According to the Position of Axis of Shaft
(a) Parallel
(b) Intersecting
(c) Non-intersecting and non-parallel
According to the peripheral velocity of the gears
(a) Low velocity, less than 3 m/s
(b) Medium velocity, between 3 and 15 m/s
(c) High velocity. more than 15 m
According to the type of gearing
(a)External gearing
(b) Internal gearing
(c) Rack and pinion
According to position of teeth on the gear surface
(a) straight
(b) inclined
(c) curved