Worm Gear Set

A worm gear set is a set of gears consisting of a worm and a worm wheel, often used when a high ratio is required and space is limited. The pinion meshes with the teeth of the worm wheel at 90 degrees, and motion is transmitted to the worm wheel when the worm pinion is rotated. Since the pinion is captivated axially, this rotation causes the worm wheel to rotate. The ratio of the worm set can be altered by changing the number of teeth on the wheel or changing the number of starts on the pinion.

Worm gears are the most compact type of system and provide high-ratio speed reduction. They are often the preferred type of gearing system when space is limited and large gear reductions are needed. Worm wheels can be used to either greatly increase torque or greatly reduce speed. They are also the smoothest and quietest of the gear systems, as long as they are properly mounted and lubricated. Another advantage of worm wheels is that they have good meshing effectiveness. To be most effective, it is important that they are manufactured with high-quality standards to ensure all gear requirements are precisely met.

Worm gear sets are used in many applications where low speed and a relatively large amplification of power are required. They appear in simple, everyday home devices as well as heavy machinery such as an elevator. it is the non-reversible property of worm wheels that makes them valuable to the mechanics of an elevator. While they have an operational function, the worm gears of an elevator also act as a failsafe secondary braking system which prevents the lifts from freefalling down the shaft (should the primary braking mechanism fail).