波胆历史 的零件都是由若干表面组成，各表面之间有一定的尺寸和相互位置要求。零件表面间的相对位置要求包括两方面：表面间的距离尺寸精度和相对位置精度（如同轴度、平行度、垂直度和圆跳动等）要求。研究零件表面间的相对位置关系离不开基准，不明确基准就无法确定零件表面的位置。基准就其一般意义来讲，就是零件上用以确定其他点、线、面的位置所依据的点、线、面。基准按其作用不同，可分为设计基准和工艺基准两大类。
1、设计基准
在零件图上用以确定其他点、线、面的基准，称为设计基准，就活塞来说，设计基准指活塞中心线和销孔中心线。
2、工艺基准
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，又分为定位基准、测量基准和装配基准。
The parts processed by Dalian Machinery are composed of several surfaces, with certain dimensions and mutual positioning requirements between each surface. The requirements for the relative position between the surfaces of parts include two aspects: the accuracy of distance dimensions between surfaces and the accuracy of relative position (such as coaxiality, parallelism, perpendicularity, and circular runout). The study of the relative positional relationship between the surfaces of parts cannot be separated from a reference, and without a clear reference, the position of the part surface cannot be determined. In its general sense, a benchmark refers to the points, lines, and surfaces used on a component to determine the position of other points, lines, and surfaces. Benchmarks can be divided into two categories based on their different functions: design benchmarks and process benchmarks.
1. Design Basis
The reference used on the part drawing to determine other points, lines, and surfaces is called the design reference. For pistons, the design reference refers to the centerline of the piston and the centerline of the pin hole.
2. Process benchmark
The reference used in the processing and assembly of parts is called the process reference. Process standards are divided into positioning standards, measurement standards, and assembly standards according to different purposes.
