Worm gears are usually used when large velocity reductions are 
needed. The decrease ratio is determined by the number of worm wheel china starts of the worm and quantity of tooth on the worm equipment. But worm gears have sliding get in touch with which is quiet but will produce heat and also have relatively low transmission efficiency.
As for the materials for creation, in general, worm is made of hard metal while the worm gear is manufactured out of relatively soft metallic such as aluminum bronze. That is because the number of teeth on the worm equipment 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 may be the need of specialized machine for gear slicing and tooth grinding of worms. The worm gear, however, may be made with the hobbing machine utilized for spur gears. But due to the various tooth shape, it isn’t possible to cut many gears at once 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 rate adjustment by utilizing a big speed reduction is necessary. When you can rotate the worm equipment by worm, it is normally not possible to rotate worm by using the worm gear. This is called the personal locking feature. The self locking feature cannot continually be assured and another method is preferred for accurate positive reverse prevention.
