This is not a war on oil vs water vs diamond stones. Merely an observation.
While at a friends shop he was showing me his diamond stones he uses to sharpen his knives. He also has a few wood chisels he hasnt sharpened and asked if i would show him what i do. While flattening the back of the first chisel, i noticed that even the 600 grit plate was leaving deeper scratches than my oilstone that is advertised as 320 grit. We were using glass cleaner as a lubricant.
Now his diamond stone isnt anything high end, and that may have a lot to do with it, but does anyone know why this is?
I guess i have a theory that maybe as my oilstone has worn down it has become finer, and the metal particles suspended in the oil act as maybe a polishing compound similar to a waterstone?
Anyway, it was an interesting observation.