GD&T question

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  • GD&T question

    If the 2 bigger holes are datums and are part of the main alignment (B & C) can you have position callout for the small hole in relation to B & C since the small hole is on the angled surface?


  • #2
    Your print isnt coming thru


    • #3
      How about now?



      • #4
        typically with an angled ID, the Basic dimension will be established at the intersection of a surface usually on angled face.
        This is point that would be used for position results to be based from.
        If you have MMC then you need to construct a feature to use feature of size value in the calculations to determine acceptance.
        If you dimension an angled cylinder it self then the basic nominal will change and/or not usually line up with the basic dimensions.


        • #5
          From more of a high level theory perspective:

          Datums are theoretical perfect geometry that does not exist in the real world. We identify Datum Features on parts. We mate those to Datum Feature Simulators. From the Datum Feature Simulator we Construct the Datum Reference Frame. We then evaluate the other features on the part in relation to the Datum Reference Frame, not the Datum Features.

          So in the case of your small hole, it can absolutely be constrained for position relative to the Datum Reference Frame established from the Datum Features even though they are displaced by a BASIC angle as Rich mentioned along with giving you a good nuts and bolts step by step of how to do it on your CMM with pc-demon.

          HTH & ymmv

          sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery


          • #6
            Thanks guys, customer is making drawings for the future parts and I am partially involved in review so just wanted to know how it should be done correctly on the drawing to avoid future problems.


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