The first single-bevel knife I ruined was a 240 mm usuba. I was two years into working the line, I had a decent 1000 grit stone, and I sharpened it exactly the way I sharpened my gyuto: both sides, same angle, same pressure. Twenty minutes later the back of the blade was a flat, scratched-up mess, the hollow was gone, and the knife would never again release a cucumber sheet the way it did when it left Sakai.
Sharpening single bevel knives is not harder than sharpening a double-bevel knife. It is different. A yanagiba, usuba, or deba is not a symmetrical wedge. It has a flat upper face, a ridge line called the shinogi, a wide bevel running from that ridge to the edge, and on the back a shallow concave hollow called the urasuki with a hair-thin flat rim around it. Each surface is sharpened in a specific way. Get it right and the knife gets better every time you touch the stone. Get the back wrong once and you have permanently changed how the knife cuts.
This guide covers the geometry, the stone technique for the front (kiriha) and the back (uraoshi), the grit progression I use, why stone flatness matters more here than anywhere else, and the mistakes that show up again and again on r/sharpening and in my inbox.
The Anatomy of a Single Bevel Blade: Shinogi, Kiriha, and Urasuki
Pick up a yanagiba and hold it edge-down at eye level. On the front face (the omote, the right side on a right-handed knife) you will see two distinct surfaces separated by a crisp line.
Hira is the flat upper face, from the spine down to the ridge. On a traditional kasumi knife this is soft iron cladding with a hazy, matte finish.
Shinogi is the ridge line where the hira meets the bevel. It is the most visible indicator of how well a knife has been sharpened. On a well-kept blade it runs dead straight from heel to tip, parallel to the edge. On a badly kept one it wanders, widens in the middle, or fades out.
Kiriha (the blade road) is the wide bevel from the shinogi down to the cutting edge. This is the actual sharpening surface, usually 10 to 15 mm wide and ground at roughly 10 to 15 degrees. It is where the hard steel (hagane) shows through the cladding, and on a properly polished knife it takes a near-mirror finish against the hazy hira above it.
Now flip the knife over. The back (the ura) looks almost flat but it is not.
Urasuki is a very shallow concave hollow ground into the back, running almost the full length and height of the blade. Depth is fractions of a millimetre, but it does two things. It reduces friction, because only a thin rim of steel touches the food or the stone. And it makes the back easy to keep dead flat, because you are only ever flattening a narrow rim rather than a whole face of steel.
Ito-ura (literally "thread back") is that rim: a flat band of steel, ideally 0.5 to 1.5 mm wide, running around the urasuki along the edge, the tip, and the spine. It is what rides on the stone when you sharpen the back, and what guides the blade during a draw cut. When people say a single-bevel knife "steers left", the ito-ura is the rail it steers along.
One more term, because the two get confused constantly: uraoshi is not a part of the knife. It is the sharpening step where you lay the back flat on a fine stone and press. Ura is the back, urasuki is the hollow, ito-ura is the rim, uraoshi is the action. Once those four are straight in your head, everything below makes sense.
How to Sharpen the Kiriha Without Rounding the Shinogi
The front bevel is where the edge is created and where most of your time goes. The principle is simple: the entire kiriha, from shinogi to edge, lies flat on the stone. There is no angle to hold. The knife holds it for you.
- Soak or splash the stone according to its type, and set it on something that does not move.
- Lay the kiriha flat. Edge facing away from you, spine raised until you feel the whole bevel sit down. On a 270 mm yanagiba you work in sections: heel, mid, tip, with the blade angled across the stone so 8 to 10 cm of edge is in contact at a time.
- Finger pressure on the kiriha, not the spine. Two or three fingertips of the left hand rest directly on the bevel, just above the edge, on the section currently on the stone. This is the part beginners get wrong. Fingers on the spine lever the shinogi off the stone and grind only the edge. Six months of that and the shinogi line thickens, wanders, and starts to disappear.
- Push forward with pressure, pull back light. Keep the pressure even across the whole bevel. Lean harder toward the edge and you create a convex micro-bevel and lose the crisp shinogi.
- Check for a burr. After 20 to 40 strokes per section on a 1000 grit stone, run a thumb across the back of the edge, perpendicular to it (never along it). Do not move on until the wire edge runs heel to tip.
- Repeat on finer stones, fewer strokes each time, until the kiriha is uniformly polished and the shinogi line reads as a clean straight edge under a raking light.
The shape is the jig. Your job is not to add anything, it is to not take away the wrong thing.
Uraoshi: Sharpening the Back Flat and Why Coarse Stones Ruin It
Now the back. This is the step that ruined my usuba, so read it twice.
The ura is only ever sharpened dead flat on the stone. Zero angle. The spine and the edge both sit on the stone at the same time, and the only steel touching the stone is the ito-ura rim. The urasuki, the hollow, floats above the stone and is never touched.
The purpose of uraoshi is not to sharpen. It is to remove the burr you created from the kiriha side, and to keep the ito-ura clean and flat so the edge closes properly. That means:
- Fine stones only. 4000 grit as the minimum in normal use, 6000 to 8000 grit ideally. A 1000 grit stone removes too much steel per stroke. Reserve it for the ura only when you are repairing a chip, and even then, only a handful of strokes.
- Very light pressure. The weight of the blade plus one or two fingers resting on the flat above the hollow. Nothing more. You are polishing a rim less than 2 mm wide; it does not need force.
- Very few strokes. Three to eight strokes per section, edge trailing, and then check. If the burr is gone, stop. Every extra stroke widens the ito-ura.
- Keep the whole blade flat. Do not lift the spine, ever. Do not rock. If you lift the spine even a couple of degrees you are grinding a second bevel into the back, and the moment you do that the knife is no longer single-bevel in any meaningful sense. It will start pinching in the cut and pulling hard to one side.
Here is why coarse stones are a problem. Every stroke on the back removes steel from the rim, and as the rim wears the flat band gets wider, because the shallow hollow behind it is getting shallower. On a fine stone that widening is measured in microns per session and a knife lasts decades. On a 1000 grit stone, pushed hard, you can take the ito-ura from 1 mm to 3 or 4 mm in a single sitting. At that width the back drags against the food and the only fix is having the urasuki re-ground on a wheel. Most European chefs do not have that person on speed dial.
Grit Progression That Works: 1000, 4000, 8000
There are as many stone setups as there are sharpeners, but for single-bevel work I have settled on three stages and I rarely need more.
1000 grit: correction. The workhorse for the kiriha. It sets the bevel, raises the burr, fixes small chips, and brings back an edge after a week of service. The Majin #1000 ceramic stone is what sits by my sink for this: it stays flat longer than a soft waterstone, needs only a splash of water, and cuts hard steel fast enough that I am not spending 40 minutes on a yanagiba after a long shift. The kiriha spends 80 percent of its stone time here. The ura spends almost none.
4000 grit: the edge. Where the working edge is actually formed. The 1000 grit scratches get replaced with an even polish, and this is the first stone I use for uraoshi on a normal day. Fewer strokes than the 1000, burr check after every section.
8000 grit: the finish. On a yanagiba this is not decorative. The polished edge is what lets the blade release fish without dragging, and the mirror on the kiriha against the haze on the hira shows at a glance that the geometry is intact. Final uraoshi strokes happen here: two to four per section, almost no pressure, edge trailing.
What you do not need: a 220 grit stone, unless the knife has been dropped, and a strop. The 8000 does the job, and a strop on a single-bevel knife rounds exactly the crisp geometry you just spent an hour protecting.
Why a Dished Stone Destroys Single Bevel Geometry Faster Than Anything Else
If you take one thing from this post: flatten your stones, and flatten them more often than you think you need to.
A double-bevel knife forgives a stone that has worn slightly concave. You are holding a freehand angle anyway, and a little dish changes it by a degree or so.
A single-bevel knife is the opposite. The kiriha is meant to lie flat against a true plane. On a dished stone the shinogi and the edge ride the high edges of the stone while the middle of the bevel floats. A few sessions later the kiriha is convex, the shinogi line is wavy, and the knife wedges in the cut instead of gliding.
The back is even less tolerant. The ito-ura is a flat rim pressed onto what needs to be a flat plane. On a dished stone it contacts only the ends of the dish, so the rim wears wider near the heel and tip and stays untouched in the middle. That is exactly the pattern I see on knives that come to me for rescue.
The fix is cheap and boring: a flattening plate and a pencil grid drawn across the stone. Rub until the lines are gone. On a ceramic stone like the Majin that is a 30-second job every four or five sessions; on a soft waterstone it is every session. A stone that is not flat is not a tool for single-bevel knives. It is a tool for ruining them slowly.
Common Mistakes: Finger Pressure, Angles, and the Back
Most of the damage I see on single-bevel knives comes from a small set of habits. All of them are fixable if you catch them early.
Fingers on the spine instead of the kiriha. This is the number one cause of a fading shinogi line. If the pressure is on the spine, the bevel tilts and only the edge contacts the stone. The shinogi migrates upward and blurs. Move your fingers onto the bevel itself.
Uneven pressure along the blade. Pressing harder at the heel than the tip, or vice versa, makes the shinogi line curve. Under a raking light the line should be as straight as a ruler. If it bows, you are pressing unevenly. Work in short sections and use the same two fingers, same weight, the whole way.
Lifting the spine on the back. Even two degrees creates a secondary bevel on the ura. Once it is there the knife pinches and steers badly, and grinding it out means losing steel from the ito-ura. Keep the whole back flat, every stroke.
Treating the back like the front. Same stone, same strokes, same pressure. This is what I did to my usuba. The back gets a fraction of the stone time, on the finest stones, with almost no weight.
Trying to "fix" a factory ito-ura that looks uneven. Many knives arrive with a slightly uneven rim. Leave it. It evens out over a year of correct uraoshi. Chasing it with a coarse stone removes the urasuki entirely.
Pull-through or electric sharpeners. I should not have to write this, but I have seen it. They grind both sides. One pass and the knife is a double-bevel with a hollow on one side. There is no coming back from that.
Keeping the Geometry Alive Between Sharpenings
Most of the wear does not happen on the stone. It happens on the line.
- Wipe and dry after every use. Carbon steel single-bevels rust in an hour on a damp bench, and rust pitting on the ito-ura cannot be sharpened out without widening the rim.
- Store on a magnet or in a saya, never in a drawer. A chipped yanagiba means 1000 grit time on a knife that should only see 4000 and up.
- One knife, one job. A yanagiba is for the draw cut on fish. Lever a bone with it and you chip the hard steel at the edge. A deba exists for that.
- Do not let it get dull. Five minutes on the 4000 and 8000 every couple of services is easier on the geometry than a 1000 grit rescue once a month.
If you are buying your first single-bevel knife to practise this properly, start on something you will not be afraid to use. The TKG Yanagiba 270mm is the knife most working chefs put in apprentices' hands first: molybdenum-vanadium stainless that forgives a missed wipe-down, with proper Sakai geometry and a real urasuki so everything above applies. Pair it with the Majin #1000 for the kiriha, add a fine stone for the back, and you have what you need. Still deciding between a yanagiba and a double-bevel slicer? Read Yanagiba vs Sujihiki: Choosing the Right Service Slicer first.
The shinogi line on a well-kept knife is a record of every sharpening it has ever had. Keep it straight and the knife will outlast your career.
FAQ: Sharpening Single Bevel Knives
What is the urasuki on a Japanese knife? The urasuki is the shallow concave hollow ground into the back (ura) of a single-bevel Japanese knife like a yanagiba, usuba, or deba. It reduces friction against food and makes the back easy to keep flat, because only a thin rim around the hollow (the ito-ura) ever touches the stone or the cut surface.
What is the difference between urasuki, ito-ura, and uraoshi? Urasuki is the hollow itself. Ito-ura is the thin flat rim of steel surrounding the hollow along the edge, tip, and spine. Uraoshi is the sharpening step: laying the back dead flat on a fine stone with light pressure to remove the burr and maintain the ito-ura. Two are parts of the knife, one is an action.
What angle do you sharpen a single bevel knife at? You do not hold an angle. The kiriha (the wide front bevel) is placed flat on the stone so that the whole surface from the shinogi line to the edge is in contact. The back is placed completely flat at zero degrees. The knife's geometry sets the angle for you.
Should I sharpen the back of a yanagiba? Only lightly, and only on fine stones. The back is flattened (uraoshi) on a 4000 to 8000 grit stone with very light pressure for a few strokes per section, purely to remove the burr raised from the front. Never sharpen the back on a coarse stone in normal maintenance, and never lift the spine.
What grit whetstone should I use for single bevel knives? A 1000 grit stone for setting the front bevel and correcting damage, a 4000 grit stone for forming the working edge and the first pass on the back, and a 6000 to 8000 grit stone for final polish and final uraoshi. The 1000 grit should almost never touch the back.
Why does my single bevel knife pull to one side after sharpening? Usually one of two causes. Either a secondary bevel has been ground into the back by lifting the spine, so the ito-ura no longer guides the cut; or the kiriha has been rounded by pressing on the spine instead of the bevel, so the shinogi line is no longer straight. Both are technique on the stone, not the knife.