"George E. Cawthon" wrote in message
...
big snip---

On sublimation of diamond. Although 3550 degree C is listed
as a melting point in several references some of the same
references indicate that it actually sublimes. Still, these
references don't fit what appears to be a valid reference
that says diamond breaks down at a much lower temp, and that
reference gave breakdown temps in the presence of oxygen and
in the presence of nitrogen. I believe that was in one of
Bob Powell's references.

My lack of education makes it difficult for me to grasp the entire concept,
but I wonder if what's happening at lower temps is the oxygen combines with
the diamond to create CO2.

Glad there are no hard feelings.

I'd like to think I'm a little better than that. I know when I'm wrong I'll
willingly admit so, and offer an apology when required, and admire those
that are willing to do the same. I detest those that slink away silently
when they are wrong, refusing to even acknowledge the error of their ways.
Takes a much bigger man to admit to being wrong, and for that you deserve,
and have, my respect.

Looks like you do know how to "back out gracefully".

I'm still having a hard
time getting my head around the fact that none of my basic
references say anything about diamond dissolving in iron or
any other metal.

That's likely because under normal circumstances it doesn't, unlike precious
metals, that willingly migrate into some other metals when brought into
intimate contact, even at room temperatures. Bear in mind that it's also
a fairly recent discovery, although the phenomenon had long ago been
identified, but perhaps not well understood. Same goes for silicon carbide
dissolving in steel. . One of the references I have, which I am having
trouble locating again, makes mention of the "phenomenon" of the abrasive
apparently dissolving in steel, and they hadn't quite concluded exactly what
the score was. The entire concept was not fully accepted as late as the
mid 40's, apparently. Pretty much all the literature I have came from my
grinding mentor, who was a journeyman grinder at that point in time. While
he was not much as a machinist, he was an outstanding hand at precision
grinding. That seemed to he his calling.

The reaction apparently requires considerable heat in order to occur. That
likely explains why you find small drill pointers that run a diamond wheel,
but likely at slow speed. I'm not sure about that, though.

Does it make you wonder if there would be a lot more diamond in the world if
it weren't for the abundance of iron in nature? Could be diamond would
have formed in lots of places had the carbon not been absorbed by iron.

Harold