424 APPLIED SCIENCE 



used for turning all cylindrical work, both straight and 

 tapered; for boring and thread-cutting, both internal and 

 external; and for turning spherical work or parts of spheres 

 by means of special devices. Most of the other machines 

 used in the machine-shop have been evolved from the lathe. 

 Machine-shop lathes have been perfected and specialized 

 during recent years, until there are now many forms of this 

 machine. They may be classified into : (1) turning, (2) engine, 

 (3) speed, and (4) turret lathes. 



487. Engine Lathe. An engine lathe (Fig. 198) is the 

 commonest form of this type of machine and is used mostly 

 for turning straight pieces. It is constructed to support a 

 spindle which is free to revolve through the medium of 

 stepped-cone pulleys and belts. The spindle is supported 

 by the head-stock, which is fastened to the bed which rests 

 on legs of convenient height. The work is revolved or driven 

 by centers, face plates, or chucks. The chucks are fastened 

 to the spindle. If the casting or metal requires a support at 

 both ends, the tail-stock with an adjustable center is used and 

 is operated by a hand-wheel. When used for turning, a 

 tee rest is employed to support and assist in guiding the tools. 

 Cylindrical or round work is held between centers, and the 

 tool is gripped in a tool post, which in turn is part of the 

 carriage. The carriage is advanced by means of a screw feed, 

 or through gears driven by means of a feed rod. 



488. Engine, Turret, and Speed Lathes. The engine 

 lathe, described above, is also used for general work, such as 

 turning, boring, facing, reaming, and other machine operations. 



The turret lathe is a special machine device for the manu- 

 facture and rapid production of studs, bolts, screws, collars, 



