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Circularity/Roundness as a Datum Feature

Circularity/Roundness as a Datum Feature

Circularity/Roundness as a Datum Feature

(OP)
Presently trying to figure out the relationship of a spherical profile (.001) GD&T referencing circularity (.001 as Datum A MMC). Does this mean that the profile tolerance follows the circularity tolerance at the circles' (±.001) maximum material condition? Does this imply a bonus? How does this differ from "form"?

RE: Circularity/Roundness as a Datum Feature

Quote:

Presently trying to figure out the relationship of a spherical profile (.001)
"A spherical profile (.001)" means that the actual or measured spherical surface must be contained within a bilateral boundary of .001 wrapped about the specified basic spherical size.

Quote:

GD&T referencing circularity (.001 as Datum A MMC).)
This comment makes no sense!

Quote:

Does this mean that the profile tolerance follows the circularity tolerance at the circles' (±.001) maximum material condition? Does this imply a bonus? How does this differ from "form"?
These comments make no sense either! Show us a sketch of the part and its specifications.
Paul

RE: Circularity/Roundness as a Datum Feature

If you mean that the circularity callout on the spherical datum feature includes a material modifier (MMC), then the callout is not legal.  Form controls cannot (in '94) have a modifier of MMC or LMC, and are required to be RFS.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

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