What are Splines?
Splines are ridges or teeth type keys that are made integral with the shaft that mesh with grooves in a mating hub to transfer torque. For example, a bevel gear mounted on a shaft might use a male shaft spline that matches the female spline on the gear as shown in figure 1.

It’s used when there is a need for axial movement or the torque transmitted is too high for keyed joint.
