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Platinum casting with Ney centrifugal machine

There are two main reasons why one uses a vertical centrifugal
casting machine for platinum. One is the fact that a vertical
machine has much more power. Using gravity in addition to a
powerful spring, up to 40G can be produced. This force is needed
to create a dense and useful casting in platinum. The second
reason, and in my opinion the most important one, is safety. I
cant think of a single caster who has not had a blow-out in the
machine. Red hot beads of gold or silver raining against the
splashwall of the casting machine, and , we have all done and
seen it, some beads can be heard flying clear across your
shop…Gold and Silver will actually stick to the splash wall,
whereas Platinum just slows down a bit…as it comes through. In a
vertical machine, the spill is confined to a narrow band that is
aiming from floor to ceiling, rather than waist high and covering
your entire shop, as is the case with a horizontal machine. I
agree with my friend Ed, who is a very fine and accomplished
platinum caster, that it is possible to cast platinum in a Ney
centrifuge, but I would make a few additional suggestions to make
it safe. First let me say that not all horizontal machines are
suitable for this. Be sure the splash wall is re-enforced, and
you are using the proper crucible. The line up of the flask with
the opening of the crucible is important. Usually a spill occurs
when the broken arm snaps into position and the crucible/flask is
not lined up correctly. I have seen platinum burn through the
1/4" backplate of a casting machine… So if you have made the
modifications Ed suggested, I recommend you add an additional
shield that is placed between you and the machine and is as high
as the top of the Ney. It could be a 3/4" plywood wall, that has
some sheet metal on the front. If you have a spill, it is not
really hitting you as you cast. I also recommend you have a
second person with you when you cast. The flame is very hot and
long and you are wearing #11 or #12 goggles, so except for the
light reflecting from the crucible…you see nothing. I am rather
safe than sorry. Having done these things, and using the proper
investment, I think it is not difficult to cast small quantites
of platinum that way.

Jurgen J. Maerz
Manager of Technical Education
JA Certified Master Bench Jeweler

Ed/Jurgen et al:

I have followed this thread of casting Platinum with great
interest. I hope to move on to Pt after I have my technique down
in gold. My question is, has anyone been successful with Pt with
vacuum casting? It would be easier for me to get a 6CFM vacuum
pump for my perf caster than get a Ney or a vertical caster.

Roy (Jess)