Carson City Mint Coin Press #1 back in operation
northcoin
Posts: 4,987 ✭✭✭✭✭
Just came across this reporting of likely interest to those with Carson City minted coins:
https://nevadaappeal.com/news/local/coin-press-demonstrations-resume-at-nevada-state-museum/#
Here is an excerpt from the Nevada newspaper's announcement:
"After more than a year, visitors to the Nevada State Museum can watch the museum's historic Coin Press No. 1 carry on a mission it started nearly 150 year ago in the same building.
The venerable press — which churned out millions of dollars in silver and gold coins during stints at U.S. Mints in Carson City, Philadelphia, San Francisco and Denver between 1870 and 1964 — is once again minting medallions after being down for much of 2017 for repairs."
For those interested in learning more about the Carson City Mint, here is a link to my thread discussing both the Carson City Mint and its iconic Coin Press No. 1 with photos I took. Added details of relevance are provided in the responses.
Comments
Glad to hear it! I need to visit it sometime!
Thanks for the link(s).... Being a CC fan, I find all references interesting. Cheers, RickO
The old Carson City Mint is a very cool place to visit.
Next time I'm in Nevada...
YN Member of the ANA, ANS, NBS, EAC, C4, MCA, PNNA, CSNS, ILNA, TEC, and more!
Always buying numismatic literature and sample slabs.
We visited in 2008, the coiner signed the card.
Of, course, the medal has a CC mintmark.
Pacific Northwest Numismatic Association
I read a report last year indicating that the coin press had suffered some breakdowns due to over-stressing it when striking 38mm (silver dollar size) medallions. So they have switched to 30mm (half-dollar size) medallions from now on.
I don't know if that report is true, but it seems plausible.
Pretty neat!
HAPPY COLLECTING
Very interesting/informative post. Visiting the CC mint is definitely on my bucket list. Plan to take some of my CC's with me when I visit. (sort of like they will be returning home, for a short visit.)
Nice!
I think I found the "report" to which you reference:
"After being down for several months for repairs, the press is expected to be back in operation in September, pressing medallions for the public's view and purchase — but with a variation. The medallions the press will produce will be smaller, 30 millimeters, than the silver dollar-size of past years.
The change is being made at the urging of a coin press consultant (structural engineers) from the Oakland, Calif.-based company that repaired the 12,000-pound press, from a restoration specialist at the Nevada State Railroad Museum and from independent analysts. They say the striking pressure required to imprint designs onto the blank coins — between 150 and 170 tons — is more than the 147-year-old press can handle. Switching to smaller medals, about half dollar sized, can be done with less strike pressure (a maximum of 110 tons) and therefore, less stress on the machine. Decreasing the tonnage will aid in the preservation of the press."
https://nevadaappeal.com/news/local/historic-coin-press-returning-to-operation-at-nevada-state-museum/
Thanks for posting that. That is what I thought.
Don't be surprised if they mint some legal tender CC coins in 2019 or 2020.
You heard it here first...............
I'd be surprised since the CC Mint is now a state museum, not a Federal one. Of course, I don't mind being pleasantly surprised. Imagine overstrikes with a CC mintmark.
That would be an interesting commemorative..............Silver half dollars with Morgan dollar design and cc mint mark with funds raised going to museum.
The Carson press has been rebuilt and modified several times and does not fit the original configuration. The iron arch, stake, rods and other basic parts might be original or replacements. Feeder, table, and all related parts are not original.
RE: "They say the striking pressure required to imprint designs onto the blank coins — between 150 and 170 tons — is more than the 147-year-old press can handle."
If the pressure quoted in the article is correct, then there is a major problem in planchet/die preparation. The only time 150 tons was used for dollar production was in Dec. 1921 for a day for the first Peace dollars. Other than that, typical pressure was about 120 tons/sq. in. or less depending on design and die details.
Maybe someone has more information that will clarify the article?
To the coin press itself, the tons per square inch doesn't matter. It is only the total tonnage load of the strike that matters. The tons per square inch load only matters to the dies themselves. A 200 ton total load would likely damage small 3-cent silver dies, but that loading would not usually affect larger silver dollar dies. In either case, the coin press itself wouldn't care which dies were installed - all that matters to it is the total tonnage load.
A silver dollar is about 1.75 square inches. If that required 100 tons per square inch, then that would be 175 tons total load on the coin press. A half dollar is a little under 1.25 square inches. At 100 tons per square inch, a half dollar would require a total load of under 125 tons.
It's a little more complicated than what Mr. Carr proposes because force exerted on the stakes, die holder, rods and arch (resulting in stress on metal and fatigue) depends on resistance and spacing of components. Coining force is regulated only by the adjustment wedge above the die chuck, so it is not a fixed quantity.
The Mint measured force in tons per square inch, not tons over the face of the planchet or die. A reported tonnage of "150 tons per sq. in." was actually 150 tons spread over the dollar's area of 1.77 sq. in. or approx 85 tons. This approach was used consistently by the US Mints. Understanding this and calculating the actual force used will show the real relationship between coin size and the force necessary to bring up a specific design. It also can show the reduction in necessary force as the engravers made changes to master dies and hubs. These data are available in published documents.
But, disagreement aside, the bottom line is that the press was built to strike standard silver dollars, so unless it has degraded - which is possible - it should be able to strike 39mm bronze or soft brass tokens.
The CC coin press would not likely break, even at 400 tons per square inch, if it was only striking dime-sized pieces (because the resulting total load on the coin press itself would only be about 150 tons). In contrast, striking a 38mm piece at only 85 tons per square inch would result in a total load on the coin press of about 150 tons.
The point is, tons per square inch is a useless statistic as related to the coin press. This statistic only has meaning for the dies themselves. Even the US Mint currently uses total tonnage of the strike rather than a tons per square inch metric. For example, this article quotes the US Mint statistic that the new WW1 dollars are struck three times at 218 metric tons (about 240 US tons): https://coinworld.com/news/us-coins/2017/12/philadelphia-mint-striking-world-war-I-silver-dollars.all.html
What RogerB fails to consider is that the diameter of the dies is not the only aspect of the dies that determines the necessary total force for a full strike. Aspects of a die that will increase the necessary striking force include:
1) Depth of relief (deeper engravings require more force to strike up, of course);
2) Flat fields (dies with dished or "basined" fields are generally easier to strike, especially in the centers);
3) Raised devices that are in close proximity to the rim;
4) Narrow rims (pieces with wider and shallower rims are generally easier to strike fully);
5) Proof finish.
Looking at some modern products from the CC press #1, it appears that they meet criteria #2, #4, and #5 above. And even though they are generally low relief, some also have fairly high rims which would still meet the criteria for #1 (deep engraving on the rims). Some also have #3 (devices which extend all the way to the rim).
So why would the new WW1 Dollars require 240 tons of striking force ?
See #2, #3, and #5 above.
I do not know who makes the dies that the CC museum mint uses. But a different approach could possibly yield higher relief pieces with less tonnage required.
With the amount of breakage that the Nevada State Museum mint has experienced with the coin press over the years, I would think that they would have evaluated and addressed the planchet hardness already.
PS:
The only thing that I would consider to be anything like "soft brass" is leaded brass. There are obvious health reasons why mints would not want to use lead in their products, and so modern brass planchets generally do not contain any lead.
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RE: "What RogerB fails to consider is that the diameter of the dies is not the only aspect of the dies that determines the necessary total force for a full strike. Aspects of a die that will increase the necessary striking force including..."
Mr. Carr listed some specific issues that affect the force necessary to bring up a design. I mentioned this only peripherally as, "It also can show the reduction in necessary force as the engravers made changes to master dies and hubs." But that does not answer the question about statements in the newspaper article. Possibly, it was a "preservation" decision and not really based on empirical measurements.
In any event it is nice that the press is back in public operation and providing education and amusement to visitors. Back in the days of large expositions, the Mint and Treasury usually had a press on site striking half-dollar size medals for sale to visitors.