Two important ideas in gearing are pitch surface area and pitch position. The pitch surface area of a gear is the imaginary toothless surface area that you would possess by averaging out the peaks and valleys of the average person teeth. The pitch surface area of a typical gear is the shape of a cylinder. The pitch angle of a equipment is the angle between the face of the pitch surface area and the axis.

The most familiar types of bevel gears have pitch planetary gearbox angles of significantly less than 90 degrees and therefore are cone-shaped. This type of bevel gear is called external because the gear teeth point outward. The pitch surfaces of meshed exterior bevel gears are coaxial with the gear shafts; the apexes of both areas are at the idea of intersection of the shaft axes.

Bevel gears that have pitch angles of greater than ninety degrees have teeth that point inward and so are called internal bevel gears.

Bevel gears which have pitch angles of specifically 90 degrees have teeth that point outward parallel with the axis and resemble the points on a crown. That is why this type of bevel gear is called a crown gear.

Mitre gears are mating bevel gears with the same amounts of teeth and with axes at right angles.

Skew bevel gears are those for which the corresponding crown gear has the teeth that are straight and oblique.