ISO GD&T Question concerning two adjacent planes on a primary datum non-cylinder.

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  • ISO GD&T Question concerning two adjacent planes on a primary datum non-cylinder.

    I am looking at a drawing I clearly don't understand. I have a part that does mount on two surfaces although the surfaces are perpendicular to one another. Datum A on my drawing is parallel to the to the X-Axis. Datum D is a plane perpendicular to the X-Axis. I then have 3 cylindrical holes and one slotted hole in line on the Z Axis running through the Datum A plane. One cylindrical hole is Datum B and the slot below it is Datum C. When I come to the feature control frames for the holes / slots it goes like this. True Position | Ø.2 | A – D | B | C |
    Planes A-D would make an line axis in the z direction? With datum B hole tie down the x direction rotation? With Datum C being the “Z” direction zero? I know that’s not right because all the drawing dimensions are coming the Datum B.

    I cannot wrap my head around the reason the engineer did not believe it would flush up against datum A and then rotate to datum D and align to datum B.

  • #2
    Can you post the print? Or at least a copy where you've blacked out all non-essential stuff to your question...so we can see your callout without having you violate confidentiality requirements?

    Comment


    • #3
      As I understand, I think A-D is a line constructed from a perfect angle between A and D (the defects should be equally distributed between both datums) and it defines Z axis.
      This line should also be the vector of a plane.
      The holes and the slot axes must be parallel to this plane (or perp to the line).
      B hole should define theX direction projected on the plane (it's a secondary datum) and the Y and Z origin.
      C define the a 0° angle from Z axis (you could have a non zero angle and have to check the alignment of holes)

      Hope it's clear, it's just a way of creating the tolerance zone without draw...

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      • #4
        Here is what it looks like.
        Attached Files

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        • #5
          Can you insert a larger picture ?
          Like this, I think your text is clearer tan the picture !!!!!

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          • #6
            Capture.JPG

            (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
            They say "Nobody's Perfect." I must be Nobody.

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            • #7
              We can't see the picture T Schmidt

              Remove the small pic and re-upload it doing it like this please

              Capture.PNG

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              • #8
                ezgif.com-resize1.gif

                Wonder if he/she is ever gonna put a bigger print?
                Last edited by KIRBSTER269; 02-14-2018, 12:57 PM.
                (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
                They say "Nobody's Perfect." I must be Nobody.

                Comment

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