The primary benefit for worm gears is their capability to provide high reduction ratios and correspondingly high torque multiplication. They can be used as velocity reducers in low- to medium-rate applications. And, because their reduction ratio is based on the number of gear teeth by itself, they are more compact than other styles of gears. Like fine-pitch business lead screws, worm gears are usually self-locking, which makes them perfect for hoisting and lifting applications.
Although the sliding contact reduces efficiency, it provides incredibly quiet operation. (The make use of dissimilar metals for the worm and gear also plays a part in quiet operation.) This makes worm gears suited to use where noises should be minimized, such as for example in elevators. Furthermore, the use of a softer materials for the apparatus means that it can absorb shock loads, like those experienced in serious equipment or crushing equipment.
The meshing of the worm and the gear is an assortment of sliding and rolling actions, but sliding contact dominates at high reduction ratios. This sliding actions causes friction and heat, which limits the productivity of worm gears to 30 to 50 percent. In order to minimize friction (and for that reason, heating), the worm and gear are made of dissimilar metals – for example, the worm could be made of hardened steel and the gear made of bronze or aluminum.
Like a ball screw, the worm in a worm gear might have a single start or multiple starts – and therefore there are multiple threads, or helicies, on the worm. For a single-start worm, each complete flip (360 degrees) of the worm increases the gear by one tooth. Therefore a gear with 24 teeth will provide a gear reduced amount of 24:1. For a multi-begin worm, the apparatus reduction equals the quantity of teeth on the gear, divided 
by the amount of begins on the worm. (That is different from most other types of gears, where in fact the gear reduction is usually a function of the diameters of the two components.)
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