1. gears with parallel shafts (cylindrical gears)

spur gears (spur gears): straight cylindrical gears with ribs parallel to the axis.

Rack: a straight strip gear that meshes with a spur gear, which can be said to be a special case when the pitch of the gear becomes infinite. Internal gear: the internal gear of a straight cylinder that meshes with the spur gear.

Helical gear: a cylindrical gear with helical ribs.

Helical rack: a linear gear that meshes with a spiral gear.

Double helical gear: a helical gear formed by left and right helical ribs.

2. Gears with orthogonal axes (bevel gears)

Straight bevel gear: bevel gears with teeth ribs consistent with the generatrix (straight lines) of pitch cones.

Spiral bevel gear: an bevel gear with a curved line with spiral angle.

zero spiral bevel gear: a Zerol bevel gear with zero spiral angle.

3. Gears with staggered shafts (Worm Wheel and worm)

Worm gear: Worm gear is the general name of worm and wheel.

screw gear: this is a cylindrical screw gear, which is called by using the transmission between shafts to be crossed (also called skew shafts).

4. Other special gears:

Face gear: a disc-shaped face gear that can mesh with spur gear or spiral gear.

Concave worm gear: the general name of concave drum worm and the gear engaged with it.

Hypoid gear: a conical gear that conveys staggered shafts. Shaped like a curved bevel gear.