Bevel Gears

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• Straight bevel gears: These gears have a conical pitch surface and straight teeth tapering towards an apex
• Zero bevel gears: This is similar to a bevel gear except the teeth are curved. In essence, Zero Bevel Gears are Spiral Bevel Gears with a spiral angle of zero
• Spiral bevel gears: The teeth are curved teeth at an angle allowing too contact to be gradual and smooth
• Hypoid bevel gears: These gears are similar to spiral bevel except that the pitch surfaces are hyperboloids rather than cones. Pinion can be offset above or below gear center, thus allowing larger pinion diameter, and longer longer life and smoother mesh, with additional ratios e.g., 6:1, 8:1, 10:1

The design of bevel gears results in thrust forces away from the apex. With the bearing limitations the gears have to be carefully designed to ensure that they are not thrown out of alignment as they are loaded.

  The tooth-bearing faces of the bevel gear are conically shaped. These bevel gears are mounted on shafts that are 90 degrees apart, but they can conveniently be designed to work at other angles as well. By using bevel gears with different numbers of teeth (the teeth can be straight, spiral or hypoid), the rotational speed can easily be changed.

Bevel gears can be used to change the direction of drive in a gear system by 90 degrees. A good example is seen as the main mechanism for a hand drill. As the handle of the drill is turned in a vertical direction, the bevel gears change the rotation of the chuck to a horizontal rotation.

  The bevel gears in a hand drill have the added advantage of increasing the speed of rotation of the chuck and this makes it possible to drill a range of materials.