example of tertiary datum with MMB

[MikeF]

Does anyone have a good example of a simultaneous evaluation of bolt circles with a tertiary datum hole with MMB? I have a guy that just can't get it.
thanks

[JacobCheverie]

Primary - Mating Face
Secondary - Mating Cylinders
Tertiary - Clocking slot

With MMB on a slot, the part can rotate a bit as you depart from MMB to help line up a bolt pattern.

[JacobCheverie]

T.jpg

It's a very crude drawing but reference the bolt holes 3X [Position|Ø .XXX|A|B (M)|C (M)].
MMB on C will control a little rotational error. I forgot B in the side view.

[Douglas]

a crude drawing... for me is a napkin, for you apparently solidworks

[JacobCheverie]

Douglas well thanks, it was MS Paint but I guess my skills aren't as bad as I thought

[MikeF]

thanks, but I need something to convince this guy he can't add tolerance to the position tolerance from the tertiary datum hole

[JacobCheverie]

ASME Y14.5-2009 7.3.6.2.2(a)
"Effect on Considered Features. The amount of the datum feature's departure from MMB does not provide additional positional tolerance for each of the considered features in relation to each other within the pattern."

[JEFMAN]

Look here :
https://support.hexagonmi.com/s/arti...-1527312026428
https://books.google.fr/books?id=XdA...%20mmb&f=false

[MikeF]

thanks, I wish I could print that out.

[JacobCheverie]

Use snipping tool?