Cut off wheels blow up pretty easy when used as grinding wheels, they work good until they fly apart lol.
I use surface prep wheels for sharpening axes, they do a even better job than cut off wheels. They come in different grits, start with a coarse one and end with a fine one and you will get a pretty good edge with very little effort, it also doesn't get the axe hot enough to hurt the temper like a grinding wheel does.