机械工程专业英语第四课文及阅读材料

Lesson 5 lathe, shaper, grinding and milling machine 1, lathes and lathe operations Lathes are generally considered to be the oldest machine tools . although woodworking lathes were originally developed during the period 1000-1 B.C., metalworking lathes with lead screws were not built until the late 1700s .the most common lathe (figure 2.1) was originally called engine lathe because it was powered with overhead pulleys and belts from nearby engines . today these lathes are set up with individual electric motors. 1) Lathe components Lathes are equipped with a variety of components and accessories . the basic components of a common lathe are described below. i) Bed The bed supports all major components of the lathe. Beds have a large mass and are rigidly built ,usually from gray or nodular cast iron . the top portion of the bed has two ways , with various cross-sections ,that are hardened and machined for wear resistance and dimensional accuracy during use . ii) Carriage The carriage ,or carriage assembly ,slides along the ways and consists of an assembly of the cross-slide , tool post ,and apron .the cutting tool is mounted on the tool post ,usually with a compound rest that swivels for tool positioning and adjustment . the cross-slide moves radially in and out ,controlling the radial position of the cutting tool in operations such as facing. The apron is equipped with mechanisms for both manual and mechanized movement of the carriage and the cross-slide by means of the lead screw . iii) Headstock The headstock is fixed to the bed and is equipped with motors , pulleys , and V-belts that supply power to the spindle at various rotational speeds . the speeds can be set through manually...