Worm gear drive is commonly used to obtain higher velocity ratio when compared with other forms of gearing. Here, the shafts are non-intersecting and nearly make an angle of 90 degree with each other. The worm, which is usually the driver, is a special form of helical gear, in which the helix angle is such that the tooth becomes a thread. The driven member is also a helical gear in which the helix angle is the complement of that of the worm. Worm and worm gear system can provide very high-speed reduction (usually from 30 to 300). However, the efficiency is very poor (usually from 50% to 85%). Often this drive is self locking, which means rotation of worm gear will not cause worm to rotate.

Machines
Worm gear drive is commonly used to obtain higher velocity ratio when compared with other forms of gearing. Here, the shafts are non-intersecting and nearly make an angle of 90 degree with each other. The worm, which is usually the driver, is a special form of helical gear, in which the helix angle is such that the tooth becomes a thread. The driven member is also a helical gear in which the helix angle is the complement of that of the worm. Worm and worm gear system can provide very high-speed reduction (usually from 30 to 300). However, the efficiency is very poor (usually from 50% to 85%). Often this drive is self locking, which means rotation of worm gear will not cause worm to rotate.