Datum on an FCF with 4 Holes

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  • Datum on an FCF with 4 Holes

    I have a Cylindrical part datum C is attached to a feature control frame with four bolt holes. Would the datum be the hole it is pointing at or the center of the circle created by the four holes. Im evaluating the profile of the flange that the holes are located on, whats the proper way to do this with PCDMIS. Any help is appreciated, Ive attached a rough drawing (its very rough DATUM A is the top plane datum B is the cylinder it is attached to) Datum C is my issue.
    Attached Files

  • #2
    Datum C would be the center of the hole pattern.


    • #3
      Thats what I was thinking but I needed confirmation. Thank you for the help.


      • #4
        Datum C would be all four holes together for clocking use best fit for rotation only


        • neil.challinor
          neil.challinor commented
          Editing a comment
          Depends on the version of PC-Dmis you are using. In 2020 R2 with the geometric tolerance command you would simply reference all four holes a the datum. In older versions that use XactMeasure, you would need to construct the set.

        • Richardbeyer87
          Richardbeyer87 commented
          Editing a comment
          I am using 2020 R2, I have not used that yet so I shall look into it. Thank you kindly sir.

        • vpt.se
          vpt.se commented
          Editing a comment
          Pretty sure that it won't accept a group of features as tertiary (XactMeasure)... (pre-2020 R2)

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