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1、,机电技术专业英语,2,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 headst
2、ock 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 particl
3、es 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.
4、 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
5、 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 Th
6、irteen,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 accom
7、plished 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 reversed with trip dogs. A unique grinder is the centerless grinder of which there are several types: the cylindrical grinders fo
8、r grinding circular external surfaces, internal centerless grinders for grinding internal circular surfaces, and centerless thread grinders. These grinders may be used to grind cylinders, tapers, spheres, threads, and so on.,Lesson Thirteen,Figure B.9 Sketch of a surface grinder,Lesson Thirteen,In a
9、ll case at least three points of contact with the work are employed. The work is supported by a blade, or roller. A regulating wheel which has a higher coefficient of friction than the grinding wheel is the second support point. The grinding wheel is the third support point. This is shown in Figure B.10.,Figure B.10 Sketch of a centerless grinder,Lesson Thirteen,New Words and Expressions,Lesson Thirteen,谢谢观赏,,Thank You !,
