constructing a very tiny circle !?!?!!

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  • constructing a very tiny circle !?!?!!

    Still a newbie to CMM and PC DEMON. Is it possible to construct a circle
    using 3 points that are less than .001" apart? I'm trying to come up with a way to estimate position between the cylindrical hole inside an externally
    threaded cylinder and the pitch of the external thread . The inner diameter is about 1.8" and the external threads are 2.4-16. I'm supporting the part by the threads held by a fixed thread ring gage held in a vice. In one position I am taking 3 hits deep in the cylinder to get a circle then taking 3 hits
    shallow in the cylinder to get a second circle. I'm then rotation my part 120
    degrees then finding the same circles. The process is then repeated once more after a second 120 degree rotation . I'm trying to construct a circle using the 3 "inner " circles then doing the same with the two "outers" suspecting that the diameters of said circles might describe the position that I'm after. Everything seems great til I try to construct the circles- I'm getting the "MATH FAILED"..." FEATURES DO NOT..." message.
    Can any of you youngins help out an old guy? or any of you really old guys
    help out a youngin?
    Thanks
    MJB
    "listening for the last trump... looking toward the eastern sky"

  • #2
    Work plane?
    RFS Means Really Fussy Stuff

    When all you have is a hammer - everything looks like a nail....
    sigpic

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    • #3
      Originally posted by kbotta View Post
      Work plane?
      That would be my guess...
      sigpic
      Xcel 15-20-10 - PFXcel 7-6-5 - Merlin 11-11-7 - Romer Absolute 7525SI
      PCDMIS 2012
      Windows Office XP

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      • #4
        The work plane looked good to me. it should be the same plane that the circles were generated in, shouldn't it?

        Tks
        MJB
        "listening for the last trump... looking toward the eastern sky"

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        • #5
          Should be. The only other thing I'm thinking is that maybe you are getting a false hit because it is such a small diameter and the 3 hits are unable to form a circle (since 3 hits is the minimum it takes to make a circle).
          sigpic
          Xcel 15-20-10 - PFXcel 7-6-5 - Merlin 11-11-7 - Romer Absolute 7525SI
          PCDMIS 2012
          Windows Office XP

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          • #6
            Are you trying to create the circle from the other 3 circles? I've not had much luck trying to create circles from circles. Are these partial circles or 3 circles with different centers (clover shaped)? If they are partial circles with the same center, I don't think you will be able to do what you want. If you change your partial circles to individual points for each hit, you can create a circle from those. If the 3 circles form a clover shape then try creating a point at the center of each circle and then create a circle from those 3 points.

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            • #7
              They are complete circles. They look good on the graphics display. I tried
              constructing cast points at the center of each then constructing a circle from
              each set of 3. I checked the distance between each point/set and the distances were apx .0004,.0002,and.0012. Not much distance but I was
              still hoping to construct a circle then find the diameter. I may just have to take the distances and calculate the dia. elsewhere.
              Thanks
              MJB
              "listening for the last trump... looking toward the eastern sky"

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              • #8
                1-Please check the vectors of the points
                2-If the vectors are fine , project all points to a plane-| Then try to construct the circle
                3-Try to use BFRecomp

                HTH

                Saliha
                sigpic
                Either seem as you are or be as you seem.M.J.Rumi

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                • #9
                  The points are constructed as "cast points" at the center of circles. The vectors of the circles are good ,I assume, because the graphics display indicates a proper orientation of the circles. I haven't tried steps 2 and 3 yet.

                  Thanks!!
                  MJB
                  Last edited by MJBolster; 03-01-2007, 05:36 PM. Reason: goof
                  "listening for the last trump... looking toward the eastern sky"

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