Edge & Blade Geometry

Blade geometry refers to how a knife tapers from the spine down to the cutting edge. This taper plays a major role in how a knife moves through food—affecting thickness behind the edge, resistance, and food release.

In double-bevel knives, this taper is created evenly from both sides of the blade and can take several forms. Common grind styles include full flat, half flat, hollow, and S-grinds. Each offers a different balance of cutting performance, durability, and feel.

While these shapes define how the blade passes through food, they do not determine how the edge is sharpened.

Knives with asymmetrical blade geometry taper more on one side than the other. This creates a directional cutting feel and is typically designed for either right- or left-handed use.

Because the blade itself is uneven, the edge should be sharpened to match. When the blade is offset, the edge should follow.

This type of geometry is most commonly found in Japanese cutlery, though some modern Western makers incorporate it as well.

Different variations of offset taper—such as convex, flat, or partial—affect how the blade moves through food and how aggressively it tracks during a cut.

These knives are not ambidextrous.

Edge geometry refers to how the cutting edge is applied to the blade. On double-bevel knives, the edge is sharpened on both sides to form the cutting apex. The sharpening angle (degree) remains consistent from side to side—whether the edge is symmetrical or asymmetrical.

A symmetrical edge (50:50), regardless of the chosen angle, is sharpened equally on both sides, creating a balanced, centered cutting edge. This results in a neutral cutting feel and is suitable for both right- and left-handed users.

An asymmetrical edge (such as 70:30, 80:20, or 90:10) is sharpened at the same angle on both sides, but with more material removed from one side than the other. This creates a thinner, more directional cutting edge that allows the knife to track more precisely through food. Because of this bias, offset edges are set up for either right- or left-handed use.

On double-bevel knives with uneven tapers, the edge must be sharpened to match. The asymmetry comes from the sharpening ratio—not from changing the angle from side to side. `

Asymmetrical edges are common in Japanese double-bevel knives, but can also be applied to Western knives with even blade tapers based on user preference.

Whether the blade taper is even or uneven, the way the edge is applied ultimately determines how the knife performs in use.

Single-bevel knives use a different blade and edge geometry system altogether. Originating in Japan, they are designed for highly specific tasks such as fish butchery, vegetable preparation, noodle work, and precision slicing. These knives are commonly used in professional Japanese kitchens, especially in sushi.

Unlike double-bevel knives, single-bevel knives are sharpened primarily on one side. The front side forms a wide bevel that creates the cutting edge, while the back side is slightly concave. This geometry produces a more aggressive taper, allowing for extremely precise and efficient cuts.

Edge angles typically range from about 10° to 18°, depending on the knife. Thicker knives like a Deba are ground at wider angles for strength and durability, making them suitable for heavier tasks like fish butchery. Thinner knives like a Yanagiba use narrower angles for cleaner, more delicate cuts.

These knives are always hand-specific.

Because of their asymmetrical design, single-bevel knives will naturally steer slightly during use and require more control and technique. Once understood, they offer a level of precision that is difficult to achieve with double-bevel knives.

Within this geometry, there are three primary approaches to finishing the edge: Koba, Hiratogi, and Hamaguriba.