基准是位置误差检测的基本依据,图样上位置公差要求中给出的基准都是理想要素,而实际加工后的零件上的实际基准要素不可避免地存在形状误差,在位置误差检测时,不能直接作为基准使用。因此,要根据实际基准要素建立基准,并在检测时采取正确方法体现。一、基准要素及其分类零件上用来确定被测要素的方向或位置的要素,称做基准要素,在图样上都用基准符号标注出来。基 Benchmarks are the basic basis for position error detection. The references given in the position tolerance requirements on the drawings are all ideal elements. However, the actual reference elements on the actual machined parts inevitably have shape errors. In the case of position error detection, they can not be directly Used as a benchmark. Therefore, based on the actual benchmark elements to establish the benchmark, and take the correct method of detection. First, the reference elements and their classification Parts used to determine the direction of the measured element or position of the elements, called the reference elements, are marked on the pattern with reference symbols. base