This standard specifies hexagonal flange nuts without chamfers with thread specifications M5~M20, performance grades 8, 9, 10, 12 and A2-70, and product grades A and B. Grade A is used for D≤16mm; Grade B is used for nuts with D>16mm. For the inspection of hexagon and flange, see Appendix A (standard appendix). If other technical requirements are required, they should be selected from current standards (such as GB/T 196, GB/T 3098.2 and GB/T 3103.1).