The primary good thing about worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can be utilized as swiftness reducers in low- to medium-swiftness applications. And, because their lowering ratio is founded on the number of gear teeth by itself, they are more compact than other types of gears. Like fine-pitch business lead screws, worm gears are usually self-locking, which makes them suitable for hoisting and lifting applications.
Although the sliding contact decreases efficiency, it provides very quiet operation. (The use of dissimilar metals for the worm and equipment 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 application of a softer material for the gear means that it can absorb shock loads, like those skilled in major equipment or crushing machines.
The meshing of the worm and the apparatus is a mixture of sliding and rolling actions, but sliding contact dominates at high reduction ratios. This sliding actions causes friction and high temperature, which limits the efficiency of 
worm gears to 30 to 50 percent. So that you can minimize friction (and therefore, heat), the worm and gear are made from dissimilar metals – for instance, the worm could be made of hardened steel and the gear made of bronze or aluminum.
Just like a ball screw, the worm in a worm gear may have a single start or multiple starts – meaning that there are multiple threads, or helicies, on the worm. For a single-start worm, each total turn (360 degrees) of the worm advances the equipment by one tooth. Hence a gear with 24 teeth will provide a gear reduced amount of 24:1. For a multi-commence worm, the gear reduction equals the amount of teeth on the apparatus, divided by the number of begins on the worm. (This is different from almost every other types of gears, where in fact the gear reduction is definitely a function of the diameters of both components.)
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