• Worm and Worm Gears
Worm is similar in shape of a screw with multiple threads and where worm gear is like spur gears. Worm gears are being used when large speed reduction is required. The reduction ratio is determined by number of start on the worm and number of teeth on worm gear. For the same reduction ratio, worm drive arrangement is considerably smaller in size. However, worm gears tend to produce heat and have lower transmission efficiency.
Worm gear is usually made of soft metal such as aluminum bronze whereas worm is made of hard metal. The reason is that there is a high degree of sliding between worm threads and the gear teeth. Bronze material has lower coefficients of friction