Check other digging tools for the side on which they were previously sharpened. Remove all excess metal, nicks, and chips from the cutting edge. File or grind a new cutting edge into the tool. Spades and hoes should be sharpened to their original angle. If this is unknown, sharpen to a 20 to 30 degree angle.
Axes have a rounded metal side behind the cutting edge.
This convex shape requires a special sharpening technique called convex grinding. The blade of the axe should face up on the edge of the grinder. Use an up and down motion as the axe blade is drawn across the face of the grinding wheel. Stop the downward motion when sparks first appear to prevent the dubbing off of the axe blade. A whetstone can be used to remove the wire edge created by the grinder and to put a fine cutting edge on the axe.