Two important concepts in gearing are pitch beval gear china surface area and pitch position. The pitch surface area of a gear is the imaginary toothless surface that you would have by averaging out the peaks and valleys of the average person teeth. The pitch surface 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 they are cone-shaped. This kind of bevel gear is called external since the gear teeth point outward. The pitch areas of meshed external bevel gears are coaxial with the apparatus shafts; the 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 possess teeth that point inward and so are called internal bevel gears.
Bevel gears which have pitch angles of precisely 90 degrees possess teeth that point 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 equal numbers of teeth and with axes in right angles.
Skew bevel gears are those that the corresponding crown gear has tooth that are directly and oblique.