The lathe is undoubtedly the oldest form of machine tool. Its prototype is the drilling machine. Each of these machine tools probably developed from that earliest example of mechanical rotary motion of which we have a record, the "potters' wheel".
Fig. 87. Typical Speed Lathe for Hand Turning.
This term includes that line of lathes illustrated in Fig. 87, which shows a typical design. These machines are sold in the open market in a variety of sizes from the smaller jewelers' lathe to those having a swing of 12 inches. All types and all sizes are designed to be used with hand-controlled cutting tools, and are often designated as hand lathes. If desired, they can be driven by foot power and are then often termed foot lathes.
In turning brass and composition the tools cut by a scraping action, and are almost always held at or below the center. The three tools shown in Fig. 88, called the planisher, graver, and round nose, are typical of all the tools necessary for turning brass, etc. The manner of holding these tools in -connection with the T-rest is illustrated by the planisher in Fig. 89. Fig. 90 shows another view of the T-rest. Typical hand tools for cutting iron and steel are the diamond point or graver and the round nose, shown in Fig. 91. They are used differently from hand tools for brass, in that the cutting edge is carried above the center, and the metal is removed by cutting instead of scraping.
Fig. 88A. Planisher.
Fig. 88B. Graver.
Fig. 88C. Round Nose Fig. 88. Cutting Tools for Hand Turning.
The graver frequently takes the place of the planisher, for it can be used as shown in Fig. 92, either on the outside or on the end of a piece of work. The graver can be used on brass for a great variety of operations; but its use, except in the hands of an expert workman, is attended by the danger of catching in the soft metal and thus breaking the tool or spoiling the work.
Fig. 89. Hand Tool Rest with Tool in Position.
Fig. 90. Simple Hand Tool Rest.
Fig. 91. Typical Hand Tools for Steel Turning.