Helical Spur - The helical teeth result in a greater tooth width which enables increased load and power transmissibility for a given gear size. Also they result in a smoother engagement and so are less noisy in operation than straight spur gears. The helical teeth result in an induced axial load; a helix angle of 30' is used in the British system.

Internal Spur - The meshing arrangement enables a greater load carrying capacity with improved safety (since meshing teeth are enclosed) compared to equivalent external gears. Shaft axes remain parallel and enable a compact reduction with rotation in the same sense. Internal gears are not widely available as standard.

Rack and Pinion - A rack is usually a gear without curvature (ie of infinite diameter) and when used with a meshing pinion enables rotary to linear movement or vice versa.

Double Helical - Although expensive to manufacture and not generally available as standard, the herringbone arrangement has the advantage of greater load and power transmissibility without the disadvantage of a net resultant axial load with other helical gears.

Skew or Crossed Helical - They are rarely produced as standard but as specials for skew (that is non-intersecting and crossed) axis shafts.

Straight Bevel - They are used where shaft axes intersect. Standard versions are available for 900 angles.

Spiral Bevel - These have greater tooth widths enabling improved load and power transmissibility compared with straight bevel gears. A spiral bevel with offset axes is a special case and is called a hypoid gear.