The primary good thing about worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can be employed as swiftness reducers in low- to medium-speed applications. And, because their lowering ratio is based on the quantity of gear teeth alone, they are more compact than other types of gears. Like fine-pitch lead screws, worm gears are usually self-locking, which makes them ideal for hoisting and lifting applications.
Although the sliding contact reduces efficiency, it provides extremely quiet operation. (The utilization of dissimilar metals for the worm and gear also contributes to quiet procedure.) This makes worm gears ideal for 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 knowledgeable in weighty equipment or crushing equipment.
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 performance of worm gears to 30 to 50 percent. So that you can minimize friction (and for that reason, heating), the worm and equipment are made from 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 well have a single start or multiple starts – meaning that there are multiple threads, or helicies, on the worm. For a single-start worm, each complete convert (360 degrees) of the worm increases the gear by one tooth. Consequently a gear with 24 teeth will provide a gear reduced amount of 24:1. For a multi-start worm, the gear reduction equals the quantity of teeth on the apparatus, divided by the amount of starts on the worm. (This is different from most other types of gears, where the gear reduction is usually a function of the diameters of the two components.)
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