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Casting coins


#1

I need to make some round 2 its coins and have a cnc router or mill
and would like to machine a pattern to cast these in pewter. I would
like to give these every time someone says when I get a round 2 it I
will buy it so they won’t have that excuse anymore. I have been
trying different woods with no luck and foam board. I heard of making
wax from plastic bags. will this work. if I can’t pull this off My
next project will be to make coining dies and stamp what I need.

Thanks Randy
AKA Enjen Joes


#2

machine a positive model in a hard jewelers carving wax (ferris
file-a-wax green, for example) or even in aluminum or other easy to
machine metal. Then make a silicone rubber mold of that initial
model. You can cast pewter directly in the silicone molds. Keep the
original model in case you eventually need to make a new mold…

Peter


#3

I just happen to have about a half dozen of them already carved. I
was just waiting to get around to making a master for molds for
them. They’re about 1" diameter and have “tuit” carved in several
different looks. I’ll be glad to take a few quick shots of them, if
you’re interested. Contact me off list.

Diane


#4

Draw up what you want. Get a CAD person to put it in something like
Rhino and output it to a mill in regular carving wax. If you like the
result make a mold and then cast as many as you want in the metal of
your choice.

Justine


#5

Randy,

Try Alumilite. A 2 part casting resin which machines very well and
gives really durable models, for flat stuff it will even stand up to
hot vulcanizing (sometimes even twice :slight_smile:

Jeff
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#6

Hi Randy;

There’s a great tradition of “round tuits”. See the following Google
image search for inspiration:

http://tinyurl.com/445qzb

For something like this, if you’re using regular jewelry techniques,
a first-generation metal master is going to be better than a
casting. From that, you can make vulcanized wax injection molds to
cast multiple sub-masters for pewter casting. Alternatively, you can
carve multiple identical masters with your CNC mill to use in a
rubber “doughnut” spin-casting mold.

To make wax more carvable, melt paraffin wax (the white wax used for
candles, not British kerosene) in an electrically controlled pot
(use one with an infinite range control, so you can dial the
temperature in exactly). Add about 1/3 by weight LDPE plastic (this
is the flexible clear plastic that grocery store plastic bags are
made of)and stir it in as it melts. Pour into a metal mold with
draft, and carve two-sided with your CNC mill. The resulting wax
positives can be invested and cast for metal masters.

Coining dies, of course, would be the best solution. Cut the coin
pattern negative into opposing pieces of annealed tool steel, then
harden it with heat-treating and quenching procedures (which vary
according to the specific steel being used). Provide registration
pins around the edge. Then introduce a coin blank and smack it hard
with the high-tonnage press. Whatever you do, let us know how it
goes - whenever you get a round tuit…

Andrew Werby
www.computersculpture.com


#7
I heard of making wax from plastic bags. 

You can make a very good machining wax using plastic bags but doing
so is pretty dangerous - I nearly set myself on fire the first
time!!! What you do is dissolve ordinary plastic carrier bags, bin
liners etc. in hot paraffin wax. Sounds impossible - but it works…
The problem is that the wax has to be very hot and you have to stir
it for a long time - if there are any naked flames about, the fumes
will very easily catch light and set the whole batch flaming and
spitting out globs of red hot, sticky wax!! You have been warned!!
The finished product, however, compares very favourably with the
commercial machinable waxes. Oh, I nearly forgot to mention - you use
equal weights of plastic bags and paraffin wax…

Best wishes,
Ian
Ian W. Wright
Sheffield UK


#8

I have all the toys I have a good cad program and a good cam program
that lets me design jewelry. and I have the machine to cut the
design. But were do you find the Alumilite and the casting supplies
for pewter. I built the machine to do the carving and have been
doing carved relief’s in wood plaques, The detail I have been able to
achieve has been compared to a laser. and have been playing with a
design for the tuits. But have been getting request for period coins
and tokens for reenactment groups for there shows. I have done sand
casting and can make my own petrobond sand but casting this small
will be a good challenge.

Thanks Randy
AKA Enjen Joes


#9

For the best results, spin cast pewter using rubber molds in a
centrifugal casting machine. Unless you really want to get into it,
I’d recommend farming it out. Mill a prototype out of wax and cast
it or mill it out of butterboard or Renshape then provide that for
mold making. You can gravity pour pewter at home into rubber molds
but it leaves a lot to be desired in terms of finish.

Contenti has plenty of supplies and info for spincasting.

Harry Hamill
www.harryhamilldesigns.com