Talk:Roundness
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Needs something drawn to show the inscribed / circumscribed circles. The NIST reference would be a start (NIST? Is that PD US Gov annyway?) Andy Dingley (talk) 12:31, 14 August 2013 (UTC)
November 2011[edit]
The grain morphology link is broken
ISO 1101 Ratio or Difference?[edit]
> The ISO definition of roundness is the ratio of the radii of inscribed and circumscribed circles, i.e. the maximum and minimum sizes for circles that are just sufficient to fit inside and to enclose the shape.
Is this correct? ISO 1101 B.4 says:
> The roundness of a single toleranced feature is deemed to be correct when the feature is confined between two concentric circles such that the difference in radii is equal to or less than the value of the specified tolerance. The location of the centres of these circles and the value of their radii shall be chosen so that the difference in radii between the two concentric circles is the least possible value.
This seems to indicate that the roundness measure is actually the difference between the radii of the circlesl, instead of the ratio.
This is also supported by the other reference (https://web.archive.org/web/20131007200643/http://www.rank-instrument.com/download/Introduction%20to%20the%20Measurement%20of%20Roundness.pdf) which displays the "RONt" measure as a value in milimeters, not as a ratio.