Questions for Review
Describe the proper construction of a pair of tongs. What sort of steel should be used in making lathe tools? What operations are employed in making them? What is the color of the temper? If they were tempered to a blue, would they be tempered harder or softer? Are forging and hardening heats the same? State the difference in grinding a boring and a threading tool. Explain the difference in making a right- and a left-hand diamond point tool. How should a side tool be hardened? Why shouldn’t the head of a cold chisel be cooled off quickly when it is finished? Explain the difference between tempering a cold chisel and tempering a lathe tool. Describe the shapes of the hot and the cold cutter. How should they be tempered? How are the square-edged set and the flatter treated in place of tempering. Explain how it is done. Describe different methods of making eye or ring bolts. How should measurements be made on stock to be bent? State what has been said about scarfing flat or oblong material for rings.
CHAPTER VI
Steam Hammer, Tools, and Exercises
112. A Forging.—A forging is an article made of metal, generally steel or iron, and produced by heating and hammering. It may be used for either practical or ornamental purposes. The various forgings already described were made by methods such as the older class of smiths practiced, and are called hand forgings. From a practical standpoint these smiths were familiar with the characteristic composition of metals and with the knowledge of how they should be worked.
Many forgings are produced at present by machinery. The product is satisfactory for most practical purposes, and is generally equal to that made by hand. The machines used are the drop hammers, horizontal and vertical presses, steam hammers, and numerous other devices. The power used for operating them may be either steam, air, water, or electricity.
113. The Drop Hammer.—The drop hammer is provided with a pair of dies made of cast steel, one upper and one lower, having suitably shaped depressions made in them for forming the forgings. The lower die is held stationary on a solid foundation block, and the upper one is secured to a heavy weight or hammer. This is raised perpendicularly and allowed to drop upon the metal, which is held on the fixed die by the smith, thus forming the forging.
If the work is small and simple, all depressions may be made in a single pair of dies, and the forging can be completed with one hammer and without changing the dies. Work somewhat complicated may require two or more pairs of dies, with various shapes of depressions. The stock is broken down or blocked out by the first pair and then completed by the stamping and finishing dies. Larger pieces may require also a number of pairs of dies, then an equal number of hammers may be used, each fitted with a set of dies. The material is passed from one to the other, and the work completed without changing dies, and possibly without reheating the metal.