数控技术应用专业英语教学课件作者刘小芹2.Lathe课件幻灯片.ppt

 English on Mechanical Engineering Lesson 2 Lathes Text The basic machines that are designed primarily to do turning, facing and boring are called lathe. In turning the workpiece, a cutter moves in the direction parallel to the axis of rotation of the workpiece or at the angle to the axis, cutting off the metal from the surface of the workpiece. The bed is the backbone of a lathe. Two sets of parallel, longitudinal ways, inner and outer, are contains 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. 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 rotating the work at various speeds. It consists, essentially, of a hollow spindle, mounted in accurate bearings, and a set of transmission gears though which the spindle can be rotated at a number of speed. Most lathes provide from eight to eighteen speeds, usually in a 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. The inner end of the spindle protrudes from the gear-box and contains a means for mounting various types of chucks, face plates, and dog plates on it. Text The tailstock assembly consists, essentially, of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location. An upper casting fits on the lower one and can be moved transversely upon it on some type of keyed ways. This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapers. The third major component of the assembly is the tailstock quill. Text This is ho