Compression molds?

Has anyone tried pouring small gold buttons and then using a small steel compression mold to make gold ingots? Sort of like using a hydraulic press to swedge steel nubbins to wire rope? Seems it would be fairly easy to machine a mold and put a high polish on it. I'm not interested in duplicating exact weights, just small ingots that are fairly uniform in shape and size.

Thanks, Robert

Yep, it occurred to folks several thousand years ago. The first coins were made just that way. But you'll be limited in the quality of image you'll be able to produce.

Making a die isn't easy. To stand up to repeated use, it will need to be made from steel and heat treated when it's finished.

To make even a small coin, you'll need a serious press. Think around 100 tons to start.

If you can make the dies and have the press, you'd be able to make consistent weights by pouring an ingot, rolling it to thickness, then punching out blanks.

You can try making a die and whacking it with a big sledge hammer, but again, the lack of control over that process will affect your ability to produce quality results.

I'm not trying to discourage you. If you're successful, there are many here who would probably like to follow your example. There are a few threads on the forum about making coins.

Dave

I think he wants to make ingots Dave, unless I read that wrong. Most ingots are poured though Robert, weighed and stamped. It's late so I may be way off.

Yeah, small ingots in the 1 gram range. Exact weights and purity aren't an issue. I figured to smelt my placer and then weigh out a gram, melt and pour or possibly press for a more consistent shape. Then just stamp with a logo of some kind.

Thanks for the replies.

1g is tiny mate. It would be so fiddly to do properly with such a small amount for a number of reasons that spring to mind.

rsmuff said:

Yeah, small ingots in the 1 gram range. Exact weights and purity aren't an issue. I figured to smelt my placer and then weigh out a gram, melt and pour or possibly press for a more consistent shape. Then just stamp with a logo of some kind.

Thanks for the replies.

Click to expand...

Smelting is the process of extracting values from ores by furnace. That's not what you're talking about. What you intend to so is MELT. I make mention because we try to avoid misinformation on this board--which often leads to an overload of the stuff. I don't want to see other readers start using that term improperly.

As has been suggested, such a small amount of gold will be quite troublesome for you. When you melt, it may or may not deliver from the dish fully. And, unless you can sell the resulting ingot/coin for well over spot, the time you're going to spend making them is going to be at a loss. If you choose to continue the course, do it because you want to make them, not because it's a good idea in the way of marketing.

Harold

http://tinyurl.com/q7ve6sq
Best regards Richard.

Sure Richard, those are produced on a mass basis by professional refineries. If the OP is one of those then I'll stand corrected however I'll wait for confirmation of that before commenting further.

A gram of gold has a volume of .003162 in3 or .0518 cm3

If my math is right:
A .2515" X .2515" X .05" (24 gauge) sheet of 24K gold weighs about 1 gram.
A .562" X .562" X .01" (30 gauge) sheet of 24K gold weighs about 1 gram.
A 1" X .3162" X .01" sheet of 24K gold weighs about 1 gram.

You will never be able to pour ingots that thin. Not even the .05" thick one. And, even if you could, it would only be about 1/4" square.

You can buy 30 gauge, 24K (or other karat) gold sheet for about 20%-30% over spot. If dead soft, you could probably cut it to size with a steel ruler and an X-Acto knife. You can buy it in various hardnesses, thicknesses, and karats.

https://www.google.com/search?q=gauge+gold+sheet&ie=utf-8&oe=utf-8

An alternative would be to take your pure gold to a jeweler and have them roll it to a desired thickness.

Just some ideas

Not mis-information Harold. I'm talking about furnace smelting placer with a 70% PM flux and then remelting. All placer contains some surface or ground-in impurities such as iron or manganese oxides, black sands etc and should be smelted unless it's nuggetty or jewelry grade. My placer is 20+K from high grade epithermal gold/gold and gold/silver deposits. After smelting and knocking off the slag, I've got high K gold with silver as an impurity. For my purposes, not a bad combo. To get a higher grade would involve inquartation with all the acids and washings and so on. My goal here is to simply make the best looking small plain ingots I can from my smaller and finer placer. Thanks for the input.

rsmuff said:

Not mis-information Harold. I'm talking about furnace smelting placer with a 70% PM flux and then remelting.

Click to expand...

Which was not mentioned in your first post, thus misleading readers to think that smelting is the proper term for melting. That was my point. Beyond that, smelting is a process of recovering values from ores. If you are melting placer (which is not an ore in the true sense of the word), it doesn't really qualify as a smelting operation.

That being said, the act of melting with flux, alone, may or may not serve the purpose you propose. All depends on what other elements might be present, some of which can (and will) destroy the ductility of the alloy. Might be wise to run a small sample to determine if it's still ductile after it has been melted. It may not be, although I suspect it will be.

Harold

I've had the ore that my placer came from assayed by ALS Global, Chemex labs and had full rock analysis with 40 element acid digestion spectography plus fire assay for gold, silver and PGM's so I've got a pretty good idea what I'm working with. Thanks for setting the record straight on smelting vs melting.