Precision machining is a process of changing the overall dimension or performance of the workpiece with machining machinery. According to the temperature state of the workpiece to be processed, it is divided into cold processing and hot processing. Dalian precision machining is generally processed at room temperature and does not cause chemical or phase changes of the workpiece, which is called cold machining. Generally, processing above or below normal temperature will cause chemical or phase changes of the workpiece, which is called hot processing. Cold working can be divided into cutting and pressure machining according to the difference of machining methods. Hot working commonly includes heat treatment, forging, casting and welding.

Precision machining mainly includes fine turning, fine boring, fine milling, fine grinding and grinding.

① Fine turning and fine boring: most precision light alloy (aluminum or magnesium alloy, etc.) parts of aircraft are processed by this method. Generally, natural single crystal diamond tools are used, and the arc radius of the blade is less than 0.1 micron. Machining on a high-precision lathe can obtain an accuracy of 1 micron and a surface roughness with an average height difference of less than 0.2 micron, and the coordinate accuracy can reach ± 2 micron.

② Finish milling: used to process aluminum or beryllium alloy structural parts with complex shapes. High mutual position accuracy is obtained by relying on the accuracy of guide rail and spindle of machine tool. Accurate mirror surface can be obtained by high-speed milling with carefully ground diamond cutter head.

③ Finish grinding: used for machining shaft or hole parts. Most of these parts are made of hardened steel with high hardness. Most high precision grinding machine spindles use hydrostatic or hydrodynamic liquid bearings to ensure high stability. The limit accuracy of grinding is not only affected by the stiffness of machine tool spindle and bed, but also related to the selection and balance of grinding wheel and the machining accuracy of workpiece center hole. The dimensional accuracy of 1 micron and out of roundness of 0.5 micron can be obtained by fine grinding.

④ Grinding: select and process the irregular convex parts on the machined surface by using the principle of mutual grinding of mating parts. Abrasive diameter, cutting force and cutting heat can be accurately controlled, so it is the machining method to obtain the highest precision in precision machining technology. The hydraulic or pneumatic mating parts in the precision servo components of aircraft and the bearing parts of dynamic pressure gyro motor are processed by this method to achieve the accuracy of 0.1 or even 0.01 micron and the micro unevenness of 0.005 micron.