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Thread: Hole referencing a perpendicular plane

  1. #1
    Associate Engineer
    Join Date
    Nov 2016

    Hole referencing a perpendicular plane

    I am trying to analyze a drawing and cannot make sense of a true position datum on a hole. It is referencing a perpendicular center plane bisecting two surfaces that are dimensioned from the hole itself. I think there are multiple things wrong with doing it this way, and I cannot link the original drawing, so I have attached analogous example. I really am not sure how to make it "correct." so any advice would be helpful.
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    Last edited by Kelly_Bramble; 11-11-2016 at 05:37 PM.

  2. #2
    Principle Engineer Cragyon's Avatar
    Join Date
    Feb 2013
    Newark, NJ
    Change the Position to Perpendicularity. Sometimes folks think using position is OK here but it is incorrect..

  3. #3
    Project Engineer
    Join Date
    May 2011
    And make sure they really want the datum to be labeled like that -- it is implying that the center plane of the 5.750 span is the true datum. That's fine, but I ask because often on parts like this the datum is meant to be taken from one face (or the other). To indicate that, the datum triangle symbol would have to be nudged up or down so that it's not in line with the dimension line of the 5.750.

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