* * Chas said:
Chalo said:
ddog said:
Also look for SS bolts if possible.
Quoted message said:Stainless steel fasteners are much weaker than the sorts of graded
alloy steel fasteners being discussed here. They are suitable
replacements for ungraded chrome-plated generic bike fasteners, but
not for 8.8/10.9/12.9 metric or Grade 5/Grade 8/hardened inch
fasteners.
The advantage of stainless fasteners besides corrosion resistance is that
they will stretch a lot more before breaking. That's why they are used in
some aerospace applications.
Copper and wrought aluminum fasteners will usually exhibit more
stretch than hardened alloy steel, too-- but that does not make them
appropriate replacements for graded fasteners in most applications.
Hardened fasteners are often used in places where their strength isn't
necessary, but unless you know where they are and aren't necessary,
it's not a good idea to replace hard with soft.
By the same token, it's sometimes not a good idea to replace ductile
fasteners with hard ones. I know that for racing motorcycles,
sometimes ductile bolts are used for steering and control components
so that they will loosen rather than break on overload. I imagine
that the aerospace applications you mention are similar. However, in
my experience making structural parts for aerospace engineers, they
were usually concerned about the fastener tensile strength being at or
above their worst-case load plus margin, and not concerned about the
fasteners' ductility.
It's a largely academic concern in this case, since so few bicycle
parts require graded or hardened fasteners. I'd expect to see them
used mostly to attach cranks to spindles, and to clamp saddles to
posts.
Chalo
