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1.0000 - 0.9998 CMM Calibrated to .0002

Discussion in 'Sampling, Standards and Inspection' started by David Hehir, Jul 29, 2020.

  1. David Hehir

    David Hehir New Member

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    Hello All,

    I'm working at a smaller aerospace company on contract, and they are qualifying parts on a CMM. To me it seems to be within the tolerance zone of the machine. Is this a grey area or is it like I have been trained at other company's not a qualified measurement.

    1.0000 - 0.9998 CMM Calibrated to .0002

    From my previous experience it measure within two tenths 1.0000-0.9998 I would need a CMM calibrated to .00001 not .0002. Are many CCM's calibrated to this level or is this just a grey area where many measurements to .0000 are sometimes done within this range. How expensive is it to obtain a CMM that measures in .00001 millionths?

    Thanks for your thoughts.

    Just stumbled on this board today. Very good content keep up the good postings everyone.
     
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  2. Mike S.

    Mike S. Member

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    Many aerospace companies use a simple minimum 4:1 rule regarding measurement device accuracy relative to the specification tolerance. For example, if the spec tolerance was +/- .0001 the measurement device accuracy required would be +/- .000025
     
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  3. S1D3K1CK

    S1D3K1CK Member

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    I work in the automotive field and we have to have our CMM calibrated through an accredited source per IATF standards. The calibration company that we go through uses tolerances for Linear Accuracy in X, Y, and Z-Axis to +/- .000100", Squareness X-Y, Y-Z, and Z-X to +/- .000050" and the Repeatability for all Axis is .000000". I assume aerospace would be more meticulous. But remember, it also depends on the customer's requirements. Oh and make sure the granite surface plate is calibrated.
     

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