The rapid development of machining, now is the basic industry of the national economy, but also the economy of the equipment industry, are responsible for the various departments of the national economy, the industry to provide technical equipment and production tools tasks.
 Machining is a process of using the machinery of the dimensions of the workpiece or performance changes. Is in accordance with the workpiece temperature state, divided into cold and hot processing.
Generally above or below the normal temperature processing, can cause chemical or phase change material of the workpiece, said thermal processing. Cold processing method according to the differences can be divided into cutting and pressure processing. Thermal processing common with heat treatment, forging, casting and welding.
 Another often use cold processing assembly.For example: the bearing inner ring in the assembly tend to make it into liquid nitrogen cooled dimensional shrinkage, heated to the appropriate size of enlarged outer ring, and then fitted together. Train wheels outer heating method is also used to cover the substrate binding to ensure its robustness during cooling (this method still applies now turn with certain parts of the process).