Circularity of hole
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: Circularity of hole
: Circularity of hole -- ignatiuschew	Post Reply	Top of thread	Dimensioning & Tolerancing GD&T Forum

Posted by: Kelly Bramble ® 10/01/2010, 22:02:01 Author Profile eMail author Edit

Unless a Circularity tolerance is specified, there is none... Though, technically for the ASME and ANSI standards, Circularity is included in the limnits of size specification. Which means, the hole is simply manufactured between the MMC and LMC size an all is accepted (Rule #1 should be considered). If the engineering drawing standard is ISO 1101 - again the Circularity is included in the limits of size - but not Cylindricity.

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: : Circularity of hole
: : Circularity of hole -- Kelly Bramble	Post Reply	Top of thread	Dimensioning & Tolerancing GD&T Forum

Posted by: ignatiuschew ® 10/01/2010, 22:15:33 Author Profile eMail author Edit

Thanks Kelly, But in the drawing, there is a callout for reference to ISO 2768m-H. Even though circularity was not call-out for that hole. Based on ISO 2768m-H we still need to follow the general tolerance. Am I right? So based on the MMC and LMC size, is the tolerance supposed to be 0.02mm or 0.04mm (total tolerance range of the diamter)?

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: : : Circularity of hole -- ignatiuschew	Post Reply	Top of thread	Dimensioning & Tolerancing GD&T Forum

Posted by: Kelly Bramble ® 10/01/2010, 22:41:50 Author Profile eMail author Edit

ISO 2768m-H is embraced in several GD&T standards, US and within the EU - such as EN 22768-2:1993 The specific notes on Circularity are: "The general tolerance on circularity is equal to the numerical value of the diameter tolerance, but in no case shall it be greater than the respective tolerance value for circular radial run-out given." So, MMC = (34.2 - 0) and LMC = (34.2 + 0.039) The Circularity is built into the limits of size or is equal to 0,039 when some elements of the hole are manufactured at LMC and zero when all elements are manufactured at MMC.

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