Hello,
We came across this profile callout today and I'm not sure I've ever seen this before. I want to be sure we understand correctly and I'm not finding this in any of our books.
Can anyone please explain?
Thank you!
That profile of a surface specification is given within a "composite feature control frame".
The upper horizontal tolerance specification is referred to as the "Profile Locating Control (PLC). Which specifies a larger tolerance for the location of the profiled feature. The datums specified serves to locate the feature profile tolerance zone by basic dimensions, relative to the specified datums.
The lower horizontal tolerance specification is referred to as "Profile Refinement Control" and specifies a smaller profile tolerance for the profiled feature. The datums (if present) would specify the limits of size, form, and orientation of the profiled feature. In general, the lower horizontal frame locates the feature surfaces to one-another and orients the feature tolerance zone to the specified datums.
The Profile Refinement Control tolerance zones are always contained within the Profile Locating Control tolerance zones.
For the latest standard on GD&T (ASME Y14.5-2018) see:
Geometric Boundaries IV, Interpretation and Application of Geometric Dimensioning and Tolerancing
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