The second time I lapped my Norton on abrasive paper (Imperial WOD 600), I got grit embedded in the surface that I could not remove (you feel and hear the razor hit it). The hone was unusable until the flattening stone arrived. I flatten other stones (coticule, Chinese 12K) on abrasive paper but, IMO, the Norton (being a synthetic stone) is too porous and easily gets contaminated with embedded grit. Good luck, but you're going to be forced to buy a flattening stone, or diamond hone sooner rather than later.