Profile Shift of Helical Gear

I was out of town and read your call for help with a great delay. I do not know if it is already solved your problem or not anyway here are some comments and NOMINAL values (without tolerances and without a warranty):

Since your teeth are not parallel to the gear axis you cannot use wires only balls or measure either the tooth profile in normal section or the length over a given number of teeth (common tangent).

The choice of corrections (profile shift) was wrong since the small gear should have had a + correction and the big a negative one if the correction was at all necessary.

For the given data the correction values are : small gear -0.2233 big gear +0.152. All values are relative to the module.

I have a doubt on the β angle (helix) since for me the _52' is not clear as meaning.

The helix angle has to be same for both gears as value but in opposite directions to maintain the two axes parallel. It is usually specified as a value tolerances has to be very small due to the negative effect on load transmission.

If you want to measure the tooth profile you need a special tool having the possibility to place the transverse measuring edges at a specified depth with respect to the tooth top.

Values are : small gear transverse value 7.435 at 2.129 and for the big gear 8.1327 at 2.9605

You could also measure in a position NORMAL to the teeth the common tangent provided that your big gear is more than 19 mm wide:

small gear 27.342 over 4 teeth big gear 77.935 over 10 teeth all values in mm.

The second control way is the simplest since you can make usage of always available instruments.

Normally the designer -if he is a good one - should have given to you as well control nominal as tolerance values. The choice of the shifts make me think that he has not a very good experience with gears. Tolerances are important in order to avoid dry friction since if the gaps are not as they should be the risk of oil film interruption is very high.

If you send your mail on the private message channel I will send you a full book about gears so that you will be much more independent.

The best would be to buy a book about gears (mine is not the best and the best I have is in a language you will have some problems to read if yours is English). if you google you can find a good one for less than $50.

If any aspect unclear, you may ask either in the general file or on the private channel.

Nick Name.

I am sincerely sorry that no mechanical eng. took your question as serious and gave an answer.