The scale I have been using is: 120 150 220 320 400 600 800 1200 1500 2000 2500 3000
I chose the scale based on the assumption that the grits appear (to me at least) to run somewhat logarithmically.
I stopped at 3000 since it seems hard/expensive to find finer grits and its not clear you gain much beyond that.
I started at 120 because based on my limited experience that seems like the coarsest one would want to go without totally chewing up the metal.
Any comments or suggestiong for improvement on the above approach? I am open to changing the grit scale to other common sizes if mine seems wrong.