The main surface of shaft parts is the outer cylindrical surface, and may also include conical surfaces, threads, keyways and other structures. In the mechanical transmission system, shaft parts play an important role in transmitting torque and supporting rotating parts, so there are high requirements for their accuracy, surface quality and mechanical properties.
For example, in the spindle of a machine tool, it requires a high-precision cylindrical surface to ensure the precise rotation of the tool or workpiece, and its radial runout and axial runout tolerance requirements are very strict. At the same time, in order to be able to effectively connect with other parts (such as gears, pulleys, etc.) and transmit power, there will be keyways, threads and other structures on the shaft, and the dimensional accuracy and position accuracy of these structures are also critical.