Best choice of gearing when high drive reduction is required. Worm Wheels resemble spur gears with the addition of a throat cut into the O.D. of wheel. The throat permits the worm wheel to fully envelope the threads of the worm. Threads, not teeth are cut on the worm, and by adjusting the number of threads, different ratios can be achieved without altering mounting arrangements. A unique feature of Worm and Wheel assemblies is their ability to prohibit back driving
Worm gears use screw threads to make large reductions to shaft speed while transmitting motion at a right angle. They transmit motion from worm to gear and cannot be reversed. For gears and worms to mesh correctly, they must have the same pressure angle and pitch.