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horseshoe3
4th January 2011, 07:34 AM
Does anyone know how they change the dates on dies? I'm assuming they don't make a new die for each year, but the dates are so seamless with the field that they must have some special way of doing it.

Dogman
4th January 2011, 07:41 AM
Does anyone know how they change the dates on dies? I'm assuming they don't make a new die for each year, but the dates are so seamless with the field that they must have some special way of doing it.


If for coins, all the dies I am aware of are single year use. New dies for every year, I can see them
keeping the art work the same, but when engraving the actual dies used in stamping, That is when I can see changing the year on the die , Thinky!

horseshoe3
4th January 2011, 07:49 AM
That would make sense. I guess I'm just too cheap to scrap out a perfectly good die just because the calendar flipped. I would be more like the Mexicans and keep minting 1947 coins until the end of time if I couldn't figure out how to change the date on the same die.

Dogman
4th January 2011, 07:54 AM
it probably could be done. grind down and build up the area to be changed. and engrave the new date/year. You did ask a very good question!

mamboni
4th January 2011, 08:14 AM
That would make sense. I guess I'm just too cheap to scrap out a perfectly good die just because the calendar flipped. I would be more like the Mexicans and keep minting 1947 coins until the end of time if I couldn't figure out how to change the date on the same die.


A die is only good for so many strikes, so it is used only once. New dies are made each year. I assume it requires many dies to produce a coin such as the SAE given that millions per annum are struck.

madfranks
4th January 2011, 09:40 AM
Here's a general breakdown of how it works. They generally have one master die for each coin design, and they use this master die to create all the secondary dies for striking. The master die does not have a date (or mintmark) on it, so they add the date on the secondary dies. So when the year changes, if the coin design does not change, they still use the same master die, but simply add a different date on the striking die. Like mamboni said, each die is only good for a number of strikes before it breaks so they will create as many dies as they need from the master die.

Of course, there can be more than one master die, in which case you'll have a number of "die varieties" for that coin. We discussed yesterday how some Morgan dies have a different number of feathers than others, taken from different master dies.

horseshoe3
4th January 2011, 12:52 PM
So that means the master die is a positive image and is used to create the negative images of the striking dies?

Also, I understand that the striking dies are pretty hard. The master die must be extremly hard to create several striking dies. Or is that not the way it works? Do they use some other process to transfer the image to the striking dies?

SLV^GLD
4th January 2011, 12:58 PM
I was under the impression each striking die was hand engraved.

We used to have a die engraver around here.

madfranks
4th January 2011, 01:34 PM
So that means the master die is a positive image and is used to create the negative images of the striking dies?

Also, I understand that the striking dies are pretty hard. The master die must be extremly hard to create several striking dies. Or is that not the way it works? Do they use some other process to transfer the image to the striking dies?


They'd use a lathe to transfer the image from the master die to the working dies.



I was under the impression each striking die was hand engraved.

We used to have a die engraver around here.


Yeah, I think his name was scratchmo or something like that; he didn't make the transition from GIM to GSUS. :(

madfranks
4th January 2011, 01:36 PM
It looks like today the US Mint uses even more advanced technology to create their dies. Here's a site (http://www.bakercoins.net/learn/articles/tour/part2.html) with a neat description of how it used to be done and how it's done today.

Die Making Process:

From 1792 till 1836, each die was hand engraved. The main design elements of the die were engraved in the Master Die. Inscriptions, dates or stars were applied to each working die. The die blanks were covered with a thin layer of transfer wax. The design of the die was placed over the die, and then rubbed with a smooth instrument. Then the engraver would cut the design. Because of this process, no two dies were exactly alike.

In 1836, the Philadelphia Mint installed a French Portrait Lathe. The use of this lathe eliminated the need of the engraver to cut the Master Die. A hard model of the die was made and then the lathe would rotate clockwise and cut the design into the Master Hub. Once completed, the Master Hub was used to produce the Master Dies. This lathe was used until 1868.

In 1868, the Hill Reducing Lathe was installed. This lathe allowed the model to be larger than the coin it would later produce. This process would improve the quality of the coins. The Hill Reducing Lathe was used until 1907.

In 1907, the Janvier Lather was installed and is still in use today. During this die making process, the model could be much larger than the coin. The first two digits of the date would no longer need to be punched into the Working Die. This now would be included in the model, called a Galvano.

The Janvier Reducing Lathe would track the Galvano and cut the images into the Master Die. The Janvier Reducing Lathe turned clockwise very slowly. It could take days to cut a Master Hub.

Now the Master Hub, with the first two numbers of the date, could be used for years.

In the mid 1980’s, the Galvano was produce with all four digits of the date. A new Master Hub has been produced each year since.

During the hubbing process, the Master Hub was impressed on a blank die. This is done with a slow hydraulic pressure of about 100 tons. It would take several hubbings to place the design of the Master Hub on the Master Die. After each hubbing, the Master Die would be placed in an annealing furnace and heated to cherry red. The Master Die was then removed and allowed to cool to room temperature. This softened the Master Die.

Then the process would begin again. It was normal for three or four hubbings to occur on small coinage. It was not uncommon for the Morgan dollar to require ten or twelve hubbings before the Master Die was completed.

A few Master Dies would be produced and these Master Dies would then be used to produce many Working Hubs. The hubbing process would be the same when producing the Working Hubs.

Each Working Hub would produce hundreds of Working Dies. Now remember that the hubbing process is repeated each time a new Working Die is created.

In the early 1980’s, the Mint started using a new “One Squeeze” process for Lincoln cents. In this process, the Master Hub is still produced from the Galvano. But this is where the process stops. The Master Hub is then used in a new “One Squeeze” Hubbing machine. The Master Hub is used to produce the Working Die.

The “One Squeeze” Hubbing machine uses hundreds of tons of hydraulic press to squeeze the design elements of the Master Hub into the Working Die. This is done with only one hubbing.

A few years later the Philadelphia Mint started producing nickel and dimes with this “One Squeeze” process. In the early 1990’s, quarters, half dollars and SBA dollars were converted to the “One Squeeze” process.