What is a Bevel Gear?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Images By: Petroris, William Warby
  • Last Modified Date: 08 October 2019
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A bevel gear is a gear which is designed to connect with a gear mounted on an axis which may be positioned at any number of angles. Classically, bevel gears are used at 90 degree angles to each other, although other types of angles may be used as well. This is by contrast with other types of gears, which must generally be used either parallel to each other, or at right angles, in some specialized cases. Bevel gears are used in a number of applications, including the differential gear of a car.

As the term “bevel” would suggest, the face of a bevel gear is angled. Typically, a bevel gear is conical in shape, with the teeth running along the side of the cone, and the angle of the sides can be varied, depending on the application for the gear. The beveled design allows the gear to intermesh with another bevel gear at several different angles, depending on how it has been machined.


In a straight bevel gear, the teeth are straight, running vertically along the cone. The problem with straight toothed gears is that all of the impact comes down on a single tooth, making the gear rather rough, and leading to chipping along the teeth of the gear over time. For this reason, some people prefer spiral gears, in which the teeth are set at an angle, allowing the pressure to be distributed so that the gears mesh evenly and smoothly. Spiral bevel gears are readily available for a range of tasks.

Hypoid bevel gears are specialized bevel gears with axes which do not intersect. These gears utilize a large ring gear with a smaller meshing gear, and they are used in applications like car differentials, in which it may be necessary for gears to turn at different rates of speed in some situations. Hypoid gears require custom lubricants, because they are often subjected to a significant amount of strain.

One example of a bevel gear can be found in the workings of many garage doors. The gears used to turn the door are often set at right angles to each other, as can be seen upon close examination. Bevel gears are also used in other types of doors and gates, such as sluice gates for dams which are often operated by a user's manipulation of a screw which turns a bevel gear to open or close the gate.


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Post 3

@Viktor13 - Big dams use pretty much the same arrangement, except the gears are about as big as you are and are driven by a big motor.

At that size, just making and installing the gears is an impressive project. The small bevel gears you can carry around by hand or on a small cart. The big ones need trucks, cranes, and teams of people to get them hoisted into place and lined up correctly.

Post 2

There is a small dam in a state park near me that has a manual bevel gear setup to open and close the sluice gate. You actually have to turn a little hand wheel to make it work.

They have it padlocked to keep some passing comedian from messing with the water level, but if it weren't locked it would be nothing to crank the wheel and change the level of thousands, or even millions of gallons of water.

It's interesting to think about what engineering was able to do even 50 or 100 years ago, with no computers, calculators, Internet, or any other advanced tools. The first time I saw the sluice gate work, I was really impressed that it was all designed by hand.

Post 1

When I read this, the first thing I though of was a garage door opener, because I just had to replace the bevel gear drives in mine. I never realized why they set them up that way until I had it apart.

It looks like the angled arrangement lets them make the mechanism fit in a smaller space, so that garage door openers are not some huge box that people would have trouble fitting in their garage.

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