It's a little more involved than you'd think. Looks like there are a number of different specifications, with different numbers for different "particle" sizes. Your 80 grit from one outfit might not be as coarse or as fine as someone else. Factor in the structured abrasives, and things get even more interesting. Some google-fu sent me over to blade forums where one of the members there put up a link to a spreadsheet he had done on Google Docs. I did a search here and didn't find anything similar, just error notices. Maybe I'm not searching the forum properly, but it really should be a sticky somewhere. Maybe @Mythtaken can solve that one. Anyways, without further ado... BEHOLD! https://docs.google.com/spreadsheets/d/1VaTf3MXuwuvH-QLwOci4f9B9Zhkbuu1wjoSCZIUsR-o/edit#gid=0
