On Jan 5, 3:30*pm, "Edward Hennessey"
wrote:
I once had the pleasure of quarrying alongside a
delightful gentleman wielding what he said was a
self-sharpening pick with a 12 pound head. Though
I did not investigate the particulars of the tool
at the time--except to note that both striking ends
remained exceptionally keen in extended use and
necessarily wore protective covers when we adjourned
for the night--dulling experience with my own tools
gave later pause to ruminate on its makeup.

My over-thinking speculation was that a tool with
progressively softer layers of steel alloys radiating
out from the harder core could form the material for
such an implement. But my Internet searches over time
for either a historical exemplar, available modern
pick or other excavating hand tool of such self-sharpening
nature proved unavailing.

An immediate and unexpected stimulus to this post was
a provocative article on the discovery of self-sharpening
teeth in sea urchins, the text of which appeared in
"Science Daily" seen at:

http://www.sciencedaily.com/releases...1222162404.htm

The urchin teeth differ from my naive preconception in
that the hard hard layers in the structure all of the same
durability among which are interspersed eroding soft layers.

This idea and its reality is elegant for simplicity.
Because the leading striking edge of a penetrating implement
wears first and the most during use, it is now clear how this
would result in a taper both in a pick and urchin tooth.

If anyone can either generally corroborate and specifically
describe occurrences of such self-sharpening mining tools (a
hefty pick foremost) or give me a pointer to any current
manufacturers whom might provide more information or the
implements themselves, I would be grateful.

Advance thanks to all for any direction.

Regards,

Edward Hennessey

Differential tempering would be the way it's done, probably would take
a LOT of experimenting to leave the center hard while softening the
surrounding metal. The tempering would have to be done so the heat is
just getting to the center when quenching occurs. Custom knife makers
do this a lot, in two dimensions but not three, leaves a hard edge and
a softer back for flexibility. As far as current manufacturers, there
are probably none out there that do it that way, would be very hard to
do on a production basis. Easier(and cheaper) to dump the lot into a
furnace at so many degrees for such and such a time, then out.
Probably the original was some small manufacturer's output that was
basically handmade. You might be able to find a blacksmith or
bladesmith with the knowledge to duplicate it these days.

Stan