worm gear shaft

The primary benefit for worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can also be used as velocity reducers in low- to medium-acceleration applications. And, because their lowering ratio is based on the number of gear teeth alone, they are smaller sized than other styles of gears. Like fine-pitch lead screws, worm gears are typically self-locking, making them suitable for hoisting and lifting applications.

Although the sliding contact minimizes efficiency, it provides incredibly quiet operation. (The use of dissimilar metals for the worm and equipment also plays a part in quiet operation.) This makes worm gears well suited for use where noise 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 large equipment or crushing equipment.

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 action causes friction and warmth, which limits the proficiency of worm gears to 30 to 50 percent. As a way to minimize friction (and for that reason, heat), the worm and equipment are created from dissimilar metals – for instance, the worm could be made of hardened metal and the gear manufactured from bronze or aluminum.

Such as a ball screw, the worm in a worm gear might have an individual start or multiple starts – meaning that there are multiple threads, or helicies, on the worm. For a single-start worm, each full flip (360 degrees) of the worm increases the equipment by one tooth. Therefore a gear with 24 teeth will provide a gear reduction of 24:1. For a multi-start worm, the gear reduction equals the quantity 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 a function of the diameters of the two components.)