axym (Industrial)
5 Mar 12 16:26
pmarc,
This will open up another can of worms or two. But I think you already know that ;^).
In Case #1, I don't remember if the presence or absence of extension lines makes any difference to which of the OD's are included in the continuous feature. If both are included, then the datum axis would be established using the minimum circumscribed cylinder of the two OD's.
In Case #2, the datum axis would be established using simulators shrinking down on both A and B. But Y14.5-2009 is not completely clear on the details of exactly how the simulators would shrink down. Some say that the axis would be established using the minimum circumscribed cylinder of the two OD's, identical to the CF case. This would allow the possibility of an unstable axis, if A and B were different as-produced sizes. Others say that the A and B simulators would keep shrinking down independently, until a stable datum axis was established.
Evan Janeshewski
Axymetrix Quality Engineering Inc.