How Does a Worm Gear Work?

What is a Worm Gear?

A worm gear is commonly used when large gear ratios are required. Worm gears can be used for reductions as high as 300:1 or more. Worm gears are usually in line with one shaft and drive a perpendicular shaft. Worm gears are common in equipment such as milling machines, where small increment movements are needed, as little as .001 of an inch.

How a Worm Gear is Designed

A worm gear looks very much like a screw. The gear is usually designed so that a single tooth runs in a spiral along the length of the gear. The angle of this tooth is what creates the large ratios. The worm gear is usually meshed with an ordinary-looking gear.

Special Characteristics

Besides the ability to create large ratios, a result of the steep angle of the worm drive which results in a low efficiency of the gear, a worm gear set has another unique feature. While the worm gear can always drive the opposing gear, however, dependent on the angle of the worm gear, the gear may or may not drive the worm. This is very useful for certain machines like conveyors where the feature can act as a brake.