Gear Mating

In internal gears it must be X1 = X2. The correction factor is the hob real position in relation with the center of the gear. the most important effect that we are going to have is that the pitch diameters are going to change. In external gears, if you have a positive factor in the pinion, the pitch diameter is going to be bigger. To have the same center distance, it is necesary to have a lower wheel pitch diameter. In Internal gears, if the pinion pitch diameter is bigger, you need a bigger wheel pitch diameter.

But it is no so easy to have correct gears. You must know how much circular and radial clearance you need (it depends of the lubricant), how much torque the gears are going to support (remember that having a positive correction factor increase the resistant torque), the posibility of having interferences (much bigger in internal gears) and much more considerations before starting the calculation.

thanks alot mate, that really clear up the doubt.

Well let me see if I digest it correctly, so does that means that irregardless of the gear type, a positive 'x' will always means that the PCD is going to be larger and in reverse, a negative 'x' will shrink the gear PCD. So for internal gear, +x1 = +x2 will result in both gear mating in the same center distance. right?

Yes, that is.

In both cases (internal and external gears) you must look for positive 'x' values (you are going to have stronger teeth and to avoid interference problems).

thanks, you have been a great help