinery Fig. 33. Examples of Work done on Multiple- spin die Machine threads of two different diameters and unequal pitches, owing to its construction. The outer member of the die-holder is spring controlled in its action, so that it can lead out in ad- vance of the other part of the holder, thus enabling threads of different pitches to be cut. Another example of work which can be produced to better advantage, by dividing the forming cuts between two tools, 302 SCREW MACHINE PRACTICE is shown at B, Fig. 33. Both forming tools are required to take long, heavy cuts, so that rigidity is absolutely neces- sary. In order to keep the feed up to a point where a good production is possible, the arrangement shown in Fig. 35 was adopted. This consists in placing the first forming tool in the fourth position instead of in the first,, as usual, and cutting off the completed piece in the third position. It is evident that the cut-off tool does not need to be held nearly so rigidly as a form tool, and can be held on an extension bracket. This arrangement allows the rough-forming to be done in the fourth position (where the stock is fed out), and the finish-forming in the first position. If the stock were fed out in the first posi- tion, the rough-forming would have to start at this point, which would not be advisable, as the wide formed surface could not be machined with an extension tool. The arrange- ment shown in Fig. 35 is commendable, in that it obviates all flimsy construction, and enables the work to be produced much more rapidly. The operations are as follows : In the fourth position the diameter is rough-formed, and the large hole drilled part way with drill A . In the first position, the forming cut is finished, and the large hole is drilled to the required depth with drill B. In the second position, the small hole is drilled with drill F and the diameter finished all over by a shaving tool D\ the end is also faced with a cutter held in the holder E which is attached to the holder G carrying the drill F. In the third position, the hole is counterbored and taper-reamed, and the work is cut off. Cold-rolled steel, as a rule, can be worked at from 90 to no surface feet per minute. It is found by calculation that a spindle speed of 100 revolutions will be about the desired speed at which to rotate the work. The rough-forming tool will stand a very much heavier feed than the finish-forming tool, and, as both tools have to travel the same distance, it is evi- dent that the finish-forming operation will be the one on which it will be necessary to base our calculations. The form tool is made up of two sections and the smallest diameter formed Fig. 34. Tool Equipment for Producing the Steel Part shown at A in Fig. 33 on "Acme " Machine Fig. 35. Arrangement of Tools for Operations illustrated at B in Fig. 33 304 SCREW MACHINE PRACTICE is iJ- inch. Therefore, it would be inadvisable to use a feed exceeding 0.0015 inch per revolution of the work. Figuring on a travel of 0.350 inch for the finish-forming tool, at the rate of 0.0015 inch feed per revolution, 233 revolutions will be required to complete this operation. As the forming cut is the longest single operation, we find from this the time to make one piece. The spindle speed used is 100 revolutions per min- ute, and the revolutions required for forming are 233, which is equivalent to 2 minutes 18 seconds ; adding the time required for the idle movements 4.6 seconds a total of 2 minutes 23 seconds, approximately, will be required to complete one piece, or 26 pieces per hour. Assembling Parts in Screw Machine. The assembling of parts in the automatic screw machines is a practice which is not widely followed, but represents an interesting develop- ment. The examples to be described include not only the assembling operations, but also the making of the parts to be assembled from the same bar at the same chucking. This not only decreases the cost of making the parts, but also eliminates the necessity of handling them a second time. Machining and Assembling a Bolt and Nut. In Fig. 36 is shown a small brass bolt and nut which a jobbing shop had been making for several years, each part being made on a sepa- rate machine. The assembling was done by hand, and consisted of screwing the nuts on the bolts. These parts are now made in a No. o Brown & Sharpe automatic screw machine at the same chucking, and assembled without rehandling. The most interesting feature of the present method is the indexing of the turret twelve times during one revolution of the cams; that is, the turret makes two complete revolu- tions while the cams make one ; the necessity for this will be explained later. The machine spindle is reversed three times. The additional revolving of the turret and reversing of the spindle are accomplished by the use of extra tripping dogs. The method of applying the circular tools and the assem- bling tool is shown in Fig. 36. The form tool A forms the body of the bolt and cuts off the nut, and B is the tool which ASSEMBLING IN SCREW MACHINE 305 cuts off the bolt. This latter tool is mounted on the front cross-slide. This lay-out requires but one feeding of the stock for both pieces. The turret tool, which is a carrier for the nut, comes forward just before the nut is cut off, and the spring chuck C closes over it. (The stock at this point is running backward.) The clutch finger D allows the carrier C to revolve in the holder E, thus preventing the nut from turning in the spring chuck and wearing off the corners. When the nut is inserted in the chuck C, and has been cut off, the spindle is reversed to run forward, the clutch finger pre- venting the carrier from turning. This clutch also acts while the nut is being screwed on the bolt. The clutch is more clearly shown in the sectional view to the right. The order of operations -is as follows: Revo- Hun- Order of Operations lutions dredths Feed stock to stop 18 3 Revolve turret 18 3 Drill o.i 78-inch rise at o.oo34-inch feed v . . 53 9 Revolve turret 18 3 Tap in 12 2 Tap out 12 2 Cut off o. 145-inch rise at o.ooi 7-inch feed 83 14 Revolve turret twice and bring carrier forward (36) (6) Form with tool on rear slide o.i3o-inch rise at o.ooo85-inch feed: 159 27 Back away form tool to clear threading die 12 2 Revolve turret five times (90) (15) Thread on 17 3 Thread off 17 3 Revolve turret 17 3 Thread on nut 12 2 Reverse spindle and withdraw turret 12 2 Cut off bolt o.237-inch rise at o.ooig-inch feed 124 21 Revolve turret twice (36) (6) Clearance 6 i Total revolutions 590 100 With a spindle speed of 1474 revolutions per minute, this lay-out gives a gross production of 1500 pieces in ten hours, or 1350 pieces net. The time required to make and assemble both pieces is 24 seconds. After the stock is fed out to a length sufficient to make both pieces, the end is drilled and tapped for the nut, which is then inserted in the carrier and cut off. The problem which now arises is to index the turret a sufficient number of times to bring the carrier into position to screw the 306 SCREW MACHINE PRACTICE nut on the finished bolt, as soon as the latter has been threaded. This is successfully accomplished by indexing the turret twice while cutting off the nut, and five times while forming the bolt. The most interesting part of the job is the laying out of the cams. The usual set of three cams is shown in Fig. 37, the outline of the lead cam being shown as a solid line. It will be noticed that the lobe for centering is omitted from the lead cam. This is done because of the shallow depth of the hole Machinery Fig. 36. Method of Applying the Circular Tools; the Carrier or Assembling Tool, and Nut and Bolt to be made and Assembled to be drilled, and also because the work is not required to be very accurate. The lobe which operates the carrier when gripping the nut is shown from 28 to 36 on the lead cam, Careful calculations are necessary to determine the exact position of this lobe, so that the carrier will grip the nut before it is cut off. The method used to determine the position of this lobe is as fol- lows: During the time from 22 to 28, which is equal to 36 revolutions of the spindle, the cut-off tool has advanced at the rate of 0.0019 inch per revolution, or 36 X 0.0019 = 0.0684 mcn - The diameter of the stock across the corners is 0.432 inch, and the diameter of the drilled hole is 0.125 inch. Then the thick- ness of the wall on each side of the hole when the carrier ad- vances on the work = 0.432 (0.0684 X 2) 0.125 = 0.085 inch, which is great enough to prevent the nut from breaking off when the carrier closes over it. ASSEMBLING IN SCREW MACHINE 307 The hook-shaped lobe from 74 to 76 threads the nut on the bolt, and the sudden drop pulls the carrier off the nut. The spindle is then reversed, so that it will be rotating in the correct direction to cut off the finished piece. The portion of the cam surfaces from 99 to o allows the cut-off tool to drop back and clear the stock before it is fed out for the next piece. RILL THE NUT 0.237 CUT OFF BOLT / FRONT SLIDE / / / (R.T. TWICE) / / / 36 RM 0.130 BACK SLIDE (R.T. 5 TIMES) Machinery Fig. 37. Cams used for Making and Assembling Nuts and Bolts Assembling by Means of Spinning Tool. An assembling operation which is a little more difficult than that previously described is shown at A, Fig. 38. This operation was accom- plished in a No. 2 Brown & Sharpe automatic screw machine and consists in making and assembling the socket joint a and grooved roller b. When in use, this grooved roller rides between two tracks as shown at A, and the ball part rotates freely in the socket joint a. The work was not required to be held to 308 SCREW MACHINE PRACTICE very close limits, and the milling and drilling, as shown at B, were done in separate operations. In setting-up the machine for making the pieces a and b, the stock is first fed out by hand to the length shown at A, Fig. 39, where the bar is faced off, and the grooved roller ADE FROM % SCREW STOCK Fig. 38. Pieces to be Made and Assembled formed ; the stock is then fed out to the length shown at B where the grooved roller is cut off. When in this position, the slotting arm descends, carrying the pick-up shown at C in Fig. 40, which grips the grooved pulley, and after it is cut off lifts it out of the way ready to be brought back, when it Machinery.N.Y. Fig. 39. Positions of the Stock for the Various Operations is to be assembled in the socket joint. While the stock is in the position shown at B (Fig. 39), the hole is drilled and reamed. The reamer, shown at A in Fig. 40, is so shaped that it makes a correct seat for the ball on the grooved roller. The tapered part a (Fig. 39) of the socket joint is formed with a box-tool after the hole has been drilled and reamed. ASSEMBLING IN SCREW MACHINE 309 When this operation is finished, the slotting arm is brought down, carrying the grooved roller, and the spring stop B, Fig. 40, which is held in the turret, and forces the roller into the socket joint. The spring stop remains stationary in this position, as does the pick-up, while the spinning tool b, shown in Fig. 39, which is held rigidly to the rear cross-slide, is ad- vanced and turns the nose of the joint over the ball, thus as- sembling the two parts. When this is accomplished, the spring stop is dropped back and the stock fed out against it. The stock is now in the position as shown at C, where the completed joint is cut off and the next roller formed to shape, as shown by the dotted outline, which would leave the stock in the same position as at A. The operations for making and assembling these two pieces are as follows : Revo- Hun- Order of Operations lutions dredths Feed stock to stop 23 3 Cut off 0.3 75-inch rise at 0.002 i-inch feed 177 23 Cut off and form o.o4o-inch rise at o.ooi 2-inch feed 32 4 Clearance to bring down slotting arm while cutting off piece, take hold of piece and return slotting arm 7 i Center o.2oo-inch rise at 0.0051 -inch feed 39 5 Revolve turret 23 3 Turn with box- tool 0.3 75-inch rise at o.oo6-inch feed 62 8 Revolve turret 23 3 Drill o.387-inch rise at o.oo46-inch feed 85 n Revolve turret 23 3 Ream o.387-inch rise at o.oo82-inch feed 47 6 Revolve turret and bring down slotting arm with piece 23 3 Push in piece with holder B, held in slotting arm (Fig. 40) ... (23) (3) Spin over end with spinning tool held on rear slide 0.125- inch rise at o.oo54-inch feed 23 3 Withdraw holder and feed stock to stop 31 4 Cut off and form o.27o-inch rise at o.oo2-inch feed 131 17 Revolve turret 23 3 Total revolutions 772 100 With a spindle speed of 421 revolutions per minute, it requires no seconds to make one piece, which gives a gross production of 327 pieces in ten hours. The cams for making and assembling the pieces a and 6, Fig. 38, are shown in Fig. 41, where the lobes for performing the various operations are clearly outlined. Assembling a Roller on its Bearing. Another operation requiring assembling is shown in Fig. 42. A No. 2 Brown & 3 io SCREW MACHINE PRACTICE Sharpe automatic screw machine was used. This part is made up of a stud a, on which turns the roller b, held in place by the washer c, the latter being pressed on the stud. The part is shown disassembled at B. There are two unusual operations to be performed. The first is to ream a large hole behind a small one, and the second is to cut off three times, requiring the stock to be fed out three times for the completion of each assembled part. In operation, the stock is first fed out to the length shown at A in Fig. 43, where the hole is centered, drilled, and the washer shown in section at a is reamed to 0.375 inch in COIL SPRINQ TOOL STEEL SPRING TEMPERED Machinery, N.Y. Fig. 40. Reamer, Assembling Tool, and Pick-up diameter. The remainder of the hole, which is in that part of the stock that will form the roller, is bored with a recessing tool to 0.380 inch. Meanwhile the circular form tool b has turned the hub c to 0.377 inch in diameter, and also formed the groove in the roller. The form tool leaves sufficient stock around the bottom of the hole to hold the parts together. Before cutting off the washer, the special tool shown at B comes forward and enters f inch into the hole. The pilot of this tool is slotted and spring-tempered, so that it will take hold of the washer when it is cut off. When the washer is separated from the bar, the cut-off tool drops back and the stock is fed forward sufficiently to allow the roller to be cut off. The pilot tool has now entered the hole of the roller as seen at B, which also shows the relative position of the washer. ASSEMBLING IN SCREW MACHINE 311 This pilot tool is also used as the stop, the stock being fed against the face d. The pilot, holding both the roller and the washer, now moves forward until the end comes in contact with the stud at e, when the turret still advances sufficiently to push the roller onto the stud, and also to press the washer onto the end, thus holding the roller in place. In the meantime, the pi- lot has been held against the end of the stud by the coil spring /. The work is now fed forward to the over-all length, and cut off as shown at C. Provision is made for the slight burr which is left around the edge of the hole when the roller is cut off, by cutting a groove g in the stud, as shown at A. The outside diameter of the washer is turned with a box-tool, which obviates the necessity of using an extremely wide form- ing tool. The order of operations is as follows : Revo- Hun- Order of Operations lutions dredths Feed stock to stop 27 2 Revolve the turret 34 i\ Turn and center with box-tool o.i45-inch rise at 0.0054- inch feed 27 2 Form o.35o-inch rise at o.ooi-inch feed (350) (25) Revolve the turret 41 3 Drill o.56i-inch rise at o.oo45-inch feed 125 9 Revolve the turret 42 3 Ream o.i45-inch rise at o.oo52-inch feed 28 2 Revolve the turret 41 3 Recess front cross-slide cam, o.on-inch rise at o.ooi-inch feed 14 i Recess lead cam, o.26o-inch rise at o.oo74-inch feed 35 2\ Revolve the turret 42 3 Cut off the washer o.36o-inch rise at o.oo2-inch feed 180 13 Take hold of washer with pilot Clearance 14 i Feed stock against pilot holder 27 2 Cut off roller o.554-inch rise at o.oo2-inch feed 277 20 Clearance 28 2 Push on roller and washer o.375-inch rise 42 3 Revolve the turret 42 3 Feed stock to stop 28 2 Cut off finished piece 0.5 54-inch rise at o.oo2-inch feed 277 20 Clearance 14 i Total ^385 loo With a spindle speed of 277 revolutions per minute, it requires 300 seconds to complete one assembled part, which gives a gross output of 120 pieces in ten hours. In this case, 312 SCREW MACHINE PRACTICE REVOLVE TURRET 4 DESCEND SLOTTING ARM WHM.E CUTTING OFF Machinery. N.Y. Fig. 41. Cams used for Making and Assembling a Grooved Roller and Socket Joint PRESS FIT ' LOOSE FIT :I; _ Machinery Fig. 42. The Assembled Part and its Details Machinery Fig. 43. Positions of Stock for the Various Operations ASSEMBLING IN SCREW MACHINE 313 a combination box-tool and center tool was necessary, as the turret was filled with tools. Referring to the lay-out of the cams shown in Fig. 44, it will be seen that there are a number of short lobes on the lead cam. These lobes, when made accurately, will work just as well as the longer ones, because the cam is turning very slowly. The front-slide cam from 26^ LEAD FRONT REAR Machinery Fig. 44. Lay-out of the Cams for Machining and Assembling Operations to 27^ feeds the recessing tool in at right angles to the spindle, and from 27^ to 30 is a dwell, while the .recessing tool is fed forward by the lead cam. The front slide drops back a little ahead of 30, so as to release the recessing tool, before it is withdrawn by the turret. From 33 to 46, the front cam ac- tuates the cut-off tool, separating the washer from the bar, and, after dropping back enough at 46 to allow the roller to be fed out, it again advances and cuts off the roller. After again 314 SCREW MACHINE PRACTICE feeding the stock, the finished part is cut off by the lobe from 79 to 99- The dwell on the lead cam which follows the recessing lobe keeps the spring pilot in the hole of the washer while it is being cut off. From 47 to 49, the stock is fed forward preparatory to cutting off the roller. The rise from 71 to 74, which pushes the. roller and washer onto the stud, was not made when the job was first set up, as it was a case of cut-and-try, in order to obtain the proper advance. The shape of the curve shown in the illustration was finally arrived at and was successful. When the stock is fed (77 to 79 on the cam), it reaches the length shown at C in Fig. 43, and when it is again fed (o to 2 on the cam), it reaches the length shown at A. The weight of the piece causes it to drop before the cut-off tool has reached point 99, so that no interference occurs when revolving from one stop to the other. It might be well to give the reason why one stop could not be used for these last two feeding movements of the stock, thus allowing space in the turret for a centering tool instead of using the combination box-tool and center. The reason this could not be done is that the difference in the length between the two feeding movements is so great that the cam from 77 to 79 would have to be cut very much lower than it is from o to 2 , and, in rising from the low to the higher point of the cam, the stop in the turret would strike the work before it was cut off ; of course, cam space could be allowed to prevent this, but it would mean lost time. Thread Rolling in the Screw Machine. The formation of threads by rolling is effected by hardened rolls or dies having threads or ridges which roll grooves into the blank and raise enough material above the surface of the blank to form a thread. When threads are rolled in the automatic screw machine, the tool used is in the form of a disk having a threaded periphery and mounted so as to revolve freely when forced against the blank to be threaded. Thread rolling is done in automatic screw machines, when a thread is required behind a shoulder where it would be impossible to cut it with a die. THREAD ROLLING 315 In this way, a second operation on the work is obviated. The roll used for forming the thread should be large enough in diameter to turn freely on the pin on which it is mounted. The thread on the roll should be the opposite hand to that which is to be produced on the work ; that is, if the thread required on the work is to be right-hand, then the roll should be left-hand, and vice versa. For rolling a right-hand thread, the work should revolve in the same direction as when a thread is cut in the lathe. Whenever practicable, the roll should pass under the work. The roll-holder should have a vertical adjust- ment so that the roll can be set to the proper height. Thread rolling in automatic screw machine practice is gen- erally only applied to brass and similar materials, owing to the difficulty of securing a roll that will withstand the severe service incident to rolling threads in harder metals. Thread rolls for steel work, however, have given fairly good results, when made of chrome-nickel steel containing from 0.15 to 0.20 per cent of carbon. Thread rolls for brass and similar materials should be made from 3-per cent nickel steel contain- ing about o.i 2 per cent of carbon. The heat- treatment recom- mended is as follows : Carburize six hours in straight coarse bone (not bone dust), heating to a temperature of 1600 de- grees F., and allow the rolls to cool in the pots. Then heat to 1600 degrees F. and quench in oil. Reheat to 1400 degrees F. and quench in water, after which draw the temper to 400 degrees F. in oil. The following information applies to the rolling of threads in brass and other soft materials, and is largely based upon experiments made by the Brown & Sharpe Mfg. Co. . Obtaining the Blank Diameter. As a rule, the diameter of the blank for brass should be approximately equal to the pitch diameter. When rolling a U. S. standard thread, the diameter of the blank should be slightly less than the pitch diameter of the thread, because of the impracticability of using a thread roll with a flat top. If the threads on the roll are not made sharp at the top, considerably more pressure will be required to force the roll into the work, and it will not produce 316 SCREW MACHINE PRACTICE as smooth and perfect a thread. Therefore, all thread rolls, whether for forming a sharp V or a U. S. standard thread, are made with a sharp V, top and bottom. It is not necessary to make the bottom of the thread on the roll sharp, but there would be no advantage in having it flat, as the outside di- ameter of the screw is governed by the diameter of the blank. The shape of the thread produced by a thread roll, when the U. S. standard form is required, is shown in Fig. 46 (central illustration). The pitch diameter B is the same as the pitch diameter of the U. S. standard form, Fig. 45. The root di- ameter C, however, is less than the root diameter A of the U. S. Figs. 45, 46, and 47. Dimensions involved in Calculating Blank Diam- eters for Thread Rolling standard thread. The approximate diameter of the blank can be found by the following formula, in which D = diameter of the blank ; B = pitch diameter of the screw ; F = depth of U. S. standard thread = 0.6495 P ' D = B - i F. The pitch diameter B = d F, in which d = nominal ex- ternal diameter of the screw. When rolling a thread having a sharp V-form, the pitch diameter , Fig. 47, can be used as the approximate diameter of the blank. The pitch diameter for a V-thread is found by the formula : E = d H, in which H = 0.866 p. The cor- rect diameter of the blank, in any case, must be determined by experiments, owing to variations in the hardness of differ- ent materials. It is a simple matter, however, in the automatic screw machine, to reduce or increase the diameter of the blank so as to obtain a screw of the required diameter. THREAD ROLLING 317 Size of the Thread Roll. The best results are obtained by using a thread roll with a single thread, but, when the piece to be rolled is less than f inch in diameter, it is necessary to make the roll with a multiple thread, because the diameter of the roll must then be made twice the diameter of the blank. The Brown & Sharpe Mfg. Co. has found that the pitch di- ameter of the roll should not be an exact multiple of the pitch diameter of the finished piece, but slightly less. The pitch diameter of the roll for a U. S. standard thread can be found by the following formula, in which K = pitch diameter of roll ; N = approximate ratio between pitch diameter of roll and pitch diameter of piece to be threaded ; D = outside diameter of blank ; G = depth of thread : K = NX(D-G). For a sharp V-thread, the root, pitch, and outside diameters of the roll are found by the following formulas, in which DI = pitch diameter of thread roll ; D 2 = root diameter of thread roll ; D$ = outside diameter of thread roll ; N = ap- proximate ratio between pitch diameter of roll and pitch diameter of piece to be threaded ; E = pitch diameter of thread or diameter of blank ; H = depth of thread = 0.866 p : D 1 = NX(E-^H); D^D.-H; D 3 = D,+ H. The thread rolls used by the National-Acme Mfg. Co. are made from ij to 2j inches in diameter and sometimes larger, multiple threads being used when the work is smaller than the outside diameter of the thread roll. Assuming that DI = outside diameter of thread roll ; n = number of " starts" or threads on the roll ; d = outside diameter of part to be threaded (diameter after completion of thread) ; G = depth of thread ; then : Di=nX(d- 1.25 G). When making a thread roll, the outside diameter is turned to the size required, and the end should be beveled to an angle of 45 degrees (as shown to the right in Fig. 48), to prevent the thread at the end from chipping or breaking out. Thread rolls are usually lapped after hardening, in order to obtain a smooth finish on the threads. This may be done by mounting SCREW MACHINE PRACTICE the roll on an arbor and rotating it while the threads are lapped, by using a piece of hard wood charged with some fine abrasive and oil. Preparation of Work for Thread Rolling. In most cases, that part of the work on which a thread is to be rolled can be turned by a formed tool. The thread to be rolled is usually at the rear of a shoulder and, in such cases, it is desirable to use a formed tool of such a shape that it will cut an annular groove next to the shoulder, as shown at A in the view to the left of Fig. 48. The diameter at B should also be reduced at the point where the work is to be cut off from the bar of stock. The angle a should be 45 degrees, and the distance C equal H G -H -+\P p-PITCH \L '' V s^ V f i j \ i 1 I Fig. 48. Preparing a Part for Thread Rolling Thread Roll with a Double Thread to at least half the single depth of the thread, so that the part B will be slightly smaller than the root diameter of the threaded part. The distance E should be made equal to C and dimen- sion F equal to at least the pitch of the thread. Application of Thread Roll to Work. Thread rolls, like knurls, are presented to the work either radially or tangen- tially. The method of holding and applying the roll is gov- erned, in many cases, by the relation that the thread rolling operation bears to other machining operations. The de- sign of the holder for the thread roll is also governed to some extent by the type of screw machine for which the holder is intended. Several types of holders adapted to different con- ditions and different designs of machines will be described. THREAD ROLLING 319 Thread Roll Applied to Top Side of Work. The holder shown in Fig. 49 is intended for a Brown & Sharpe machine. It is attached to the cross-slide and operates tangentially on the top side of the work. When no other tool is operating at the same time as the thread roll and there are no chips to interfere with the thread rolling operation, the roll can be held more rigidly than by passing it under the work instead of over it. When the roll is fed over the work, there is a ten- THREAD ROLL-HOLDER THREAD ROLL CIRCULAR CUT-OFF TOOL Machinery Fig. 49. Application of Thread Roll to Top Side of Work dency to raise the cross-slide, whereas, when the roll operates on the under side of the work, the pressure is downward and, consequently, the holder is more rigidly supported. The thread roll shown in Fig. 49 rotates on a pin and is inserted in a slot cut in the end of the holder. The roll should closely fit both the pin and the slot in the holder, because any lost motion would result in marring the thread. The set-screw at the rear of the holder is used for setting the roll to the proper depth. The cutting-off tool is located back of the thread roll 3 20 SCREW MACHINE PRACTICE so that the work will be severed from the bar before the roll returns. The roll should be moved in to within about o.oio inch from the work on the quick rise of the cam, and then be fed in until the roll is directly over the center of the work, at a feed which usually varies from about 0.002 to 0.004 inch per revolution of the work. The roll should then be moved past the work rapidly, thus bringing the cutting-off tool into position. Thread Roll Applied to Under Side of Work. The thread- roll holder shown in Fig. 50 is attached to the cross-slide, and the roll is so located that it passes beneath the work when CIRCULAR CUT-OFF TOOL CROSS-SLIDE Machinery, Jf.Y. Fig. 50. Holder used when the Thread Roll is passed under the Work forming a thread. The set-screw A bears against the cross- slide and is used for adjusting the roll to the proper depth as well as for supporting the holder. This type of holder may be used when no other tool is operating on the work at the same time and there are no chips to interfere with the thread rolling operation. The cutting-off tool located back of the roll severs the work after the thread is finished, so that the roll does not come into contact with the thread on its return movement. Swing Tool for Thread Rolling. When the thread roll cannot be carried on the cross-slide of a Brown & Sharpe machine, a swing type of tool, similar to the design shown in THREAD ROLLING 3 2I Fig. 51, is employed. For instance, if it were necessary to feed in the cut-off or form tool more than once on the same piece, a swing holder should be used in preference to the cross- slide type. The swing holder operates upon the same prin- ciple as an ordinary swing tool for turning. There is a swinging arm which carries the roll and which is moved inward, for bringing the roll into contact with the work, by means of a raising plate attached to the cross-slide which engages the set- screw located at the end of the swinging arm. The shank of the holder is inserted in a hole in the turret. If the length of the work exceeds about 2\ times its diameter, the Fig. 51. Swing Holder for Thread Rolling swing-roll holder should be equipped with a support. A hole is drilled through the shank of the holder and a set- screw is provided for holding the supporting member. The method of applying this support is governed by the shape of the work. Cleveland Thread-rolling Attachment. The thread-rolling attachment shown in Fig. 52 is similar in construction to the independent cut-off attachment used on the Cleveland auto- matic, except that the roll holder and thread roll replace the cut-off blade and holder. The thread roll A rotates on a pin B, and arm C is pivoted at the center and operated by a cam attached to a disk on the camshaft seen at the rear. This cam 322 SCREW MACHINE PRACTICE may be adjusted according to requirements. The roller at the rear end of arm C, which engages the cam, is mounted on an eccentric stud so that fine adjustments may be obtained for the thread roll. Acme Thread-roll Holder. A type of thread-roll holder commonly used on the Acme multiple-spindle automatic screw machine is shown in Fig. 53. The thread roll is presented radially to the work and slightly off center, so as to permit the tool to spring away a certain amount to Fig. 52. Thread-rolling Attachment Applied to Cleveland Automatic follow the curvature of the stock. This makes it unneces- sary to set the tool absolutely correct in regard to position for depth of thread. The spring of the tool should not be excessive, but just enough to relieve the strain which would be imposed on the tool if it were in a central position. Fig. 54 illustrates how a thread roll and holder of similar form is applied to the work on an Acme machine. The thread roll is held in a side-working slide in the third position and, in this particular case, a shaving tool operates in the second position. CUTTING HELICAL GEARS 323 Cutting Helical Gears in Screw Machine. The ribbon spools of a certain typewriter are rotated by a system of shafts and gearing, which includes a pair of small spiral or helical gears. These gears formerly were cut on small hand-operated gear-cutting machines of special design, which performed the operation in the same way that helical gears are cut in a milling machine ; that is, the blank was fed forward and rotated at the same time under a revolving formed cutter. It was then returned to the starting position again, indexed and fed for- ward for a second cut and so on until all the teeth were formed. The tools and operations employed for doing this work on a Brown & Sharpe automatic screw machine will be Machinery Fig. 53. Thread Roll used on Acme Multiple-spindle Automatic ' described. The effectiveness, rapidity, and comparative sim- plicity of the mechanism indicate the versatility of the auto- matic screw machine. Helical Gear Generating Tool. The tool used for generat- ing the teeth of the helical gears is shown in Fig. 55. When this tool comes into action, the blank has been formed in the ma- chine as shown at C in Fig. 56. The hole has been drilled and reamed and the outside diameter formed to the required dimensions. When the tool is brought up to the work, the three-cornered driving center G enters the drilled hole, and is thereby caused to revolve with the blank. As it is screwed firmly into the long driving gear H (Fig. 55) the latter is also set in motion in unison with the spindle of the machine. Gear H has helical teeth cut on it engaging mating teeth in helical gear /, which is mounted on a short horizontal shaft having 324 SCREW MACHINE PRACTICE spur gear K keyed to it at the rear end. This gear, through a large idler L, drives gear M, which is keyed to the cutter spindle S. Cutter N mounted on the spindle has the form of a helical gear properly cut to mesh with the gear to be formed. It is made of hardened tool steel and is ground on one face, which face is set as shown in the end view, so that it is in the plane of the axis of the work. By means of the train of gear- ing just described, cutter N may be caused to revolve in uni- son with the work as if it were in mesh with the latter after the teeth have been cut. Fig. 54. Shaving Tool and Thread Roll on an "Acme" Multiple- spindle Automatic Driving center G and the . front bearing of gear H are sup- ported in a sliding bushing seated in the body P of the tool. A plunger Q in the shank of the tool is pressed by a long and stiff spring against the end of the bearing of gear H. This serves to keep G pressed into the hole in the work. As the tool advances over the work, center G and gear H are forced back with relation to the holder, remaining stationary so far as endwise movement is concerned with relation to the work. The thrust between Q and the end of H is taken by a hardened ball-pivot bearing as shown, so that there is little friction. The extended lip on the bushing is simply for the purpose of providing the long keyway shown, which engages CUTTING HELICAL GEARS 325 a pin in the body P to prevent from turning. When the tool is not in contact with the work, screw R limits the outward movement of G, H, and produced by spring plunger Q. Operation of Cutting the Teeth. Consider now that there is a gear blank in the machine with the teeth all cut, but not Machinery Fig. 55. Tool for Generating Teeth of Helical Gears in Automatic Screw Machine yet severed from the bar, and suppose the cutter N to be meshed with it as shown at D in Fig. 56. Suppose further that the spindle of the machine has been stopped. If now the turret- slide be moved forward or back from the position shown, so that the generating tool is moving forward or back over the 326 SCREW MACHINE PRACTICE work, center G and gear H remain stationary with reference to the work, but move back and forth with relation to the tool- holder. This axial movement of gear H will evidently rotate helical gear /, which, through the train of spur gears K, L, and M will rotate the cutter N. The ratio of this train of gear- ing is such that the rotary movement given to N by the longi- tudinal movement of the tool-holder in either direction keeps CENTERING AND FACING _ CUTTING THE TEETH COUNTER- BORING REMOVING BURRS WITH FORM TOOL CUTTING OFF Machinery Fig. 56. Successive Operations on Helical or Spiral Gears produced in Automatic Screw Machine it exactly in step with the teeth of the work. Thus the move- ment of the turret-slide rolls the cutter on the work just as if the cutter were mounted perfectly free on its axis and were rolled by the teeth of the work, instead of through the train of gearing described. Consider further, with the cutter and the work set in the relation shown in Fig. 56, that the turret-slide of the machine is fixed in position, but that the spindle and the work is ro- tated. The rotation of the gear revolves the three-cornered CUTTING HELICAL GEARS 327 driving center G, which, in turn, transmits its motion to gear H (Fig. 55) and thence to gears /, K, L, M, and cutter N. The ratio of this train of gearing is again such that the rotary movement thus given the cutter is in the proper ratio to keep the latter in step with the teeth cut in the work, so that the work and cutter revolve together as if they were a pair of heli- cal gears driving each other, with no connection through the train of gearing. It has thus been shown that the cutter will be kept in step with the work, if the tool is moved axially back and forth over the work while the latter is stationary. It has also been shown that the cutter will keep in mesh with the work, while the latter is revolving and the turret-slide and the tool are stationary. Since the cutter and work are kept in step under these two conditions separately, they are still in step when the two movements are combined. This tool and its arrange- ment of gearing can thus be moved back and forth over the revolving work without throwing the teeth in the cutter and the teeth in the work out of step with each other, assuming that the tool is not moved back so far that driving center G loses its contact with the work, as the proper meshing of the cutter depends upon the driving connection between G and the blank. If G is ever moved back out of contact with the blank, this connection is broken, and, when the cutter is again moved forward onto the work, it will probably be found out of step. The action of cutter N will be readily understood, now that the method of driving has been explained. The face, which is in the plane xx of the axis of the work, as shown in the end view, is the cutting edge. As the tool is forced onto the work, this revolving cutting edge, having the exact shape of the helical gear which is to engage with the work, cuts teeth of that exact shape on the blank as it is gradually forced over it. The opera- tion is an example of the molding-generating principle, the cutter N molding the proper surface to mesh with its own teeth. Details of Generating Tool. The shank of the tool is made very long, as this permits the use of a spring for plunger Q 328 SCREW MACHINE PRACTICE which is long enough so that its pressure will not be materially greater when the cutter is pushed clear over the work at the completion of the cut, than when center G first enters the hole in the work. If the pressure should materially increase, there would be danger that G might be pressed further into the edge of the hole, thus disturbing the axial relation of G and the blank, and, consequently, throwing the cutter and the work out of step with each other by that amount. The use of the long spring prevents such trouble. The cutter spindle 5 is mounted in bronze-bushed bearings in front and back plates T and U, which are clamped together and to the body P of the tool by studs and nuts V. These studs, as shown in the sectional view, pass through elongated slots in the body, so that the cutter spindle may be adjusted for a larger or smaller diameter of work by means of set-screws W, the adjustment being locked by nuts V. This adjust- ment would, of course, disturb somewhat the correct meshing of gears L and M. Gear L is, therefore, mounted on a stud X which floats in an enlarged hole in the body, and so may be adjusted by means of suitable set-screws which bring it into proper mesh with both M and K. The shaft on which the latter is mounted is also carried in a sliding block F, by means of which gears / and H can be moved into closer or freer mesh. After the cutter has been set to the proper diameter for the work, the whole system of gearing may thus be adjusted to mesh properly. It is advisable to have as little backlash as possible between the cutter and the driving center to pre- vent the former from jumping or chattering when first begin- ning the cut. When there is much backlash, the ends of the teeth where the cut begins are not formed to quite the proper shape. While there is no great harm in this in the case of a helical gear, in which the contact takes place in the center of the face, it gives a poor appearance to the work, and so should be avoided. The thrust of the revolving work, pressing down on the cutter when the tool is in action, is taken by a ball bearing at Z. This is the only point where there would be any great CUTTING HELICAL GEARS 329 danger of excessive friction, so that the probability of G slipping in the work, due to too great a resistance in the mechanism it has to drive, is obviated. As previously ex- plained, the cutting edge of the cutter must be in the plane of the center-line of the work. In the tool shown, no special pro- vision is made for maintaining this condition. As the face of the cutter is sharpened, it is necessary to pack it out with filling washers. In later designs, adjustments are provided for bringing the cutting point on a line with the center. Order of Operations in Making the Gears. The first operation after feeding the stock is centering and facing, as shown at A, Fig. 56. This is done with a tool held in the turret. The turret is next revolved two holes, and the drill is brought into action. Then the turret is revolved again and the hole is reamed. The reamer is mounted in a "floating holder" which enables the reamer to be centered accurately, so that it will cut to size and take off an equal amount with all of its teeth. While the drilling and reaming are going on, the blank is being formed by a circular form tool mounted in the front cross-slide, as shown at B and C. The operation of cutting the teeth at D has already been described. At , the hole is count erbored. This counterboring incidentally re- moves the marks made by the sharp corners of driving center G. At F, the completed piece is severed from the bar. While the counterboring is in progress, and during the first part of the cutting-off operation, the front form tool, as shown at E and F, is again brought down to clean off the burrs produced by the gear-cutting tool. The gear proper has a face width of 0.187 i ncn an d a diameter of 0.421 inch. The material is brass, and the time for making one gear complete, 22 seconds. Measuring Screw Machine Chips. It is the practice of some screw machine operators to measure the thickness of the chips in order to determine the feeds of the tools. This prac- tice is misleading because of the tendency of the metal to compress in one direction and swell and stretch in the other, when separated from the bar by the cutter. In order to ob- tain data on the difference between the feed of the cutter and 330 SCREW MACHINE PRACTICE the thickness of the chips, some tests were made on a Brown & Sharpe automatic screw machine. A cam, the exact size and travel of which was known, was placed on the machine, and the machine was geared to rotate the cam at a given speed. The exact speed of the spindle was also determined, and in this way the exact feed of the cutter was known. These tests showed that a form tool, J inch wide, having a feed of o.oo i inch per revolution, cut a chip which measured 0.0025 inch when cutting brass, while a form tool f inch wide, with a feed of 0.0015 inch per revolution, cut a continuous chip 0.005 mcri thick. A cut-off tool f inch wide, cutting brass and fed o.ooi inch per revolution, produced chips from 0.0015 to 0.002 inch thick. The proportions between the feed and the chip for the turret tools were slightly greater than for the cross-slide tools ; that is, the chip expanded slightly more. The tests for steel indicated a smaller expansion than for brass. Often a cam designer is criticized by the operators for providing excessive feeds, when this is not really the case, the apparent error being due to the erroneous method used by the operators in measuring the feed. The error that would result in the design of cams, if the draftsman worked to data obtained by measuring the chips is, however, apparent. Speeds and Feeds. The following information on the speeds and feeds for automatic screw machine operation is intended only as a general guide, since both the feed and speed are often affected considerably by the nature of the operations, variations in cutting qualities of tools made from different kinds of steel, and differences in degree of hardness of material of the same general class. The type and general condition of the machine that is used may also be important factors. The feeds and speeds given in the accompanying table are not intended to represent either the minimum or maximum in any case, but the average range of feeds and speeds used on machines of ordinary size. In referring to this table, it is important to bear in mind that the rate of feed per revolution is often affected considerably by the speed, some automatic screw machines being naturally adapted for comparatively SPEEDS AND FEEDS 331 Ordinary Ranges of Speeds and Feeds for Automatic Screw Machines Material Type of Cutting Tool Steel used for Tools Surface Speed, Feet per Minute Feed per Revolution, Inch Box-tool Box-tool Carbon High-speed 160-180 225-250 0.004 to 0.015 Hollow Mill Hollow Mill Carbon High-speed 160-180 225-250 0.005 to 0.017 Brass Forming Forming Drills Carbon High-speed Carbon 150-175 200-275 160-180 0.0008 to 0.003 0.003 to 0.015 Reamers Reamers Dies Carbon High-speed Carbon 115-125 145-160 4.06"; 0.007 to 0.030 Dies High-speed 80130 Cutting-off Carbon 150-175 0.0015 to 0.004 Box-tool Box-tool Carbon High-speed 80-90 100-130 0.003 to o.oio Hollow Mill Hollow Mill Carbon High-speed 80-90 100-130 O.OO4 tO O.OI2 Gun Screw < Forming Forming Cutting-off Carbon High-speed 75-90 90-125 O.OOO5 tO O.OO2O O OOI2 to O OO2C Iron Drills Drills Dies Carbon High-speed 60-70 100-125 2C 5O O.OO2 tO O.OIO Reamers Reamers Carbon High-speed 35-40 60-75 0.008 tO 0.020 Box-tool Box-tool Carbon High-speed 35-45 45-60 0.003 to 0.007 Drill Rod and TVrl Hollow Mill HoUow Mill Forming Dies Carbon High-speed High-speed High-speed 35-45 45-60 45-60 IC-2S 0.0035 to 0.008 O.OOO2 tO O.OOIO Steel Drills Drills Carbon High-speed 30-40 40-60 0.002 tO O.OIO Reamers Reamers Carbon High-speed 20-25 30-40 0.006 to 0.015 high speeds and fine feeds, whereas other machines rotate the work more slowly, but are capable of heavier feeds. The feed for box-tools not only varies for different materials, but should 332 SCREW MACHINE PRACTICE be selected with reference to the thickness of the chip or the depth of the cut. The feed for forming tools should be varied in accordance with the width of the tool and the diameter of the smallest part to be formed. In general, a tool from about J to y 3 e inch wide is adapted to the coarsest feed. For tools that are either very much narrower or wider, the feed should be reduced accordingly. The effect which the tool width and the minimum diameter have upon the feed account for the wide range of feeds given in the table for forming tools. The following general information on feeds and speeds is given by the Brown & Sharpe Mfg. Co. The feeds and speeds referred to are merely intended as a general guide, and, in order to obtain satisfactory results, it is necessary to use an ample supply of good cutting oil or cooling lubricant, such as lard oil. Speeds and Feeds for Brass. For brass of ordinary quality, the machine can run at its fastest speed. In the case of a No. oo machine, the maximum spindle speed is 2400 revolutions per minute, and the largest diameter that can be turned is -IQ inch, so that the maximum surface speed is 197 feet per minute. On the Nos. o and 2 machines, the maxi- mum speeds are 294 and 275 feet per minute, respectively. Hollow mills when used on brass can be given a feeding move- ment of from 0.006 to 0.015 inch per revolution, the amount depending upon the depth of the cut. The feed of box-tools for finishing brass should be about o.oio inch per revolution, and, for cutting-off tools, from 0.0015 to 0.002 inch per revolu- tion, the feed being reduced as the tool reaches the center of the work. Forming tools are usually fed from 0.0008 to 0.0015 inch per revolution, although the feeding movement is reduced to 0.0005 inch, in some cases. Drills varying from J to J inch in diameter can be fed from 0.003 to 0.006 inch per revolution ; for smaller drills, the feeds are reduced from 0.003 to 0.0015 inch. Speeds and Feeds for Gun Screw Iron. Gun screw iron, when using a fine feed, can be given a speed of from 80 to 90 feet per minute for either hollow mills, box-tools, cutting-off SPEEDS AND FEEDS 333 tools, or forming tools. Hollow mills for roughing can be fed from 0.004 to 0.012 inch per revolution. Box-tools for finish- ing, when taking a finishing cut of average depth, which is about o.oio inch, can be fed from o.oio to 0.012 inch per revolution, but the feed should be reduced, if the tool is to be used for facing shoulders or for similar operations. Cutting- off tools can be fed from 0.0012 to 0.0017 inch per revolution. For forming tools, the feed usually varies from 0.0002 to o.ooi inch, the amount depending upon the width and finished size of the work. Drills should be fed about one-third lower than for brass, and, when drilling deep holes, the feed should be reduced towards the bottom. Dies and taps, when operating on gun screw iron, should not have a cutting speed exceeding 30 feet per minute. Speeds and Feeds for Machine Steel and Drill Rod. Soft machine steel can be cut off and formed at a speed of about 80 feet per minute, but, for threading operations, this should be reduced to from 20 to 30 feet per minute. The feed per revolution can usually be about the same as for iron. It is often necessary to run bronze at about the same speed as machine steel. Drill rod is often operated at speeds varying from 50 to 60 feet per minute, but only when using very fine feeds. The feed usually ranges from 0.003 to 0.007 i ncn per revolution. For threading drill rod, the speed should not exceed 15 or 20 feet per minute. It is the practice of the Brown & Sharpe Mfg. Co. to use fast speeds and fine feeds for most operations, although the relation of the feed and speed is often varied to suit different classes of work. The speeds and feeds referred to in the fore- going are intended for carbon steel tools. When using high- speed steel, these speeds can be increased approximately 50 per cent for mild steel and from 30 to 35 per cent for drill rod, assuming that the same feeds are used. Feed for Thread Rolling. When rolling threads, the feed is varied in accordance with the diameter of the blank to be threaded and the number of threads per inch. The type of holder used also affects the feed. If the roll is held in a holder 334 SCREW MACHINE PRACTICE attached to the cross-slide and is presented either tangen- tially or radially to the work, it can be fed at a faster rate than if it is held in a swing tool, because, in the former case, it is held more rigidly. The feeds for thread rolling may vary from 0.0005 to o.oio inch per revolution, and, in some cases, coarser feeds are employed. When using a cross-slide type of roll- holder, the following feeds would prove satisfactory on a Brown & Sharpe machine : For 80 threads per inch and a blank di- ameter of J inch, o.oo6-inch feed ; for a blank diameter of \ inch, o.oo8-inch feed ; for a blank diameter of i inch, .010- inch feed. For 40 threads per inch and a blank diameter of \ inch, 0.003 -inch f ee( i > f r a blank diameter of \ inch, 0.005- inch feed ; for a blank diameter of i inch, o.ooy-inch feed. For 24 threads per inch and a blank diameter of J inch, 0.0005- inch feed; for a blank diameter of | inch, o.oo25-inch feed; for a blank diameter of i inch, o.oo45-inch feed. When using a holder of the swing type, these feeding movements should be reduced about 25 or 30 per cent. Feeds for Drilling. When selecting the feeds for drills, the diameter of the drill should be considered. For instance, when drilling brass, a drill -jV inch in diameter should be given a feed of about 0.0018 inch per revolution; if the drill di- ameter were \ inch, the feed should be increased to approxi- mately 0.003 or 0.004 i ncn ; ^ the drill diameter were \ inch, the feed should be from 0.005 to 0.007 mcn ; and, if the drill diameter were \ inch, it should be from 0.007 to o.oio inch per revolution, and, for larger sizes, still coarser feeds could be employed. When using Brown & Sharpe automatic screw machines, the best results are generally obtained by employing light feeds for drills and rather high peripheral velocities. High- speed steel drills are preferable for drilling Norway iron, machine steel, tool steel, etc., but ordinary carbon steel drills are suit- able for brass and similar materials, when the cutting speeds do not exceed those given in the table. When the cutting speed is relatively low, the feed can be increased accordingly, but it is more satisfactory in general practice to use a fine feed SPEEDS AND FEEDS 335 and a high speed, as a straighter hole can be produced by this method. Counterboring and Reaming Feeds. The surface speed for counterboring should be slightly less than the speed for drilling. The feed depends upon the type of counterbore used, as well as the material being cut and the depth of the cut. When using a counterbore having three cutting edges, the feed for brass usually varies from about 0.003 to 0.008 inch per revolution, the amount depending upon the diameter of the counterbore and the depth of the cut. For machine steel, the feed would be somewhat less, ranging from about 0.002 to 0.006 inch per revolution. The feed used for reaming depends not only upon the diameter of the reamer and the material being reamed, but also upon the allowance left for the reaming operation, and varies widely, as shown by the table. In gen- eral, the allowances should be as follows : Diameter of hole, | inch, allowance, 0.005 i ncn > diameter of hole, J inch, allow- ance, 0.007 inch; diameter of hole, ^ inch, allowance, o.oio inch; diameter of hole, i inch, allowance, 0.016 inch. INDEX ACCELERATING type of reaming attachment, 207 Accelerating type of cross-drilling at- tachment, 202 Acme accelerating reaming attachment, 207 Acme cross-drilling attachment, 202 Acme milling attachments, 209 Acme multiple-spindle automatic, 39 adjustment of, 170 camshaft, 44 camshaft speed-changing mechanism, 45 feeding stock through spindle, 51 general description, 39 indexing mechanism, 49 mechanism for threading, 52 operation of cross-slides, 48 operation of spindle chuck, 50 operations on, 290 speed of main driving shaft, 47 spindle-driving mechanism, 43 standard tool positions, 41 Acme over-cut box-tools, 98 Acme thread-rolling tool, 322 Adjustment of automatic screw ma- chines, 148 Allowances for reaming, 125 Allowances for shaving cuts, 130, 131 Aluminum, use of roller supports in turning, 109 Angle of centering tool, 115 Angles, cutting, for box-tool cutters, in Application of automatic screw ma- chines, general, 7 Assembling parts in automatic screw machine, 304 Attachment, for hobbing worm and spiral gears, 215 Attachment for self-opening dies, 137 for drilling, 200 for forming squares and hexagons, 213 for milling, 209 for screw slotting, 197 magazine feeding, 219 Automatic, application of term, 2 Automatic screw machines, adjust- ment, 148 advantages of single- and multiple- spindle designs, 8 classification, 4 development of multiple-spindle type, 6 development of single-spindle type, 5 general features, 3 multiple-spindle designs, 39 single-spindle designs, n BACK-SLIDE cam, method of lay- ing out, 241 Boring and recessing tools, 125 Box-tool cutters, cutting angles, i T i holding and adjusting, 106 methods of applying, 104 radial and tangential positions for, 104 size of steel, 113 Box-tools, 94 over-cut type, 98 spring-releasing type, 99 setting, on Acme machine, 178 taper turning, 101 Box-tool work supports, 108 holding and adjusting, 109 position relative to cutter, 112 Brass, speeds and feeds for, 332 Brown & Sharpe burring attachment, 205 338 INDEX Brown & Sharpe cross-drilling attach- ment, 201 Brown & Sharpe index drilling attach- ment, 200 Brown & Sharpe screw machines, deflec- tor for chips, 1 8 general method of setting up, 158 general description, n operation of cross-slide, 15 operation of turret-slide, 16 reversal of spindle for threading, 18 sample record of cam and tool equip- ment, 159 spindle speed changes, 18 stock-feeding and chuck-operating mechanism, 15 Brown & Sharpe screw slotting attach- ment, 197 Brown & Sharpe tap and die revolving attachment, 206 Brown & Sharpe taper-turning tool, 102 Brown & Sharpe turret .drilling attach- ment, 205 Burring attachment, 205 blanks, Brown & Sharpe, 234 Cam circumference, proportioning, 233 Cam design, allowance for tool clear- ance, 247 effect of cutting speed on, 225 general procedure, 225 lobe for thread cutting, 243 rise for drilling, 255 Cams for making a screw, 227 Cams for recessing, laying out, 253 Cams for screw machines, designing, 224 Cams, function of lead, front-slide and back-slide, on B. & S. Machine, 224 Cam-lever templets, use of, 250 Cast iron, use of roller supports in turning, 109 Centering and facing tools, 114 Centering-tool holder, 115 Centering tool, included angle of point, "5 Centering tools and drills, setting, 154 Change-gears, table of No. oo Brown & Sharpe machine, 233 Chicago screw machine, general de- scription, 35 camshaft and main cam, 36 chuck feeding mechanism, 36 feeding movements for tools, 38 method of cutting threads, 37 operation of cross-slides, 37 turret mechanism, 36 Chips, measurement of, to determine feed, 329 Circular forming and cutting-off tools, holder for, 88 setting, 149 Circular forming tools, methods of applying, 85, 89 Clearance for circular tools, 90 Clearance for tools in laying out cams, 247 Cleveland automatic, adjustment of, 161 chuck-operating mechanism, 22 examples of work on, 281 feed-regulating drum, 29 general description, 20 operation of cross-slide, 28 spindle-driving mechanism, 22 stock-feeding mechanism, 25 turret and turret-slide, 26 variable feeding mechanism, 28 Cleveland independent cutting-off at- tachment, 211 Cleveland magazine feeding attach- ments, 219 Cleveland silent die-holder, 135 Cleveland slotting and slabbing attach- ment, 199 Cleveland thread-rolling attachment, 321 Compensating stops for multiple-spindle machines, 60 Cone-point turning in screw machine, 274 Counterbores, amount of taper for, 120 holders, 123 location of cutting edge, 120 reasons for defective operation, 119 INDEX 339 Counterbores and reamers, setting, 154 Counterboring and drilling from cross- slide, 266 Counterboring and reaming feeds, 335 Counterboring tools, 119, 122 Cross-drilling attachment, 201 Cross-drilling attachment of opposed spindle type, 204 Cross-drilling, example of work requir- ing, 294 Cutters for box-tools, 104 cutting angles, in holding and adjusting, 106 position relative to work supports, 112 size of steel, 113 Cutting-off and forming tools, rake of, 93 setting on Acme machine, 177 Cutting-off attachment, Cleveland, 211 Cutting-off tool-holder, universal, 91 Cutting-off tools, 92 inclination of cutting edge, 229 thickness of blade, 93 DAVENPORT multiple-spindle auto- matic, 55 cam equipment for, 192 compensating stops, 60 cross-slides and swinging arms, 58 driving mechanism for camshaft, 58 general description, 55 indexing the spindle head, 60 method of cutting thread, 62 method of driving spindles, 55 operation of tool spindles, 56 sample record of operations, 193 setting-up, 189 speeds and feeds recommended, 63 Deep-hole drilling, designing cam for, 257 Die- and tap-holder, telescopic, 136 Die and tap revolving attachment, 206 Die-holders, 133 Cleveland silent type, 135 releasing, 134 Dies and taps, setting, 155 Dies, attachment for self -opening, 137 Dies for screw machine work, 132 Drill-holder, high-speed, 118 Drill-holders for screw machines, 118 Drilling and Counterboring from cross- slide, 266 Drilling and milling attachment, Acme, 209 Drilling attachment, cross-, 201 index, 200 Drilling, feeds for, 334 laying out cams for, 255 Drill rod, speeds and feeds for, 333 Drills and centering tools, setting, 154 Drills, flat, 122 for screw machine work, 116 END-MILLING or slotting attach- ment, 211 facing and centering tools, 114 pEED, determining, by measuring chips, 329 for thread rolling, 333 Feeding attachments, magazine, 219 Feeds and speeds, 330 for different tools and materials, 331 Feeds, for Counterboring and reaming, 335 for drilling, 334 Flat forming tool-holders, 90 Flutes, number in taps, 139 Forming and cutting-off tools, rake of, 93 setting, on Acme machine, 177 Forming operations, examples of, 260 Forming tools, methods of applying, 85,89 tool-holders for flat, 90 Front-slide cam, method of laying out, 242 gears, helical or spiral, cutting in screw machine, 323 (~^UN screw iron, speeds and feeds for, 332 Gridley multiple-spindle automatic, 71 camshaft and cams, 74 feeding movements, 73 340 INDEX Gridley multiple-spindle automatic, general description, 71 idle movements, 73 method of cutting threads, 76 tool-slide, 73 Gridley single-spindle automatic, ap- plication of motor drive, 35 arrangement of cams, 33 arrangement of turret, 30 general description, 30 operation of forming and cutting-off tools, 33 fjAYDEN multiple-spindle auto- matic, 64 adjustable cams for tool spindles and cross-slides, 68 chuck-closing mechanism, 66 general description, 64 operation of master cam, 66 thread cutting operations, 71 time required for making one piece, 69 Helical gears, cutting in screw machine, 323 Hexagon and square forming attach- ment, 213 Holders, for centering tools, 115 for circular forming and cutting-off tools, 88 for counterbores, 123 for flat forming tools, 90 for reamers, 127 Hollow mills, 113 Hollow mills or box-tools, setting, 153 Hollow roughing mill, 98 INDEX drilling attachment, 200 KNURL-HOLDER, double type for cross-slide, 143 opening and closing type, 143 Knurling tools, 140 Knurls, concave, 145 different methods of applying, 144 spiral, 146 straight, 145 Knurl teeth, angles for different mate- rials, 145 calculating depth of, 145 LEAD CAM, function of, on Brown & Sharpe machine, 224 method of laying out, for Brown & Sharpe machine, 236 MACHINE steel, speeds and feeds for, 333 Magazine feeding attachments, 219 Milling attachments, Acme, 209 Multiple- and single-spindle designs, relative advantages, 8 Multiple-spindle screw machine de- velopment, 6 Multiple-spindle screw machines, 39 BRITAIN multiple-spindle screw machine, 76 indexing mechanism, 80 spindle construction, 78 thread cutting mechanism, 82 tool slide, 79 Non-releasing type of die-holder, 133 OPERATIONS on screw machines, miscellaneous, 258 pointing end of work, 259 PRODUCTION rate, calculating for Acme machine, 172 RAISING block for swing tools, 128 methods of setting on Brown & Sharpe machines, 157 Reamer holders, 127 Reamers and counterbores, setting, 154 Reamers for screw machine work, 125 Reamers, taper of, 125 Reaming allowances, 125 Reaming and counterboring feeds, 335 Reaming attachment, accelerated, 207 Recessing and boring tools, 125 Recessing, laying out cams for, 253 Recessing operation, 265 INDEX 341 Recessing swing tools, 129 Record of cam and tool equipment on Brown & Sharpe machine, 159 Record of operations on Davenport machine, 193 Releasing die-holder, 134 Roller supports for box-tools, 95, 96, 109, in Rolling threads in screw machine, 314 Roller type of steadyrest, 113 Rotary magazine attachment, 221 gCREW MACHINE, adjustment, 148 cams, designing, 224 classification, 4 development, 5 general features, 3 multiple-spindle designs, 39 operations, miscellaneous, 258 origin of term, i relative advantages of single- and multiple-spindle designs, 8 single-spindle designs, n use of, for machining and assem- bling, 304 Screw slotting attachments, 197 Setting-up automatic screw machines, 148 Shaving operation, allowances for, 130, 131 Shaving tools for screw machines, 130 Single- and multiple-spindle designs, relative advantages, 8 Single-spindle screw machine develop- ment, 5 Slab milling attachments, 209 Slotting and slabbing attachment, 199 Speeds and feeds, 330 for different tools and materials, 331 Spiral gear-hobbing attachment, 215 Spiral gears, cutting in screw machine, 323 Spiral knurls, determining lead of teeth, 147 determining number of teeth around circumference, 146 Spring-releasing box-tools, 99 Spring screw threading dies, making, 132 Square and hexagon forming attach- ment, 213 Steadyrest of roller type, 1 13 Steel for box-tool cutters, size of, 113 Steel for box-tool supports, 109 Stop for stock, setting, 152 Supports, work, for box- tools, 108 holding and adjusting, 109 Swing tools, for turning, 128 methods of setting raising block for operating, 157 raising block for, 128 recessing, 129 setting, 156 TAP- and die-holder, telescopic, 136 . Tap and die revolving attachment, 206 Taps and dies, setting, 155 Taps, chamfer for different pitches, 139 cutters for fluting, 139 for automatic screw machines, 138 for Norway iron and machine steel, 140 number of flutes for, 139 width of lands, 139 Telescopic die- and tap-holder, 136 Templet for dividing cam circumfer- ence, 238 Templet for laying out screw machine cams, 235 Templets, use of cam-lever type, 250 Thread cutting, development of cam lobe for, 243 dies for screw machines, 132 number of revolutions for, 229 on Acme machine, 181 on Davenport multiple-spindle auto- matic, 192 on Gridley multiple-spindle auto- matic, 76 on Hayden multiple-spindle auto- matic, 71 on New Britain multiple-spindle automatic, 82 reversal of spindle for, in B. & S. machine, 18 342 INDEX Threading-die holders, 133 Threading dies, methods of making spring screw type, 132 Thread rolling, Acme type of holder for, 322 attachment, Cleveland, 321 by means of swing tool, 320 calculating blank diameter, 315 Cleveland attachment for, 321 feeds for, 333 holder for passing roll over work, 319 holder for passing roll under work, 320 inclination of thread on roll, 315 in screw machines, 314 preparation of work for, 318 shape of thread on roll, 316 size of thread roll, 317 steel for thread rolls applied to steel, 3i5 Thread roll, size of, 317 Tilting magazine attachment, 219 rotary type of, 222 Tool clearance, allowance for, in cam design, 247 Tool equipment for screw machines, 84 Tool-holders for boring and recessing tools, 125 Tool-holder, universal cutting-off, 91 Turret drilling attachment, 205 UNIVERSAL cross-slide knurling tool, 141 Universal cutting-off tool-holder, 91 VERTICAL magazine feeding attach- ment, 220 parts, making, in screw machine, 271 Worm gear bobbing attachment, 215 RETURN CIRCULATION DEPARTMENT 202 Main Library LOAN PERIOD 1 2 3 HOME USE 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS Renewals and Recharges may be made 4 days prior to the due date. Books may be Renewed by calling 642-3405. DUE AS STAMPED BELOW AUTO. DISC. OCT 21986 \lV^ #5 uo m m. NOV osw 3 FORM NO. DD6, UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA 94720 GENERAL LIBRARY -U.C. BERKELEY 392309 /4-*r Ces^ UNIVERSITY OF CALIFORNIA LIBRARY