How to Sharpen Chisels and Plane

If you look at a dull edge under a magnifying glass, you'll see that it's ragged, rough and rounded. Your goal is to make this cutting edge as thin, straight and shiny as possible. You do this by rubbing the tool's bevel back and forth on progressively finer sharpening stones until all traces of roughness are gone and the edge has a mirror-like sheen. That's all there is to it.

Using the steps shown here, you can sharpen edge tools on sandpaper placed on a flat surface like a piece of thick glass. You'll get better results, however, if you invest in a couple of good sharpening stones. Oil stones are the most popular type. Lubricate the stone with a squirt of thin honing oil or kerosene to keep the stone from getting clogged with tiny particles of steel and losing its sharpening ability. Diamond stones steel plates with embedded particles of industrial diamonds and Japanese water stones are good alternatives to oil stones. These stones use water as a lubricant instead of oil.

A combination stone coarse grit on one side, fine grit on the other will give you a decent edge. But for the very best edge, you'll also want to buy a "hard Arkansas" finishing stone. This very fine, hard stone gives a mirror polish and produces a sharper, longer-lasting edge.

If your chisels are nicked or butter-knife dull, you'll need to grind the edge on a grinding wheel first before sharpening. You can hone out nicks on an extra-coarse stone, but an electric grinder is faster and much easier if the edge is in bad shape.

Step by Step

1. Grind if necessary. Grind your blade only if the edge is nicked or extremely dull.

Adjust the angle of the tool-rest on your grinding wheel so that the bevel of the blade rests flat on the edge of the wheel. Turn on the grinder and, moving the blade sideways, make a light, smooth pass across the wheel. After each pass, immediately dip the edge in water to cool it. Easy does it too much heat from friction will destroy the temper of the blade. (If the edge turns blue, the temper is shot. Gently grind off the discolored area.) Inspect the edge and adjust the rest if necessary to get the correct angle. Make sure the edge is square to the blade. Repeat the process until you have a cleanly ground edge.

Tip from the pros: A 60-grit or 80-grit white or pink aluminum-oxide wheel grinds cooler than the more common gray silicon-carbide wheels.

2. Using your coarse stone, flatten the back of the chisel or plane blade. You need do this only once. Squirt enough honing oil on your coarse flat stone to create a light film of oil, and rub the back of the blade back and forth until it's flat. (It may take 100 strokes or more.) Bear down hard on the blade and add oil as necessary to keep a light film of it on the stone. Concentrate on the area near the cutting edge. When the back is flat (look for an even scratch pattern across the back), switch to your fine stone and repeat the process until the back is flat and shiny.

3. Hone the bevel using your coarse stone. Start with the coarse stone. Squirt a light film of honing oil on the surface. Hold the blade at the proper angle about 25 to 30 degrees so the bevel sits flat on the stone. (A honing guide is an optional gadget that clamps on the blade to maintain the right angle.) Rub the bevel back and forth on the stone, keeping the angle constant. Avoid rocking the tool or you'll round its edge. Keep rubbing until you raise a very fine "wire edge" on the back side of the chisel. You can feel this wire edge with your finger but won't be able to see it without a magnifying glass.