The cylindrical pin has a simple structure and is easy to achieve high precision during manufacture, so it is mainly used as a positioning pin to prevent the relative offset of the connected parts. It is used for positioning between parts, usually not subject to load or bearing a small load, the number is generally not less than two, and they are distributed in the symmetrical direction of the overall structure of the connected parts. The farther the two positioning pins are, the better the positioning effect. the better. The pin is fixed on the connected parts by interference and should not be disassembled many times, otherwise the fixation and accuracy of the connection will be damaged.