Decision tree for adding/removing datums?

[ptruitt]

Has anyone seen such a thing in print anywhere? I can imagine that anyone attempting such a feat would immediately solicit controversy, but it seems as though a good one could be very helpful. If it is out there somewhere, I would like to study it.

Peter Truitt
Minnesota

 

[pmarc]

I am not sure what you exactly mean, but there is a kind of decision diagram in Y14.5-2009, appendix E, fig. E-2 "Datum Selections". No such diagram in Y14.5M-1994 though.

 

[ptruitt]

Thanks, pmarc. I need to study harder. I have breezed past that diagram in the past but will focus on it now. Figure E-2 is probably the best way to handle what can become a struggle with complex parts. Another way might not be best, but I was thinking about part function, available methods of inspection such as adding features to a part that only serve to facilitate inspection, inspection method costs, and the utility of simultaneous requirements which may, in some situations where composite tolerances are used, be better than adding datums...

Peter Truitt
Minnesota

 

[fsincox]

I would think it would be based on an assement of functional tolerance stack requirements vs. manufacturing process capibility in the perfect world.
Frank