精密机械加工是通过机器改变工件尺寸或性能的过程。根据工件的温度状态，将其分为冷加工和热加工。通常在常温下进行机械加工且不会引起工件化学变化的称为冷加工。一般来说，高于或低于正常温度的过程会引起工件化学变化的机械加工称为热加工。冷加工可按不同的机械加工方法进行划分。它用于切削和压力加工。热加工常用于热处理、煅烧、铸造和焊接。
Precision machining is a process of changing the size or performance of workpiece by machine. According to the temperature state of the workpiece, it can be divided into cold processing and hot processing. Cold processing is usually carried out at room temperature without causing chemical changes in the workpiece. Generally speaking, the process above or below normal temperature will cause chemical changes in the workpiece, which is called hot working. Cold processing can be divided into different machining methods. It is used for cutting and pressure processing. Hot working is often used in heat treatment, calcination, casting and welding.