Screw Rod and Nut

The bolt head of the screw rod and nut is generally hexagonal, with external threads on the shank. Screws are small-sized, featuring flat heads, cross heads, etc., and also have external threads on the shank. A stud should actually be called a "stud bolt," with external threads at both ends and a generally smooth shank. The longer threaded end is used for connecting to deep holes, and the shorter one is connected to a nut. Standard fasteners are divided into twelve categories in total, and their selection is determined according to the application occasions and performance requirements of the fasteners.

Screw rods and nuts are widely used in detachable connections in mechanical manufacturing, usually used in conjunction with nuts (generally plus one or two washers). General-purpose nuts come in various types, such as hexagon nuts and square nuts. Hexagon nuts are widely used with hexagon bolts and are classified into product grades like Grade A, B, and C according to manufacturing precision and product quality. Thin hexagon nuts are used as secondary nuts in anti-loosening devices to play a locking role, or in places where the threaded connection pair mainly bears shear force.

Screw rods and nuts are mostly used in connections that require frequent disassembly. Square nuts are used with square-head bolts; wrenches can grip them tightly without slipping, so they are often used in rough and simple structures (see GB41, GB6170～6177, etc.). Slotted nuts mainly refer to slotted hexagon nuts, which have slots processed on the top of hexagon nuts. They are used in conjunction with bolts with holes on the shank and cotter pins to prevent relative rotation between bolts and nuts (see GB6178～6181, etc.). Lock nuts refer to nuts with locking functions, including hexagon lock nuts with nylon inserts and all-metal hexagon lock nuts, etc.