The primary good thing about worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can even be used as acceleration reducers in low- to medium-rate applications. And, because their lowering ratio is based on the amount of gear teeth alone, they are more compact than other types of gears. Like fine-pitch lead screws, worm gears are usually self-locking, making them suitable for hoisting and lifting applications.
Although the sliding contact decreases efficiency, it provides very quiet operation. (The usage of dissimilar metals for the worm and equipment also contributes to quiet procedure.) This makes worm gears well suited for use where noises should be minimized, such as in elevators. In addition, the use of a softer material for the gear means that it could absorb shock loads, like those skilled in serious equipment or crushing machines.
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 action causes friction and temperature, which limits the productivity of worm gears to 30 
to 50 percent. So that you can minimize friction (and therefore, high temperature), the worm and gear are made of dissimilar metals – for instance, the worm may be made of hardened steel and the gear manufactured from bronze or aluminum.
Just like a ball screw, the worm in a worm gear may possibly have a single start or multiple starts – and therefore there are multiple threads, or helicies, on the worm. For a single-start worm, each total transform (360 degrees) of the worm increases the equipment by one tooth. Hence a gear with 24 teeth provides a gear reduction of 24:1. For a multi-commence worm, the apparatus reduction equals the number of teeth on the apparatus, divided by the amount of begins on the worm. (This is different from almost every other types of gears, where the gear reduction is definitely a function of the diameters of the two components.)
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