Worm gears resemble screws. A worm gear is usually meshed with an ordinary looking, disk-shaped gear, which is called the gear, wheel, or worm wheel.
Worm-and-gear sets are a simple and compact way to achieve a high torque, low speed gear ratio. For example, helical gears are normally limited to gear ratios of less than 10:1 while worm-and-gear sets vary from 10:1 to 500:1. A disadvantage is the potential for considerable sliding action, leading to low efficiency.
Worm gears can be considered a species of helical gear, but its helix angle is usually somewhat large (close to 90 degrees) and its body is usually fairly long in the axial direction; and it is these attributes which give it its screw like qualities. The distinction between a worm and a helical gear is made when at least one tooth persists for a full rotation around the helix. If this does occur, it is a 'worm'; if not, it is a 'helical gear'. A worm gear may have as few as one tooth. If that tooth persists for several turns around the helix, the worm will appear, superficially, to have more than one tooth, what one in fact sees is the same tooth reappearing at intervals along the length of the worm gear. The usual screw nomenclature applies: a one-toothed worm gear is called single thread or single start; a worm gear with more than one tooth is called multiple thread or multiple start.
B&H Gears manufacture a wide range of high quality worm gears and worm wheels. Click on the contact us button or phone us with your requirements on 0161 627 4610.