Fixtures are also called fixtures, which are usually composed of positioning elements, clamping devices, tool setting guide elements, indexing devices, connecting elements, and clamping bodies. 1. According to the scope of application of the fixtures (1) General fixtures: General fixtures are fixtures with standardized structures and a larger range of applications, such as three-jaw chucks and four-jaw chucks for lathes, flat-nose pliers for milling machines, and Indexing first class.　　 (2) Special machine tool fixture: Special machine tool fixture is a fixture specially designed and manufactured for a certain process of a certain workpiece. The special machine tool fixture is suitable for applications where the product is relatively stable and the output is large.　　(3) Modular fixture: Modular fixture is a fixture assembled with a set of pre-manufactured standard components and parts. The structure of the modular fixture is flexible and changeable, the design and assembly cycle is short, and the fixture parts can be reused for a long time. It is suitable for applications in a variety of single-piece small batch production or new product trial production. (4) Group fixtures: Group fixtures are fixtures designed and manufactured for each part group when group processing is used. When changing and processing another part of the same group, only the individual components on the fixture need to be adjusted or replaced , Can be processed. It is suitable for application in multi-variety, medium and small batch production. (5) Accompanying fixture: It is a mobile fixture used on the automatic line. Before the workpiece enters the automatic line processing, the workpiece is installed in the fixture, and then the fixture and the processed work piece are moved from one work position to the next along the automatic line. In the next station, the workpiece will not be removed from the fixture until the workpiece exits the automatic line processing. The accompanying fixture is a fixture that always moves along an automatic line with the workpiece.　　2. According to the type of machine tool used, 　　 Different machine types have different fixture structures. The fixtures can be divided into lathe fixtures, drilling fixture fixtures, milling machine fixtures, boring machine fixtures, grinding machine fixtures and modular machine tool fixtures.　　3. According to the clamping power source of the fixture, according to the clamping power source of the fixture, the fixture can be divided into manual clamping fixture, pneumatic clamping fixture, hydraulic clamping fixture, pneumatic and hydraulic clamping fixture, electromagnetic fixture, vacuum fixture, etc.