Worm and worm gears are used to connect two shafts which are at right angles to each other. A higher speed reduction can be obtained by using the worm and worm gear. A worm gear can be single, double or triple start.
Terminology of worm gears:
Axial pitch: It is the distance measured along the direction of axis. It is the distance between the corresponding points of two adjacent teeth.
Lead: Distance moved by the helix along the axis for one rotation of gear.
Lead angle: Angle at which the teeth are inclined to the normal to the axis.