1. In order to ensure the precision of precision machining. A large number of workpieces are subjected to cutting force, clamping force, and heat generation, so rough machining and finishing should be carried out separately. Due to rough machining. It is easy to cause surface hardening, and there is a large internal stress inside the workpiece. If the finishing and roughing are continuous finishing, the precision of the precision parts will be redistributed with the stress and will soon be lost. For some parts with high machining accuracy. Low temperature annealing or aging treatment should be carried out after rough machining and before finishing to eliminate internal stress. Precision machining

     2. The main process of roughing is to cut off most of the machining allowance, and the roughing machine only needs high-power and low-precision processing. Finishing requires more precise machine tools. Rough and fine machining are performed on different machine tools, and higher machining accuracy is not required. therefore. It can not only give full play to the performance of the equipment, but also prolong the service life of precision machine tools.

     3. Heat treatment is often required during machining. The arrangement of the heat treatment process is as follows: in order to improve the cutting performance of the metal. It is usually done before machining. In order to eliminate internal stress, such as annealing, normalizing, quenching and tempering, etc. Such as aging treatment and quenching and tempering treatment, etc., generally after rough machining, before finishing. In order to improve the mechanical properties of the parts, carburizing, quenching, tempering, etc., are generally carried out after mechanical processing. If there is deformation after heat treatment, the final processing procedure must be arranged.