4.1 / Best Fit Circle question

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  • 4.1 / Best Fit Circle question

    I have a part that I am trying to apply Best Fit to a diameter, 30mm hole +.013 -0

    I am taking 12 surface points around an ID and then creat a best fit circle using those hits, and max inscribed.

    Now as I understand it, this is simulating a "hard" gage or plug gage, like using Deltronic pins.

    now the question.....wouldn't the "form" of this "created" circle be 0 (zero)?

    thanks
    bob
    Which one gets ridden today? MPH vs MPG..tough choice, both are FUN
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    Starrett RGDC 4028-24 :alien:
    Demon vintages 3.7, 4.1, 4.2, 4.3, 2009

  • #2
    I think your looking for max inscribed, but I'm sure the actual form is always reported.
    I would be careful about using non-vectored hits in a circle. An autofeature is still the best way to go, apart from full scanning elements.
    G
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    • #3
      I agree with Cumofo, scanning the diameter with that tight a tolerance is your best bet. I would definely try a correlation study between the pins and your readings.
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      "You cant vote 'present' as the President of the United States"

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      • #4
        max inscribed only uses the three highest points - scanning would give the most density to find those points. Only 12 might give you repeatability problems. Vectoring should not be a problem, but I dont understand why you use surface points instead of basic hits, auto-circle would be much easier.

        Are you best fitting and then max-inscribing?
        Last edited by cmmguy; 05-02-2007, 07:47 AM.
        Links to my utilities for PCDMIS

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        • #5
          vectors are not a problem..created one hit with proper vector the did paste with pattern

          best fit was done WITH max inscribe

          I'm now taking 36 hits and getting better results

          now here is a funny thing showing up.......
          The program is created in metric due to the nature of the drawing being metric,
          The results are in metric for same reason
          I also have this one diameter in inches (as well as mm) due to the fact the machinists are working in inches
          I added form to the diameter results (inches)
          the form results on the "edit" screen are in inches but on the "report" screen show in mm. WTF?
          Last edited by bob mappes; 05-01-2007, 02:10 PM.
          Which one gets ridden today? MPH vs MPG..tough choice, both are FUN
          sigpic

          Starrett RGDC 4028-24 :alien:
          Demon vintages 3.7, 4.1, 4.2, 4.3, 2009

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