Although a couple of past Tips have dealt with composite versus single segment callouts, I continue to get questions regarding the difference. So, here we go again.
Watch Out for the Subtle Difference with Regards to Datums: Single Segment Tightens Location - Composite Doesn’t (#159)
(In accordance with Y14.5M-1994 standard)
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Single segment simply means that there are two separate geometric callouts which should be read independently. Both requirements must be met.
Composite, on the other hand, is represented using a single geometric characteristic symbol with multiple tolerances shown. The primary purpose of the lower segment of a composite position tolerance is to control the location of features within a pattern. If any datums are repeated in the lower segment, they refine the orientation (perpendicularity, parallelism or angularity) of the pattern relative to the referenced datums.
The holes may not be out of location relative to one another and datum A by more than 0.1. Relative to the complete datum reference frame, the pattern may move and rotate in a plane parallel to Datum A by 0.4 mm.
Composite Refines (tightens) Location within the Pattern and Orientation to any Referenced Datums
The holes may not be out of location relative to one another by more than 0.1. And the pattern must remain parallel to Datum A (as the arrows indicate) even though it may be out of location relative to Datum A by as much as 0.4mm.
