Classification of Toothed Wheels

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