worm pinion gear
Worm gears are often used when large velocity reductions are needed. The decrease ratio is determined by the number of starts of the worm and quantity of tooth on the worm gear. But worm gears have sliding call which is noiseless but tends to produce heat and also have relatively low transmission proficiency.
For the materials for development, in general, worm is constructed of hard metal while the worm gear is made from relatively soft metallic such as aluminum bronze. This is since the number of tooth on the worm equipment is relatively high in comparison to worm using its number of starts being usually 1 to 4, by reducing the worm equipment hardness, the friction on the worm teeth is lowered. Another characteristic of worm manufacturing may be the need of specialized machine for gear trimming and tooth grinding of worms. The worm equipment, alternatively, may be made out of the hobbing machine used for spur gears. But because of the different tooth shape, it is not possible to cut many gears simultaneously by stacking the apparatus blanks as can be carried out with spur gears.
The applications for worm gears include equipment boxes, fishing pole reels, guitar string tuning pegs, and in which a delicate acceleration adjustment by utilizing a huge speed reduction is needed. When you can rotate the worm gear by worm, it is usually not possible to rotate worm by using the worm gear. This is called the self locking feature. The self locking characteristic cannot continually be assured and a separate method is preferred for true confident reverse prevention.
Also there is duplex worm gear type. When using these, you’ll be able to change backlash, as when the teeth 
use necessitates backlash adjustment, without requiring a change in the center distance. There are not too many producers who can make this sort of worm.
EP’s worms and worm gears provide an effective answer for electric power transmission applications requiring high-ratio acceleration reduction in a limited space using right position (90°), non-intersecting shafts. When properly used, worms and worm gears provide the smoothest, quietest type of gearing.
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