[TR] Threads and Bolts

Randall TR3driver at ca.rr.com
Thu Nov 24 23:00:24 MST 2016

So, did the later Triumphs actually use SAE graded hardware?  The original
bolts on a TR3 appear to be made to British specifications that aren't
exactly the same.  In particular, there isn't a slash in sight, even on
bolts that are obviously harder than others.

Also worth pointing out, perhaps, that Grade 8 is by no means the ultimate
in bolt strength.  Stronger alloys have been known since before WW2.  Of
course those fancy alloys are more expensive, so you don't see them much on
cars.  But just an ordinary socket-head cap screw (ASTM 574) is about 15%
stronger than SAE Grade 8.

ISTR it was Carroll Smith that pointed out that all fasteners are, in
effect, very stiff springs.  Sometimes that springiness is important, like
when you try to clamp aluminum parts with steel fasteners and heat up the
resulting assembly.  Aluminum expands with heat much faster than steel does,
so the ultimate fastener load depends on how easily the steel stretches to
accommodate the growth in size of the aluminum.


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