Internal gears have cylindrical pith surface with teeth parallel to the axis. Gears make an internal contact with these gears. They have
the teeth cut on the inside of the rim rather than the outside. When they are used with the pinion more teeth carry the load and are evenly distributed. This even distribution decreases the pressure intensity and increases the life of the gear. The center distance of a given velocity is shorter.
An internal gear is one with the teeth formed on the inner surface of a cylinder or cone. For bevel gears, an internal gear is one with the pitch angle exceeding 90 degrees. Internal gears do not cause direction reversal.