Bevel gears are gears that have intersecting axes and tooth-bearing faces that are conically shaped or tapered. The number of teeth on the mating gears need not be equal. While they can be used to transmit power, bevel gears are usually used to transmit motion, primarily to change the direction of a shaft’s rotation. They can transmit motion at an angle, although a perpendicular direction is most common.
Miter gears are mating bevel gears with an equal number of teeth on both faces, with axes at right angles to each other, and a pitch cone angle of 45°.
The biggest advantage of bevel gears is their ability to change mechanical advantage. They are suitable for use in situations requiring high load capacity, but smooth and quiet gear operations. The uneven number of teeth in the mating faces of a bevel gear can help alter the rotational drive and torque, either by increasing speed and decreasing torque, or decreasing speed and increasing torque. Miter gears cannot be used to change speed. However, the 90° intersecting axes of miter gears result in highly efficient operations, and hence these gears are used in applications that demand high efficiency.