Ok!
From PSL Catalogue Page 19
Classification of Bolt Yield Point (MPa) Rp0.2
8.8 10.9 12.9
640 940 1100
I would hope that the nuts would have to be
at least this high. I will keep checking
other resources.
The values that Shigley shows in his book again
is only for the bolts, rivets, sems, etc. and
is as you probably know is that the whole number
represents the utimate tensile x 100
where the decimal is the approximate ratio of
the yield strength to the tensile.
The PSL catalogue shows that the testing strenght
of the nuts must be equivalent to the Tensile
Strength of the Bolts so that is no help either.
Will keep looking. Shigley at least shows the
yield strength for all of the metric grades of
bolts. I am starting to see your dilemna.
Will keep looking!