The manufacturing shop differs very essentially from the jobbing shop. In the lattershop very few forgings are made at the same time exactly alike, while in manufacturing, each forging is generally duplicated a large number of times and special machines are used for doing the work.
Drop hammers are used for quickly forming complicated shapes out of wrought iron or steel. They consist, as the name indicates, of a head that may be "dropped" from any desired height upon the piece to he shaped. The head of the drop and the anvil are in the form of dies into which the metal is forced to flow, and thus take on the form desired. In drop-forging, the metal must be heated to a high temperature so as to be soft and plastic. A common type of drop hammer used for this kind of work is shown in Fig. 19. The hammer in this case is fastened to a board and is raised by the friction rollers at the top of the frame being pressed against the board. When the hammer reaches the top of the frame it is dropped by releasing the rollers from the board. This may be done automatically or by a foot treadle. Drop hammers are also built in the same general way as steam hammers, as referred to in the sections on Heavy Forging and Drop Forging. Dies for drop forging generally consist of a roughing or breaking-down die where the rough stock is first given approximately the desired shape and a smoothing die when the finishing is done. These dies have in their faces holes of the same shape as the required forging. Power Hammers. Another tool which is used to quite a large extent in manufacturing, as well as in the jobbing shop, is the power hammer. These are run by belts and are used where a quick rapid blow is wanted. The type shown in Fig. 20 is known as a Justice hammer; that shown in Fig, 21 is a Bradley. Shaped dies are frequently used on these hammers.
Fig. 22 shows the Beaudry power hammer. This hammer has many claims in its favor - superior elasticity; perfect control of blow struck. These are obtained by a device which is simple and effective, allowing the ram the greatest freedom of throw and causing it to rebound the instant the blow is struck.
This hammer has no beam, saddle, rubber cushions, leather straps, nor coiled springs. Its ram or head is of steel and has an internal curve or track of 0 shape, as shown by the sectional cut, Fig. 23. Two steel spring arms with hardened tool-steel rollers at their lower extremities operate within the ram which, with increased speed of hammer, acquires increased travel and force of blow.
This simple and positive action of the spring arms perfectly controls the ram and causes it to rebound the instant the blow is struck, without reaction or jump or sudden undue strains on any of the hammer parts. The elasticity and force of the blow is obtained thus, and by it the full stroke can be had as readily on a piece 4 inches square as on a piece 1/8 inch in thickness, and no change of adjustment is necessary excepting for unusually heavy work.
The hammer is started, stopped, and regulated by a foot treadle which extends around the base of the machine and through a varying pressure on which there is obtained instantly any desired speed or force of blow of from 1 pound up to its full capacity, which latter is an estimated maximum blow of six times the weight of the ram.
The anvil clears the main frame casting as shown in Fig. 24, allowing any length bars to be worked either way of dies. It is an independent casting having no connection with the frame, and thus preventing crystallization of the hammer parts; it is held in place by its own foundation bolts and stands in the center of the hammer foundation. To it is keyed an independent show die and to that in turn is keyed the bottom die.
Presses may be of either the gear-driven or the hy-draulically operated type. They serve the same purpose as drop hammers. They do the work more slowly, however. The class of work is, in some respects, the same, the principal difference lying in peculiarities of shape that require different time intervals for the flow of the metal. Where the shape is such that the metal must move slowly in order to acquire its new shape or fill the die, the press should be used.
A particular type of forging press is the flanging press. This is used more particularly in boiler work and is generally a heavy hydraulic press. The flanging is done by placing the heated metal on the bed of the press and closing the dies together by hydraulic pressure.
This is a tool used for bending and consists of a heavy cast-iron bed with a block or bolster at one end, and a moving head which slides back and forth on the bed. A common type is shown in Fig. 25. Heavy dies are clamped against the bolster and on the moving head, of such a shape and in such a way that when the moving head is nearest the bolster, the shape left between the two dies is exactly the shape to which it is desired to bend the stock. In operation, the moving head slides back and forth on the bed. The bar to be bent is heated and placed between the dies when the head is farthest from the bolster. A clutch is then thrown in and the head moves forward to the bolster, bending the iron as it goes.
These are really upsetting machines that form the heads of bolts upon straight rods. Owing to the rapidity with which they do their work, they are invariably used for manufacturing bolts in quantities.
Where heavy work is to be handled, it is necessary to have some means of conveying the work from one part of the shop to another. This is done by means of cranes of two general types: (1) the traveling crane; and (2) the jib crane. The former type runs on an overhead track from one end of the shop to the other, generally.
The jib crane type is used more commonly for handling work under the hammers, and is merely an arm or boom swinging around a post and having a suitable arrangement for raising and lowering the work. When handling heavy work, whenever possible, it is suspended from the crane by its center, in such a way that it nearly balances. The suspending is generally done by means of an endless chain such as illustrated in Fig. 26, and in this way it may be easily rolled and swung from side to side. For ease in handling large forgings, a bar or handle known as a porter bar is sometimes welded on.