Balancing a centrifuge

How do you know when you have the right amount of weight on there?
Thanks!

On Mon, 25 Aug 2008 21:01:56 -0700, in rec.crafts.jewelry "dan *5"
wrote:

How do you know when you have the right amount of weight on there?
Thanks!

Before burning out the flask, put it in the casting cradle, along with the metal
to be cast and the crucible pushed into casting position. Loosen the nut
tightening the casting arm onto the spring base. You'll find the arm is set on
a supporting pin, upon which it can tilt back and forth, like a see-saw, or a
balance scale. Adjust the weights until the arm appears to balance, not tipping
towards the weights or towards the flask. Retighten the mounting nut. Now,
the unfired flask contains some water weight, which will go away, but the metal
is also in the crucible, not in the mold cavity farther out the arm, so this
will end up pretty close to the right balance. If you want real precision, and
if you always cast the same amount of metal, you can make a dummy flask cast in
the right weight of bronze or something. Don't quench it, but instead, save it
as a precision weight, that you can use to balance the arm. If you then do your
real castings with the same weight all the time, you can get a casting arm to
spin with almost no vibration at all. Most of the time, though, the first
method is good enough. If the machine is mounted well, a small amount of
imbalance won't shake things up too much.

Peter