A fastener is a general term for a type of mechanical part used to fasten two or more parts (or components) into one piece. In automotive products, the number of fasteners is large and varied. In practical use, it is simply referred to as standard parts, which include bolts, studs, screws, washers, retaining rings, pins, rivets, welding studs and assemblies and connecting pairs. The surface treatment methods of fasteners include metal plating (such as galvanizing, tin, nickel, chromium, etc.), conversion film technology (such as phosphating and oxidation) and cathodic electrophoretic coating. Different surface treatment methods affect fasteners. Appearance, rust prevention, electrical conductivity, friction properties, etc.
The selection of fasteners is subject to certain strategies to ensure assembly quality, reduce design defects and save labor costs.
Fastener selection principle
(1) Matching relationship between bolt and nut: The bolt is higher than the nut.
(a) Class 8.8 bolts with grade 6-8 nuts; (b) Class 10.9 bolts with grade 8-10 nuts.
(2) Selection of fastener length.
(a) Bolt/nut/screw length specifications are generally 5 times uniform; (b) The length of fasteners for the same type of parts of different models is recommended.
(3) The dimensions of the heads of the fasteners are uniform. It is recommended to unify the head-to-edge dimensions of the same type of parts fasteners for different models; it can reduce the number of working hours for employees to replace the fastening sleeves.