Need ideas for a coin press.

The other thing to keep in mind is that you probably won't want people coming in to your shop using a screw press capable of smashing fingers between dies or breaking arms with the throw-arm. Well, maybe you will, but your insurance company won't.

 

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With all due respect, this idea sounds a little half-baked.

There seems to be some confusion over what the plan is – I read it to be a press that strikes coins, not a coin elongating press. I think the elongated coin angle was mentioned as being comparable to what the struck coins would be like – custom designs relating to local topics.

I press that would strike anything like a dollar or even half dollar size would be enormous, expensive (tens or hundreds of thousands of $$), and extremely powerful. If you wanted to strike a coin half the size of a dime, for example, then a screw press or kick press could be used.

There is someone in Alaska who makes his own presses for minting – he has written a book about it - it might be called "Striking Gold in Alaska" or something similar. He has more recently designed a simple drop press (using only gravity) to strike larger coins, but he has a high rate of rejects and the designs are quite simple/shallow. The press is, as I recall, 15 feet tall or so, and you need to pull a rope to lift a very heavy weight to the top in order to release it to strike the coin. He uses his outdoors.

My suggestion is to stick with a simple manually operated elongating press, or use a small press for a small counterstamp on existing coins. You could have two dies made so you would get an obverse and reverse counterstamp. Examples are the nickels stamped with “No More Lies”/”No More War”. I think these were the subject of an earlier thread here on CT. The Shirepost Press specializes in small coins/tokens and this type of double counterstamp.

You can also check out Daniel Carr’s website to get an idea of what he had to do to start minting his own material.

My vote is for a custom counterstamp on both sides of a coin.

 

At least you have the gist of the idea of what I am envisioning. I never assumed or thought it would be cheap or easy, but definitely a draw to the public and especially coin collectors who would want to experience a simpler version of what we all enjoy so much.

Obviously I cant articulate exactly what I am trying to accomplish but my main thoughts were either something simple like an old screw press that could generate enough force to strike a dollar sized coin (or slightly smaller) with the weight of half dollar or half ounce planchet. So I dont think the extreme force would be necessary as say for coining something that is as thick as a traditional half dollar or dollar coin.

Other brainstorming options consisted of a hydraulic press that was geared for the same scenario above as far as planchet so it didnt have to be super heavy duty. This machine also isnt going to be repeatedly and repetitively making coins, about as much use as an elongated penny machine.

The other thought that I had was some sort of crank press that uses lots of gears at very low ratios (Like the elongating machine) with a reverse lock on the crank like a boat winch to always keep the pressure moving forward and downward to impress on the blank, but also safe with the reverse lock so the arm doest free spin back around and hurt anyone.

The last option seems the cheapest in my mind and probably most cost efficient. I am envisioning two dies aligned above and below one another with cranks and gears on the inside and outside of the housing, and then either a wheel like a captain/vault wheel, or just a simple crank. Does that not mechanically seem possible?

 

The force necessary to impress an image on a "coin" is -mostly- related to the crossectional area of the coin--not to the thickness of the planchette.

Other factors are:

Brinell hardness of the metal making up the planchette

and

Depth of the design (relief)


So, a smaller diameter "coin" will require less force to strike all other factors being equal.

 

Neon beat me to it. The force needed is not related to the thickness of the planchet, but the size (diameter) of it. So, a dollar or half-dollar sized coin is a huge (prohibitive) undertaking, regardless of thickness.

Don’t get me wrong – I hope you can find a way to do it – I would then be interested in the details so I can do it myself also. But, I am pretty sure a large coin is not going to work unless you want to invest many thousands of dollars and lots of space. In that scenario, it is best to just pay someone to make your medals.

You can build a small minting contraption - basically a die you strike like a chisel against a planchet that is resting on top of the other die (see the reference to the Alaska guy) but we are talking much smaller coins. Elongating or squeezing is much easier. Striking like a coin is a far bigger challenge. If you are willing to sacrifice relief and details then you can do something simple with hammer-struck dies – the pewter tokens I saw being done at an ANA show were about the size of a nickel as I recall.

You MIGHT (not sure) be able to do something with those hydraulic shop presses you can buy in Harbor Freight Tools for a couple hundred dollars. It would need some custom work to make it suitable for coins, and you would then need to buy dies.

I would start with whatever process is readily available and work up from there.

 

OK with a better description of what he wants I think what he needs is a rocker press. They are small, compact, and do not require as much force to operate. On the down side making the curved dies is not easy and the coins often come out with something of a S type warping to them. This was the type of press used to make the willow and oak tree shillings (and possibly some of the large planchet pine tree shillings.)

It is kind of like the elongated cent machine except that it doesn't attempt to reduce the thickness and elongate the blank so the pressure is much lower. It also uses both and upper and lower dies.

Something like this.

 

I am ok with reducing the diameter if that will create a better coin than reducing the thickness. Ive got no problem with that, and I actually have a 1/4 ounce copper token that would be about the largest of the size i would like to see if I have to limit the diameter to create what I want. I wouldnt want to be much if any smaller than a Susan B. Anthony though and as close to a 1/2 ounce of whichever precious metal

I am totally against custom medals or tokens, this is a novelty item to draw people into a hypothetical shop and be something better and more unique than the elongated penny machines found at every park, attraction, or museum. (Not to say i dont collect those or enjoy making each one, but as a coin nerd, I want something more)

I was also thinking a fairly cheap hydraulic press machine would accomplish what I wanted. Maybe even find a way to heat the coin enough to make an easier impression. I dont know, I am still brainstorming here.

I wonder if this could be modified to where the pressure is constantly moving downward and squeezing harder and harder as you turn the crank versus just squeezing the planchet through and distorting the image. It wouldbt be difficult to install a mechanism much like what you would find on a boat winch to stop backlash motion as a safety mechanism.

I also think this could work if you had two dies aligned above and below one another and simply turning a screw that brings bottom and top together while keeping the mechanism safe by utilizing a back stop, and creating enough pressure by altering the amount of gears and the ration involved.

The basic principle is one planchet being squeezed between two vertical dies and just bringing those together with enough pressure to leave an impression on both sides with relative relief and clarity, i dont really care about time as long as a crank can be turned within 5-7 minutes to produce the piece.

The item pictured above is clearly mounted on a table top and I am imagining something similar or about the same size and possibly able to stand on its own housing. It also appears as if that lever was only meant to be pulled down until is was fully engaged. I wonder how much pressure you could create using a crank instead with a different gear setup.

Thanks to all who have responded, I think we are bringing this idea together and at least figuring out if its even possible and worth doing.

Cost isnt a terribly huge issue on this venture, as I would find ways to sell the product to walk ins, and maybe even write some of it off as advertising or something, im not sure, but I dont think a primitive piece of equipment like what I want would be terribly costly to manufacture or especially difficult. The dies may be a different story, but I think the press can be done, and I feel like it can be done without hydraulics or electricity necessarily.

 

Actually, a large part of the reason that rocker press can be so "small and lightweight" is because it isn't impressing the entire image all at once. It starts out impressing the image on one edge of the "coin" and then as the crank is turned and the dies rotate the image is progressively impressed towards the middle then to the other end. This means the press only has to generate enough force to move metal along a narrow band (the bit that is directly under the dies at the time) rather than across the whole face which is what happens in a standard vertical axis press.

If you try to force two dies together to create the image across the whole coin all at once you will need much more (edit) force (edit).


By the way, that rocker press is GORGEOUS!! Wish I had that in my shop! Thanks for posting Conder101!

 

I'm actually kinda' bummed the OP isn't going with an overgrown version of the elongated penny roll press.

I had visions of someone walking into his shop with an artificially toned morgan. With much pomp and ceremony the ill fated coin would be dropped into a slot, then a giant lever pulled.

First the coin would roll onto an annealing stage complete with blow torch. After annealing it would fall through a trapdoor directly into the gaping maw of two hardened steel rollers with images carved into them. Then, after several seconds of gears turning and rollers rolling, the morgan would be rolled out into a long ellipse with an image of Uncle Sam sticking his tongue out at all those who would dare harshly clean or artificially tone coins

(just kidding morgan collectors)

 

How do they make medals? I thought they were stamped in a press like coins? If that's the case, I think that's the tool he's after.

 

just thinking outside the box, could a 3D printer do what you want?

 

Check post number 3

 

Just out of curiosity, does anybody have a reference as to how one would calculate the amount of striking pressure necessary to mint a coin given the metallic composition and dimensions of the planchet and the desired relief of the finished coin?

 

Can't say about gold coins but as rough figures US cents and dimes run around 40 tons, quarters and small dollars around 75 tones, silver dollars around 120 tons. You could probably use those as rough estimates based on diameter, gold being a softer metal would probably be slightly lower.

 

You could alter the amount of effort required to make your tokens by annealing the coins/ rounds you are intending to work with

 

Here are some photos I found regarding what I think you are trying to achieve here:

 

And - you have to watch this video:

 

It really would be fun to walk into somebody's coin shop and squish a coin on a fly press (which is the type of press being used in OdedPaz's video) Although, I think the shop's insurance agent would be coming unglued if anyone was allowed access to the press.

Trey, you could probably source a substantial enough fly press on Craig's List for less than two grand. Just gotta find the right listing.

You would have to limit the diameter of the coins you wanted to make, probably to less than 22mm. And use really soft planchettes. Maybe pure tin? Or, if you used pure indium you could strike coins the size of dinner plates

Then, once again, it all comes back to having the dies machined. If it were me, I would probably find a machine shop set up to do sinker EDM (electrical discharge machining).