How Worn Can A Die Be and Still Strike MS Coins?

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@GDJMSP I'm not so certain that @rmpsrpms really looked at your 18 Mercury dime you posted but that dime tells the whole story if one knows what their looking for. One problem is these flow lines are better seen in 3D and it’s something you can’t get with digital. One reason I don’t have a digital scope or view my coins with digital images. Much more detail can be observed with the eye through glass lenses. At 45x magnification looking at Lincolns, which display very similar flow lines to your pictured dime. I can see the way the metal flowed by how its laid down something missed with 2D images. I can see it on the dime but I know what I’m looking at from looking at Lincoln cents. All I collect are Lincoln cents so it’s what I’ve got but like I stated above a Lincoln cent presents very similar flow characteristics to the 18 Mercury dime.
Reed

 

Another "hole" is actually the space between the upset edge of the planchet and the collar. The highest pressure areas are where the fields are coming together. Metal must flow from within the bulk of the planchet to fill the devices, and it must also flow outward from the bulk until it is constrained by the collar and the die rim. At that point the only unconstrained part is the small gap around the perhiphery of the die, and at some point with strong enough striking force this area will form a "wire rim". Usually the machinery is adjusted so this does not happen, since excess striking force shortens die life.

In my extreme example of having no devices to fill, the only movement is outward. When devices are present, some metal will flow into them, causing some net inner movement at the die surface near those devices, but there will also be a net movement near the the edges of the coin similar to the case with no devices. Somewhere in the middle, depending on the relative volumes that are being moved, there will net zero, though vs time that net zero will probably move, supporting your correct contention that there is always some movement in all areas of the die surface.

 

Indeed I did look at the Dime, but it only supports what I am saying. What do you see on that coin that causes you to believe that the metal at the edge of the coin is flowing inward toward the devices rather than outward toward the rim?

 

It’s more of a grain and how it lays down that I see. The upset in the planchet is more material than the rim needs thus the excess material flows away when struck. That’s my thought anyway. I now have looked at many coins that exhibit wear flow lines and they generally look the same like any excess moves in when the coin is struck.
Reed
Here’s my microscope a vintage Swift stereoscope 15x to 45x magnification

 

I was sitting here looking at this planchet and comparing the upset rim with the rims of the coins you see in the image. It just looks to big to fill the space that is the rim of the coin just what I “see”.
Reed.

 

Yes, it indeed flows away, but not toward the center of the coin! To do that there must be some good reason for it. Filling a void in the die is a good reason, but it does not take metal from closer to the rim to do that. Local metal from the bulk of the planchet is sufficient for that purpose. To make metal flow inward, there must be some inward force. The force from the collar is not a net inward force, just a reactionary force due to the OUTWARD force from the strike. Equal and opposite, so the metal hits a wall when it expands to the collar, but the collar force doesn't exist until metal has flowed outward to meet it.

 

The coin is in there the metal just has to be impinged upon..

 

You have that point sir. Albeit very slightly the metal has to fill the collar and to do so it must move away from center but the majority of excess material has to flow away from where it can’t be to be where it can the high spots of the coin. Or the low pressure areas of the design.
Reed

 

I have this penny that I found when working as a cashier. I kept it cause it was cool looking. Im just wondering if its a legit error or what is it and why does it look this way. Thanks in advance.

 

Yes, we are very close to the same understanding, but your insistence that metal flows inward everywhere on the surface of the coin still keeps us apart. In your post 101 you also seem to neglect the basining of the die, which generally causes the fields around the bust or innermost devices to be first to be struck, so your sequencing is not quite right, and this has some effect on where we differ.

 

The coin grades are indications of wear up to 59.
MS starts at 60 and goes to 70. But I dont know what they grade in this area.
MS means Mint State, or uncirculated. Probably the ten grades were based on bag marks when big coins like halves and dollars beat themselves up in bags. It was possible to get a scratched up coin fresh from the mint.
Now, methods have improved, somewhat, and coins are made of tougher metals that wear better. Its a rare clad that shows significant wear.
I always wondered how the old large cents were accurately graded. They were made in a manual press, had large differences from front to back, and between individual coins.
How do you tell an LDS, late die state, from a worn coin? Especially since most are 200 years old?

 

Since this thread is not about your coin, you should start your own thread.

 

Planchets have 3 dimensions so the metal is flowing in at least 3 directions; in toward the void of the devices in the center of the Planchet and then up and down into the die voids on the obverse and reverse all at the same time...

 

Very true. And the force that makes the metal move is coming from the flat fields of the dies, pushing against each other, and squeezing on the metal.

 

I have to say I agree. A lot of this excellent discussion is now down to the tolerances of fit of the collar, the volume of metal in the upset rim, and the contours of the surfaces of the dies. It is well-known in the auto industry that in order to strike complex shapes, such as a hood with various contours, that the metal must be drawn over intentional uneven areas in the forming die. This stretches it out a bit before the final strike so there aren't wrinkles or grooves from forming all at once.

As I recall, the Lincoln cent was one of the first coins with a compound curvature in the fields. This may be partly a design element, but is more likely there for metallurgical reasons, to guide the flow of the metal into the voids during striking.

I took the liberty of blowing up your planchet. I have my own, but it is as punched from the sheet copper, and before going through the upsetting mill. Yours is better for this discussion.

I measured a nickel planchet that was upset, like your cent planchet.

Edit: Actually I am not sure if this has been through the upsetting mill or whether the elevation near the rim is from being punched out. If the latter, the planchet will be even smaller after it gets out of the upsetting mill. That would not invalidate any of the succeeding comments.



It has a diameter of .825 inch. I measured a 2004 uncirculated nickel and it measured .836 in. In short, the upsetting mill squeezes and reshapes the metal at the edge of the planchet, making it a smaller diameter. Then, during striking, this metal in the rim is pressed back down and slightly outward (and upward, too) until it hits the collar. I measured the thickness and the finished rim is actually thicker than the unstruck planchet, so there is some actual flow upward to produce a sharp and flat edge on the rim.

But this seems a bit trivial - sure, this has to flow down under compression, and a bit out, and a bit inward since the upset looks like it contains more metal than needed to fill out the rim. (We could do the math here if I had a measurement of the pre-upset planchet.)

I find one observation especially illuminating, that the fields are the main impact point that hammers the metal into the voids. The planchet is made thinner in the fields and thicker elsewhere. In many cases we find that there is just not quite enough metal to fill the voids, leaving flat spots on the high points, and the highest point of the voids never receive any impact at all.


On another point, the original question of this thread - "How worn can a die be and still strike MS coins?"


If you look at the Registry Set web site you can see a clone of this coin that is NGC MS65. This one was MS 62 from ANACS.

I think even the TPGs have trouble telling how to grade something like this. Yes, they both grade it MS in spite of the die deterioration, but they are all over the place on exactly where to put it within the MS range.

 

I hate it when folks try to go back on what they say. Let me remind you what you said in your first post on the subject of metal flow:

And then you doubled-down in your second post:

It is these incorrect statements that I have issue with. Simply admit they are wrong and we'll be on the same page.

And now you have made the statement that dies are completely flat, which is of course completely wrong. There is a significant amount of curvature to the fields in some US coins such as Wheat Cents, Mercury Dimes, Buffalo Nickels, etc. Some modern coins are indeed very flat, so perhaps that's what you're thinking of? The example I like to give is the Lincoln Wheat Cent, which has a nice tub-shaped field, with lowest points behind the neck and in front of the throat. These low points are there to ensure better filling of the bust, and are very high wear areas for die erosion. They also are the place where die clashes occur since they are first to come in contact with the reverse die, which BTW has a much flatter field!