Worm screws, worm wheels

In machine and tool construction, a worm screw is a shaft with one or more spiral(s) cut into it. When combined with a worm wheel, they form a worm drive. The axes of the worm screw and the worm wheel intersect at 90°. Worm drives are ideal for translating large ratios into a slow speed. The worm screw is normally the driving element. Very high ratio's from very slow to 100:1 can be realised with a worm drive with just one stage. Self-locking is possible depending on the ratio used.