文档介绍：英文原文 1 Lathe s Lathes are machine tools designed primarily todo turning, facing and boring, Very little turning isdone on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations tobedone with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool. The ponents ofa lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod. The bed is the backbone ofa lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other ponents are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way inone or both sets, They are precision-machined to assure accuracy of alignment. On most modern lathes the way are surface-hardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways are not damaged. Any uracy in them usually means that the accuracy of the entire lathe is destroyed. The headstock is mounted ina foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists ofa hollow spindle, mounted in accurate bearings, and a set of transmission gears-similar toa truck transmission — through which the spindle can be rotated ata number of speeds. Most lathes provide from 8 to18 speeds, usually ina geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy ofa lathe is greatly dependent on the spindle, it