Axle parts are one of the typical parts often encountered in hardware fittings. It is mainly used to support transmission parts, transmit torque and bear load. According to different types of shaft parts, it can be generally divided into optical axis, stepped axis and special shape. Axis three types; or divided into solid shaft, hollow shaft and so on. They are used in machines to support gears, pulleys, and other transmission parts to transmit torque or movement. Shaft parts are rotating parts, whose length is greater than the diameter, generally consisting of the outer cylindrical surface, conical surface, inner bore and threads of the concentric shaft and the corresponding end face. According to different structural shapes, shaft parts can be divided into optical axis, stepped shaft, hollow shaft and crankshaft, etc.