[Rhodes22-list] New Toy

Peter Thorn pthorn at nc.rr.com
Mon Mar 15 21:29:06 EST 2004


Wow, Roger, that's an amazing knife!   Before reading your post, I used to
think my Smith and Wesson SWAT knife was pretty neat.  It's non-magnetic
stainless, but certainly not precipitation hardened.

Do you think the non-serrated version would be easier to sharpen?

PT




Hi Everybody,

Well, I'm ready for a new topic.  I just received a new toy today that is
totally cool.  The March, 2004, Volume 30, Number 5 & 6 double issue of
"Practical Sailor" magazine ran a comparison test on sailor's rigging
knives.  They rated the Spyderco SALT 1 as a best buy.  The thing about this
knife that caught my eye was the description of the H1 precipitation
hardened stainless steel in the blade.  In my ME250, Engineering Materials,
class last semester, we learned about precipitation hardening of aluminum
alloys.  Precipitation hardening is how the really strong, hard, yet ductile
aircraft aluminum alloys like Al 7075-T6 are made.  I had never heard of
anything analogous in a stainless steel alloy and I was curious.

So, I went & looked up the properties of H1 stainless steel in the
metallurgical literature at the SVSU library.  The H1 alloy is produced by
the Myodo Foundry in Japan and it appears to be a real materials
breakthrough.  Normally, with knife blade materials, there is a tradeoff
between the hardness & ability to keep a sharp edge of high carbon tool
steels and the corrosion resistance and nonmagnetic properties of the 300
series stainless steels.  Up until now, it was impossible to have both
corrosion resistance and a really sharp blade in the same alloy.  The H1
alloy works differently.  Precipitation hardening refers to the formation of
precipitates or particles of ceramic intermetallic ferric nitride and
chromium nitride compounds.  These intermetallic compounds are soluble in
the base alloy composition above a certain critical temperature, allowing
the metal to be hot-worked into the shape of the blade.  As the metal is
cooled according to a proprietary heat treatment schedule, the intermetallic
compounds become insoluble, drop out of solution, & nucleate into tiny
particles.  For reasons I won't get into, these particles tend to
preferentially nucleate & grow along grain boundaries in the metal.  The
presence of these particles distorts the face centered cubic (FCC) crystal
lattice structure of the base alloy & tends to lock adjacent metallic grains
together.  Think of the particles as being sort of like the key that fits
into the keyway that locks a pulley onto a shaft.  Having the grain
boundaries of the metal locked together makes the metal much more resistant
to deformation and yielding.  (i.e. it is much harder)  But, it has not been
work hardened or tempered like heat treated high carbon steel blades must
be.  The H1 alloy has a low carbon content and the base alloy grains have an
overall austenitic microstructure. (i.e. nonmagnetic and corrosion resistant
like 300 series stainless steel)  The H1 alloy has a hardness and yield
strength comparable to a high carbon tool steel while maintaining the
overall corrosion resistance, ductility, ultimate elongation, and
nonmagnetic properties of a 300 series stainless steel.  As I said, the H1
alloy appears to be a genuine materials breakthrough!

Naturally, I had to have one!  I ordered the knife on-line from The Knife
Center:

www.knifecenter.com

SP88SBK Spyderco SALT H1 Stainless 3" Serrated Blade Black Zytel Handle:
$49.95 + S&H

The Salt 1 is available with either a plain or a serrated edge blade.  I
choose the serrated edge because it was recommended by Practical Sailor for
quick 1-pass cutting of tough lines.  Note: By the standards of high end
blades, $50 is not a particularly expensive knife.

Anyway, my new toy arrived via UPS over the weekend & I took it to school
today.  In the materials lab, we did some cutting experiments on tough,
exotic materials like Kevlar, Spectra, and Carbon Fiber.  With the factory
supplied edge, my new Salt 1 is so sharp, it's almost scary!  It cut thru
several layers of stacked woven prepreg cloth like butter & these were
materials that are a lot of work to cut a single layer with a good pair of
scissors.  Under the microscope at 100X magnification, there was no
detectable wear on the edge before vs. after cutting these materials.  The
hardness of the blade checks out at >75 on the Rockwell C scale!  The edge
is sharpenable on a good Arkansas stone with cutting oil, although with
quite a bit more effort than I am used to with even high carbon tool steel
blades.

The Salt 1 rigging knife is a folding, locking design.  It has a belt clip &
is deployable with either hand.  Note that the H1 alloy is also available in
fixed blade versions with a sheath.  I'm strongly considering getting a
fillet knife and a hunting knife.  If you have anyone on your gift list that
uses & appreciates really good cutting tools, they will absolutely love
something like this!  It will instantly become their favorite knife.

Roger Pihlaja
S/V Dynamic Equilibrium
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