re: stainless steel metric fasteners

["Hardwick, Robert C" <Robert.Hardwick@PSS.Boeing.com>]

Regarding tensile strength, etc of stainless steels vs alloy steel:
A286 is a very ductile, 160ksi ult. tensile strength and very corrosion
resistant steel used for fasteners.  It should be stronger than just
about any joint it is used on.  Unfortunately, typical SS hardware store
fasteners use 303 which has only 125 ksi ult. tensile strength.  This
may still be quite enough for most joints.

Moving on to the thread specification:  English unit fasteners can be
obtained with some really crummy (sloppy tolerance and stress raising)
specifications.  Preferred thread spec for English is MIL-S-8879.  The
equivalent metric is ANSI B1.21M-1978, MJ profile, e.g.  MJ 10 x 1.25,
for a 10mm dia, 1.25mm pitch fastener.  This will give the highest
fatigue and static strength.  

Now, unless you know someone at Aerospatiale, I'm not sure where you can
find aerospace quality metric fasteners.:)  It may be good enough to
know that there is a difference in the stuff and realize that except at
really critical locations, auto manufacturers use as cheap of a zinc
plated bolt that they can acquire.  Therefore, any decent grade bolts
that we find at a specialty shop, like Tacoma Screw or High Strength
Bolt & Screw here in Seattle, are bound to be an improvement.

On a final geeky note, 440 stainless is indeed a very strong bearing
steel, and way too brittle for use when not under compression - like a
bearing.  It's also got fairly limited corrosion resistance, but better
than nothing, i.e. no substitute for short lube intervals.

hope this helps, robert hardwick, seattle usa

PS don't forget the antiseize cmpnd