Clamp the hoe tightly in a vice. It should be face-up, giving you easy access to the outer side of the blade.
Clean the blade by brushing it vigorously with steel wool. This will remove any caked-on dirt and other debris.
Hold the end of a flat, single-cut metal file against the outer cutting edge of the hoe at a 30- to 45-degree angle.
File the cutting edge in long, even strokes. Only move the file away from you; do not rub it back and forth along the cutting edge.
Continue filing the cutting edge until it is sharp. Work on the blade as a whole; sharpening small sections at a time will result in an uneven blade.
File the inner edge of the cutting blade once to remove any metal burrs. Overfiling the inner edge can dull the hoe again.