A decently sharp edge penetrates so very much easier and therefore takes less effort to use. Either of these fine tools does the trick. Pros use them and depend on them all the time. Our 10'' Bastard-Cut Flat Mill File (made by the German firm Pferd) is the very best in class. It's relatively coarse cut will sharpen even lawn mower blades quickly and efficiently. Is the best tool for shovels, spades and axes.
