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Metal Content Of Dies?

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mklpatrick's Avatar
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 Posted 01/15/2009  12:42 pm Show Profile   Bookmark this topic Add mklpatrick to your friends list Get a Link to this Message Number of Subscribers
Does anyone know what type pf metal the dies that the U.S. Mint use are made of?
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MtnCoinMan's Avatar
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 Posted 01/15/2009  1:29 pm  Show Profile   Bookmark this reply Add MtnCoinMan to your friends list Get a Link to this Reply
The process of making dies to strike coins in today's mint has quite a few steps. First, an artist creates a large plaster model of the coin. The plaster model is then coated with rubber. The rubber mold is then used to make an epoxy galvano. All of this takes place on a scale of around eight inches. Next, a Janvier reducing lathe takes several days to reduce the image onto a steel master hub in a process that has not changed in over a hundred years. The master hub is then tempered to make it hard. A small number of master dies (incuse) are then made from the master hub. These are then used to make working hubs. The working hubs are then used to make working dies. With each step, the number goes up. The working dies are then used to strike coins. All dies are incuse, and all hubs look like the coin being struck (with the devices raised.) This article is about the building material. ... Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. ... Epoxy or polyepoxide is a thermosetting epoxide polymer that cures when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in the United States. ...


The final step of course is that the dies are used to strike images onto the planchet so that it becomes a coin. A planchet is a round metal disk that is ready to be struck as a coin. ...


Of course, mistakes can happen at any stage of this manufacturing process, and these mistakes are something that certain collectors look for. Coin errors that occur on the die are generally more desirable than errors made at the time of the strike. For example, a doubled die, where a date or another device appears twice slightly offset, is often a highly desired error. Strike errors are generally unique, whereas all coins struck with an error die will have the same characteristic. This makes them more easily collectible. The most famous doubled die in the past hundred years is the 1955 double die Lincoln Cent. These trade for hundreds of dollars because the error can easily be seen by a casual observer. Many doubled die errors require at least a jeweler's loop (if not a healthy imagination) to be seen. Doubling can occur at the hub stage as well. Some more recent errors are hub doubled. Most famously, there is a 1995 doubled die cent that is hub doubled. The 1955 doubled die is a minting error that occurred during production of the one cent coin at the United States Mint, in 1955. ...


Since coin production in the United States has exceeded 20 billion coins in some recent years, this means that a lot of dies must be manufactured as well.
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MtnCoinMan's Avatar
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 Posted 01/15/2009  1:33 pm  Show Profile   Bookmark this reply Add MtnCoinMan to your friends list Get a Link to this Reply
Here is a definition of TOOL STEEL, which is used to make dies:

Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures (red-hardness). Tool steel are generally used in a heat-treated state.

With a carbon content between 0.7% and 1.4%, tool steels are manufactured under carefully controlled conditions to produce the required quality. The manganese content is often kept low to minimize the possibility of cracking during water quenching. However, proper heat treating of these steels is important for adequate performance, and there are many suppliers who provide tooling blanks intended for oil quenching.

Tool steels are made to a number of grades for different applications. Choice of grade depends on, among other things, whether a keen cutting edge is necessary, as in stamping dies, or whether the tool has to withstand impact loading and service conditions encountered with such hand tools as axes, pickaxes, and quarrying implements. In general, the edge temperature under expected use is an important determinant of both composition and required heat treatment. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc.

Tool steels are also used for special applications like injection molding because the resistance to abrasion is an important criterion for a mold that will be used to produce hundreds of thousands of parts.
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mklpatrick's Avatar
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 Posted 01/15/2009  1:36 pm  Show Profile   Bookmark this reply Add mklpatrick to your friends list Get a Link to this Reply
Thanks MtnCoinMan. I saw that on Wikipedia, but I was curious as to what the composition of the actual dies are. Tool steel? Some type of high temp steel? A version of stainless?

Ah! You responded the same time I did. So it IS tool steel. I wonder which one.
Edited by mklpatrick
01/15/2009 1:41 pm
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desertgem's Avatar
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 Posted 01/15/2009  1:53 pm  Show Profile   Bookmark this reply Add desertgem to your friends list Get a Link to this Reply
In an article from 1995, it was mentioned that the mint uses 52100 steel for coinage dies ( iron with minor or trace components of carbon, chromium,manganese,phosphorus,sulfur, and silicon. Before ,W-1 tool steel was used.

Article was reprinted in W.W.White's book "Coin Chemistry" from the Gobrecht Journal 3/95.

Jim
Edited by desertgem
01/15/2009 1:55 pm
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 Posted 01/15/2009  2:01 pm  Show Profile   Bookmark this reply Add mklpatrick to your friends list Get a Link to this Reply
I think we used to call that a type of bearing steel. It's pretty hard stuff. The W1 is the original water quenched tool steel, again annealed in that process for extreme hardness.
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desertgem's Avatar
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 Posted 01/15/2009  3:56 pm  Show Profile   Bookmark this reply Add desertgem to your friends list Get a Link to this Reply

Yes, there is the info that W-1 was brine quenched and that the change which had occurred a few years before 1995 ( no specific date given) was for "mechanical reasons" rather than corrosion resistance.

Jim
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