Profile of Surface vs Profile of Line
Profile of Surface vs Profile of Line
(OP)
Hello, I'm a CAD guy learning GD&T so you may see me on here quite frequently as I run into roadblocks. And yes, my company does have its eyes open for training.
I've searched through past threads and found some information, but some of it seems to contradict what I'm reading in a book (Dimensioning & Tolerancing Handbook by Paul Drake Jr.) Under the Profile of a Line Tolerance section, the book says "As the entire feature surface is swept by the tolerance zone plane, its intersection with the plane shall everywhere be contained within the tolerance zone."
So if the profile of a line tolerance is swept over the surface, doesn't that make it the same as profile of a surface?
I've searched through past threads and found some information, but some of it seems to contradict what I'm reading in a book (Dimensioning & Tolerancing Handbook by Paul Drake Jr.) Under the Profile of a Line Tolerance section, the book says "As the entire feature surface is swept by the tolerance zone plane, its intersection with the plane shall everywhere be contained within the tolerance zone."
So if the profile of a line tolerance is swept over the surface, doesn't that make it the same as profile of a surface?





RE: Profile of Surface vs Profile of Line
I'm sure someone else can explain it better.
David
RE: Profile of Surface vs Profile of Line
Since the profile of a line tolerance zone applies to each line element individually, so profile of a line provides a limited coverage of a surface, it is usually applied in addition to other dimensions and tolerances that control the surface.
Yes, someone else will give more in details
SeasonLee
RE: Profile of Surface vs Profile of Line
How would you control the warping/bowing of a surface? From what I understand the straightness, flatness and profile tolerances adjust to the surface as they sweep across, so the tolerance zone controls the surface undulations, but not the warping of the surface as a whole. Would referencing a profile of surface to a DRF take care of this? Since then the tolerance zone would be locked in place, so the surface couldn't warp out of it?
RE: Profile of Surface vs Profile of Line
One unique aspect of profile control is they can be used with datum feature references as a related feature control. Profile controls can also be used without datum feature reference as a form control. When no datum features are referenced, the tolerance zone applies where the part surface actually exists.
If the form is critical to you, then you may use multiple single segment profile control to refine the size and form.
SeasonLee
RE: Profile of Surface vs Profile of Line
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RE: Profile of Surface vs Profile of Line
Let me give you an example of how you might use profile of a line as a refinement of profile of a surface.
Consider a wing. A big wing. For the entire surface of a wing related a DRF there may be a some reasonable value that establishes a 3D total width zone from wing root to wing tip. However, for cross section of the airfoil itself at any cross section along the wing, the design may require, and often does, a tighter form tolerance which can be accomplished with the profile of a line. Thus, a two single segment profile control.
Hope this helps.
Norm Crawford
GDTP-S
Applied Geometrics, Inc.
www.GDandT.com