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Is the helical gear tooth profile in the transverse plane an involute?

Is the helical gear tooth profile in the transverse plane an involute?

Is the helical gear tooth profile in the transverse plane an involute?

(OP)
Colleagues
I have a helical gear. A helical gear has a normal pressure angle which is different to the transverse pressure angle. The tooth profile in the normal plane is an involute.
Question 1:- Is the tooth profile in the transverse plane also an involute?
Question 2:- Is the base diameter in the normal plane the same as the base diameter in the transverse plane?

JWC
Mechanical/Structural
Brisbane, Australia

RE: Is the helical gear tooth profile in the transverse plane an involute?

everything should be true in the transverse plane - I think. The normal plane is then slightly "corrupt" and you have to use the virtual diameters

RE: Is the helical gear tooth profile in the transverse plane an involute?

You can't have it both ways, but leisure17 is correct, the profile in the traverse plane is off.

RE: Is the helical gear tooth profile in the transverse plane an involute?

(OP)
Colbourne, 1987: "all the geometric relations for a spur gear  can be applied to the transverse section of a helical gear".

This is consistent with comment by leisure17.

We therefore calculate the "true" base diameter from the transverse geometry.

When rating the bending strength we use a "virtual" base diameter.

 

JWC
Mechanical/Structural
Brisbane, Australia

RE: Is the helical gear tooth profile in the transverse plane an involute?

Visually, I like to think of a helical gear as being made from a deck of cards, where each card matches the spur/involute form and the deck is twisted into the helix shape.

RE: Is the helical gear tooth profile in the transverse plane an involute?

helical gears are given in normal DP & PA, however all all calculations resultant in the transverse. profiles are mfg & Inspected in the transverse. That why the helix angle is an impotant factor in the calcs.

Mfgenggear

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