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Either basic or directly toleranced - so what matters is not how it's applied "to the tolerances" is it?
If it was decided that it was parallel planes push against the radii , the mid plane of this would not give me dimension i am looking for.
As a 3rd datum what would be the best way to accurately set up a Datum Ref frame
Rwelch9 said:2x surface of a profile on the full R , Relative to A + B ?
I totally understand now about in that specific FCF datum C would be the primary Datum ( thanks for that )
Rwelch916 Jun 20 10:06 said:2x surface of a profile on the full R , Relative to A + B ?
although I don't know what to make of the fact that if the parallel planes are rocked to find the minimum separation, the points they contact would not be opposed other than at only one orientation of the planes. So technically there is only one "feature of size" condition for the simulation
chez311 said:The parallel planes would be contracted to find a minimum
chez311 said:There is no requirement that the feature actually contain opposed points (directly or indirectly) - that is a rule of thumb to determine if a feature is a FOS or nonFOS, and/or can be contained by an AME. It is not a requirement for simulation.
chez311 said:This is not a rFOS, its an iFOS(a)
Perhaps the transformation from rFOS to iFOS(a) during the attempt to achieve minimum separation does not in itself invalidate the simulation result.
Y14.5-2009 said:(b) Primary Datum Feature: Width RMB. The datum is the center plane of the datum feature simulator of the datum feature. The datum feature simulator (or unrelated actual mating envelope) is two parallel planes at minimum separation (for an external feature) or maximum separation (for an internal feature) that makes maximum possible contact with the corresponding surfaces of the datum feature.
It should be said if not mentioned before, that the issues discussed here would not occur if the feature was referenced secondary it tertiary, with the rotational DOF that causes instability pre-constrained.