Calibration Sphere

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  • Calibration Sphere

    Just curious to find out how often a calibration sphere should be sent out for calibration to
    verify size and roundness. Our 3 C.M.M.'s are calibrated weekly with this ceramic sphere.
    Should the calibration of the sphere be yearly? Once every 3 years? Once every 5 years?
    Thanks for your input !

  • #2
    I send ours out once every two years.
    When the going gets weird, the weird turn pro. Hunter S. Thompson

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    • #3
      Never send it...
      Maybe I'm wrong, but I believe that uncertainty of laboratories is greater than the difference that they could find between two calibrations...

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      • #4
        Never have sent one, never had a question about it.
        sigpic

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        • #5
          I would be more worried about metal sphere. Ceramic holds shape well (it's very rigid) and cannot be dented like metal can (which is quiet elastic when compared to ceramic).

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          • #6
            Originally posted by JEFMAN View Post
            Never send it...
            Maybe I'm wrong, but I believe that uncertainty of laboratories is greater than the difference that they could find between two calibrations...
            +1
            Poleaxe

            Beware the environment you live in for it will shape you
            Be careful the friends you choose for you will become like them.

            sigpic

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            • #7
              Yeah, I didn't used to send ours but got bi*ched at by the TS auditor a few years back and decided it wasn't worth it to argue, so now I send it out every 2 years.
              When the going gets weird, the weird turn pro. Hunter S. Thompson

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              • #8
                Originally posted by JEFMAN View Post
                Never send it...
                Maybe I'm wrong, but I believe that uncertainty of laboratories is greater than the difference that they could find between two calibrations...
                +1...and there is a very good reason for that. I had 2 calibration spheres & for a while I complied with the 'Quality Directives' from above & sent the unused spare out each time.

                Very amusing to ponder the results & accompanying certificates when it came back. Quite often it dipped out of tolerance & then miraculously back in again next year.

                They never did find out but I did have to let the Quality Engineer upstairs in on the escapade as he had been instructed to conduct ‘Minitab’ GR&R studies on the results… again to comply with some ‘know it all’ customer’s QA department.
                Poleaxe

                Beware the environment you live in for it will shape you
                Be careful the friends you choose for you will become like them.

                sigpic

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                • #9
                  Some auditors are picky about it, some aren't.
                  Never had an issue til last year.
                  Now the spheres are on the calibration list.
                  Lately, it occurs to me
                  What a long, strange trip it's been.

                  2017 R1 (Offline programming)

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                  • #10
                    My primary concern was traceability if the ISO auditor would question when the spheres were last calibrated.
                    We do have the original Certs. from Brown & Sharpe and Renishaw.
                    Thanks for all of the input !

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