Involute spline couplings are used to transmit torque from a shaft to a gear hub or other rotating component.
External gear teeth on the shaft engage an equal number of internal teeth in the hub. Because multiple teeth engage
simultaneously, they can transmit much larger torques than a simple key and keyway assembly. However, manufacturing
variations affect the clearance between each pair of mating teeth, resulting in only partial engagement.
In general, bevel gears and curvic couplings are completely different elements. Bevel gears rotate on nonintersecting axis with a ratio based on the number of teeth. Curvic couplings work like a clutch (Fig. 1).