Always? They certainly didn't use a machine in the 1700's or 1800's. And I know we've disagreed on this before, but die polish can absolutely criss-cross. For instance, there are many, many large cents that exhibit criss-crossing die polish lines. Now modern Lincolns are another story entirely..... Perhaps you define "polish" differently than I do?
While I have never been able to find any references about how they polished dies in the 1700's or earlier, they most definitely used machines to polish them in the 1800's and all since then. I cannot give you an exact date Mike, but it was fairly early in the US Mint history that a spinning zinc disk was used to polish dies. And since this disk was many times the diameter of the diameter of a die, it is physically impossible for the die polish lines to crisscross. Now I'll readily agree that there are lines on many coins that do indeed crisscross. The point in question is whether those lines are actually die polish lines - or not. Yes, they are often called die polish lines, but that does not mean that they are die polish lines. There are several other things that can create fine lines on the surface of a die. Die scratches for one and flow lines for another - and both are extremely common, especially on older coins like large cents. And both are extremely similar in look to die polish lines. So it is very easy for people to mistakenly identify those lines that crisscross as die polish lines when they are not.
