Diameter of a circle at specific angular offsets

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  • Diameter of a circle at specific angular offsets

    Hello,

    I need to define the diameter of a circle at 8 different paths through the center. Is it possible to construct lines through a circle-center at specific angles? For example, if I needed to know the diameter of the circle in the image from points 1 to 4, 2 to 5, and 3 to 6, etc., what would be the proffered method? (assuming line 3-6 is 90deg off of line 1-4, and 45deg off from 2-5)

    Any help is appreciated. Thanks.

    CIRCLE_IMG.jpg

  • #2
    I'm thinking align to that circle first then just take hits at the angles needed and you have points to work with forget the intersections... what sort of tolerance/variation are you looking for?

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    • #3
      I would probe the hole, then origin to it. Then create 6 points (or 12 points at 2 different levels if you want 3D eval) at the polar angles you need, and make sure all noms and vectors are correct. Then measure the distances between the points. HTH

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      • Mike Ruff
        Mike Ruff commented
        Editing a comment
        Dang, Douglas beat me to it!

      • Douglas
        Douglas commented
        Editing a comment
        only because I included less detail probably

      • ryan_volkmann
        ryan_volkmann commented
        Editing a comment
        I don't know how to do most of what you are describing, but now I have the proper search terms to go learn. Thanks

    • #4
      Measure point 1 Copy/paste with pattern -45 degrees (twice)

      copy/paste with pattern above 3 points -180 degrees

      measure points and report distances

      B&S CHAMELEON/PCDMIS CAD++ V2011

      There are no bugs, only "UNDOCUMENTED ENHANCEMENTS!"

      sigpic

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      • ryan_volkmann
        ryan_volkmann commented
        Editing a comment
        I don't know how to copy/paste patterns. I will google-it and learn. Thanks

    • #5
      a better answer would have been... teach those people who want to see it this way how circularity works, that is a an old school millwright method when only 2 point measure is available... stick mic.

      EDIT: I take that back if and only if it is being used to check the alignment of 2 half circles, like a bearing bore in a split case gear box... still CMM can do better

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      • ryan_volkmann
        ryan_volkmann commented
        Editing a comment
        I wish the client would just accept a circularity value.. I'm not 100% certain what their end use-case is.

    • #6
      Probe dia, origin to it, probe dia again using autovector points, polar dist from ctr to each pnt, bingbangboom easy peasy

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      • #7
        Originally posted by Douglas View Post
        I'm thinking align to that circle first then just take hits at the angles needed and you have points to work with forget the intersections... what sort of tolerance/variation are you looking for?
        I guess I don't know how to take hits at specific angles - that's a simpler explanation of my issue. The tolerances vary, but the tightest are 0.001" in this case.

        I'd also like to be able to check this on previously run inspections where I no longer have the item to take more hits. That is why i wanted to be able to construct lines/points.

        Thanks

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        • Douglas
          Douglas commented
          Editing a comment
          once you are aligned to the circle, your alignment will need rotation, but an auto circle with 8 hits will give you the points you need, use the 'to points' check box and pcdmis will create the circle and all 8 points

      • #8
        Originally posted by DAN_M View Post
        Probe dia, origin to it, probe dia again using autovector points, polar dist from ctr to each pnt, bingbangboom easy peasy
        I'll have to learn how "Auto Vectors" work. Thanks

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        • Douglas
          Douglas commented
          Editing a comment
          the auto circle I described in the other reply will be made up of vector points, the 'to points' check box automatically creates the vector points as well

      • #9
        Originally posted by Douglas View Post
        a better answer would have been... teach those people who want to see it this way how circularity works, that is a an old school millwright method when only 2 point measure is available... stick mic.

        EDIT: I take that back if and only if it is being used to check the alignment of 2 half circles, like a bearing bore in a split case gear box... still CMM can do better
        Tried to talk the client into this. Previous inspections were done by super-micrometer (hence the 2-point stuff). They want the data reported the same way for "consistency".

        Thanks

        Comment


        • vpt.se
          vpt.se commented
          Editing a comment
          ...which also is the way to check local size in ISO world (two point).

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