Cylindricity using MMC modifier in ISO 8015 : Tolerance Analysis

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Cylindricity using MMC modifier in ISO 8015

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AWeaver

Post subject: Cylindricity using MMC modifier in ISO 8015

Posted: Wed Sep 23, 2009 7:24 am

Joined: Thu Jul 23, 2009 12:36 pm
Posts: 9
Location: Chicago, IL

I have another question about the ISO 8015 spec. Does this specification allow Cylindricity to use a MMC modifier? I have two requirements on a print a Cylindricity of 0 @ MMC in a CZ of 3 cylindrical features and a Cylindricity of 0.01 @ MMC in a CZ of 6 cylindrical features. Is this an acceptable use of Cylindricity under ISO 8015? If so, how is it interpreted?

I know under ASME you cannot use the MMC modifier with Cylindricity.

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Anthony J. Weaver
Supplier Development Engineer
BorgWarner Drivetrain Systems

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joeyd

Post subject: Re: Cylindricity using MMC modifier in ISO 8015

Posted: Wed Sep 23, 2009 3:53 pm

Joined: Fri May 01, 2009 4:26 pm
Posts: 12

Anthony, interesting question! It was my understanding that ASME and ISO handled cylindricity in the same way. True, ISO does not automatically invoke the Rule #1 Envelope principle as does ASME (perfect form at MMC). All things are independent in ISO unless otherwise stated, but if a drawing specifies ZERO cylindricity error at MMC, isn't that the same thing as "perfect form at MMC"! ISO allows for the use of the "CIRCLE E" symbol to invoke the Envelope principle. I didn't think the MMC modifier could be used with cylindricity in either ASME or ISO but this could be another way of an "ISO approach" to applying the Envelope principle. In that case the maximum cylindricity error would be the bonus from the cylindrical size tolerance.

Just my thoughts.... 8-)