An Internal Gear may be described as the opposite of an external gear in that the teeth point towards rather than away from the center, and addendum and dedendum take reverse positions. Internal Gears provide a compact parallel shaft transmission drive with large speed reduction. Used with a standard spur pinion the ratio is the same as that of two external gears, but the center distance is much smaller. In cases where it is necessary to have two parallel shafts rotate in the same direction, the internal gear eliminates the use of an idler gear.

Internal Gears possess several advantages when properly applied. One such advantage is reduced sliding action. The corresponding working surfaces of the teeth of an internal gear and pinion are more nearly of the same length than is the case with an external gear and pinion having the same tooth ratio and tooth length. Therefore the relative slippage of the teeth is less in the case of the internal. This point presents one of the advantages of using Internal Gears. The sliding action of one tooth over another causes friction; and as friction results in tooth wear, a reduction in the amount of sliding action is desirable.

Internal Gear drives may be operated with the gear in a fixed position and the pinion rotating along the pitch line, or the gear may be free to rotate with the pinion rotating in a fixed position.

When mating pinions are too close in size to the gear, interference may result. Therefore, the difference in teeth of the pinion to the gear should not be less than 15.

Rushgears.com™ offers standard Internal Gears in STEEL, STAINLESS STEEL, CAST IRON, BRONZE, ALUMINUM, DELRIN and NON-METALLIC (PHENOLIC). We will gladly manufacture made to order Internal Gears to your requirements.