英文材料 Lathe and Turning The Lathe and Its Construction A lathe isa machine tool used primarily for producing surfaces of revolution flat edges. Based on their purpose ,construction , number of tools that can simultaneously be mounted , and degree of automation ,lathes or, more accurately, lathe-type machine tools can be classified as follow s: (1) Engine lathes (2) Toolroom lathes (3) Turret lathes (4) Vertical turning and boring mills (5) Automatic lathes (6) Special-purpose lathes In spite of that diversity of lathe-type machine tools, they all have all mon features with respect to construction and principle of operation .These features can best be illustrated by considering monly used representative type, the engine lathe. Following isa description of each of the main elements of an engine lathe , which is shown in . Lathe bed . The lathe bed is the main frame , involving a horizontal beam on two vertical supporis. It is usually made of grey or nodular cast iron to damp vibrations and is made by casting . It has guideways to allow the carriage to slide easily lengthwise. The height of the lathe bed should be appropriate to enable the technician todo his or her jib easily fortably. Headstock. The headstock is fixed at the left hand side of the lathe bed and includes the spindle whose axis is parallel to the guideways (the silde surface of the bed) . The spindle is driven through the gearbox , which is housed within the headstock. The function of the gearbox is to provide a number of different spindle speeds (usually 6up to18 speeds) . Some modern lathes have headstocks with infinitely variable spindle speeds, which employ frictional , electrical ,or hydraulic drives. The spindle is always hollow , ,it has a through hole extending lengthwise. Bar stocks can be fed througth that hole if continous production is adopted .A lso , that hole has a tapered surface to allow mounting a plain lathe center . The outer surface of the spindle is 2 threaded to allow mo
