This part stipulates that the thread specifications are M1.6~M64, and the performance grades are 8.8, 10.9, 12.9, A2-50, A2-70, A3-50, A3-70, A4-50, A4-70, A5-50, A5-70, CU2 and CU3, hexagon socket head cap screws of product grade A. See Appendix A for the reference quality of screws. If other technical requirements are required, they should be selected from current standards (such as GB\T 196, GB\T 3106, GB\T 3098.1, GB\T 3098.6, GB\T 3098.10 and GB\T 3103.1).