This part of GB/T 889 specifies the type, size, technical conditions and marks of hexagonal lock nuts with fine thread type 1 non-metallic inserts. This part applies to type 1 non-metallic insert hexagon lock nuts with nominal thread diameter D = 8 mm ~ 36 mm, fine thread, property classes 6, 8 and 10, product classes A and B . Grade A is used for nuts with D≤16 mm; Grade B is used for nuts with D>16 mm.