Here is a Tip inspired by one of our regular readers of the Tips. He pointed out that in the examples of composite tolerancing in the Y14.5 standard that explain the meaning of a datum reference in the second segment, the pattern of features seems to always be conveniently oriented squarely to the datum reference frame. His question was, "What if the pattern is at a compound angle to the datum reference framework?" Well, it doesn’t matter what angle the pattern is from the datum reference frame. Any datum reference in the second segment of a composite feature control frame tightens up the orientation of the pattern. Of course, the other purpose of the tolerance in the lower segment is to tighten the location of the features in the pattern to one another. In this example, the tolerance zones of the composite callout are shown in blue and yellow in the isometric views.t, they refine the orientation (perpendicularity, parallelism or angularity) of the pattern relative to the referenced datums.