Pins are usually used for position, can be used to connect or lock parts, and can also be used as overload shear elements in safety devices.

a) Cylindrical pin: Cylindrical pins are mostly used for fixing parts on shafts, transmitting power, or as position elements. Cylindrical pins have different diameter tolerances, which can be used for different matching requirements. The cylindrical pin is generally fixed in the hole by interference, so it is not suitable to disassemble it. See GB119～120, GB878～880, etc.;

b) Taper pin: Taper pin has a taper of 1:50, which is easy to install and can also ensure self-locking. It is generally used as a position element and a connecting element, and is mostly used in places that require frequent disassemble. Internal threaded taper pins and threaded taper pins are used in holes that do not pass through or in holes where it is difficult to punch a pin. The end of the taper pin can be opened after being driven into the hole to prevent the pin itself from slipping out of the hole. See GB117～118, GB881 and GB877 etc.

The pin holes of cylindrical pins and various tapered pins generally need to be reamed. After multiple assembly and disassemble, the positioning accuracy and connection fastening will be reduced, and only a small load can be transmitted. The elastic cylindrical pin itself has elasticity, is installed in the hole to maintain tension. It is not easy to loose, and is convenient to disassemble, also does not affect the matching properties. The pin hole does not need to be hinged. Hole pins and pin shafts are used for hinge joints;

c) Split pin: Split pin is an anti-loosening device for connecting parts. When in use, it is inserted into the pin hole of a nut, bolt with pin hole or other connecting pieces, and then the feet are separated. See GB91.