1. Parallel shaft gear (cylindrical gear)

(1) Spur gear: A straight cylindrical gear with tooth ribs parallel to the axis.

(2) Rack (Rack): A linear gear that meshes with a spur gear. It can be said to be a special situation when the pitch of the gear becomes infinite.

(3) Internal gear: The inner gear of a straight cylinder that meshes with the spur gear.

(4) Helical gear: a cylindrical gear with a helicoid with toothed ribs.

(5) Helical rack: a linear gear that meshes with a helical gear.

(6) Double helical gear: a helical gear formed by left and right spiral tooth ribs.

2. Right-angle shaft gear (bevel gear)

(1) Straight bevel gear: A bevel gear whose tooth rib is consistent with the generatrix (straight line) of the pitch cone.

(2) Spiral bevel gear: A bevel gear with a bevel line with a spiral angle.

(3) Zero helical bevel gear (Zerol bevel gear): a bevel gear with zero helix angle.

3. Gears with staggered shafts (worm gear and worm)

(1) Cylindrical worm gear: Cylindrical worm gear is the general name of worm (Worm) and gear (Wheel).

(2) Staggered helical gear (screw gear): This is a cylindrical helical gear, which is called when it is used for transmission between staggered shafts (also called skew shafts).

(3) Other special gears:

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

Concave worm gear: Concave worm gear and its meshing gear.

Hypoid gear: Conical gear that conveys the wrong axis. The shape is similar to a curved bevel gear.