The first drawing uses a profile of a surface tolerance to locate the surface. This tolerance is refined by a profile of a line tolerance. The profile of a line tolerance floats within the profile of a surface tolerance zone and applies to individual slices of the surfaces. This is fine if that is what the design intent of the part is.
Sometimes Profile of a Line Turns into Profile of a Surface, when Datum References Are Used (#192)
(In accordance with Y14.5M-1994 standard)
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Profile of a line is a funny control. It works well for parts like extrusions where individual slices will be checked. However, when you start adding datum references, it can turn into a profile of a surface control.
On the second drawing datum references have been added to the profile of a line tolerance. The result is that the profile of a line tolerance overrides the profile of a surface tolerance. Since every line in the surface must be located with respect to the datums, the entire surface is being controlled for location by the profile of a line tolerance. The profile of a surface tolerance is meaningless.
