Worm gears are usually used when large velocity reductions are needed. The reduction ratio depends upon the number of starts of the worm and number of tooth on the worm gear. But worm gears have sliding contact which is noiseless but tends to worm wheel china produce heat and also have relatively low transmission performance.
For the materials for production, in general, worm is constructed of hard metal as the worm gear is made from relatively soft metallic such as for example aluminum bronze. This is because the number of teeth on the worm gear is relatively high in comparison to worm using its number of starts being generally 1 to 4, by reducing the worm gear hardness, the friction on the worm the teeth is reduced. Another characteristic of worm manufacturing is the need of specific machine for gear trimming and tooth grinding of worms. The worm gear, on the other hand, may be made out of the hobbing machine utilized for spur gears. But because of the various tooth shape, it isn’t possible to cut several gears 
simultaneously by stacking the gear blanks as can be carried out with spur gears.
The applications for worm gears include equipment boxes, angling pole reels, guitar string tuning pegs, and in which a delicate velocity adjustment by utilizing a huge speed reduction is needed. When you can rotate the worm gear by worm, it is normally extremely hard to rotate worm by using the worm gear. This is called the self locking feature. The self locking feature cannot continually be assured and another method is preferred for accurate positive reverse prevention.