Which metals strike better? Does the mint consider that in die preparation?

mdwoods

I would think the softer the alloy is, the better strike you would get. However, I know zilch about the way metal flows. Anybody got any facts on this subject? Thanks, mdwoods.

Flash

I recently read that gold, being a very soft metal, is extremely difficult to strike because of the metal flow.

Jamericon

Here are a few facts for you:

Most coinage metals tend to flow the same. The pressures used on the coin presses, between 30-100 tons, actually change the metals state to that of a "semi-solid fluid" and it flows into the crevices of the die. Nickel is the hardest to press, with cupronickel next. Gold and silver are both very malleable metals in their natural state and therefore easy to coin. Copper falls in between. The softer the metal the less stress on the die and the longer its die-life. Softer metals do strike much better than harder ones.

cladking

<< <i>I recently read that gold, being a very soft metal, is extremely difficult to strike because of the metal flow. >>



If I remember orrectly this was one of Alan Herbert's statements. It is true that if you try to
strike gold with the same kind of pressure that you use on a copper nickel coin you'll "splatter"
the metal around. On simply reduces the pressure (die spacing) to compensate. This is essentially
the defining characteristic of coinability or ease of coining.

agfox

On that discovery channel us mint secrets they showed proof platinum eagles and said they had to be struck 5 times to get full detail. Thought that was interesting.

meos1

Multiple strikes is not an unusual thing. I remember that a coffee maker plant I toured as a youth actually struck a solid block of stainless twenty maybe thirety time to bring up the carafe shape. I had the honor of running a sixty ton press when I was much younger and you would definately not be using the full force of the press to mint the gold coin. A multiple strike lower force blow aides in the even flowing and most imprortantly helps abait cracking in the die or material. Jamericon had it right!

Dan

BillJones

I believe that the mint uses the same methods to make dies regardless of the metal. It's the amount of pressure that is used to stike the coins. The larger the coin, the greater amount of pressue AND from easy to hard to strike the progression goes from gold, silver, copper, copper-nickel and finally nickel.

Copper-nickel drove the personnel at the 19th century U.S. mint crazy. They called it "the devil's copper." If you would like to some evidence check out some Shield Nickels, Nickel Three Cent Pieces and some Liberty Nickels. Even in the modern era a lot of Buffalo and Jefferson Nickels are not so hot. Just ask those who are looking for full horns and capes and full steps.

keets

..........there's not really much that can be done with regard to the dies. they can't be hardened past a certain point or they'll shatter and if they're too soft the detail will deform to quickly. as others have said, the most important factor is the striking force and number of strikes.

al h.

Conder101

Sometimes a soft metal can give you extra problems. Pure gold is very soft but has a tendency to stick to the dies. Aluminun is soft and flows easily but it reacts almost instantly with oxygen in the air. So all alluminum that you see has a VERY thin layer of aluminum oxide, also known as carborundum (As in carborundum paper), on it. Carborundum has a hardness rating of 9! Much harder than the steel of the dies so it tends to wear out the dies as it flows past.

Nickel was known as Kufer-nickel or devils copper because of the extremely high temperatures needed to melt it. It has a higher melting point than any coinage metal except Platinum.

mdwoods

Wow, a ton of new information, for me, here. Thanks guys. I am fascinated with the technical details. mdwoods