Spline shaft rectangle spline shaft and involute spline shaft of the two types of spline shaft in rectangle spline shaft used widely, and involute spline shaft for larger load centering precision requirement is high, and size larger connection. Rectangular spline shaft is usually used in aircraft, automobile, tractor, machine tool manufacturing, agricultural machinery and general machinery transmission and other devices. Due to the rectangular spline shaft multi tooth, so the high carrying capacity, to neutral, oriented sex good, and characteristics of shallow root can make the stress concentration. The spline shaft shaft and hub strength weakened, more convenient processing, high precision grinding method can be used. Involute spline shaft for large loads, the centering accuracy requirement is high, and the large size of the connection. Its characteristics: tooth profile of involute. When the load on the tooth with radial force, can play the role of automatic centering, the tooth stress is uniform, high strength, long life, the same processing technology and gear, easy to get higher accuracy and interchangeability.