Two important principles in gearing are pitch surface area and pitch angle. The pitch surface area of a gear is the imaginary toothless surface area that you would have got by averaging out the peaks and valleys of the individual teeth. The pitch surface of a typical gear is the form of a cylinder. The pitch angle of a equipment 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 they are beval gear china cone-shaped. This kind of bevel gear is named external since the gear teeth point outward. The pitch surfaces of meshed exterior bevel gears are coaxial with the gear shafts; the apexes of the two surfaces are at the idea of intersection of the shaft axes.

Bevel gears which have pitch angles in excess of ninety degrees possess teeth that point inward and are called internal bevel gears.

Bevel gears that have pitch angles of specifically 90 degrees possess teeth that time outward parallel with the axis and resemble the points on a crown. That is why this kind of bevel gear is named a crown gear.

Mitre gears are mating bevel gears with equivalent amounts of teeth and with axes in right angles.

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