Spline shafts are divided into rectangular spline shafts and involute spline shafts. Rectangular spline shafts in spline shafts are widely used, while involute spline shafts are used for larger loads and require high centering accuracy and larger links. Rectangular spline shafts are usually used in aircraft, automobiles, tractors, machine tool manufacturing, agricultural machinery and general mechanical transmission and other devices. Because the rectangular spline shaft works with multiple teeth, it has high load-bearing capacity, good neutrality and good guiding performance, and its shallow tooth root can reduce the stress concentration. In addition, the strength of the shaft and hub of the spline shaft is weakened, and the processing is more convenient, and higher precision can be obtained by grinding. Involute spline shafts are used for links with larger loads, high centering accuracy requirements, and larger dimensions. Its characteristics: the tooth profile is involute, and there is radial force on the teeth when loaded, which can play a self-centering function, so that each tooth is uniformly stressed, has high strength and long life, the processing technology is the same as that of the gear, and it is easy to obtain higher precision and interchangeability.