Belt sanders may smooth floors and strip paint, but YouTube user wyldediver demonstrates how they can also breathe new life into dull blades. To sharpen yours, start with a 150-grit belt. Slowly run one side of the blade across the belt a few times using light pressure (the sharp edge should point down at an acute angle to the belt). Next, sand the other side. Turn off the sander, swap in a 240-grit belt, and sharpen again. Repeat the cycle for 400-grit, 20-micron, and finally 9-micron belts. Buff away any flecks with a leather sanding belt treated with polishing compound.