Fastener formulas : General GD&T Questions

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Fastener formulas

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weisse

Post subject: Fastener formulas

Posted: Fri Jul 10, 2009 1:33 pm

Joined: Fri Jul 10, 2009 1:30 pm
Posts: 1

Does MMC on referenced datums affect the fastener formulas?

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joeyd

Post subject: Re: Fastener formulas

Posted: Mon Jul 13, 2009 10:59 am

Joined: Fri May 01, 2009 4:26 pm
Posts: 12

The fastener formulas are based upon "hole diameter" and "fastener diameter" when both of those are at MMC. The resulting total available tolerance is then applied based on fixed or floating fastener principles. The resulting tolerance value for each related characteristic is that value when the FOS is at MMC. As the FOS departs from MMC then the additional tolerance becomes "bonus". So, the direct answer is: No, MMC does not affect the fastener formulas. But, if the tolerance is applied at MMC (use MMC modifier) then bonus tolerance is available.