Kinds of gears

There are several kinds of gears, which can transmit power to shafts that are parallel or at different angles to each other. The simplest kind of gear is the spur gear, which has straight teeth. A helical  gear has curved teeth, and it is smoother and quieter in operation tham a spur gear. Bevel gears have teeth that slant at an angle, and they transmit motion between shafts at an angle each other.