The spline shaft is a kind of mechanical transmission, and the flat key, half-circle key, and oblique key function the same, all of which transmit mechanical torque.There is a longitudinal keyway on the outer surface of the shaft, and the rotating part sleeved on the shaft also has a corresponding keyway, which can keep synchronous rotation with the shaft.and while rotating, some can also slide longitudinally on the shaft, such as gearbox shift gears.