According to the different shape of the axis, the shaft can be divided into crankshaft and straight shaft. According to the bearing capacity of the shaft, it can be divided into:
① rotating shaft, which bears both bending moment and torque when working, is the most common shaft in machinery, such as the shaft in various reducer.
② Spindles are used to support rotating parts and only bear bending moment without transmitting torque. Some spindles rotate, such as those of railway vehicles, while others do not, such as those supporting pulleys.
③ Transmission shaft is mainly used to transfer torque without bearing bending moment, such as long smooth shaft in crane moving mechanism, driving shaft of automobile, etc.