Posted by Web Gear Services on May 24, 2000 at 21:05:13:
In Reply to: help - test radius vs. m.o.w. posted by david on May 23, 2000 at 18:17:35:
What probably is happening is that your test radius and composite tolerances are being stacked up according to the AGMA standards. There is an error in how this calculation is done in the AGMA standard.
According to AGMA, to arrive at the maximum test center distance, you take a maximum test radius for the master (based on max. tooth thickness), and add the maximum test radius for the tested product (based om max. tooth thickness), and you add the TCT to the sum. For the minimum test center distance, you do not apply the TCT.
This is not practically correct since effectively if your tooth thickness goes to the minimum tolerance, your test center distance would either right at the minimum with no allowance for runout or other error effects.
I have discussed this with a member of the original AGMA 2000-A88 committee. His interpretation is that the technical committee was incorrect in their standard. He has suggested that a correction should be made to the standard; namely, half the TCT should be added to the plus side, and half reduced from the min side.
This could be why it is not uncommon to see the conflict with M.O.W. that you have seen.
Our company sells excel based gear design software. Our master gauge design software package calculates test center distance based on the funtional way, not the standard.
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