The directions that came with my norton 4k/8k hone said to lap it either with their lapping stone or 600 grit wet/dry. I found the norton needed frequent lapping both to keep it even, and to expose fresh abrasive. Anytime I noticed it getting really slow I could fix it by giving it a few laps on 600 wet/dry. I'm glad I got rid of it. The Norton is an all around aggravating stone to use.