机电技术专业英语 教学课件 作者 徐起贺 张庆良pata b lesson Thirteen.pptVIP

* 机电技术专业英语 Lesson Thirteen Text There are many types of grinding machines. The two most widely used are the cylindrical and surface grinders. Other grinding operation include those using vertical spindles, internal and centerless grinders, and jigs. The cylindrical grinder is equipped with a headstock and tailstock between which the work is mounted and rotated as a grinding wheel in contact with the work removes metal from its circumference (Figure B.8). The operation is somewhat similar to that of a lathe. The grinding wheel replaces the tool bit, and the thousands of little abrasive particles in it may be thought of as little tool bits. They in fact produce little chips during the cutting operation. Grinding Machines Lesson Thirteen Figure B.8 Sketch of a cylindrical grinder Lesson Thirteen The headstock center may or may not revolve with the work. The tailstock center is always dead. Operating a cylindrical grinder with both centers dead eliminates any possible eccentricity which may result from the live center runout. Precision grinding is done between two dead centers. Feeding the grinding wheel into the work may be done automatically or by hand in increments as low as 0.0001 in. per pass. The range of infeed of the wheel into the work is from about 0.002 in. per pass for roughing to about 0.0005 in. for finishing. Hydraulically controlled infeed grinders are also available with mechanisms for automatic table retraction when the grinding operation is complete. Lesson Thirteen The surface grinder is used for grinding flat surfaces(Figure B.9(a)). The table mounts a magnetic chuck used for holding the work during the grinding operation. The table oscillates under the wheel, as shown in Figure B.9(b). With each pass the table feeds transversely. This feed may be accomplished automatically or by hand. The automatic control may by with hydraulic power or a mechanical indexing mechanism. As the table moves longitudinally the direction is reve