The older Power Distribution Board for the cRIO used metric M6 bolts for the battery input.
http://www.andymark.com/product-p/am-0865.htm
Not to be confused with 10-28 fine thread SAE which is very close.
Personally robots should be like so many American cars:
Totally unable to decide what should be SAE and what should be metric
Gotta keep those tool and die makers in business somehow.
Seriously: rivets just get the hole close.
I once pulled down a pan on an Oldsmobile transmission and inside it was stamped Ford.
At some point I guess you use what you got.