Coining dies for making miniature replica St Gaudens-Tom Maringer

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Coining Dies

Hi Capped...
Noticed this thread.... tools and techniques!

Well, to start with, here's a webpage that is a brief tour of my workshop:
http://www.shirepost.com/ShopTour.html
so you can see some of the presses, the lathe, and a few other things.

What you don't see is shelves full of hubs and dies. I have been collecting such tooling whenever possible and now have a collection of over 5000 vintage pieces on virtually any conceivable theme. Some people may have noticed a few years ago when a large magazine ad appeared in some high-end rags like Nat. Geo., Atantic Monthly, New Yorker etc that was advertizing a very small St Gaudens replica. It was being offered by one of the large eastern private mints. Well... when that mint went under I was able to purchase a number of their original hubs, including this pair.

So... I buy bars of annealed W-1 tool steel which is cut to length and turned off square on one end and coned on the other. The polished coned end is held point-up in a sleeve mounted on the press-bed of the gray screw press. The hub is mounted point-downward on the ram. I strike the hub into the coned end of the steel die-blank to impress the negative image. Since no matter how hard I try they NEVER come out perfectly centered, I then have to do a lot of messing around with the lathe to get the image centered so I can turn the shank around it. Once the shank is turned I mount clamp the die face up on a Gorton P1-3 pantomill to cut the date and mintmark. They always need a little finishing work with a graver under 20x binocular scope. When it's finally ready they go into the electric furnace and warm up to 700 degrees before being coated with antiscale compound, then finally they are taken up to 1550 degrees f and held there to "soak" for at least 20 minutes to dissolve all the carbon evenly, then quenched in water and immediately tempered for an hour at 350 degrees F. After that I use a torch to heat the top ends to about 750 or 800 degrees f to give them a soft temper to resist chipping from the hammer. And I do a bit of finish grinding around the rim at the tip of the die to make the projecting rim even and smooth.

I don't know how many hours it takes... but at least a day per pair.... something like that.

 

Tom
On the centering issue, have you tried a captive shoe set or leader pin setup similar to a stamping die or plastic injection mold? That may help.

 

I hadn't tried anything like that yet. The set-ups that Denis Cooper shows the US mint using in THE ART AND CRAFT OF COINMAKING are quite a bit more sophisticated and involved the coned die blanks having a tapered back-shank. Ron Landis showed me a trick that he uses for centering the hub using a custom made live-center on a large floor lathe. There are solutions... I'm just trying to one-off the things. I'm not imagining I'll sell more than five or six of these sets.

 

Fascinating!

 

Being an ex toolmaker I can really apreciate all the work you put into it , very nicely done .
rzage