I ask this question to geotol pro if I can use runout as datum and the answer is no. Runout should be reference to axis. And runout callout cannot be attach to dimension. Conclusion. They should overhaul gd&t.
The key difference here in this example is the fact that the runouts for datum features A and B are in reference to datum axis "A-B" which is a completely different axis then datum axis A or datum axis B, which is completely legal to see/inspect and in fact a very common design.
The inclusion of runout callout for datum A and B, with a diameter tolerance of 1.5 +.000 -.002, is unnecessary since the size tolerance is smaller than the runout tolerance. This incorrect example contributes to confusion among beginners and diminishes the widespread use of GD&T.
Thanks for the repy! This is actually a very common dimensioning scheme, but i can understand the confusion. Runout is controlling location of the axis of the feature, in addition to its form. And since the the datum axis is created from both datum feature A and B, it is NOT in reference to the same axis as the feature we are controlling. Thus the size tolerance can hold a tighter form of the feature, while the runout will allow a slightly looser coaxiality error. I hope this helps clarify things for you!
