Precision machining belongs to the finishing of mechanical processing, according to the temperature state of the workpiece being processed, divided into cold processing and hot processing. Generally processed at room temperature, and does not cause chemical or phase changes of the workpiece, called cold processing. Generally in higher or lower than normal temperature state of processing, will cause the chemical or phase changes of the workpiece, called hot processing. Cold processing can be divided into cutting and pressure processing according to the difference of processing methods. Hot processing commonly includes heat treatment, calcination, casting and welding. The machining accuracy of precision machining is generally 10~0.1μm, the tolerance grade is above IT5, and the surface roughness Ra is below 0.1μm. Precision machining technology can improve the machining accuracy and surface quality of workpiece. Tooling and fixture usually require high machining accuracy of metal products, precision machining and even ultra-precision machining workpiece can meet the requirements of product matching.