I am starting to find time again to do woodworking now that my son is 1 and a half. In my free time I've started to get my tools set up and ready so I can start making things but I've dished out my stones, I have Shapton Kuromaku series stones an need to replace my lapping stone(Atoma 400) since its been misplaced. I over looked the grit of my coarsest stone when I bought my original lapping stone, what can I use that is capable of handling a 320 Shapton and the rest of my stones?

Thank you in advanced!