fH¯ values for tooth trace angle deviation

[Transmissions]

Hallo!
I need to specify the tolerances for a certain gear according to the DIN3962. In the Part 2, where “Tolerances for Tooth Trace Deviations” are specified for a given gear tooth quality, I can find the values for Fß, fHß and fßf, with the tolerances given in micrometers. My question is: When I read a value “18” for the tooth trace angle deviation ‘fHß’… is it an absolute value for the tolerance (±9)? Or it means that I could have ±18 for the lead tolerance?
I would really appreciate your comments about it!

Thank you in advance,

Lina

 

[diamondjim]

I am not familiar with that DIN Standard
but most gear tolerance on deviation are
maximum allowed ie 0 to 18 in your case.
Hope others can give you a more definitive
answer.

 

[gearman1234]

The new AGMA 2015-1-A01 which replaces AGMA 2000-A88 is very similar to DIN.

fHß actually indicates the deviation from the design helix angle. On a given gear it can be only in one direction. Assume that fHß tolerance is 18 microns and suppose that the gear is RH helix and the value shown on the gear chart is +17 microns for an actual gear when measured using a gear analyser.Then the gear will be still in tolerance.
Plus sign usually indicates that the actual helix is larger than the design helix. Negative vaule indicates the the actual helix is smaller than the design helix.

You asked -- " When I read a value “18” for the tooth trace angle deviation ‘fHß’… is it an absolute value for the tolerance (±9)? Or it means that I could have ±18 for the lead tolerance?"--- The meaning is that the helix slope deviation on either side ( plus or minus) should not exceed 18 microns.