Flatness call out for partial surface
Flatness call out for partial surface
(OP)
Hello
I was wondering if anybody had some advice on the proper way to call out a flatness tolerance using GD&T but only for a partial surface. The application is a mechanical seal. I've attached a drawing for illustration. The surface in question is labeled datum A with the .001 flatness call out. The only section of the surface that requires this control is enclosed in the rectangle. I'm just not sure how to properly notate this call out on the drawing. Thanks in advance for any advice.
I was wondering if anybody had some advice on the proper way to call out a flatness tolerance using GD&T but only for a partial surface. The application is a mechanical seal. I've attached a drawing for illustration. The surface in question is labeled datum A with the .001 flatness call out. The only section of the surface that requires this control is enclosed in the rectangle. I'm just not sure how to properly notate this call out on the drawing. Thanks in advance for any advice.





RE: Flatness call out for partial surface
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NX8.0, Solidworks 2014, AutoCAD, Enovia V5
RE: Flatness call out for partial surface
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Flatness call out for partial surface
RE: Flatness call out for partial surface
If you're using the surface/portion of the surface as datum that does add another level of complexity as Belanger mentions.
I've also introduced functionally unnecessary steps on a surface to help clarify which area needs tighter control but that's a last resort to me - though in some cases may help with likely manufacturing methods.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Flatness call out for partial surface
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Flatness call out for partial surface
I noticed your response after I updated the drawing. In what way will this impact the call out?
RE: Flatness call out for partial surface
RE: Flatness call out for partial surface
Given your latest picture, I would probably go with the chain line suggestion rather than the "between X & Y" arrow.
Also note that the flatness tolerance would still be seen as extending into the picture for the full surface depth, within that strip of .247. If you wanted a limitation in the depth direction also, then you'd have to do something else to indicate that.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Flatness call out for partial surface
Yes, indeed.
Also, the purists may note that use of reference letters was defined for Profile tolerance and they are expected to indicate "extremities" of the features, that is, places where the features end rather than arbitrary points in the middle of said features.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Flatness call out for partial surface
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Flatness call out for partial surface
Yes, the datum feature will only be the the area of the surface indicated by the flatness call out and chain line. I've attached another updated drawing.
RE: Flatness call out for partial surface
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Flatness call out for partial surface