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Grade 8 Bolts

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I have an long-time industrial client who recently replaced a bunch of
*missing* structural bolts with "Grade 8" (I assume SAE, Grade 8) bolts.  I
can only guess what happened to the original bolts.  I'm sure they weren't
stolen, so that leaves the options of working loose or breaking under
repetitive load cycles -- This is a vertical bolt, attaching a crane girder
to a column cap plate.  Can anyone say, "fatigue"?

I'm not comfortable with this replacement.  So far as I can tell, the grade
8 machine bolt is hard, tough, and *brittle*.  'Sounds like courting
disaster to me...

I recommended replacing the *new* bolts with A325, but the client is
reluctant to spend money twice for the same work.  

Guidance and counsel, anyone?  

Fountain E. Conner, P.E.
Gulf Breeze, Fl. 32561