I've used a file about as rough as that to sharpen really blunt axes, or where they've gotten a savage chip taken out of them where someone's missed the wood and hit a rock or something. Used the coarse file to get the basic edge, fine for honing it and to get rid of major burrs, then course then fine whetstone. I'm sure I'm probably breaking some unwritten rule somewhere, but if I'd used just the diamond coated file for those jobs, I'd be there for days. I'd rather that than use the bench grinder.