Wisconsin Extra Leaf article in Grey Sheet Monthly Supplement
EagleEye
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I wrote an article about the WI Extra Leaf quarters in the May, 2010 issues of The Monthly Supplement.
Wisconsin Extra Leaf Article
They failed to give my link to the videos, so here they are:
How the WI Extra Leaf Quarters were made (Video)
Rarity and early values of the WI Extra Leaf Quarters (Video)
Wisconsin Extra Leaf Article
They failed to give my link to the videos, so here they are:
How the WI Extra Leaf Quarters were made (Video)
Rarity and early values of the WI Extra Leaf Quarters (Video)
Rick Snow, Eagle Eye Rare Coins, Inc.Check out my new web site:
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Comments
Could you post the article for those of us that don't get the greaysheet please. I wouldn't think it'd be a copyright problem, assuming you wrote the article
Thanks
Thanks for the links.
<< <i>Could you post the article for those of us that don't get the greaysheet please. I wouldn't think it'd be a copyright problem, assuming you wrote the article
Thanks >>
The Greysheet quite religiously protects its copyrights, but I am reasonably certain that Rick, as author, could post it on his website with no problem.
TD
Rick,
A question about your CDN article re the Wisconsin quarters:
You speculate that the dies "were fresh from the annealing furnace."
As I understand the die-making process, die blanks are annealed to soften them, but then become somewhat work hardened during the hubbing process. They are then heat-treated to make them even harder, so they can be used in coining.
The marks were obviously added to the die, in whatever manner, after the design was hubbed. Are you saying that they are both annealed AND heat treated after they are hubbed?
Tom
We'll To be honest. I really didn't know, I just knew that the marks had to have been made on the die when they were annealed (see the video to find the answer to that one). So I asked my friend Chris Pilliod (mentioned in the article and video) about this. This was his reply:
Rick/Tom... I'll copy some metallurgical junkies here as well.
Die metallurgy does get a bit confusing for the nonindoctrinated. Tom makes a good point here-- the processing order Rick states in CDN is not correct.
Actually, as far as I know the Mint in reality never performs annealing anymore-- or at least I can see no reason why they would need to. The necessity of annealing vanished when the Mint employed single-press hubbing.
Bars used for die stock come fully annealed as shipped by the supplier. The Mint can't anneal the bars because they are very long as shipped into the Mint, perhaps 10 to 14 feet long. Because of the exacting operating requirements of the Mint for machining tolerance they prefer to bring the bars in at this length then cut and machine themselves. In reality suppliers such as Carpenter Technology (my employer) use a special type of anneal known as "spheroidized anneal". It is a low temperature anneal , maybe 1400 to 1500F for a very long time (perhaps a day) followed by an extremely slow cool. This makes the die steel "dead soft" as compared to a more standard anneal, whcih while imparting a lot of softness to the die, would still be too hard to hub.
After polishing and hubbing the dies do work harden somewhat as Tom mentions, but the amount of increased hardness is quite minor and more importantly very localized to the surface. Metallurgists often discuss "work harden rates". In other words if you deform two different metals, perhaps nickel and iron, the same exact amount they will NOT harden the same amount and for some metals or alloys they barely work harden at all. On the other hand some metals go nuts... I am working on a project for work-hardened armor plate for the Abrams tank, and this alloy was designed in part reason for fast work-hardening rates. I can't give you the entire composition but will say we discovered that adding nitrogen to metals has an enormous impact on work-hardening rate. I joke to these guys "this stuff gets hard when I stomp on it!!!". We can double the tensile strength with just 20% cold-work. Why work-harden metals? The simple answer is a lot of metals are not "heat treatable".
It gets confusing... the temperatures used for annealing and heat treating are very close and sometimes the same for the same metal. But annealing is a softening operation and heat treating always-- always!-- refers to a hardening operation. In the case of 52100 die steel the MInt will heat to 1500F or so and then quench in oil or polymer, and man, does this stuff get hard-- like Kelsey's knuckles.
A lot of metals can't be heat treated, so metallurgists work harden them to boost the tensile strength (hardness). But even work hardening the most work-hardenable alloys will never get close the the hardness the Mint needs for operational dies. Die steels are over 300,000 psi tensile. So a 1" by 1" die steel can lift over 300,000 lbs before it breaks! That's a lot of cars. Get this... this stuff is so hard we don't even pull tensile bars because it would bust up the machines. So the specs just call out Rockwell hardness requirements, a simpler test that correlates well with tensile.
So when did the extra leafs get put in the Wisconsin dies? It happened after the hubbing and before heat treatment when the dies were still soft. Once heat treated all the King's horses and all the King's men can't make that big of a dent. I am confident it was an intentional act, a guy playing around most likely pretending to be Van Gogh or something. I agree with Rick these are really cool varieties... I very much like them and have several sets. If those dang State Maps had these varieties in them they'd all be worth $3000+.
Chris
So, it seems I should have said "...fresh from being hubbed" instead of "...fresh from the annealing furnace" .
I remembered that back in the good old days, when U.S. coins had relief on them, it took two or more hubbings to completely sink the design into the die, and it was commonly believed that the first hubbing work hardened the die to the point that it was necessary to anneal the partially-hubbed die before the second hubbing.
However, the reliefs and techniques (and most likely the die steels) have changed so much since then that anything is possible.
I am still waiting for an explanation of the similar-appearing semi-circular die gouge at the ear on a 2003 dime, and similar-appearing (though much smaller and shallower) semi-circular die gouges around the tiny Lincoln figure on the reverse of at least two Philadelphia cent dies in this era. Did a mint employee start adding grafitti to dies in Philadelphia and then get transferred to Denver?
TD
<< <i>The dime is a 2004-D. I think there is a connection. >>
You're right. It was a 2004.
But the cents I showed you are P-mint, and I think they are related also.
TD
Maine_Jim
Very enjoyable reading. Because of your work these coins will be very valuable one of these days.
"Live long and prosper"
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