"Tim Williams" wrote in message
...
"Harold & Susan Vordos" wrote in message
...
That is one method for case hardening, packing in carbon being another.
Coked peach pits were the carbon of choice for pack hardening where I
worked as a young man.

Must be because of the cyanides..

I have often considered the same thing, but have never read that is the
case. There has to be a good reason the industry goes out of its way to
carbonize (coke) peach pits.


BTW... what kind of temps and soak times are required to get how much case
thickness? I tried case-hardening a bit of keystock (galv. mild CRS) the
other week by cycles of heating it (the thin layer of galv. oxidized/burnt
off) to orange and dipping in powdered oak charcoal for a few minutes.
Also
tried coating it with borax and dipping that in the carbon. (As sticky as
borax is, it doesn't seem to do much with powders. Bah!)

Afterwards I quenched it and it seemed harder, maybe up to a 1030-1040
range
I guess, Idunno... Spark test didn't show much, although I shouldn't be
expecting it to, eh?

Tim
No, you shouldn't expect much by that process because of the brief exposure
of the metal to carbon monoxide. Pack hardening yields a depth of carbon of
about .015" for the first hour, then drops off to roughly .010" per hour
afterwards. By the time you have a thickness of roughly .090", the deposit
tends to drop off to zero, although I'm sure there must be exceptions.
Where I worked. they'd cook things for hours to get the depth desired The
parts were placed in steel boxes with snug fitting lids, along with the
peach pits, which were still very recognizable, but resembled typical coke
otherwise. Temperatures for proper transformation run from 1,500F to
1,800F, depending on the material at hand.

Harold