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# Coefficient of Profile Shift

## Coefficient of Profile Shift

(OP)
If a profile shift of +0.5 increases the working pitch diameter of an external spur gear, does the same +0.5 shift increase the pitch diameter of an internal gear? Or do you use a -0.5 shift to increase the pitch diameter of an internal gear?

### RE: Coefficient of Profile Shift

Brian,
I cannot keep the -profile shift in my
mind. If the pitch diameter or the internal
gear gets larger, then the center distance
will increase.  If the pinion of the pair
increases only, then the center distance gets
smaller.  If they both get larger by the
same amount, then the cd remains the same.

### RE: Coefficient of Profile Shift

Dear Sirs,
please quote the calculation and DXF-generation of a gear profile, which it was copied by hand as the following sketch.
A first calculation and generation(attached) were made, but its profile is not exactly equal to the true gear.
It seems that the pressure angle is different than 20 degrees.
We are sending to analysis:

Z20.jpeg = true teeth profile, which it were copied by hand from the true gear
HG-Geometrie-Z20-P&H.txt = first calculation of its geometry
Perfil da Engrenagem-Z20.dwg = first generation of the teeth profiles

When we put the above true teeth with the generated profiles, they were not exactly equal.
The basis of the true teeth are wider. Maybe these teeth, just shaved, need a special cutting tool.

Please quote all work as soon as possible. And we have such others gears to be analyse later.
Regards,
Renato Penchel
Geartech Ltda.(Brazil)
Homepage: http://netpage.em.com.br/geartech

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