A spin caster will work for brass, silver, gold, pewter, etc.  But, steel casting is another animal entirely, and needs done by a foundry set up to do it.  

I have a centrifugal casting machine, wax injector, mold making frames, etc to do production casting.  For the easy metals, investment plaster is enough for the mold.  For steel, they use ceramic shell casting techniques, where the initial mold is created by dipping the wax in a liquid ceramic that forms a hard, slick shell.  That is repeated until a satisfactory thickness is achieved, and then that is usually further encased in another setting plaster investment.  I think most steel casting is done with gravity feed, or maybe with vacuum assist rather than with centrifugal.  Because of that, it needs sprued and treed differently than jewelry metals.  It's usually best to give the foundry the waxes, and let them sprue it up for the casting, as they know what their process needs.

For what it's worth, I've had good luck using plastic instead of wax for models.  I've done that for preprinted letters, numbers, etc. as well as some shapes of items I've found in plastic that I wanted in metal.   It may be possible to 3d print models from a 3D program like solidworks, and then use those for the "wax" for the cast.  That would be an easy way to proportionally size up for the shrinkage.  I've even had pretty good luck with some light woods like cedar and balsa, as long as I was real careful to shake out the ashes from the investment mold after I burned out the model.

I've got a correction to what I posted earlier on shrinkage of steel.  Doing some research online, it appears that a shrinkage of about 2% is typical for steel.  Some additional is lost due to surface finishing loss.

Brass is about half of that, so if you do a check piece in brass and modify that for your mold master, keep that in mind.

I heard Jim Kibler of Kibler Longrifles say that he used a special foam material for his patterns a few years ago.  I believe he said it was specifically for pattern making and is very dense.  Anyone know what this is?   
I use to be able to email Jim with questions, but his business has gotten so large that I think he doesn’t have time anymore.
Bob

At Boulder River they had rubber moulds to cast the wax impressions of the parts.  Then this lady would take a bunch of the wax forms and affix them to a wax stalk with a funnel shape at the top.  She used a little electric soldering iron type thing to melt the stuff together.  The final result looked like a tree of wax parts.

They’d take this wax tree and dip it in a slurry of some kind of porcelain and let it dry between dips.  When it was thick enough, they’d put it upside down into an oven.  They’d run it at low heat until most of the wax melted out, and they recovered this for reuse.  Then they’d turn the oven up to firing heat and fuse the ceramic. This would burn the remaining wax away.

They’d put the parts “tree” right side up in a crucible and pour and pack fine sand around it.  They’d have a bunch of these crucibles sitting around the furnace, and when the metal was melted they’d fill all of them.

When the metal cooled, they’d pour out the sand for reuse, break the ceramic, and there was a “tree” of fully formed metal parts.  They’d cut the parts off and scrap the extraneous metal, no reuse of that metal once they cast it.

The parts would go into the machine shop for final machining and finishing.  Very little needed to be taken off; the Sharps castings looked much less bulky than the Highwall castings shown.

The guy who ran the foundry was the son-on law of Shiloh’s owner.  He told me that Kirk had come to him and said he was tired of being pushed to the end of the line every time Pine Tree Castings got a big run for a military contract and asked Bob if he’d like to run the foundry he was going to set up at Shiloh.  Bob said, “I’d be glad to help, but I drive a lumber truck; I don’t know anything about foundry practice.” And Kirk told him, “Looks like we’re both going to learn a lot, then.”

From every indication I saw, they’d learned it and learned it well.

I wonder how hard it would be to find a place and then have them make the rubber molds? I have all the parts in as cast condition that I would consider having molds made for. I also wonder how hard it would be to make a few small changes to the rubber molds to make small changes on the final parts?
Sam

ssdave, your mind and mine kind of run on the same track. I have a complete casting set for a #7 rolling block but its not one of Rodneys, that I know of. I have 2 of Rodneys castings that I have been working on. The virgin set is different in that it has the rear sight base cast in place and the breach block has the notch cast in place for the sliding extractor. My thoughts were if I could find a place to make me the rubber molds I could go from there. I know that there is a small company here in PA that could most likely make the molds I just have to do the leg work to track them down. I happened to run onto them on a PBS program that highlights PA businesses.  I guess some phone calls are in order. One change that I would like to make is to reduce the cast in hole for the barrel shank so that it could be threaded 3/4 instead of 7/8". That would allow you to use a smaller barrel if you wanted. With a 1" receiver thickness and a 7/8" barrel shank it doesn't leave you a lot of room for a shoulder. 
Sam

nuclearcricket wrote on Jan 22^nd, 2025 at 1:18pm:
 
You need to consider the issue of shrinkage. The waxes must be a known percentage larger then the desired cast dimension to compensate for the shrinkage of the metal from the molten state to the cooled solid state. Which for steel would probably be around 2.5 to 4%. In other words a 1" thick casting you might have now and you used it as a model for the wax, when cast in steel it could only be .960" thick.
I think in the past some guys, selling casting kits, tried that route and ran into all kinds of fit, function, and form issues.

Deadeye Bly wrote on Jan 24^th, 2025 at 8:30am:

Welcome to the world of molding engineering. The world I lived +40 years before retiring