1、 Selection principle of varieties

d) Screws for special purposes: such as set screws, non-release screws and eyebolts, see GB72, GB828-829, GB837-839, GB948-949 and GB825.

④ Stud

a) Unequal-length double-head studs: applicable to occasions where one end is screwed into the body of the component for connection or fastening, see GB897-900;

b) Equal-length double-head studs: suitable for both ends matching with nuts for connection or spacing. See GB901, GB953, etc.

⑤ Wood screws are divided into many varieties due to different head types and groove shapes. The head types include round head, countersunk head and semi-countersunk head. The head groove types are slotted (slotted) and cross groove, see GB99 ～ 101 and GB950 ～ 952.

⑥ Self-tapping screw

a) Ordinary self-tapping screw: the thread conforms to GB5280, with large pitch, suitable for use on thin steel plate or copper, aluminum and plastic, see GB845-847, GB5282-5284, etc;

b) Self-tapping locking screw: the thread conforms to the common metric coarse thread, which is suitable for use in places where vibration resistance is required, see GB6560 ～ 6564