What a wonderful information hunt!  Almost as good as Myst!  Anyway,
material sources.
Belmont Equipment Co.
Western Office & Warehouse
743 Dunn Way
Placentia,  CA  92670-6884
is a source of EDM carbon.  They carry graphite from Union POCO,
Ameri-Graph, Airco, UCAR (Union Carbide) and Great Lakes. I borrowed a
manual for POCO Graphite, Inc., a  Unocal Co., in Decatur, Texas, -- yes
it is a division of the Unocal oil company.  The manual explains how the
stuff is made.  They start with calcined petroleum coke (amorphous
carbon.)  The coke is then milled to various particle sizes and mixed
with coal tar pitch.  This mixture is then pressed or extruded into
billets.  The billets are baked in an oxygen-free atmosphere to drive
off the volatiles from the pitch.  The result is an amorphous carbon
product, which is held together with carbonaceous pitch residue.  This
carbon is transformed to graphite (graphitized) by further heat treating
at extremely high temperatures.  Belmont cuts it up and can machine to
order for use by the tool and die customer.  My friend indicated to me
that he allocates about $4 / cu.in for the graphite cost.  Just for
comparison, the costs from McMaster-Carr (who are not the cheapest, but
certainly one of the easier companies to deal with for small, odd lot
quantities) is shown below.  They can be accessed on the web at:
http://www.mcmaster.com/

$0.448/cu.in   (5.3 cu.in / $2.38  for =BE=94 dia. x 12=94 long copper co=
ated
welding rods)
$0.853/cu.in   (72 cu.in / $61.43 for 6 x 12 x 1 carbon arc welding
plates)

Based on this, I=92m ordering a couple of =BE=94 welding rods.  Best bang=
 for
the buck, if they work.  But it will be awhile before the results are
in.  I know the =BC=94 rods I have are diamagnetic, so I=92m encouraged. =
 (I
tried one local welding store for carbon rods.  They would only sell in
box quantities of 50, which for 3/16 was about $15, but they didn=92t hav=
e
=BE and I=92m not interested in about $100 worth of carbon rods, so I
passed.)

Diamagnetic properties:
 I found some interesting tables for values of magnetic properties,
including diamagnetic properties, of various substances:

goto: http://www.backto-newton.com/backtonewton/magnetism.html
and then click on Table I, II, and III where a R.J. Hengstebeck has
listed quite a few substances in conjunction with a dissertation on a
new theory of magnetism.   As to the rest of his magnetic theory, I am
not a physicist, so I=92m totally unqualified to comment.  Perhaps someon=
e
else might want to.

At: http://enpc1644.eas.asu.edu/Carbon/elemagpr.htm
is a table indicating that diamond and graphite should be almost
identical in diamagnetic performance. (For those of you with a lot of
loose cash lying about!)

At:  http://curricula.mit.edu/6.013/chapter9/9.4.html
is part of a course (?) on magnetism with a table containing diamagnetic
and magnetic values.

And for Karl at:
http://curricula.mit.edu/6.013/chapter9/9.5.html
which is the next page of the previous course, a discussion of AC
diamagnetism (they call =94Artificial Diamagnetism=94) caused by conducti=
ve
spheres.  You can equivalently think of shorted turns as rejecting a
magnetic field, and thereby equivalently say the slug is diamagnetic.
So use whatever analogy is most convenient, you=92re right too!

Well that=92s probably a lot more than you ever wanted to know about the
subject, but enjoy.

Charles R. Patton



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