GD&T and me

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  • GD&T and me

    Here's the short version...

    I measure several diametrical features in the free state and a few areout of tolerance. So my boss suggested I get the fixture, clamp it down and remeasure those same features... I did and they were WAY out. Then I toleranced them in coordinate (XYZ)... The actual "measured" number was hugely different...

    So the question is, How can it be that when I tolerance diametrical true position (MMC to the feature and -B- and -C-...) I get a substantially different number in simple axis tolerancing?

    Okay that was the GD&T part... the ME part is it's driving me NUTS!!! Help if you can please...
    Thomas Stewart
    Quality Technician/CMM Programmer

    2010 MR1
    Mitutoyo BN715
    CMMC-3 Controller

  • #2
    "How can it be that when I tolerance diametrical true position (MMC to the feature and -B- and -C-...) I get a substantially different number in simple axis tolerancing?"

    Depends on what the Datum Structure is.
    If doing True Postion at MMC, are -B- and -C- at MMC? What version PC-DMIS, how is part aligned, alittle more info, and someone can probably help ya out. There has been a lot "discussion" About GD&T here and in other places.

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    • #3
      Lynn is very wise in here second post. Welcome Lynn. It is the Datum scheme you are using. Do you have a pic of the scheme? Are you using CAD? What type of part? Stamping, Plastic ?
      I can help you get nuttier, If you give us half a chance.
      sigpicSummer Time. Gotta Love it!

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      • #4
        It may also (not knowing what this part is actually like) be that in a constrained condition the part shape has been altered.....?????

        I have several parts that the notes say to apply things like flatness in a "constrained condition"

        bob
        Which one gets ridden today? MPH vs MPG..tough choice, both are FUN
        sigpic

        Starrett RGDC 4028-24 :alien:
        Demon vintages 3.7, 4.1, 4.2, 4.3, 2009

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