An Internal Gear could be described as the opposite of an external gear in that the teeth point 
towards instead of away from the center, and addendum and dedendum take invert positions. Internal Gears provide a compact parallel shaft transmitting drive with large rate 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's important to possess two parallel shafts planetary gearbox rotate in the same direction, the inner gear eliminates the use of an idler gear.
Internal Gears possess several advantages when properly used. One such advantage is reduced sliding actions. The corresponding working areas of the teeth of an internal gear and pinion are more nearly of the same duration than is the case with an external gear and pinion getting the same tooth ratio and tooth length. Which means relative slippage of one's teeth is less regarding the internal. This aspect presents among the advantages of using Internal Gears. The sliding actions of 1 tooth over another causes friction; and since friction results in tooth use, a reduction in the quantity of sliding action is certainly desirable.
Internal Gear drives may be operated with the apparatus in a set position and the pinion rotating along the pitch line, or the apparatus may be absolve to rotate with the pinion rotating in a fixed position.
When mating pinions are too close in size to the gear, interference may result. Consequently, the difference in teeth of the pinion to the gear should not be less than 15.
RUSH GEARS inc. provides standard Internal Gears in STEEL, STAINLESS STEEL, CAST IRON, BRONZE, Aluminium, DELRIN and NON-METALLIC (PHENOLIC). We will gladly manufacture made to purchase Internal Gears to your requirements.