I have seen a lot of references to using mm up to 12000 to finish pens. When I look for a supplier, I find MM advetised up to 3600. Where do you get mm12000 and all other grits above 3600?
http://www.woodchipshome.com Charles is a member of this site and has some good deals on MM as does International Violin http://www.internationalviolin.com