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How Worn Can A Die Be and Still Strike MS Coins?
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<p>[QUOTE="rmpsrpms, post: 3504616, member: 31773"]What a beautiful coin!</p><p><br /></p><p>I think you might be making the assumption that the metal which fills the devices comes from the surface of the coin, moving against the die as it is forced into the raised areas. However, this is simply not the case. Only a small amount of metal actually moves across the die surface. The vast, vast majority of the metal comes from the bulk of the planchet, well below the surface. The only places where significant metal moves to fill the raised devices is on the device edges. Because of the general metal flow (from below) to fill a large device such as a bust, metal on the surface is "pulled along" near the device, but in general this movement does not extend a great distance beyond the device. I believe you can see where the flow changes from "inward" to "outward" in this coin very clearly. It is those dark areas in front of the face and behind the head. I think the dark area at the forehead is probably die polishing remnants but it may be another of these "ambiguous flow" regions as well. </p><p><br /></p><p><br /></p><p><br /></p><p>It's easy to prove this is incorrect simply by looking at what happens with a broadstrike. Broadstrikes cause the metal to flow outward toward the rims, making the coin larger than normal. In a normal strike the collar constrains this flow, but the general direction of the forces is still the same. Indeed the central devices are still filled due to metal moving from below to fill the voids in the die, and I would expect some inward movement of metal at the die surface near these voids, but farther out toward the rim the direction of the forces changes, and the movement is outward.[/QUOTE]</p><p><br /></p>
[QUOTE="rmpsrpms, post: 3504616, member: 31773"]What a beautiful coin! I think you might be making the assumption that the metal which fills the devices comes from the surface of the coin, moving against the die as it is forced into the raised areas. However, this is simply not the case. Only a small amount of metal actually moves across the die surface. The vast, vast majority of the metal comes from the bulk of the planchet, well below the surface. The only places where significant metal moves to fill the raised devices is on the device edges. Because of the general metal flow (from below) to fill a large device such as a bust, metal on the surface is "pulled along" near the device, but in general this movement does not extend a great distance beyond the device. I believe you can see where the flow changes from "inward" to "outward" in this coin very clearly. It is those dark areas in front of the face and behind the head. I think the dark area at the forehead is probably die polishing remnants but it may be another of these "ambiguous flow" regions as well. It's easy to prove this is incorrect simply by looking at what happens with a broadstrike. Broadstrikes cause the metal to flow outward toward the rims, making the coin larger than normal. In a normal strike the collar constrains this flow, but the general direction of the forces is still the same. Indeed the central devices are still filled due to metal moving from below to fill the voids in the die, and I would expect some inward movement of metal at the die surface near these voids, but farther out toward the rim the direction of the forces changes, and the movement is outward.[/QUOTE]
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