Blade geometry · sources checked 2026-10-22Single-bevel vs double-bevel
Japanese knives
Short answer: a double-bevel knife (ryōba, 両刃 — gyuto, santoku, bunka, nakiri, petty) is ground on both sides of the edge so it cuts straight down and works in either hand. A traditional single-bevel knife (kataba, 片刃 — yanagiba, deba, usuba, traditional kiritsuke) has a wide bevel on the front side only and a slightly hollow-ground back (urasuki), giving an acute 10–15° total edge angle for sashimi and precision Japanese prep — but requiring dedicated sharpening technique and a reversed blade for left-handed cooks.
At a glance: Kataba vs Ryōba
| Feature | Single-bevel (Kataba / 片刃) | Double-bevel (Ryōba / 両刃) |
|---|---|---|
| Japanese term | Kataba (片刃) | Ryōba (両刃) |
| Classic knife shapes | Yanagiba (sashimi), Deba (fish filleting), Usuba (vegetables), traditional Kiritsuke | Gyuto, Santoku, Bunka, Nakiri, Petty, Sujihiki |
| Front side (Omote) | Wide primary bevel (kireha) meeting the flat (hira) at a crisp shinogi ridge | Narrow edge bevel (12–16° per side) ground symmetrically or 70/30 asymmetrically |
| Back side (Ura) | Slightly concave hollow grind (urasuki) surrounded by a thin flat rim (uraoshi) | Convex or flat blade face matching the front side |
| Apex inclusive angle | ~10–15° total (plus optional micro-bevel koba) | ~24–32° total (e.g., 15° + 15° = 30°) |
| Cutting path in tall food | Tends to steer toward the flat back unless compensated by hand technique | Tracks straight down through dense root vegetables |
| Left-handed use | Requires a dedicated left-handed (hidari-yō) blade with reversed geometry | 50/50 blades work identically in either hand |
1. Anatomy of a single-bevel blade (Kataba)
A true Japanese single-bevel knife is not simply a flat piece of steel sharpened on one side. In Sakai’s forging and sharpening tradition, it is a laminated two-layer structure (ni-mai) with five distinct geometric zones:
- Hagane (鋼) and Jigane (地金): the thin cutting layer on the back side is high-carbon steel (such as Shirogami #2 or Aogami #2), forge-welded to a thicker body of soft iron or mild steel (jigane) on the front bevel that absorbs shock and makes hand-sharpening the wide bevel practical.
- Shinogi (鎬) and Kireha (切刃): the ridge line running along the front of the blade is the shinogi. Below it slopes the wide primary bevel (kireha or “blade road”), which moves food away from the cut.
- Urasuki (裏スキ): the back face of the blade is ground slightly concave on a large-diameter wheel. When slicing raw fish or rotary-peeling daikon, this hollow prevents suction and keeps the cut surface glossy.
- Uraoshi (裏押し): surrounding the concave urasuki is a narrow, dead-flat perimeter rim along the spine and cutting edge where the back rests flat on a finishing whetstone.
- Koba (小刃): many sharpeners finish the very apex of the kireha with a tiny micro-bevel (koba) at 18–25° to keep the acute edge from micro-chipping, especially on the heel of a deba used against fish bones.
2. Why double-bevel (Ryōba) is the standard for everyday cooking
On a double-bevel knife — whether a 3-layer san-mai blade with core steel sandwiched between two cladding layers or a monosteel blade — the wedge forces on the left and right faces balance each other. When you push a gyuto, santoku, bunka or nakiri through a tall carrot, onion or sweet potato, the blade tracks straight down to the board without steering sideways.
Some Japanese double-bevel chef’s knives are ground with an asymmetric 70/30 or 80/20 bevel (wider facet on the right side for right-handed cooks). Unlike a true single-bevel kataba, an asymmetric double-bevel still has a full flat/convex left face with no hollow urasuki, and can be resharpened to 50/50 if desired. Compare exact edge angles in our interactive sharpening angle & spine-height calculator.
3. Left-handed buyers: when you must order a left-handed knife
For any 50/50 double-bevel knife, right- and left-handed cooks buy the exact same blade. For a single-bevel knife (yanagiba, deba, usuba or single-bevel kiritsuke), geometry is hand-specific:
- Right-handed single-bevel: the sloped kireha is on the right side and the flat/hollow ura is on the left. As a right-handed cook slices sashimi from right to left, the flat back rests smoothly against the block of fish while the sloped front gently pushes the cut slice away.
- Left-handed single-bevel (Hidari-yō / 左用): the kireha is forged and ground on the left side and the hollow ura on the right. If a left-handed cook tries to use a right-handed yanagiba or deba, the sloped bevel digs into the fish fillet instead of gliding along the bone.
Which geometry should you choose?
| If… | Choose |
|---|---|
| You want an all-around kitchen knife for vegetables, meat and boneless fish | Double-bevel (Ryōba) — Gyuto, Santoku, Bunka or Nakiri |
| You want a long slicer for roast meat and occasional sashimi without single-bevel steering | Double-bevel Sujihiki or double-bevel Kiritsuke Gyuto |
| You fillet whole fish along the bone or slice raw sashimi blocks in single drawing strokes | Single-bevel (Kataba) — Deba and Yanagiba |
| You are left-handed and buying a deba, yanagiba or usuba | Left-handed (Hidari-yō) single-bevel — verify before checkout |
Compare all nine profiles in our Japanese knife types & shapes hub, explore how steels behave in the 15-steel composition chart, or check the guide to buying a Japanese knife from Japan.
Frequently asked questions
- Why do traditional Japanese single-bevel knives have a hollow back (urasuki)?
- The slight concavity on the back (urasuki) serves two purposes: first, in the kitchen, it creates an air pocket that reduces friction and prevents delicate slices of raw fish or daikon from sticking; second, on the whetstone, only the thin outer rim (uraoshi) touches the stone, making it possible to remove the burr flat without grinding across the entire width of hard steel.
- Why does a single-bevel knife steer or curve when cutting carrots or potatoes?
- Because only the front side has a sloped bevel (kireha), food pushing against that slope forces the blade sideways toward the flat back side. Professional Japanese cooks use this asymmetry intentionally to peel paper-thin sheets (katsuramuki) or lift sashimi slices cleanly away from the block of fish.
- Can a left-handed cook use a right-handed single-bevel knife?
- Not effectively. On a right-handed single-bevel knife held in the left hand, the bevel faces inward toward the food you are keeping, so the blade wedges into the fillet or vegetable rather than slicing cleanly off the outside. Sakai makers such as Sakai Ichimonji Mitsuhide and Sakai Takayuki state that left-handed cooks must choose a dedicated left-handed (hidari-yō) single-bevel knife.
- Why are left-handed single-bevel Japanese knives more expensive?
- Blacksmiths and sharpeners set up their forging hammers, jigs and water-wheel stances for right-handed bevels, which make up over 90% of orders. Forging and grinding the hard steel layer (hagane) and hollow back on the opposite side requires reversed hand work in small batches, commonly adding 20–50% to the retail price.
- What is a 70/30 asymmetric double-bevel knife?
- Some Japanese gyutos and sujihikis are double-bevel knives whose edge facet is ground wider on the right side (70%) and narrower on the left (30%). Unlike a true kataba, they have no hollow back (urasuki) and still cut straight down, while offering slightly cleaner food release on the right side.
Sources
- Tokyo Metropolitan Board of Education: teaching material on Japanese knives (ryōba vs kataba)
- Kai: choosing a Japanese-style knife (single-bevel structure and uses)
- Sakai Hamono association: Q&A on Sakai single-bevel and double-bevel knives
- Sakai Ichimonji Mitsuhide: left-handed single-bevel deba (why left-handed users need a reversed bevel)
- Sakai Ichimonji Mitsuhide: single-bevel vs double-bevel kiritsuke wa-gyuto