Two datums adequate? 1

[TWJR]

Hello,

I know typically we use 3 datums, primary, secondary, and tertiary to restrict freedom of movement of features. However, in this case, I was wondering, since there are no internal features (holes, etc), this would be adequately defined using only two datums? I'm thinking that a 3rd datum wouldn't really do anything here...

 

[PaulJackson]

Any discussion of how it should be tolerance should beg the question "how does it function... what orients and/or locates what... what tolerance liberties and refinements are necessary for ideal function?"

If the flatness and perpendicularity were extracted leaving just the profile all over... max flatness on surface A would increase to .004 and max orientation of surface B to A could exceed .004.
I should have boxed the thicknesses... my mistake.
Paul