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<p>[QUOTE=&quot;RonSanderson, post: 3507222, member: 77413&quot;]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&#039;t wrinkles or grooves from forming all at once.</p><p><br /></p><p>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.</p><p><br /></p><p>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.</p><p>[ATTACH=full]930101[/ATTACH]</p><p>I measured a nickel planchet that was upset, like your cent planchet.</p><p><br /></p><p>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.</p><p><br /></p><p>[ATTACH=full]930158[/ATTACH] </p><p><br /></p><p>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.</p><p><br /></p><p>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.)</p><p><br /></p><p>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.</p><p><br /></p><p><br /></p><p>On another point, the original question of this thread - &quot;<i>How worn can a die be and still strike MS coins?</i>&quot;</p><p><br /></p><p>[ATTACH=full]930125[/ATTACH]</p><p>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.</p><p><br /></p><p>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.[/QUOTE]</p><p><br /></p>

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