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Gage R&R calculation for bilateral & single-sided tolerance

Discussion in 'Gage R&R and MSA - Measurement Systems Analysis' started by _Zeno_, Aug 26, 2016.

  1. _Zeno_

    _Zeno_ Member

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    Are there differences between how a R&R is calculated depending on whether the part tolerance is bilateral or single-sided?
     
  2. Miner

    Miner Moderator Staff Member

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    Atul Khandekar likes this.
  3. ncwalker

    ncwalker Well-Known Member

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    I will go zen on you and answer your question with a question. :) It is total tolerance that feeds all the equations. Is there a different way of determining total tolerance between a bilateral and one-sided tolerance?
     
  4. _Zeno_

    _Zeno_ Member

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    That's the way I've always seen the issue. Our ERP system (PLEX) has GR&R functionality that halves the R&R value if the characteristic being evaluated is single-sided (it grabs the tolerancing information from the part specification table which also feeds its control charting module). Having never encountered this in the past, I turn to the experts in this forum.
     
  5. ncwalker

    ncwalker Well-Known Member

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    That doesn't make a lot of sense. I could specify a diameter as 8.00 mm +/- 0.05 mm. Now, were this a pin I was using for a press fit operation, maintaining the SAME total tolerance, I would expect to encounter it specified as 8.00 mm +0 / - 0.10 mm. In other words, the nominal and the upper limit are aligned. If your software would see this and categorically halve the R&R value, I wouldn't agree that's correct simply because the nominal were on one of the limits. What matters is the total tolerance in the percent of tolerance calculations. Location of the nominal within this band is immaterial. Now, if the pin had a circularity control of 0.05, I would expect things to be halved because that actually IS half the tolerance of the diameter, you can't be more circular than zero.
     

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