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    Forging Operations - Machine Forging, Forging Dies and Special Forging Operations
    Forging Operations - Machine Forging, Forging Dies and Special Forging Operations
    Forging Operations - Machine Forging, Forging Dies and Special Forging Operations
    Ebook255 pages1 hour

    Forging Operations - Machine Forging, Forging Dies and Special Forging Operations

    By Anon

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    About this ebook

    This vintage book contains a complete guide to the various different operating involved in forging, covering machine forging, forging dies, heating furnaces, estimating stock, and all other related aspects. "Forging Operations" will be of special appeal to those with an interest in the history and development of forging and would make for a fantastic addition to collections of literature related to blacksmithing. Contents include: "Forging Machines", "Introduction", "Rolls", "Hammers", "Swaging Machines", "Presses", "Upsetting Machine", "Punches and Shears", "Riveting Machines", "Bulldozer", "Forging Dies", "Forms of Forging Dies", "Drop-Forging Dies", "Heading and Bending Dies", "Heading-machine dies; Bending dies", et cetera Many vintage books such as this are increasingly scarce and expensive. We are republishing this volume now in an affordable, modern edition complete with a specially commissioned new introduction on blacksmithing.
    LanguageEnglish
    PublisherOwen Press
    Release dateAug 25, 2017
    ISBN9781473339767
    Forging Operations - Machine Forging, Forging Dies and Special Forging Operations

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      Book preview

      Forging Operations - Machine Forging, Forging Dies and Special Forging Operations - Anon

      Bars

      MACHINE FORGING

      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 advantageous to forge metals at temperatures varying from ordinary atmospheric temperature to about 2,000° F. Low-carbon steel, certain brass alloys, and aluminum 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 temperature. 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.

      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 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.

      FIG. 1

      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 1/4 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, 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 roll 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 suitable gears, which are placed on the ends of the roll shafts. In other cases, the cross-rolling is done between overhanging rolls, as shown in Fig. 3; these rolls are 10 or 12 inches in diameter, to insure the necessary 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.

      FIG. 2

      The thickness 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 length of the circumference 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 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.

      FIG. 3

      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 soon as the barrel is rolled to size, the ends are sawed off to the proper length.

      FIG. 4

      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 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. 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 rolls. 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 turn 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.

      FIG. 5

      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 collars 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 accomplished 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 many other screws and bolts, from small sizes up to 1 1/2 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. The front view of a vertical thread-rolling machine is given in Fig. 7. There are two dies a and b; a is 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 f on the driving shaft. The crosshead c is moved through the connecting-rod g and yoke h by a crank on the shaft i. The shaft i is driven from the pulley j 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, one of which is shown at l, and the working faces of the dies are lubricated by oil that flows from the pipe m. The stationary die a is adjusted to roll a full thread by the wedge n and is clamped in the final position by the bolts o.

      FIG. 6

      FIG. 7

      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 circumference of the blank so that the screw will turn around, between the dies, about that number of times in forming the thread.

      FIG. 8

      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 mostly 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

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