Primary datum

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  • Primary datum

    I have a drawing with a normal ABC datum structure bottom face as -A- and -B- as the center of three slots, but I have a dimension TP|DIA .010 MMC|B MMB|F -F- being a side face, is it
    possible to have a 2d feature as a primary datum? xact measure lets me do it.

  • #2
    Sounds like an potential print error. Check with engineering or the customer.


    • #3
      Wouldn't A be a plane ?


      • #4
        Datum B should be a group of slots (feature set)?
        PC-DMIS CAD++ 2o19 R1 SP11


        • #5
          Datum B is the center of three slots, datum C in one of the slots, can this be done? F is a side angled face 35 degrees from bottom face A


          • Schlag
            Schlag commented
            Editing a comment
            I have never been so a print already or make a napkin drawing.....

        • #6
          I have added a sketch
          Attached Files


          • neil.challinor
            neil.challinor commented
            Editing a comment
            I'd say the call out is wrong and looking at the sketch the design intent was probably to level to A, origin on the centre of the pattern of slots and rotate to the top slot - but you would need confirmation of that from your customer. 2020 R2 allows patterns of slots at MMB but only as a secondary or tertiary datum so you would need to make datum A the primary. Alternatively, you may be able to construct 3D widths on each of your slots and then use the pattern of widths as datum B - which would be valid as a primary datum at MMB.

        • #7
          The part is only .040 thick


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