FIG. 19.—Result of using too light a hammer.
| Diameter of stock | Size of hammer | |||
|---|---|---|---|---|
| 3½ | in. | 250 to | 350 lb. | |
| 4 | in. | 350 to | 600 lb. | |
| 4½ | in. | 600 to | 800 lb. | |
| 5 | in. | 800 to | 1,000 lb. | |
| 6 | in. | 1,100 to | 1,500 lb. | |
Steam hammers are always rated by the weight of the ram, and the attached parts, which include the piston and rod, nothing being added on account of the steam pressure behind the piston. This makes it a little difficult to compare them with plain drop or tilting hammers, which are also rated in the same way.
FIG. 20.—Good and bad ingots.
Steam hammers are usually operated at pressures varying from 75 to 100 lb. of steam per square inch, and may also be operated by compressed air at about the same pressures. It is cheaper, however, in the case of compressed air to use pressures from 60 to 80 lb. instead of going higher.
Forgings must, however, be made from sound billets if satisfactory results are to be secured. Figure 20 shows three cross-sections of which A is sound, B is badly piped and C is worthless.
PLANT FOR FORGING RIFLE BARRELS
The forging of rifle barrels in large quantities and heat-treating them to meet the specifications demanded by some of the foreign governments led Wheelock, Lovejoy & Company to establish a complete plant for this purpose in connection with their warehouse in Cambridge, Mass. This plant, designed and constructed by their chief engineer, K. A. Juthe, had many interesting features. Many features of this plant can be modified for other classes of work.