A dowel bit, also known as a spur point bit, is one of those drill bits that must be sharpened by hand. A drill bit sharpener won't help. You'll need a fine metal file or a fine grindstone to do the work. You want a 90 degree angle between the center point and the spurs on the sides. The dowel bit should only be used on wood, never on metal. If you drill on a surface harder than wood, you may not be able to re-sharpen the bit to make it good for it's intended purpose - drilling a nice, clean hole in wood.