Sorry if I seemed to be venting at all, I was actually enjoying the discussion. I do realize that it is often difficult to read the "tone" when people are posting. I'm one of those weird guys that actually enjoy a lively debate because I think we can learn a lot that way. Sorry if I got a...
dtmbiz,
Yes, there are always 3 mutually perpendicular and intersecting planes, but in many cases those planes are purely theoretical and do not always have a direct feature that they are derived from. For example, based on the standard, it is possible to have a DRF that does not constrain all...
JMarv,
I don't think "dtmbiz" was referring to the drawing on this post but to examples in the standard. Thanks for taking the time to draw it in SolidWorks though.
If you re-read 4.17(b) it states "In other applications where a boundary has been defined using profile tolerancing, a center point, an axis, or a center plane may not be readily definable" and it refers to figure 8-24 which shows an irregular feature of size being located by it's "boundary"...
I think that the drawing is legal per the 2009 standard(ASME). Unfortunately, the standard does not give very good examples and, in my opinion, leaves it a bit open-ended. See section 4.17(a) where it states that irregular features of size... may be used as datum features and also 4.17(b)...
