How to Sharpen Japanese Chisels

Sharpen a Japanese chisel at 27 to 30 degrees, work the hollow back on a dead-flat stone only at the very edge, and never try to lap the hollow out. If you are buying stones for the job, the King KW65 1000/6000 combination is the pick for most people — it is the default first waterstone worldwide and it will sharpen these chisels properly — with a flattening stone bought at the same time, because a dished stone is how a flat-backed chisel stops being flat.

Everything that makes a Japanese chisel different from a western one shows up on the stone. A western bench chisel is a single piece of fairly hard steel with a flat back and a bevel you grind at 25 to 30 degrees. A Japanese chisel is two metals forge-welded together: a thin layer of very hard, high-carbon steel — the hagane— laminated to a thick body of soft iron or mild steel, the jigane. The hard layer is at the cutting edge and is typically taken to a higher hardness than any western chisel steel; the soft layer is everything behind it, and it exists so the hard steel can be that hard without the whole tool being brittle. And the back is not flat: it is ground with a shallow hollow, the urasuki, leaving a narrow flat land around the perimeter. Japanese vs western chisels covers why the two traditions diverged.

The hollow back, and the mistake that destroys the chisel

The urasuki is the cleverest thing about the tool. Because only a narrow land around the edge touches the stone, flattening the back is quick — you are lapping a few square millimeters rather than the whole face — and it stays flat with almost no work for the life of the chisel. Western chisels, with their full flat backs, need the whole face lapped once and frequently need real work out of the box.

The mistake is to treat the hollow as a defect and try to lap it out. It will take hours, it will cut through the hard laminated layer in places, and the result is a chisel with no hollow, no reference land, and a back that will never be flat again. Work the back only until the land at the cutting edge is bright and flat for a millimeter or two. That is finished. Stop.

There is one more consequence. Every time you sharpen the bevel you move the edge back, and the land at the edge gets narrower — until eventually the hollow reaches the cutting edge and there is no flat left to register. That is the point at which a Japanese chisel needs tapping out: the soft iron behind the edge is peened with a light hammer on a small anvil to push metal forward, re-forming a land, which is then lapped flat again. It is a real technique with a real failure mode — hit the hard steel and it chips — and it is not something to do in your first year. For most owners it is twenty or thirty sharpenings away. The Japanese chisel roundup explains which of these tools are laminated and which are not.

The bevel angle, in numbers

Japanese chisels are usually supplied at around 27 to 30 degrees, and that is a deliberately steeper range than the 25 degrees typical on a western bench chisel. The reason is the steel: harder steel holds an edge longer and chips more readily, so it needs more metal behind the edge to support it. Grinding a laminated Japanese chisel down to 25 degrees in pursuit of keenness is a reliable way to spend an evening chasing chips out of the edge.

• Paring chisels and soft-wood work: 27 to 28 degrees. The shallowest you should go.
• General bench work: 30 degrees. If you only remember one number, remember this one.
• Mortise chisels and hardwood chopping: 32 to 35 degrees. More support, fewer chips, and you lose nothing you will notice.
• A micro-bevel on top:one or two degrees steeper than the primary. It cuts the honing time dramatically, and on hard laminated steel that matters more than it does on a western chisel — microbevels explained covers the mechanics.

Our sharpening angles page has the equivalent numbers for every other edge tool on this site.

The sequence, start to finish

One: flatten the stone. Before touching the chisel. A waterstone that has dished by half a millimeter will put a curve into the back of your chisel, and on a hollow-backed chisel the land is so narrow that a dished stone can round the actual cutting edge in seconds. How to flatten a waterstone covers the method; the Norton flattening stone or an Atoma #140 plate are the two tools for it.

Two: the back, lightly. Lay the back flat on the 1000 grit and work it until the land along the cutting edge is uniformly bright. Then do the same on the 6000. A couple of minutes, not an hour. If the land is bright except for a dark patch right at the corner, that corner is below the plane of the land and the bevel work in the next step will bring it up.

Three: the bevel. Either freehand, with the bevel registered flat on the stone and your wrists locked, or in a guide. Both work; a guide gets you a repeatable angle before you have the muscle memory to hold one, and a guide that will hold a short, thick Japanese chisel is worth checking before you buy — see the honing guide roundup and freehand vs honing guide. Work the 1000 until a burr forms along the full width of the edge, then move to the 6000.

Four: remove the burr from the back. Two or three light passes with the back flat on the fine stone. Not more — this is the step where people quietly round the edge they just made.

Five: strop, if you strop. Leather and compound will take a Japanese edge further than most stones will, and the risk is the same as always: pressure plus a soft surface equals a rounded edge. Stropping explained covers doing it without that happening.

Which stones, and why these

Hard laminated steel rewards a stone that cuts rather than one that polishes, and it punishes a stone that will not stay flat. That gives three sensible setups.

The honest ranking: buy the King and the Norton flattening stone together and you can sharpen these chisels properly for the price of a cheap chisel. Buy the Shapton if you sharpen weekly and resent soaking a stone — it cuts faster, stays flatter, and its own cons note what you are paying for, which is a thin and visibly finite abrasive layer. Buy the Atoma if you own several waterstones or need to regrind a chipped edge. If you would rather never maintain a stone at all, diamond plates are the alternative and waterstones vs diamond stones and ceramic vs waterstones make that comparison properly.

Three things not to do

Do not put a Japanese chisel on a dry bench grinder. The hard layer is thin and it will overheat in seconds, and an overheated edge is a soft edge permanently. If an edge needs regrinding, do it on a coarse stone or a diamond plate, wet, slowly. Our grinder roundup is written for western chisels and says the same thing about heat.

Do not round the bevel chasing speed. A rounded bevel on a laminated chisel means the hard steel at the very edge is unsupported, and it will chip the first time you lever a chip out of a mortise.

Do not use the hooped end as a general striking surface for a steel hammer unless the chisel has the hoop. Most laminated bench chisels do; some paring chisels deliberately do not and are never meant to be struck. Chisel handle materials tells you which is which, and the mallet roundup covers what to hit each type with.