A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten multiple parts together. The two partners are kept together by a combination of their threads' friction (with slight elastic deformation), a slight stretching of the bolt, and compression of the parts to be held together.

a)Normal Nuts: There are various types, such as hex nuts and square nuts. Hex nuts are most commonly used in conjunction with hexagon bolts, and are classified into A, B, C grades according to manufacturing accuracy and product quality. Hex thin nuts are used as auxiliary nuts in the anti-loosening device to lock, or where the threaded connection pair is mainly subjected to shearing force. Hex thick nuts are mostly used in connections that are often disassembled. Square nuts are matched with square head bolts, and the wrench is not easy to slip when jammed. It is mostly used for rough and simple structures.See GB41, GB6170～6177, etc.;

b)Slotted nut: Mainly refers to the hexagonal slotted nut, that is, a slot is machined on the hexagonal nut. It is used in conjunction with screw bolts with holes and split pins to prevent relative rotation of bolts and nuts, see GB6178～6181, etc.;

c)Lock nut: Refers to the nut with locking function, including nylon insert hexagon lock nut and all-metal hexagon lock nut. The hexagon nylon insert lock nut has a very reliable anti-loosening ability. It has the advantages of not damaging the bolts and connected parts and being able to be frequently installed and unloaded under the operating temperature of -60～+100℃ and certain medium conditions. See GB889, GB6182～6187, etc.;

d)Special purpose nuts: Such as wing nuts, cap nuts, knurled nuts. Wing nuts can generally be disassembled and assembled without tools, and are usually used in places that need to be disassembled frequently and are not stressed. Cap nuts are used where end screws need to be covered. See GB62, GB63, GB802, GB923, GB806, GB807, GB809, etc.