then what makes a stone a "fast cutter"? that it takes fewer strokes to get through a particular amount of metal? if so, then how does such a stone grind down more steel without eating more metal per stroke? more steel per stroke does not entail deep scratches, just that the steel "gives" more than the abrasive surface so the steel wears away faster.
i thought grit is the size of the particulate, not the sharpness or hardness of the abrasive particulate.