Diamond hones are great for hand sharpening - the temperature stays low enough to not damage the hone. (They're made by embedding diamond powder in nickel plating.) ?Diamond drills/hole saws are a different animal. They're actually just shaped abrasive tools, so they don't cut the way a drill does, they just grind their way through. They're nice on non-metallic things, much less effective & more expensive than classic abrasives (aluminum oxide or silicon carbide) on metals.
Roy
