Is this the right place to be asking about radial die erosion?

MrEureka

Maybe not, but I'll try anyway. First, a quick explanation, then the questions.

Radial die erosion is the result of friction on the dies caused by planchets being squeezed outwards (from the center of the die) as they are struck. As more coins are struck, this effect becomes more pronounced on the dies and (in the form of visible metal flow) on the coins themselves.

Here are the the questions:

1. Where on the coin and die does the die erosion first become evident?

2. Are there any examples of radial die erosion where the radial lines reach the center of the die? If not, why?

Photo evidence would be really helpful.

Type2

1- The Rim area 2- they will remove the die befor it get's to the center.

BlindedByEgo

Apparently not, but as a curious individual, the question did set me to think... I'm hoping to read an answer from a metallurgist or engineer schooled in stress analysis.

Is it even possible for the radial erosion to ever meet in the true center? Is this effect not know as "cartwheel effect"?

Edited to add "Thanks, Type2"

notwilight

Flow is greater as you move away from the center and in fact mathematicly it depends on R and theoretically should never get to the center of the coin. Here are two of my examples:

Trime

Great thread Andy.
The pictures ofered by type 2 and blindedbyego are terrific
Let me see if I have it right:
If the radial erosion is on the die it will it be late it the life of the die and incused on the coin?

On the other hand metal flow on the coin will occur early in the life of the die, is raised from the surface as the metal flows outward and is represents cartwheeling?
Never thought about the die flow before.

pb2y

<FONT style="BACKGROUND-COLOR: #c0c0c0">Many coin flaws accur in the upsetting operation. As an upsetting die
reaches the end of its life it becomes dished. The dishing can show up
as wrinkels or as ridges near the edge of the planchet. When these enter
the coining press the legend, star relief ect will overide these flaws. The
same can happen to the working dies but it is less obvious. Coins showing
these flaws are most common in the 1800s. They did not have the
luxury of scraping out dies. The dies were kept and reworked frequently


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</FONT>

blastpak

I have a 1983 p washington that is very close to the center. I've been trying to get good pics but I don't have a good camera for coins.

gonzer

Excellent subject. Thanks for the thread!

Nysoto

Good questions and good answers.

I have some related questions. How hot do working dies get after repeated strikes, and what is the effect of heat on die erosion? The die will expand slightly with heat buildup. What is the difference in strike from cold dies vrs hot dies?

I have never read a clear explaination of bifurcated letters and drawn stars as on notwilight's bust half, other than late die state. Does the heat generated from many strikes have any effect on this?

MrEureka

edited to say "never mind"