[quote=“Brenda, post:53, topic:21742, full:true”]
What I uploaded was a actual part of a machine, truncated. Regardless of what the dimension tool reads, it still reads better for the rotated VS the chamfered edge.[/quote]
that’s because the rotated edge is an arc… do this:
• ungroup then DupEdge the two curves you’re measuring… move the edges along with the centerpoints to the side for analysis
• run the _What command on the curves… notice the one made by revolving is an arc and the one made with the chamfer tool is a nurbs curve…
i don’t think you’re making the connection as to why it’s not advisable to use the DimRadius tool on the nurbs curve so for now, pretend there is no radial dimension tool in rhino and you have to dimension it in a more manual way… a Radius is “a straight line from the center to the circumference of a circle”… so:
•draw a couple lines from the centerpoint to the curve:
• now dimension those lines (_DimAligned):
…you’ll see the bottom curve, the Arc, is perfect in all places… it’s an arc " a round plane figure whose boundary (the circumference) consists of points equidistant from a fixed point (the center)." …all points along the curve are exactly the same distance from the centerpoint and therefore it’s appropriate to use DimRadius on this curve…
the top curve, the nurbs curve, is an approximation to an arc… but when measuring the ‘radius’ manually as shown above, you’ll be able to see how close of an approximation it is… it’s incredibly close and it’s within your tolerance… in some places, the line is two ten-millionths inch longer and in other places, it’s eight ten-millionths shorter than true radius…
idk, if something in the above doesn’t click with you then i give up 
the funny thing, to me at least, is that rhino is so accurate that it allows you to measure it’s inaccuracies down to near atomic sizes.
i get it that you keep thinking this part is out by the width of a piece of hair but it’s not… it’s way more precise than that… i also get it that you think people are responding here in a sort of manner to defend their almighty rhino (or whatever ; ) ) while ignoring its faults but that’s not the case either… you really are analyzing the situation inaccurately and that’s what people are attempting to point out to you.