Lathes are designated according to their different types. Among these are (1) hand lathes; (2) machine lathes; (3) gap lathes, and (4) turret lathes.
The hand lathe was mentioned with the machinery of the pattern shop. This lathe is frequently made small enough to be mounted on a bench and is called a bench lathe.
The machine lathe, a type contrasted with the hand lathe, cuts metals by a tool fastened on the lathe carriage. A small machine lathe may be driven by foot power and is called a foot lathe. A machine lathe is designated as a screw-cutting lathe when it is equipped with a leading screw and change wheels for cutting threads.
Fig. 173. - Turret of a Turret Lathe.
Many small lathes have no live centers nor tail stocks. A chuck is screwed on the main spindle to hold a rod which is turned to shape as in the screw-cutting machine. This type is called the chucking lathe.
Large machine lathes are built to run at suitable speed for rapid cutting made possible by high-speed steel, and are designated as high-speed lathes, confusing them with small lathes run at high speed.
A very important modification of the machine lathe is the gap lathe. This lathe is built to be of use through a very wide range of ordinary work, and is intended for a shop of limited equipment. It differs from the lathe described in the preceding paragraph by having a gap in the bed just under the end of the main spindle to provide for carrying a very large face plate which holds flat work of large diameter. The lathe bed is very deep and is made in two sections divided horizontally. The upper section, which carries the carriage and the tail stock, may be slid along the lower part of the bed to open the gap under the edge of the face plate.
The feature of the turret or monitor lathe is shown in Fig. 173. The tail stock is displaced by a turret T which carries several tools which are used in consecutive order on the piece of work held in the chuck C. The turret is mounted on a vertical spindle on the slide S. This slide is moved to carry the tools into contact with or away from the work by the long hand-bars. This lathe saves much time in changing tools.