Two important principles in gearing are pitch surface and pitch position. The pitch surface area of a gear is the imaginary toothless surface 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 form of a cylinder. The pitch angle of a gear is the angle between your face of the pitch surface and the axis.

The most familiar types of bevel gears have pitch angles of significantly less than 90 degrees and therefore are cone-shaped. This kind of bevel gear is named external because the gear teeth stage outward. The pitch areas of meshed exterior bevel gears are coaxial with the gear shafts; the apexes of the two areas are at the point of intersection of the shaft axes.

Bevel gears that have pitch angles in excess of ninety degrees have teeth that time inward and are called beval gearbox internal bevel gears.

Bevel gears which have pitch angles of exactly 90 degrees possess teeth that time outward parallel with the axis and resemble the factors on a crown. That’s why this kind of bevel gear is called a crown gear.

Mitre gears are mating bevel gears with equivalent numbers 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.