52. Forging.—Forging is the operation of hammering or compressing metals into a desired shape. Seven specific operations are used. Sometimes a piece of work or forging requires two, three, or even all of them to complete it. These operations are designated by the following names: drawing, bending, upsetting, forming, straightening, twisting, and welding.
Fig. 31.—The Shearing Blow.
53. Drawing, the process of spreading or extending metal in a desired direction, is accomplished by hammering or by pressing the metal between such tools as the swages and fullers, or by holding it on the anvil and using either of the set hammers, the flatter, or the fuller. When using any of these pressing tools for drawing, a helper is supposed to use the sledge to deliver the blows upon them.
It is always best to draw round metal with the swages, as it will be smoother when finished than if it were done with the hammer; it should be rolled in the swage a little after each blow of the sledge, and after a complete revolution in one direction it should be turned in the opposite direction, and so alternately continued until finished. Especially if iron is being drawn, this will prevent twisting of the fiber, which, if prolonged, would cause the metal to crack. Figure [32] shows the method of drawing with the swages.
When drawing any shape or size of metal to a smaller round diameter, it is best first to draw it square to about the required size, delivering the blows by turns on all four sides, then to make it octagonal, and finally round. The finishing should be done with the swages, if those of proper size are at hand; if not, light blows should be used, and the metal revolved constantly in alternate directions, to make an acceptable shape.
Fig. 32.—Drawing with the Swages.
Fig. 33.—Drawing with the Flatter.