,机电技术专业英语,2,Lesson Fourteen,Text,Lathe Processing and Acuracies There are many issues that can affect the process,such as parallel faces,surface roughness,warping of circle and offset of the center. In the following,we consider the accuracies in lathe process. Making of High Surface Roughness In the lathe process,we often need to achieve a high surface finish. In such cases,the basic principles of the process are： the rotating speed should be set high and the sending speed should be set low. Because when the sending speed is too high,the edge of the cutting tool leave scars on the material(Figure B.11).,Making Accurate Parts,Lesson Fourteen,Figure B.11 Sending speed and surface roughness,Lesson Fourteen,Rechucking and Offset When a mechanical part is required to not have an offset of the center,we should not rechuck the material. In other words,the material must not remove from the chuck until finishing of the cutting. The rechucking brings the offset of the material. We should determine the correct procedure,which should not require the part to be rechucked,or should consider using a jig.(Figure B.12),Figure B.12 Rechucking and offset,Lesson Fourteen,In the case of the cutting for a long and slender part,we should use a tail stock as shown in Figure B.13. The tail stock is inserted into a hole drilled into the center of the piece. Generally the hole is drilled using a special drill,called a center drill. However,when the diameter of the piece is too small,we often cant use the tail stock,because it comes into contact with the cutting tool. In such cases,the cutting material has a taper as shown in Figure B.14 The material does not have enough rigidity to withstand the cutting process. In order to remove the taper,the cutting depth should be set to small cuts,and we repeat the cut with the same position of the tool. Also it is important to measure the diameters in detail.,Lesson Fourteen,Figure B.13 Using of tail stock,Figure B.14 Processing of shallow shaft,Lesson Fourteen,New Words and Expressions,Lesson Fourteen,谢谢观赏,www.sciencep.com,Thank You !,