零件在加工和装配过程中所使用的基准，称为工艺基准。工艺基准按用途不同又分为装配基准、测量基准及定位基准。
Parts in the processing and assembly process used in the benchmark, known as the process benchmark. According to different uses, process datum can be divided into assembly datum, measuring datum and locating datum.
（1）装配基准 装配时用以确定零件在部件或产品中的位置的基准，称为装配基准。
(1) Assembly datum the datum used to determine the position of parts in parts or products is called assembly datum.
（2）测量基准 用以检验已加工表面的尺寸及位置的基准，称为测量基准。如图32-2中的零件，内孔轴线是检验外圆径向跳动的测量基准；表面A是检验长度L尺寸l和的测量基准。
(2) Measuring datum is the datum used to check the size and position of machined surface, which is called measuring datum. As shown in Fig. 32-2, the inner hole axis is the measuring datum for inspecting the radial runout of the outer circle; the surface a is the measuring datum for inspecting the length L, dimension L and.
（3）定位基准 加工时工件定位所用的基准，称为定位基准。作为定位基准的表面（或线、点），在第一道工序中只能选择未加工的毛坯表面，这种定位表面称粗基准.在以后的各个工序中就可采用已加工表面作为定位基准，这种定位表面称精基准。
(3) Positioning datum the datum used for workpiece positioning in machining is called positioning datum. For the surface (or line, point) as positioning reference, only the rough surface can be selected in the first working procedure. This positioning surface is called rough datum. The machined surface can be used as the positioning datum in the following processes, and the positioning surface is called the precise datum.