Pieces are sometimes shaped between formed steel dies where many are to be made exactly alike. An example of this sort of work is the eye bolt, Fig. 151. Round stock is used and is first shaped like A, Fig. 152. The shaping is done in the dies shown at B, which are simply two small blocks of tool steel fastened together with a spring handle, the inside faces of the blocks being formed to shape the piece as shown. The end of the bar is heated, placed between the die blocks and hammered until it takes the required shape, being turned through about 90 degrees between each two blows of the steam hammer, and the hammering continued until the die faces just touch. For the second step the ball is flattened to about the thickness of the finished eye and the hole punched under the steam hammer with an ordinary punch, leaving the work as shown at C The final shaping is done with the finishing die D. This die is so shaped that when the two parts are together, the hole left is exactly the shape of the finished forging. In the first die it will be noticed that the holes do not conform exactly to the desired shape of the forging, being, instead of semicircular, considerably rounded off at the edges. This is shown more clearly in Fig. 153 at A, where the dotted lines show the shape of the forging, the solid lines the shape of the die. The object of the above is this: If the hole is semicircular in section, the stock, being larger than the smaller parts of the hole, after a blow will be left like B, the metal being forced out between the flat faces of the die and forming fins. When the bar is turned these fins are worked back and make a cold-shut. When the hole is a modified semicircle the stock will be formed like C, and may be turned and worked without danger of cold-shuts. Dies for this kind of work are sometimes made of cast iron. When made of tool steel it is sometimes possible to shape them hot. A master forging is first made of tool steel to exactly the shape of the required forging. The blocks for the dies are then forged with flat faces. These blocks are fastened to the handle and then heated red hot. The master forging is then placed between them and the dies hammered down over the forging, leaving the cavity just the proper shape.
Fig. 151. Eye Bolt.
Fig. 152. Shaping Eye. Bolt in Dies.
Fig. 153. Shapes of Forging and Die.