Inch & Metric Worm Gear Pairs & Sets

A worm gear pair, or worm gear set, consists of two gears: the worm, which resembles a spiral screw, and the worm gear (aka, worm wheel). For the pair to mesh, the worm and worm gear must have the same pressure angles, modules, and lead directions (left- or right-hand). A worm revolves on a shaft that’s perpendicular to the worm gear, and the shaft angle is typically 90°. Because the teeth gradually mesh as the worm rotates, there is low noise and vibration. (For more about worm gear mesh geometry follow this link.)

Text at the bottom of image is "cross section of worm gear pair." Image is a half circle with a gear vertically laid on top

Benefits & Applications of Worm Gear Pairs

Worm gear pairs offer significant speed reduction and high output torque in a small space. For example, to achieve a 30:1 ratio in a set of spur gears, a gear would need to be 30 times larger than the pinion. By comparison, to achieve the same ratio, a worm gear pair just needs to have a 30-tooth gear and worm.

A worm gear cannot be back-driven due to the friction between the teeth of the worm and the worm gear. This occurs when the lead angle is especially small; the worm wheel cannot turn the worm, locking it and prohibiting the shaft from being affected by external influence, resulting in very low backlash (more information about backlash).

Worm gears are used in a variety of applications, including medical equipment, rotary head technologies (satellite systems), metering pumps, motors, elevators, rock crushers, and vehicle power steering. We offer our worm gears and worms in stainless steel, bronze, steel, aluminum, nylon, and acetal. In pitches from 64 to 24 and modules from 0.5 to 6.

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