Two important concepts in gearing are pitch surface and pitch position. The pitch surface of a gear is the imaginary toothless surface area that you would possess by averaging out the peaks and valleys of the individual teeth. The pitch surface of an ordinary gear is the shape of a cylinder. The pitch angle of a gear is the angle between your encounter of the pitch surface area and the axis.
The most familiar types of bevel gears have pitch angles of significantly less than 90 degrees and they are cone-shaped. This type of bevel gear is called external because the gear teeth point outward. The pitch areas of meshed exterior bevel gears are coaxial with the apparatus shafts; the beval gearbox apexes of the two surfaces are at the point 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 exactly 90 degrees possess teeth that time outward parallel with the axis and resemble the points on a crown. That’s why this kind of bevel gear is called a crown gear.
Mitre gears are mating bevel gears with the same numbers of teeth and with axes in right angles.
Skew bevel gears are those for which the corresponding crown equipment has teeth that are straight and oblique.