Precautions for Using End Face Circular Runout Instead of End Face Perpendicularity:
Using end face circular runout to replace perpendicularity tolerance requirements will reduce the accuracy of end face perpendicularity. Therefore, when a certain accuracy requirement for end face perpendicularity is required, the end face perpendicularity tolerance requirement must be specified simultaneously. The measurement methods for end face circular runout and end face perpendicularity are different. Because measuring end face circular runout error is simpler, especially when measuring the perpendicularity error of shaft shoulders or box-type hole end faces is difficult and inconvenient to implement, end face circular runout can be preferred if the perpendicularity accuracy requirement of the end face to the reference axis is not high.
The functions of end face circular runout and end face perpendicularity are different. Therefore, when selecting, the functional requirements and accuracy level of the part should be analyzed before rationally choosing either positional tolerance. The erroneous designation of using end face circular runout indiscriminately without considering the function of the part's end face should be avoided. For example, the shoulder of a gear shaft that mounts a bearing, the end face of a low-speed rotating shaft of a generally fixed connection part, etc., should use end face circular runout; for the faceplate of a lathe spindle, in order to ensure the performance of the faceplate, the flatness and perpendicularity tolerances of the faceplate end face should be given.