huangyhg

flatness vs. profile
i am looking over a drawing. i have review y14.5 1994, but i am still confused.
i thought flatness can only be applied to a single surface and profile should be used for multiple surfaces.
the drawing i am reviewing has datum a applied to sever co-planar surfaces and has a flatness call out.
can a flatness call out be applied to multiple surfaces? if need be i can send a picture.
flatness is to a single surface or plane while profile of a surface can apply to multiple surfaces on the same plane.
dave d.
if the surfaces referred to have a flatness spec and the phrase "common zone" or similar, this is in accordance with iso standards. does the print specifically invoke asme y14.5m-1994? if it is a print from outside the u.s. this is very likely what you are dealing with, an iso compliant print. it has the same meaning as "profile of a surface" with "x surfaces" underneath it.
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if you have asme y14.5m-1994, look at figure 6-21. this this what they are trying to do?
note how they use datums a and b together as the primary datum.
jhg
as above, assuming to 14.5 then it sounds wrong. however, i can tell you this is a common mistake, even amongst people that have supposedly been working to asme standards for some time.
you are correct that to get the equivalent of flatness for a multi surface datum then profile of a surface is the correct control. exactly how this is applied/used can vary slightly depending if all the nominally coplaner surfaces are used to make the datum or if only some of them are used. look at section 6.5.6, although it sounds like you already have.
kenat,

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