This type of interference can occur in the process of cutting an internal gear with a When the numbers of teeth of the two gears are very close. Mesh must be assembled by sliding the gears together with an axial motion. This occurs in the radial direction in that it prevents pulling the gears apart. Interference is avoided if the difference of the number of teeth, z 1 – z 2, is larger than 9. In the meshing of an external gear and a standard internal gear α = 20°, trochoid Where α a1 is the pressure angle of the spur gear tooth tip: The condition for avoiding trochoidal interference. It tends to happen when theĭifference between the numbers of teeth of the two gears is small. The dedendum of the internal gear during recess tooth action. This refers to an interference occurring at the addendum of the external gear and Where α a2 is the pressure angle seen at a tip of the internal gear tooth.Įquation (5-3) is true only if the outside diameter of the internal gear is bigger than the base circle:įor a standard internal gear, where α = 20°, Equation (5-5) is valid only if the number of Involute interference can be avoided by the conditions cited below: It is prevalent when the number of teeth of the external gear is small. This occurs between the dedendum of the external gear and the addendum of the internal gear. Three different types of interference can occur with internal gears: In order to get a correct tooth profile, the coefficient of cutter should be taken into consideration.
That is because the cutter has a coefficient of shifted profile. Of tooth depth and root diameter, after cutting, will be slightly different from the calculation. Pinion cutters are often used in cutting internal gears and external gears.
If the center distance, a x, is given, x 1 and x 2 would be obtained from the inverse calculationįrom item 4 to item 8 of Table 5-1. It will become a standard gear calculation if x 1 = x 2 = 0. Table 5-2 Table 5-1 shows the calculation steps.
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