Two important concepts in gearing are pitch surface area and pitch position. The pitch surface of a gear may be the imaginary toothless surface that you would have got by averaging out the peaks and valleys of the individual teeth. The pitch surface area of an ordinary gear is the shape of a cylinder. The pitch angle of a gear is the angle between the face of the pitch surface area and the axis.
The most familiar types of bevel gears have pitch angles of less than 90 degrees and therefore are cone-shaped. This type of bevel gear is named external because the gear teeth stage outward. The pitch surfaces of meshed exterior bevel gears are coaxial with the gear shafts; the apexes of the two areas are at the idea of intersection of the shaft axes.
Bevel gears which have pitch angles of greater than ninety degrees have teeth that point inward and are called internal bevel gears.
Bevel gears that 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 kind of bevel gear is called a crown gear.
Mitre gears are beval gear china mating bevel gears with equal numbers of teeth and with axes in right angles.
Skew bevel gears are those for which the corresponding crown gear has tooth that are directly and oblique.