A bevel gear is used to change the direction of shaft rotation or the operating angle in machines. Different types of bevel gears also change torque and speed between machine parts. Bevel gears are found in many engines and tools.
Bevel gears consist of two gear wheels that come together at an angle, most often 90 degrees. The gears are cone-shaped and have specially cut teeth to transfer movement to a new angle. Special bevel gears, called hypoid gears, have hyperbolic-shaped pitch and spiral-cut teeth to allow movement to be changed to a different plane and a different angle at the same time. A common use for hypoid gears is connecting the drive shaft to the differential in an automobile.
Bevel gears are used in hand drills to change the direction of rotation from vertical in the handle to horizontal in the drill bit. Another common use is the mechanism to lift a heavy gate or overhead door. A handle crank moves in one direction, and the bevel gear changes the movement to the direction that lifts the door.
Bevel gears are modified to serve in many different applications. Gears with different numbers of teeth on each gear half change the speed of rotation as they change the angle. This type of bevel gear helps automobiles and other vehicles turn corners. It is also used heavily in manufacturing applications.