The 10% refers to a percentage of the diameter of the cutter. So in this case about 0.037. If you are cutting the outside profile or an internal pocket, you would move over 0.037 for each pass at 10%. If you are cutting an on size slot, there would be no stepover and you would be at 100% of the cutter diameter.
I'm not in total agreement with vertcnc in going full depth on the roughing passes, but there is nothing wrong with doing it that way. I normally reserve that for the final finish pass at about 0.010 stepover, and 0.010 DOC. I normally make my roughing passes at cutter diameter or maybe 150% cutter diameter on the DOC, with a 40% stepover. The exception to this is with roughing end mill, then I normally go up to full cutter depth at a reduced feed rate, and a 90 -100% stepover.
There is really no wrong way to do it, it's a matter of what works best for you and your machine.
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