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<p>[QUOTE=&quot;GDJMSP, post: 1483106, member: 112&quot;]Jim, it was not done by hand. Even back in the 1800&#039;s (and probably before that) they used a mechanical device to polish dies. In fact the most recent article I have ever found that describes how dies are (they still use it) and were polished was written in 1907. I have described the process many times in other posts.</p><p><br /></p><p>They used a flat, spinning zinc disk to polish dies. While I have never been able to pin down the exact size, practical considerations dictate that the disk would have to be at least 8 inches in diameter and probably more like 12. The die was held in a rigid clamp so that it was parallel to the disk and then lowered against the spinning disk. The disk was coated with diamond dust paste varying in fineness of grit for the different stages of polishing. </p><p><br /></p><p>Now, the reason that the die polish lines cannot cross is simple. If you take a disk that is 12 inches in diameter that is spinning in a circle, the portion of that disk that can touch the surface of a die varying in size from say a dime (1/2 inch) to a dollar (1 1/2 inches) is quite small. You have 2 circular objects touching each other and they touch in an arc. But the portion of the arc of the disk is equal to the size of the die. And 1/2 inch of an arc of a 12 inch diameter object is almost a straight line when viewed by itself. That is why what we see on a coin appears to be straight lines. They aren&#039;t really straight, but they are a such a small piece of a much larger arc that they appear to be straight.</p><p><br /></p><p>Anyway as the disk spins and die is stationary the grit from the diamond dust paste leaves tracks, fine lines in the surface of the die. But those tracks are all exactly parallel and evenly spaced and it is impossible for them to criss-cross each other. The laws of geometry prohibit it.</p><p><br /></p><p>Yes, I know you can show me a hundred pictures of coins with criss-crossing lines on them. But that does not mean that those lines are all die polish lines. Dies can also have scratches on them from being wiped off with a cloth to remove dirt and or grease while they are in use. They can get fine scratches on them from tools or strike-through objects or virtually anything that the face of the die comes into contact with in the course of its use. So when you view a coin that has criss-crossing lines, some of those lines might be die polish lines but the others are die scratches.[/QUOTE]</p><p><br /></p>

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