Forging Operations MACHINE FORGING FORGING DIES SPECIAL FORGING OPERATIONS 207 Published by INTERNATIONAL TEXTBOOK COMPANY SCRANTON. PA. io-s.(cO¥H T6tis .Fl . Machine Forging: Copyright, 1916, 1906, by International Textbook Company. Forging Dies: Copyright, 1916, by International Textbook Company. Special Forging Operations: Copyright, 1916, 1906, by International Textbook Company. Copyright in Great Britain All rights reserved Printed in U. S. A. ^'^-^^oy^^ International Textbook Press Scranton, Pa. 93734 CONTENTS Note. — This book is made up of separate parts, or sections, as indicated by their titles, and the page numbers of each usually begin with 1. In this list of contents the titles of the parts are given in the order in which they appear in the book, and under each title is a full synopsis of the subjects treated. MACHINE FORGING Pages Forging Machines 1-51 Introduction 1 Rolls 2-11 Hammers 12-30 Swaging Machines 31 Presses 32-36 Upsetting Machine 37-41 Punches and Shears 42-46 Riveting Machines 47-49 Bulldozer 50-51 FORGING DIES Forms of Forging Dies 1-34 Drop-Forging Dies 1-28 Heading and Bending Dies 29-34 Heading-machine dies ; Bending dies. Construction of Forging Dies 35-56 Materials and Equipment 35^6 Die-Making Operations 47-56 SPECL\L FORGING OPERATIONS Heating Furnaces 1-1 1 Miscellaneous Operations and Data 12-53 F'orging Structural Shapes 12-16 Effect of Repeated Heating on Metal 17 Estimating Stock 17-33 iv CONTENTS SPECIAL FORGING OPERATIONS— {Continued) Pages Thermit Welding 34-49 Table of Weights per Linear Foot and Areas of Square and Round Steel Bars 50-51 Table of Weights per Linear Foot of Square and Round Wrought-Iron Bars 52 Table of Weights per Linear Foot of Flat Wrought- Iron Bars 53 MACHINE FORGING Serial 1690 Edition 1 FORGING MACHINES INTRODUCTION 1. In its broadest sense, machine forging is the working of metal, either hot or cold, by means of a machine, causing it to flow in such a way as to give it some desired shape, either by slowly applied pressure or by blows. It is impossible to exclude from this machine process of working metals any forming operations on cold metals, as it has been found advan- tageous to forge metals at temperatures varying from ordinary atmospheric temperature to about 2,000° F. Low-carbon steel, certain brass alloys, and altmiinum are frequently pressed, rolled, or punched cold. Zinc is most easily worked at a temperature of between 300° and 400° F, Aluminum can be drop-forged at a temperature slightly below a dull red heat, but it is very difficult to maintain it at exactly the required temper- ature. Copper can be forged hot, and pure annealed copper can be formed cold by pressing. From this it will be seen that machine forging operations are exceedingly varied in their nature. Forging machines roll, hammer, or press the metal into the desired shape, and most forging machines may use either plain or formed dies. The use of formed dies will be considered exclusively in this Section. COPYRIGHTED BY INTERNATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESCRVEO §53 MACHINE FORGING § 53 ROLLS 2. Graded Rolling. — Work of varying thickness may be done between properly shaped rolls. This is called graded rolling, and is really forging with revolving dies. Graded rolling is usually accomplished by passing a piece of metal lengthwise between a pair of rolls, one or both of which are more or less eccentric or have dies attached, so as to give the finished piece a tapered form or a varying thickness. Silver, German silver, and brass may be rolled by this method when cold; but iron and steel are usually rolled hot. In some cases, the stock is simply passed through the rolls; that is, the piece is placed against a guide, which serves to locate it properly before starting through the rolls; the rolls then grip it and carry it from the operator, requiring no further attention from him. In other cases, dies are fastened to the rolls. These dies do not extend all around the rolls, and when the parts not covered by the dies are next to each other, an open space is left between the rolls. The rolls turn continuously, and when the open space appears the work is passed through it. As the rolls turn, the dies come together, grip the work, and roll it toward the operator. The advantage of using a machine in which the work is done Fig. 1 by rolling the material toward the operator is that where several passes are required all work can be done by one man, while with rolls carrying the work away from the operator it is necessary to have a man at the back of the machine to return the partly finished pieces. Graded rolling is sometimes done to break down stock or to rough it to shape, so that it may be finished by drop forging. 3. Some of the operations in the making of spoons are excellent examples of graded rolling with dies. The blanks are punched from a sheet j inch thick, in the form shown in Fig. 1 ; the piece a is waste, and b, c, d, e, f, and g are spoon blanks. The large end of the spoon blank, which is to form the bowl, §53 MACHINE FORGING is first made wider by cross-rolling; this is done in some cases by passing the blank sidewise between rolls about 6 or 8 inches in diameter, the rolls being ^;>.^ located between housings, as shown in Fig. 2. A part of each roU is made smaller in diameter, that is, it is cut away so as to clear the spoon handle, shown at b. The portions r r of the rolls do the cross-rolling; the rolls are connected by suit- able gears, which are placed on the ends of the roll shafts. In other cases, the cross- FiG. 2 roUing is done between overhanging rolls, as shown in Fig. 3; these rolls are 10 or 12 inches in diameter, to insure the neces- sary stiffness. The portions of the rolls between the housings are frequently used for other work. Driving gears are located on the ends of the roll shafts at the side g. The tliickness of the metal varies in different parts of a spoon and this varying thickness is produced by graded rolling. Part of the circumference of the rolls is cut away so that the -^ C^ length of the circimi- ference remaining is equal to the length of the spoon. The part of the roll that is not cut away is shaped so as to produce the desired taper on the work. A different set of rolls must therefore be made for every size or style of spoon. In Fig. 3 some cases the work passes through the rolls away from the operator and falls out on the other side, while in others it is rolled toward the operator. MACHINE FORGING 53 4. In rolling rifle barrels, steel billets are heated in a furnace and then passed through successive grooves in a pair of special eccentric or graded rolls, until the barrel is reduced to the proper size and has the required taper. As the billet passes through the first groove, it is seized by a helper at the back and passed over to the workman in front. The work passes between the rolls with the large end first, passing once through each groove, except the last, through which it is passed twice; the work is given a quarter turn between each two passes. As Fig. 4 soon as the barrel is rolled to size, the ends are sawed off to the proper length. 5. A pair of graded rolls fitted with dies for special forging work, on either hot or cold metal, is shown in Fig. 4. These rolls are provided with nuts and collars, between which the rolling dies are clamped. The dies can be removed and changed at will, so that a large variety of work can be done on one pair of rolls. The rolls turn so that the work is run toward the operator, and, as the dies do not extend over the entire § 53 MACHINE FORGING 5 circumference of the rolls, the metal is passed between them at the time in the revolution when the dies are out of the way. The work is located by guides, which control its position both vertically and horizontally. When rolling hot metals, the location is determined by a stop a on the tongs, Figs. 4 and 5. Fig. 5 It will be noticed that this is simply a clamp screwed to the tongs; it is brought against a guide fastened to the front of the rolls, to show how far the iron should be pushed in between the roUs. Sometimes the end of the tongs strikes the guide, and this serves to locate the work. After the work has been placed in position, the revolving dies catch the piece and roll it toward the operator. As soon as the dies leave the piece, the operator puts it in position for a second pass through the rolls, either giving it a quarter tiu*n and returning it through the same groove, or giving it a quarter turn and placing it in the next groove; in this way the work is continued until completed. In the machine shown in the illustration, there are three grooves, and the work is given two passes in the first groove, two in the second, and three in the third groove. 6. In Fig. 6 is illustrated the back of the machine shown in Fig. 4. In this view, the dies a are clamped between the nuts b and the coUars c on the other ends of the rolls. The work d is shown in position ready for the dies to grip it as they come around to the proper point ; the arrows show the direction in which the rolls are turning. A peculiar arrangement of gearing is used for driving these rolls, which admits of the adjustment of the distances between the rolls; this is accom- plished by driving the top roll by a train of three gears, one being an idler swinging about one of the others and meshing with both. 7. Screw-Thread Rolling. — Screw threads are rolled on wood screws, track bolts, machine screws, and manv other 6 MACHINE FORGING 53 screws and bolts, from small sizes up to 1^ inches in diameter. The thread is formed by rolling the stock between suitable dies, with sufficient pressure to force the material out of the grooves to form the thread points. That is, the cold metal is caused, by the pressure on the dies, to flow from the bottom of the spaces and form the full thread. It is in reality a cold- forging process. 8. Machines for rolling screw threads are made both horizontal and vertical, but since the horizontal and vertical machines are alike in principle only one will be described here. Fig. 6 The front view of a vertical thread-rolling machine is given in Fig. 7. There are two dies a and b;ais fastened to the frame of the machine, and b is attached to a crosshead partly shown at c. The blank that is to be threaded is placed on the feed bar d and is introduced between the dies at the proper moment by the pusher, or starter, e. To start the blank, the feed bar d is automatically withdrawn from between the dies and the starter moves forward, pushing the blank between the dies. Both the feed bar and the starter are moved by the cam / on the driving shaft. The crosshead c is moved through the connecting-rod g 53 MACHINE FORGING and yoke hhy a crank on the shaft t. The shaft i is driven from the pulley / by gearing of which k is part. The yoke h is arranged so that, when the gear k turns in the direction of the arrow, the crosshead is given a slow motion on the down, or working, stroke and a quick motion on the up, or idle, stroke. The back of the crosshead c bears on a set of rollers, Fig. 7 one of which is shown at /, and the working faces of the dies are lubricated by oil that flows from the pipe m. The station- ary die a is adjusted to roll a full thread by the wedge n and is clamped in the final position by the bolts o. 8 MACHINE FORGING §53 Fig. S 9. The threads on the dies are laid off at an angle as shown in Fig. 8, which is a die for forming a right-hand thread. The length of the die is about three or four times the circumfer- ence of the blank so that the screw will turn around, between the dies, about that number of times in forming the thread. Screw threads are rolled on many small pieces, the material being either hot or cold, depending on the size and character of the article. The rolled thread is claimed to be much stronger than a cut thread, but it is exceedingly difficult to keep dies in shape for rolling threads on hot stock; hence, this process is used mostl}^ for rolling threads cold. Fig. 9 shows how the metal is displaced by the dies to form the thread on the bolt a ; the dotted line b c shows how deep the dies press into the stock, and also how the diameter is increased on account of the thread. As the finished thread must have a definite diameter, it is very important that the stock used should be of the right size ; if the stock is large the screw will be too large, and if too small the screw will either be too small or the threads ^ will not be perfect. The size of stock required to make a rolled thread of any given diameter can be calculated, but owing to the fact that the rule is long and rather complicated, and that the diameter of stock must sometimes be changed after trial because the metal will not always flow readily into the points of the threads, a simpler but less exact rule is ordinarily used. The first trial size of stock is obtained by subtracting the depth of the thread from its outside diameter. The depth of the United States standard threads may be found by dividing .6495 by the number of threads per inch ; and the depth of V threads Fig. 9 53 MACHINE FORGING may be found by dividing .866 by the niimber of threads per inch. The diameter of stock for some of the most common sizes of rolled threads is given directly in Table I. TABLE I SIZE OF STOCK FOR ROLLED THREADS Diameter United States Standard Thread V Thread of Screw Number j- per Inch )epth Inch Diameter of Stock Inches Number j per Inch )epth [nch Diameter of Stock Inches 1 4 20 033 .217 20 043 .207 3 8 i6 040 •334 16 054 .321 1 2 13 050 •450 12 072 .428 5 8 II 059 .566 II 079 •546 3 4 lO 065 .685 10 087 .663 1 9 072 .803 9 096 ■779 I 8 081 .919 8 108 .892 li 7 093 1.032 7 124 1. 001 l| 7 093 1157 ■ 7 124 1. 126 If 6 108 1.267 6 144 1. 231 li 6 108 1.392 6 144 1356 10. To illustrate the use of the table, suppose a |-inch United States standard thread is to be rolled. How many threads per inch and what size of stock should be used? Find § inch in the left-hand column; and, following horizontally across the table, in the columns headed United States Standard Thread, it is found that there are 13 threads per inch, and the depth of the thread is .05 inch, and the stock should be about .45 inch in diameter. Again, suppose a |-inch Y thread is to be rolled. How many threads per inch and what size of stock should be used ? Find | inch in the left-hand colimm of Table I and, following horizontally across the table to the coltmms headed V Thread, the number of threads per inch is found to be 9, and the stock should be about .779 inch in diameter. 10 MACHINE FORGING 53 An example may be used to explain the determination of the size of stock when it is not obtainable from Table I. Example 1. — What size of stock should be used to make 12 rolled United States standard threads per inch, f inch in diameter? Solution. — Owing to the fact that a |-inch screw does not ordinarily have 12 United States standard threads per inch, this combination does not appear in Table I. It wiU therefore be necessary to calculate the size of stock required to make these threads. According to the explanation iust given, the depth of the thread is .6495 ^12 = .054 in. and the diameter of the stock is .75 -.054 = .696 in. Ans. It is sometimes required to find the diameter of thread that will be produced by rolling a given number of threads per inch on stock of a given size. In this case the depth of the thread should be added to the diameter of the stock, the depth of the thread being found as described in the foregoing example. Example 2. — What outside diameter of thread will be produced by rolling 10 V threads per inch on f inch stock? Solution. — The depth of the V thread is .866 ^10 = .0866 in. and the outside diameter of the thread is .75 + .0866 = .8366 which is practically .837 in. Ans. 11. Bending Rolls. — ^Plates are bent in bending rolls, which are placed as shown at a, b, and c, Fig. 10. Roll a is arranged so that it can be moved toward or away from b and c, in order to give the plate d, that is being rolled, the desired curvature. The roll a is called the bending roll and rolls b and c are the pinching rolls. The side view of a set of bending rolls is shown in Fig. 11, in which the rolls a are driven by elec- tric motors c, thi'ough gears b, d, e, g, f, and shaft h. A gear / is Fig. 10 §53 MACHINE FORGING 11 attached to each of the pinch- ing rolls, both of which are driven by gear g. The farther motor also drives gear e through gearing that is not shown, sim- ilar to b and d. The pinching rolls, which are driven, are also called live rolls; and the bend- ing roll, which is not driven, is called a dead, or idle, roll. 12. The pinching rolls are stiffened by supports / and rollers n so they will not spring down in the middle. Each pinching roll has three slots m to help start the plates squarely through the rolls. The plate is put between the bending roll and one of the pinching rolls; then, as the roll rotates, the edge of the plate is caught by one of the slots, bent up around the bending roll and started between it and the other pinching roll. Cylindrical work is removed from the rolls by turning down the end i with the bearing /, it being hinged for that purpose, and raising the roll by the rigging shown at k. The curvature of the plate may be controlled by raising or lowering the pinching roll. This is done by a mechanism partly shown at the right of the supports /. The two ends of the bending 12 MACHINE FORGING §53 roll may be moved together, or either end may be moved independently of the other end. By moving one end of the bending roll closer to the pinching rolls than the other, conical work may be formed. HAMMERS 13. steam Drop Hammer. — The steam drop hammer has many of the advantages of other drop hammers and it possesses one advantage not shared by them; that is, that steam may be used for driving the piston down more rapidly. Fig. 12 and hence an exceedingly quick and powerfiil blow can be struck; or the piston may be let down slowly until the upper die rests on the work, when the steam pressure is applied and the dies forced together with a imiform pressure, as in the case 53 MACHINE FORGING 1 *> of an ordinary power press. The work may then be finished by one or two blows of the hammer; in other words, the steam drop hammer is capable of a wider range of work than other forms, but as a rule it requires a somewhat higher degree of skill in the operator. 14. Steam Drop Press. — There is a large variety of work that must be pressed to bring it approxi- mately to shape, and then a few sharp blows from a hammer must be struck to finish it. The steam drop press, which closely resem- bles the steam drop hammer, has been brought out to meet this demand. One form of drop press is showninFig. 12. The lower die is held in place on the base a by the poppets b, which extend through the base and are se- cured by keys below. The head c that car- ries the upper die, and moves between the Fig. 13 guides d, d' , may be allowed to fall by gravity or may be forced down by steam or air pressure acting on a piston in the cylinder e. The lever / operates the piston valve in the valve chest ^, and also moves the latch h out of the way when starting the head 14 MACHINE FORGING from its highest position, where it is held by the latch when the press is not running. This type of press is used for large thin work, such as dish pans, where the work is first pressed into shape and then finished by two or three quick blows. 15. strap and Pulley Drop Press . — In the strap and pulley drop hammer, shown in Fig. 13, the weight is lifted by pulling on a strap that passes over a constantly rotating pul- ley. The pulley b is kept rota- ting by a belt on the pulley d, and when the end of the strap e is hanging loose the friction on the pulley is not sufficient to lift the weight. When the operator brings pressure on the strap, either by pushing his foot down in the stirrup at c or by gripping the strap higher up with his hand and pulling down, the friction of the strap on the pulley b is increased to such an extent that the ham- mer head is lifted. When the head reaches the desired eleva- tion, the tension on the strap is relieved, allowing it to slip over the face of the pulley as the head falls. The poppets, shown at a, are used to hold the lower die in place. They are made with long shanks that fit holes in the base of the hammer, and with adjusting screws through the tops to locate and hold the die. § 53 MACHINE FORGING 15 16. Board Drop Hammer. — One of the most common forms of drop hammer is known as the board drop hammer, one form of which is illustrated in Fig. 14. The hammer head a and board b, to which it is attached, rise and fall together. Friction rolls c on each side of the board are attached to shafts carrying pulleys d turning in opposite directions, and run by belts in the directions shown by the arrows. The friction rolls are thus run continuously in the directions required to raise the board, but in their normal position they just clear the board. The rod e operates a cam that moves the rollers c so that they grip the board and raise it and the hammer. The foot treadle h is connected by a strap g to the lever /, and is also attached to the rod i, and thus operates the latch /. 17. When not in use, the hammer head is usually held up by the latch ;, which is placed at about the highest point from which it is desired to have the hammer drop. When it is desired to strike a blow, the treadle is depressed, which pulls out the latch ;', and permits the outer end of the lever / to rise and the rod e to fall. When the hammer falls, the lug on the hammer head strikes the lower dog on the rod e, carrying the rod down and forcing the friction rolls c against the board. The hammer is then raised, the rolls remaining in contact until the hammer head strikes the upper dog k on the rod e, thus raising the rod and throwing the friction rolls out of contact with the board. The hammer then again falls, striking another blow, and carry- ing down the rod e and throwing the rolls into contact as before. This process is repeated automatically, striking continuously, until the treadle is released, and raised by the spring shown at the right-hand side of the hammer ; then the latch ; again catches the hammer head and holds it in the raised position. Light blows may be struck by releasing the treadle at each rise of the hammer before the hammer head strikes the dog k, throwing out the friction rolls and causing the hammer to drop before it has reached its full height. The operator can thus vary the stroke as conditions may require. The hammer may be set for different heights of drop by moving the latch / and the dog k up or down. Fig. 15 16 § 53 MACHINE FORGING 17 18. Crailk Drop Hammer. — A common form of crank drop hammer is shown in Fig. 15. In this type of hammer, the hfting mechanism is arranged in such a manner as to rotate the crank o, thus h'fting the hammer head b by means of the ropes c, or by a leather strap. The mechanism is driven by a belt on the pulley d, on the shaft carrying the pinion h that drives the gear i. A clutch e is so constructed as to raise the hammer after each stroke and hold it in its highest position until the treadle / is depressed. The treadle / is connected, through the rod g, to the clutch e. Bj^ keeping the treadle depressed, the hammer will strike successive blows. 19. Advantages of Board and Crank Drop Hammers. Board and crank drop hammers have a number of points that distinguish them from each other. In general, a board drop hammer strikes a quicker or sharper blow for the same weight of hammer head and same height of drop. The blow of the board drop hammer may also be quickly regulated by varying the height of the drop. The crank-liji, rope-lift, or strap-lift drop hammer, as it is variously known, is largely used for bending, shaping, straight- ening, and welding. These hammers are used extensively by the manufacturers of agriciiltural implements, and also by malleable-iron companies. The crank machines have an advantage in the lifting arrangement because the board drop hammer depends on friction for lifting the hammer, while with the crank drop hammer, the lifting is positive. The board and gearing are expensive, so that a crank machine of a given capacity and weight of drop will cost less than a board-operated machine. The form of the lifting device is not of much importance in the case of light work, but for manufacturing where large forming dies are used it is a point well worth considering. As a rule, the crank machine is simpler and requires less skill for its operation ; hence, it is preferred for rough work. It is also used very extensively for forging soft metals cold, as in making spoons, watch cases, and similar work. In many classes of work, it is absolutely necessary that the hammer head or drop should fall from two or more heights, in 18 MACHINE FORGING § 53 order to strike light or heavy blows when forging; and some- times, as the work is turned from side to side, these light and heavy blows must alternate. For such work the crank hammer is not suitable, and it is necessary to use a board drop hammer. Even for the lighter class of forgings, especially where the dies are frequently changed, the board drop hammer is generally considered the better. 20. Die Forgings. — Die forgings are produced in formed dies that are shaped more or less closely to the outline of the forging. Various machines, such as drop hammers, steam ham- mers, and presses, are used to force the stock into the dies. A drop forging is a die forging that is produced by using the force of a falling weight to drive the stock into the dies. Drop forgings may be produced on a drop hammer or a steam ham- mer. When a steam hammer is used, the force of the blow struck by the falling hammer head may be increased by steam pressure behind the piston. The general process of making die forgings will be explained by means of a simple example requir- ing but two operations and other forgings requiring these and additional operations will be described later throughout the remainder of this Section. 21. The clips used to hold the wooden and iron parts of a wagon axle together are made flat, as shown in Fig. 16, and are bent to fit the axle on which they are to be used. The ends a and b are threaded to receive nuts that hold a yoke on the clip after it has been bent. The fiat part is made very thin, sometimes only Y2 inch thick, so that it can be bent cold. Recesses in the forging dies form the round ends a and b, and the conical parts d and e that join them to the fiat part. The forging dies are shown in Fig. 17, in which (a) is a view of the face of the upper die, (6) is a section of the upper and lower dies, showing the recess in which the forging is made, and (c) is the face of the lower die. The top surface of the lower die in Fig. 16 20 MACHINE FORGING § 53 view (b) is on the line ah c d e J and the lower surface of the upper die is at a g /i ij J. From k to i the upper die does not touch the lower die, and the distance between the dies, when the upper die is clear down, gives the thickness of the fiat part in Fig. 16. 22. This forging is made from bar iron, which must be large enough to fill the die at the largest part. There are other parts of the die that such a bar more than fills and there must therefore be some provision made for the disposal of the excess metal where it can later be removed without injury to the forging. This provision is made by leaving a shallow recess k in Fig. 17 (a) and (c), called the flash, which makes a narrow opening /, in (6), around the forging impression. The excess metal squeezed out into the flash around the forging is called the fin and sometimes, also, the flash. Since these dies do not come together between h and i, that is, the stufaces m and n do not come together, the fiat part of the forging can spread out as much as necessary and no flash need be provided for this part of the forging. The part of the bar that is not needed for the forging, sticks out of the die through the sprue o. The sprue is connected with the die impression by the gate p. Fig. 18 23. The forging produced by the forging dies is shown in Fig. 18 with the fin a still attached and the fiat part h is very much larger than is required in the finished forging. The fin a is removed by a punch and die, shown in Fig. 19 (a) and (6), which also trim the fiat part h to the required size and shape. The die, or trimmer, shown in (6), is made of two blocks a and h in which an opening c has been cut. This opening is the size and shape of the outline of the finished forging and it extends clear through the trimmer. The punch d in view (a) fits in the opening c in the trimmer, and its lower surface is 53 MACHINE FORGING 21 shaped to bear evenly on all parts of the forging. The rough forging shown in Fig. 18 is laid on the trimmer, Fig. 19 (6), so that the round ends rest in the parts e and/ of the opening and the fin extends out over the surface of the trimmer. The punch is then brought down on top of the forging, forcing it through the trimmer, cutting the fin off and leaving it on the surface of the trimmer. The fin must be cut from the end of the bar from which the forging was made, so that it will not interfere with the making of the next forging. The cut-o^ g Fig. 19 is therefore fastened to the end of the punch so that it comes into action over the shoulder k when the punch has nearly- severed the forging from the fin. The cut-off must be wide enough to reach clear across the fin and cut it entirely off. The trimmer is made of two blocks, so that the opening c, when it has been enlarged by wear, can be brought back to the required size and shape. The shape of the opening in each block is first trued up and the joints between the two blocks are then faced off to make the opening of the right size. 22 MACHINE FORGING §53 24. It is not always possible to complete a forging in one die, as was done in the case just described, and the forging dies are then provided with two or more impressions, thus doing the required work on the stock in a series of steps. The niimber of blows that must be struck depends on a number of con- ditions, but must always be enough to make the upper die strike the lower die. The number of blows will be affected by such conditions as the weight of the hammer, the height of the drop, the size of the stock, the kind, quality, and. temperature of the metal, and the depth and shape of the recesses in the dies. In general, the heavier the hammer, the higher the drop, the smaller, hotter, and softer the stock, and the shallower the recesses in the dies, the fewer will be the number of blows required to finish the forging. 25. Such articles as spades, shovels, scoops, conveyor buckets, and wheelbarrow bodies may be formed in dies by drop hammers. The lower die forms the outside and the upper die the inside of the article. Some of these articles, such as wheelbarrow bodies, are made in steam drop hammers. The upper die is brought down against the stock, and steam is then turned on, pressing the stock into the lower die, and a few light blows are then struck to remove wrinkles and make the stock fit the die closely. Shovels are made under drop hammers. The heated stock is placed over the lower die and struck as many blows ! i ill as are needed to make it fit the die closely. The dies with which scoop shovels are formed are shown in Fig. 20. The lower die, shown in (a) , forms the outside of the shovel and the inside is formed by the upper die, shown in (6) . The back of each die block is planed smooth, so as to give a good bearing on the bed or the head of the hammer. The lower die is held in place by setscrews passing through poppets on the bed of the hammer. The upper die is fastened to the hammer head by bolts that pass through ears on the head, or by a dovetail (a) Fig. 20 §53 MACHINE FORGING 23 and key. Suitable stops are provided to facilitate placing the upper die properly over the lower one. 26. Automobile front axles are frequently drop-forged, the dies usually being long enough to forge half the length of the Fig. 21 axle at a time. The order in which the operations are performed and the details of some of the operations depend largely on the design of the axle and the size of stock of which the axle is being made. A front axle that is forged from square bar is illustrated in Fig. 21. The bar is large enough to make the body of the axle, but upsetting at a and b, as shown in Fig. 22, is necessary, to make the forked end a and the spring pad b. This operation is performed before the axle is taken to the forg- ing hammer, in an upsetting machine, which will be described later. The forging is done in two stages; the first is a roughing operation which spreads the end preparatory to form- ing the forked end. A steam hammer is shown in Fig. 23 fitted with the roughing dies for this axle. The upper die a is keyed to the hammer head with a key b that is formed to fit the space between the dovetail on the die and the side of the slot in the hammer head. The lower die c is keyed to the anvil. Two keys are used in this case, one driven from each end of the die. When making the dies, one end and one side of the Fig. 22 die block are first planed straight and square with the working face of the die and with each other. The impressions in the dies are then laid out so that they will come together when these squared edges are in line with each other. The squared ends are lined by moving one or the other die backward or 24 MACHINE FORGING 53 forward as may be required. The sides are lined by moving the hammer frame sidewise on the anvil block. This moves the upper die crosswise, but does not change the position of the lower die. When the dies are properly lined, the hammer frame is fast- ened down by anchor bolts d. Heavy springs are placed under the nuts on the anchor bolts so that when such a heavy blow is struck that there is danger of breaking the hammer, the hammer is lifted slightly from the anvil block. 27. Considerable scale forms on the mate- rial that is heated for forging, and some of it when loosened by the forging operation drops into the lower die. If the scale were allowed . to stay in the die, the ^ forging would be rough and not true to the die. A blast of air from the blast pipe e is therefore directed on the lower die to keep it free from scale. The dies are long enough to forge slightly Fig. 23 more than half the length §53 MACHINE FORGING 25 of the axle, so one end of the axle is heated and forged and then allowed to cool. The other end is then heated and forged in the same way. In order to facilitate the forging operation, the finishing dies are set up on a hammer beside the first one so that, when one end has been rough forged, it is taken to the finishing hammer and finished with the one heat, and the fin is trimmed in a trimming press. In this way each end is com- pletely forged and trimmed with one heat. The axle is forged straight, and is bent to the required form on a press. 28. A large axle of somewhat different design from the one shown in Fig. 21 is illustrated in Fig. 24. This axle is heavier at the middle than at the ends and it is therefore not possible to use stock large enough to fill this part of the die without leaving an excessively large fin at other parts of the forging. Stock that is larger than is required by the part of the forging at a, but not quite large enough for that at h or at c, is therefore used. The forging of each half of this axle is completed in foiu" operations with two dies. The operations are fulling, breaking down, roughing, and finishing. The first three operations are performed under a roughing die and the fourth operation under a finishing die. 29. The lower roughing die is illustrated in Fig. 25. The fiiUer, shown at a, throws the metal both ways, into the spaces h and c. The metal in h provides stock for the formation of the Fig. 25 26 MACHINE FORGING 53 axle end, and that in c provides stock for the heavier portion of the axle body. The stock is then bent in the breakdown d so that it will lie over the roughing impression. The upper roughing die is like the one shown, excepting that the break- down projects from the face of the die block instead of being cut into it. After the stock is bent, it is roughed out in the impression e. The projection in the center of this die gradually tapers out at / so as to throw the surplus metal toward the middle of the axle where it will be needed in the finishing oper- ation. The finishing impression is shown in Fig. 26. The other die of this pair is like the one shown. The impression brings the forging to size and a flash a is provided to take the excess metal that is squeezed out. These dies, like those for the other axle, forge half the axle at a time. Such dies as these are rather hea\^ and must therefore be lifted by a crane. In order to facilitate the lifting of the dies, holes b are drilled in the ends of the die block, and steel pins, over which the crane chain is fastened, are stuck into these holes. Fig. 26 30. Drop-Hamixier Foundations. — ^As it takes some appreciable time for the blow to penetrate to the center of a piece of metal, drop hammers are sometimes provided with an elastic foundation. The elasticity has the effect of distributing the force of the blow over a longer period of time, thus causing it to penetrate deeper. Such a foundation is usually made of large timbers, carefully squared and made to fit each other quite accurately, as shown in Fig. 27. The anvil a is then placed on the foundation, usually with a layer of leather belting or a rubber pad between the top of the timber and the base of the anvil. The bottom of the timbers h should be bedded in con- crete to insure an even bearing. The objection to the all- timber fotmdation is its great cost and renewal expense. 53 MACHINE FORGING 27 31. Elastic foundations have been made by placing the timbers for the foundation in a vertical position. A log large enough in diameter to receive the anvil on its top and to enter the ground 6 or 8 feet is sometimes preferred. The hole is dug 1 foot deeper than is necessary to receive the log. A foot of concrete is then placed in the bottom of the hole, and the log bedded, in a perpendicular position, on top of this. For light drop hammers, a large flat stone is sometimes placed under the bottom of the log. The space about the log in the hole should be filled with earth well tamped into place; the top of the log should be trim- med off to a true horizontal siu-face. In the case of ham- mers with openings in the center of the anvil, it is necessary to cut a depression in the center of the top of the log, with a groove leading to the outside to allow scale and dirt to pass off without accumulating under the anvil. When a log large enough for the anvil cannot be obtained, several timbers may be bolted together to form a block of sufficient size. Chestnut or oak timbers are said to be the best for drop-hammer foundations. For hammers with drops weighing 1,000 pounds or more, a masonry foundation is recommended by some builders. A hole is first dug 10 to 14 feet deep, and the masonry built up to within 4 feet of the top. On top of the masonry, oak timbers 4 feet long standing on end are arranged, and bolted closely together. The space around the timbers is then filled with concrete; the anvil is set on top of the oak timbers, as in the case of the foundations already mentioned. In some cases, masonry foundations are built up to within an inch or so of the anvil, and a thick rubber or leather pad placed under the anvil. Fig. 27 28 MACHINE FORGING 53 32. One manufacturer of drop hammers recommends the soHd foundation shown in Fig. 28. It is made by digging a hole of the required depth, and Hning it with planks, as shown. The space inside of the planks is then filled with concrete. The following proportions for the composition of the concrete are recommended : three barrels of stone, two barrels of gravel, 1^- ^__- and one barrel of cement. \ ? / f l Table II shows the dimen- sions of the foundations for various weights of the drop, generally called the weight of the hammer. The dimensions for the foundation of any hammer are found in the same hori- zontal line as the weight; Fig. 28 the letters at the head of the columns correspond to those in Fig. 28. Foundations of this kind have been built without using any elastic material between the anvil and the concrete, with very satisfactory results. Concrete foundations may be strengthened with reinforcing rods, as shown at o, when it Is thought the concrete does not supply sufficient strength. * 8 1 rtl'* rtN H'* Ml-* .Hi-* H|oo Hoo "1-* H-* "1-* -HN rtiN QnOsOnOO i-i O O rO-^^OiOO S C-HCN-^\Or^i-iro r^t^r^r^OOOOOOoM •iH uT C .2 in C a Q c o -Si O O^'O -^-^vooo w (SOOOO t^r^t^r^O\CSONON>-i M M M HH M M l-l a< ^vOOOOOcN'^roTi-(N(» lOiO^^OOOOOOCOOOOO ONON ^'^'^O O '^O'O rJ-oOOO rh vO^vot^COOO OS 0\ O O M (N- l-C h-l H-l M ^ ml-* «!-* nl-* r4|-* ml-* t-(0O rH|0O rHi-* «|-* r-l|-* n]-* rt)«.) ■^■^■^i-iOO rOONCN On-^o) CO -52 iHJt^ WlM ml-* «|Q0 rH|-* rHi-* rt|-* rt|-* r<|-« r-lj-* lO .Hi-* r^N H|N t-|00 rtjoo «|qO rH|N rtjN m|-