Weird datum

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  • Weird datum

    Hey guys
    I have a weird datum that im trying to measure. (Ref C)
    It seems to me to be the highest point (plane) at the curvature of a circle (r52.5)
    But honestly i kinda just wanna change it to centerpoint of the r52.5. I mean whats the difference?

    Anyone has any clues?
    Ill upload a clip of the drawing so its easier for you to understand.
    Attached Files

  • #2
    The plane created from the high points would be used as your ( Y ) 0.0 in this view. The center point of the RAD wouldn't be anywhere close to that location ? Datum A will be X and Z 0.0. B isn't of the page shown so I am not sure how that comes into play.


    • #3
      If the function of that datum is a stopping point for a mating component to touch down on, then using the center would not be the intent of the callout. The center can be static while any size fluctuation will move that stopping point up or down.

      It looks like you want the tangent of that radius. Construct a point and assign it the value of the center point + radius.


      • pcdmisstudent
        pcdmisstudent commented
        Editing a comment
        Hey how can i construct a point and assign it the value of the center + radius?
        I could construct a offset point from the circle + radius. but then it will construct it from nominal radius, not measured right?

    • #4
      A is a width, locks 1 coordinate and 2 directions
      B is ???, locks ??? (should be 1 direction)
      C as a high point could lock 1 coordinate
      C as a center point could lock 2 coordinates, but one of them is already locked by A, so essentially the same as the high point, but not exactly the same. Also note that you have a quite short arc of the circle, so the accuracy of the circle center will suffer...
      SW support - Hexagon Metrology Nordic AB


      • pcdmisstudent
        pcdmisstudent commented
        Editing a comment
        So how would you recommend me to measure datum C? Circle,, construct offset point with radius as the previous guy mentioned?
        And if so, how can i add the radius (from measured value) and not nominal value?

      • AndersI
        AndersI commented
        Editing a comment
        High point - if you have 2019 R2 you can use Constructed point, Tertiary datum, on a scan over the'hill'.

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