View Single Post
  #38  
Old 04-14-2008, 08:10 AM
Tom Maringer's Avatar
Tom Maringer Tom Maringer is offline
Steel
 
Join Date: Mar 2008
Location: Springdale Arkansas
Posts: 48
Default Re: Engraving coining dies

Great Question... one I was never able to find an answer to and just had to figure it out by experience. My first press was the 40 ton blue manual press. There is no way to actually measure the force of course, but presumably that represents the maximum available force when you really whang the thing.

I would give a general rule of thumb force/size chart, assuming soft metals such as copper or sterling silver as:

20 tons for a dime 11/16" ~ 17mm diameter
30 tons for a penny 3/4" ~19mm diameter
40 tons for a nickel 7/8" ~22mm diameter
70 tons for a quarter 1" ~ 25mm diameter
100 tons for a half-dollar 1 1/4" ~32mm diameter
150 tons for a silver dollar 1.5" ~38mm diameter
300 tons for a large medal of 2" ~50mm diameter
750 tons for a very large medal 3" ~75mm diameter

You can extend the range (that is, use a press for a larger piece) by using multiple strikes. At need you can even do partial strikes, anneal the blanks, and then strike again. (that works for broadstruck pieces without a collar) You can even do some REALLY tricky things by using thin wedges under the dies and "rocking" them into the work under multiple blows. This can be dangerous (I have had peiece of metal fly out at bullet-like speeds) but I've managed to do 600 ton work on a 320 ton press that way.

So once you get into these things... no matter what press you get or build... you will quickly work up to the limit of its power and begin lusting after a bigger one. I can attest that this process is never ending. I have eight of the things now... my largest is a 320 ton hydraulic... and even with that capacity (up to 2 inch diameter) I still lust after the thousand ton ones that I occasionally see for sale (capable of striking up to 3 inch diameter!)

Another thing to consider is "headroom"... that is... if you have a 50 ton press you never actually want to run it at 50 tons since you will be putting a lot of stress on the parts and could actually break the frame if you overdo it. So you use the 50 ton press to do 30 ton jobs, the 150 ton press to do 70 ton jobs, the 320 ton press to do 150 ton jobs etc. If you stay well below the rating of the tool it will last forever. If you routinely push a tool to its limit it will not last very long.

Quote:
Originally Posted by vilts
Tom, a small question. Can you tell a rule of thumb, if it exists, for press power and size of coin it is able to make? You said that 30-ton press would be enough to make dime/penny/nickel size coins. Dime is probably about 1/2 inch diameter? (sorry, never seen/user one of those in real life). So, for example, how big press would I need for 3/4" or 1" coins? Or, how much would I be able to do with 50 ton press? This is just excellent thread/info here!
Reply With Quote