Lee... If you took a dozen index cards, held them stacked together, then tried to cut them all at once with scissors, then you'd see them shift a bit so that all 12 aren't cut exactly the same. That shift is what resulted in the slight diamond cut. In looking at that old paper cutter, that wheel at the top would be turned tight against whatever you were cutting to avoid shift. The other thing to do was to cut a few sheets at a time, instead of a bunch.
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