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Message:: [QUOTE="900fine, post: 332493, member: 6036"]I'm not sure - yet. I was pondering all this before starting this thread. We've settled that the dies were concave.  Tell me if this makes any sense... If a die is concave, then as the press comes down, the edge of the die contacts the planchet's rim first, before the inner parts of the die. This exerts pressure first on the rim. As the die continues its travel toward the planchet, it progressively increases pressure toward the center of the coin. That means that, at any instant throughout the strike, the outer part of the planchet is always under more pressure than the center. At any instant, there is a pressure gradient - greater at the outside (rim), decreasing toward the center. Here's the key - all materials flow from high pressure to low pressure. Water in a pipe, winds blowing, or metal being pushed around. So the bottom line is this - basining the dies means that metal on the surface of the planchet will move radially inward toward the devices, away from the fields.  It's a way of funneling metal from the outer fields toward the inner devices. The concave surface acts like a funnel. A flat die would just press straight down on the fields. Material coming up into the device cavity would be mostly metal directly under the device. If there's anything to this, it would explain why we see so many circular die cracks near the rim of Morgans. The die cracks are where the pressure was greatest. Perhaps it also explains these "radial flow die lines" I've heard about, which contribute to the famous Morgan cartwheel effect. What do you guys think ?[/QUOTE]

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