We need to use 20mm for the hollow and 22mm for the edge. How come you guys use 10mm for the hollow?
Thanks,
hand grind is much different than machine grind. first your hand can't hold the grind stone as powerful as machine, 2nd, the grind stones are easily wear out and the section of the average quality grind stones are not even perfect round, so you will get a much bigger ROH than the radius of the grind stone. if you try it urself, u will know.