Principles of precision parts processing:
a) The "benchmark first" principle is to process the reference surface first to provide reliable positioning for subsequent processes. For example, the first process of shaft parts is generally to mill the end face and drill the center hole, and then use the center hole to locate and process other surfaces.
b) The principle of "face first, then hole" When there is a larger plane on the part that can be used as a positioning reference, always process the plane first, and then position the machining hole with the plane to ensure the positional accuracy between the hole and the plane. It is relatively stable, easy to clamp, and can avoid deflection caused by drilling on rough surfaces.
c) The principle of "primary first and secondary" first process the main surface (base surface and working surface with higher positional accuracy requirements) and then process the secondary surface (such as keyway, screw hole, fastening hole, etc.). The secondary surface is generally after the primary surface has achieved a certain accuracy, before the final finishing.
d) The principle of "coarse first and then fine" For parts with high precision requirements, proceed in order from coarse to fine, and gradually improve the machining accuracy. This is especially true for parts with poor rigidity.