Subject: Re: Casting bottle caps

From: [email-masked] (Douglas Wiggins)
Date: Thu, 16 Mar 1995 02:39:00 GMT

71:Would be glad to help in more detail if you want.  I've made and used
71:many kind of home-made foundry tools and furnaces and have used many
71:kinds of fuels, and would be glad share my experiences.

I need to set up a casting system for the manufacture of small
screw-caps for use on cosmetic bottles; the materials cast will be
bronze and/or silver, using lost-wax investment and vacuum casting
(I have a centrifuge, but it does not allow heat to continue to be
applied to the sprue button after the metal is poured). The heat
source will be oxy-hydrogen, unless someone makes a better
recommendation (hydrogen is hard to beat, though - hot and clean).

I have viewed the tapes offered by Precious Metals West (they have
two tapes on casting that they provide free of charge; they didn't
ask for them to be returned, but I just copied the tapes they sent
and returned them to help them keep their costs down). That company
is strong on wanting to eliminate dangerous chemicals from the
alloys, and they pride themselves on having developed alloys which
don't require poisons to be bright. Anyway, they use vacuum pumps
on a manifold made of one-inch (25mm) ID pipe, and a vibrating
table with a vacuum dome to get the bubbles out of the investment.

I need to know how to get from the original to the investment,
which I think will involved tooling a threaded core slightly larger
than life-size, then making an original, which is used to make a
rubber mold, which is used to make wax models, which is then
embedded into the plaster. I am having trouble trying to figure out
how large to make the pattern and how to get it from that stage to
the wax models. I have had a core machined which is 1.5% larger
than life, but this is just guessing.

Perhaps you can suggest a book which will help me to figure out
what materials and equipment I should procure.

  -Douglas Wiggins [email-masked], Portland, Oregon
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