Internal Gears / Planetary Gears

Internal gear is a gear with its teeth cut in the internal surface of a cylinder and meshes with spur gears.

In its manufacturing, because of its shape, the usual hobbing machine used in spur gear production cannot be used. Generally it is made with gear shaper (or gear shaping machine) equipped with a pinion cutter. More recently, the efficiency of internal gear cutting has been improved by a different process called skiving.