A worm is used to reduce speed. For each complete turn of the worm
shaft the gear shaft advances only one tooth of the gear.
In this case, with a twelve tooth gear, the speed is reduced by
a factor of twelve. Also, the axis of rotation is turned by 90
degrees.
Unlike ordinary gears, the motion is not reversible, a worm can
drive a gear to reduce speed but a gear cannot drive a worm to
increase it.
As the speed is reduced the power to the drive increases correspondingly.
Worm gears are a compact, efficient means of substantially decreasing
speed and increasing power. Ideal for use with small electric motors.
