图示工件中2—φ40h7、2—φ30h7的尺寸精度及形位公差较高,因此加工工艺上须安排磨削工序。而工件两端设计和使用均不能保留中心孔,所以在工艺安排中,工件的两端留有工艺料头并加工出B_3中心孔(磨削用)。当磨削加工完毕,应在卧式车床上用中心架支承φ40h7的外国加工M20×1—6H螺纹。但由于φ40h7的表面粗糙度值要求低,中心架支承过程中必然会破坏表面质量。在此情况下,我用轴承7308套在 2-φ40h7,2-φ30h7 workpiece shown in the dimensional accuracy and high form tolerance, so the process must be arranged grinding process. Both ends of the workpiece design and use of the center hole can not be retained, so in the process of arrangement, left ends of the workpiece material and process the B_3 center hole (grinding). When the grinding is completed, should be horizontal lathe with the center frame support φ40h7 foreign processing M20 × 1-6H thread. However, due to the low surface roughness of φ40h7 value, the center frame is bound to undermine the process of supporting the surface quality. In this case, I set the bearing 7308