Brother John asked for some technical info on A2:

There continues some controversy as to whether A2 can ever get quite as
sharp as O1 due to A2's larger grain size (a function of its alloying
elements; they make bigger lumps during heat treatment than the simpler
O1.) Brother Jim Wallbridge hath spake convincingly thus several times
and I agree with him. But three things prompted me to offer a line of A2
blades: 1) A lengthy chat with a maker of A2 microtome blades (those
that slice tissue for microscopic analysis in the pathology lab; they
need to be very sharp and hold an edge a long time), 2) A2's
responsiveness to cyrogenic treatment without which I don't think it's
such great stuff, and 2) market demand. I'm not sure whether the demand
is justified but if enough of you want it, sooner or later I'll offer it
(I'm no pioneer. But I still seek the ultimate unobtanium blade.) And
cryo-treated A2 does hold an edge longer. Even if that's its only
advantage, if it can get sharp enough to satisfy the user (and it does
seem to -- good feedback) the time saved in sharpening over the life of
the blade more than justifies the additional expense. 

My life as a blade maker has taught me a few things about what people
look for (or should) in a blade. Sharpenability (what good is it if we
can't sharpen it in our lifetime?), edge retention (usually the inverse
of sharpenability -- life is full of compromise), corrosion resistance
(not an issue with terrestrial woodworkers... boat builders? maybe). You
can only have two of these three so we abandoned corrosion resistance in
favor of the other two and we still have to compromise there. We could
make a blade that would hold an edge longer but it would way hard to
sharpen, etc. As for the ultimate hardness, we chose Rc62 (back before
there was anyone else to ask) for the hardest practical blade that would
hold an edge as long as possible. I've been asked a couple of times for
harder blades (fanatics!) but never for a softer one. Harder blades
(like the Japanese blades at Rc65+) will hold an edge longer but they
are often too brittle. We've sold a lot of blades in O1, O2, and A2, all
at Rc 62, I've never gotten one back for being too brittle. 

I still love our good old high carbon (AISI O1 and O2) that we've built
our reputation on, but if edge life is the most important concern, you
might consider our cryo-A2.

As for the hardness-effecting-sharpness question; I think the only issue
would be in the extremes. Harder blades are abraded more "cleanly" and
so may get sharper while a soft blade will gum around and leave a huge
burr that may damage the edge when it breaks off. I don't think you'd
notice the difference of a few Rc points when sharpening. But maybe. Not
an issue I've encountered.

That concludes today's sermon, brother and sister galoots.

Peace,
The Never-Wrong Reverend Ron

John Horobin wrote:
> 
> Vlad wrote:
> 
> > I've talked to many more learned folks than myself and
> > they all said anything higher than Rc 59/60 for A2 is
> > too much for our application - knots= blade chipping .
> >  So that's where we left it.  End of story.  Of
> > course, this can be debated forever...and I'm sure it
> > has here and elsewhere.  Perhaps Rob Lee will chime in
> > and let us knwo why LV left theirs at Rc60 too.
> >
> 
> Does the hardness have any effect on the sharpness of the edge that can be
> achieved?  It obviously effects the length of time that edge is held.  I'm
> not convince I can get quite the sharpness on A2 irons that I can on O1.
> Perhaps Ron can comment?

Oh! You wanted a short comment? Sorry...

-- 
Ron Hock (ron@hocktools.com)
HOCK TOOLS -- http://www.hocktools.com
16650 Mitchell Creek Drive  Fort Bragg, CA 95437
(707)964-2782 toll free: (888)28-BLADE [282-5233] fax (707)964-7816