机械外文翻译--车床与磨削（适用于外文翻译+中英文对照）（毕业学术论文设计）.docVIP

LATHES AND GRINDING Lathes are machine tools designed primarily to do turning, facing and boring. Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathe also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the workpiece. The accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool. Lathes in various forms have existed for more than two thousand years. Modern lathes date form about 1797, when Henry Maudsley developed one with a leadscrew. It provided controlled, mechanical feed of the tool. This ingenious Englishman also developed a change-gear system that could connect the motion of the spindle and leadscrew and thus enable threads to be cut. Lathe Construction. The essential components of a lathe are the bed, headstock assembly, tailstock assembly, carriage assembly, quick-change gear box, and the leadscrew and feed rod. The bed is the backbone of a lathe. It usually is made of well-normalized or aged gray or nodular cast iron and provides a heavy, rigid frame on which all the other basic components are mounted. Two sets of parallel, longitudinal way, 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 in one or both sets. Because several other components are mounted and/or move on the ways they must be made with precision to accuracy of alignment. Similarly, proper precaution should be taken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion. The headstock is mounted in a fixed position on the inner ways at one end of the lathe bed. It provides a powered means of