精密机械加工是一种用加工机械对工件的外形尺寸或性能进行改变的过程。按被加工的工件处于的温度状态﹐分为冷加工和热加工。一般在常温下加工,并且不引起工件的化学或物相变化﹐称冷加工。一般在高于或低于常温状态的加工﹐会引起工件的化学或物相变化﹐称热加工。冷加工按加工方式的差别可分为切削加工和压力加工。热加工常见有热处理﹐锻造﹐铸造和焊接。
Precision machining is a process of changing the size or performance of a workpiece by means of a processing machine. According to the temperature state of the workpiece being processed, it can be divided into cold processing and hot processing. It is generally processed at room temperature and does not cause chemical or physical changes of the workpiece. It is called cold processing. Generally, processing at or below normal temperature will cause chemical or physical changes of the workpiece, which is called thermal processing. Cold processing can be divided into cutting and pressure processing according to the difference of processing methods. Heat treatment, forging, casting and welding are common in hot working.