Worm Gear works in conjunction with worms to form what is known as a “worm set”. Worms and worm gears operate together on perpendicular shafts.
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A worm set is used because they provide a means to have a large reduction in ratio in relatively small compact design. Worm sets are one of the most inefficient types of gears sets due to the heat and friction created from the sliding action of the worm against the worm gear in operation.
In most cases, the worm is the driver; the worm gear is driven. (REFER TO “one direction locking device” on the “Worm Info” tab.)
Like worms, worm gears also use axial pitches. In most cases, worms are produced with special tools, called worm gear hobs. Theoretically, the worm gear hob used to cut the worm gear, should be shaped exactly like the worm. This is because unlike spur gears and helical gears, where the gear hob is fed across the face to form the tooth, a worm gear hob is fed directly into the face, producing a throat radius. It is this throat radius that actually envelopes the worm producing more tooth surface area contact and therefore more load carrying capacity through the worm gear set.
Superior Quality Worm Gears
All worms and worm gears in the stock gear catalogs are single enveloping (meaning that the worm gear envelopes or surrounds the worm). There are also worm sets, that are a lot less common, that are double enveloping (meaning that not only does the worm gear surround the worm but the hour glass shaped worm also surrounds the worm gear).
Approx 75% of the gears that we produce at Gearmakers are produced from 954 aluminum bronze. Other materials include many other types of bronzes, cast irons, steels, plastics, not metallics, etc. We have even produce hardened worm gears, although this is rare. Also, many worm gears are produced with a bronze ring, shrunk fit over a steel or cast iron hub. Many types of bronzes and cast irons are known to hold a film of oil better than other materials. This aids in making worm sets as efficient as possible and this is another reason for these choices of materials.