A ring-shaped gear with teeth pointing inward, used most often as the ring gear of a planetary set. Internal meshes are compact, have more teeth in contact than an external pair of the same ratio and turn the pinion in the same direction as the ring. They cannot be generated by an ordinary hob, so they are shaped, broached, power skived or ground with small-diameter wheels.
Internal gear on the planetary has to be shaped or skived, the hobber can't touch it.
Also heard as
- ring gear
- annulus
Related terms
Planetary gear set
A compact gear arrangement of a central sun, orbiting planets on a carrier and an outer ring gear.
Gear shaping
Cutting gear teeth with a reciprocating, gear-shaped cutter that rolls with the blank as it strokes.
Power skiving
Cutting gear teeth with a gear-like cutter spinning at a crossed axis angle in continuous high-speed rotation.