I'm going to send my triples to the powder coater next week. Before I do, I want to clean up the casting ridge on the lower and maybe grind off the handle bar mounts (may leave them to attach damper and/or accessory mounts). My question is, what grit sand paper will I have to get down to so that the scratches don't show through powder coat. I'm going to use a flap sander on my angler grinder and/or my belt sander. I think I've got 80 grit down to about 220 grit on hand.
Ask the coater what he wants, although I think if you start with the 80 and finish with 220 it should work.
From my personal experience (which isnt that much)if a good chunk of your finger nail can get caught on it, then youll want to sand it down. to where you can feel it slightly. I usually do 2-3mm of powder and that has covered up most minor scratches.
If you can feel it, but you cant really dig your nail into it, id say your fine.