Precision machining refers to high accuracy and surface smoothness which includes milling, turning etc. The tolerance can meet ±0.02mm for some metal parts. Precision machining relies on high-precision, rigid machine tools and finely ground tools. The process of cutting off an extremely thin layer of metal on the surface of the work piece with high cutting speed, small depth of cut and feed. Since the residual area during the cutting process is small and the adverse effects of cutting force, cutting heat and vibration are eliminated to the greatest extent, the surface deterioration layer left by the previous process can be effectively removed, and there is basically no residual tension on the surface after processing. The stress and roughness are also greatly reduced, which greatly improves the quality of the machined surface.