1. FOR CROSSED SHAFTS
- Sense: same sense (left or right) for the wheel and pinion.
- Size: the helix angle of the pinion is the complement of that of the wheel.
- Shaft rotation: the shaft rotation changes according to the angle of the teeth (see picture).
2. PARALLEL AXES
- Sense: left for the pinion and right for the wheel or reverse.
- Size: same size.
- Shaft rotation: the shaft rotation is opposite.