Coin Striking

[timbudtwo]

If this is in the wrong area, I apologize.

After seeing coin strikers many times, often with hand held mallets, or the things I've heard called Da Vinci's coin press, I have wanted to make one. The only thing about it is that there is so little information on it out the internet it is amazing. I am finding it easier to find access to counterfeit coin dies that how to make them. This leads me to my question.

I want to make one. I don't mind if it is one of those large winch mechanisms, or just a sledge hammer driven thing. Getting the pressure is not the issue, it is how to make the dies. I do not have access to a mill, nor do I even know where to start with metals. Casting bronze would be quite an affair as I don't plan on doing it often, so a one or two time thing would be rather wasteful. Anyone that has made these devices, how did you make your dies?

Regards,
Tim

[jcbanner]

its definatly not stricking, but I've met a few people that have cast thier own coins with pewter.  they melted it over burning charcoal, so if you have a gas stove that should be hot enough to melt the metal.

For the mold, they carved it by hand from soap stone which I've been told is relitively easy to carve by hand with an appropriate chisel.  Set the mold on a level surface, use a small ladel to pour the metal and let it set.  the only problem is that you only get a one sided coin.

there is a guy that comes out the stl renfaire that does this every year

[timbudtwo]

I was thinking about something like that. However, Large quantities of pewter are not as cheap as say http://www.gemplers.com/product/152499/Round-Blank-Aluminum-Tags-100-box

While not the ideal shape, it may suffice for my purposes. Unless there is a way to make 100 relatively small pendants (1.5") from around 15 - 20 dollars of pewter. Or really any non-toxic low melt casting metal.

[Magister]

This could easily become a story book response to your question, Tim.

But, if you wanted to make a two sided coin / medallion through casting, then your best option if you make a model of the coin both front and back in sculpy or plaster, then make a two-piece mould using RTV, or other polymer high-temperture moulding material.  The instruction for that is a little involved, but you would be able to get several thousand pours from the mould (depending on care).

If you want more information on this option let me know.

For Coining, or striking of coins.  The process, is actually probably a lot simpler than you are imagining.  You will need two dies, one for each side of the coin.  The bottom die, or usually called the anvil die in hammered coinage is set in a fixed position.  Usually in an anvil.  I make them with a post that fits in the hardy hole.  The die is usually made of iron, or steel.  Engraved.  Meaning you use various gouges, punches, etc. to place the design of the coin on to the face of the die.  This can be done while the die is either hot or cold, based on the type of tools you are working with.  If hot, and a higher carbon content metal, remember it will need to be tempered before use.

The hammer die, or top die, is made the same way.  I tend to make a purpose built cold punch with the die engraved in the end. 

Then the blank is place on the anvil die, the hammer die is set on the top of the blank, and then hit firmly with a hammer.  All goes well, you now have a struck coin.  Made well, these can last up to 20k strikes or more.

To look at a screw press, or gravity press, the only difference is that the hammer die is affixed to the press, and the pressure is applied via the screwing mechanism, or the force created when the weight is released and let to fall.

For the engraving portion of die creation, you may want to look in to using a dremel like tool with a diamond bit as well.  It does make life a little easier.

Ok.. I hope this information was a little help.  I know it was pretty general, but this is a pretty wide topic.  If you have any specific questions please don't hesitate to ask.

   - Mag

[timbudtwo]

For the engraving portion of die creation, you may want to look in to using a dremel like tool with a diamond bit as well.  It does make life a little easier.

   - Mag

Thanks! I did know a lot of what you mentioned, but you put it in laymans terms. Plus, its also a little more organized than how I found it on my searches!
As for tools, I have most things except a lathe or a mill. I have a drill press but that is a very poor substitute for a mill/lathe.

Do you have any pictures of some of the dies you have made by hand?

I was considering dremeling the end of a piece of cold rolled steel. I just figured it was going to be very inaccurate. I am terrible at drawing freehand, and would probably be bad at dremeling something like this freehand as well. I can get by pretty well in illustrator or photoshop because of the pen tool and vectors . Perhaps I just print something out and trace it?

Also, about the link to the tags that I posted. I find those are at the right price, but have the wrong hole in them. Since you have experience in striking, do you know of any good sources for relatively inexpensive striking materials? Or have you done mostly precious metals?

Thanks for all of your help.

Here is the idea I have for mine. Very simple. Its designed like this for a local machine shop I may inquire to because they do small jobs. I called them up and they have never made a coin die before, so I figured i'de give them a little extra visual explanation. Ive had them do something for 30 bucks what other machine shops did for 400. So it may be worth the money. The Coin face is 1.5 inches:

[Magister]

Unfortunately, no... I do not have any pictures handy, I'll have to dig out one of the dies.

As for tracing ... sure, why not? .. I'd imagine carbon paper, or the like works well for that.  Working with the dremel takes practice no doubt. 

I've seen guys use aluminum blanks like what you posted before.  They seem to work well.  I've mainly stuck with cast pewter / lead.  Probably a little too pricey for what you are after.

- Mag

[timbudtwo]

I have loads of lead. I was just worrying about its toxicity long term. What about bismuth? I dont know how well It would strike, or how soft it is. But it is not toxic.

I also dont like the hole in the tag

[Magister]

Yes... lead toxicity is an issue... for display or something that won't be handled constantly it's not as big an issue, but if you are making coins that people will be touching constantly it may not be best.

The only other thing might be to seal it with a lacquer, polyurethane, or the like.  I tend to try to seal anything I cast out of lead just as a precaution.

As for bismuth, my guess is on its own it would be too brittle, you'd have to have some form of alloy.  I know several companies sell "lead free casting alloy" that is not pewter, and contains part bismuth amongst others.

[timbudtwo]

Okay, that's good to know about the bismuth. I had just seen a bismuth coin on periodic table table, so I was wondering if it were possible.

I am going to a machine shop tomorrow to see what the cost would be. I had to reduce the size of the dies to 1.25" as that was the size of the tags. Unfortunately, the only other method I could find for acquiring aluminum circles in a size I wanted was to order them from china. However, the manufacturers did not have the correct die size (I contacted about 5 different ones) and to make the mold they wanted $760. The cost of the circles came later!

I will keep looking out. Thanks!

[timbudtwo]

So,
I have been corresponding with someone through e-mail who has some suggestions and might end up making one for me. I have one last spot to ask though.

I tried making my own and its not half bad for my first try with a dremel.  Plus the hardening of the steel didnt go half bad. A lot harder for sure, but not tool steel hard. I used the heat it till it looses its magnetic feature and then quench it in oil method.

Here is the result.

bad photo

[timbudtwo]

In the time between the last post and now I tested it out. Result: Not sufficient.

I set up an anvil for the base (a small 25 pounder) and made a small jig out of 4x4 to hold the die in place over the coin (i'm trying pennies and dimes). Then i took a big whack at it with the sledge hammer. Main problem, aiming the sledge hammer. You need quite a bit of force (i grossly underestimated) to get the imprint. I was able to see it faintly on one strike, but it was very uneven. I am considering just building a 5 foot tall frame from 2x4's. Nothing complex. Taking a steel pipe about 7 or 8 inches long, probably 4 inch diameter, capping one end, filling it with lead, then capping the opposite end. I would weld on little wings to each side and put a bearing on each so that it would be able to slide down some steel dowels and hit the die with the force of 10,000 giants.

Ill let you know what else is happening when it does.