Worm Gears

Worm Gears resemble screws. A worm gear usually meshes 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 gear ratio. For example, helical gears are normally limited to gear ratios of less than 10:1 while worm 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 occurs, it is a ‘Worm Gear’; if not, it is a ‘Helical Gear’.

In a Worm Gear, the worm can always drive the gear. However, if the gear attempts to drive the worm, it may or may not succeed. Particularly if the lead angle is small, the gear’s teeth may simply lock against the worm’s teeth, because the force component circumferential to the worm is not sufficient to overcome friction. Worm-and-gear sets that do lock are called self locking, which can be used to advantage, as for instance when it is desired to set the position of a mechanism by turning the worm and then have the mechanism hold that position. If the gear in a worm-and-gear set is an ordinary helical gear only a single point of contact will be achieved. If medium to high power transmission is desired, the tooth shape of the gear is modified to achieve more intimate contact by making both gears partially envelop each other.

We manufacture all kinds of Worm Gears as per customer specifications (standard/non-standard items).