Each type of gear has a specific role in a mechanical transmission system, such is the case of bevel gears. Bevel gears allow transmitting motion in a particular way, which justifies their presence in many devices. This type of gears is used when it is necessary to change the direction of rotation of a shaft. They are usually mounted on shafts 90 degrees apart, but can also be used to operate at different angles. To operate most efficiently, bevel gears must be precision machined and the shaft bearings must be able to withstand high forces.