This part of GB/T 6187 specifies the type, size, technical conditions and marks of type 2 all-metal hexagon flange lock nuts with fine threads. This part applies to Type 2 all-metal hexagonal flange face locking with nominal thread diameter D = 8 mm to 20 mm, fine thread, property classes 6, 8 and 10, and product classes A and B nuts. Grade A is used for D≤16 mm; Grade B is used for nuts with D>16 mm.