The primary advantage of worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can even be employed as acceleration reducers in low- to medium-quickness applications. And, because their reduction ratio is based on the number of gear teeth only, they are smaller sized 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 equipment also contributes to quiet operation.) This makes worm gears suited to use where noise should be minimized, such as in elevators. Furthermore, the use of a softer materials for the gear means that it can absorb shock loads, like those skilled in large equipment or crushing devices.
The meshing of the worm and the 
apparatus 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 effectiveness of worm gears to 30 to 50 percent. In order to minimize friction (and for that reason, heat), the worm and equipment are constructed with dissimilar metals – for example, the worm could be made of hardened steel and the gear made of bronze or aluminum.
Such as a ball screw, the worm in a worm gear could have an individual 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 advances the equipment by one tooth. Consequently a gear with 24 teeth will provide a gear reduced amount of 24:1. For a multi-commence worm, the apparatus reduction equals the number of teeth on the apparatus, divided by the number of starts on the worm. (That is different from almost every other types of gears, where the gear reduction is normally a function of the diameters of both components.)
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