What is Blade Geometry?

**Hasen (刃線) — Edge curve profile:** The hasen describes the shape of the cutting edge when the blade is viewed from above (plan view). The three primary types are: - **Suguha (直刃)** — Straight edge. The cutting edge follows a straight or very gently curved line from pivot to tip. Produces the most predictable cuts and the cleanest blunt lines. Preferred for precision geometric work and classic barbering. The straight edge makes full contact with the opposing blade simultaneously, requiring very precise ride line engineering. - **Yanagiba (柳刃):** Willow-leaf edge. A moderate curve between suguha and sasaba, and the usual all-round line for wet and dry cutting. - **Sasaba (笹刃):** Bamboo-leaf edge. The line with the most curve of the three. The curve lets hair slide toward the tip as the blades close, which suits slide cutting and dry texture work. **Hakei (刃形) — Cross-section shape:** The hakei describes the blade's cross-section when sliced perpendicular to the cutting edge. The three primary types are: - **Hamaguri (蛤)** — Clamshell cross-section. Both faces of the blade curve convexly outward, creating the smooth taper that produces a convex cutting edge. This is the classic premium Japanese blade profile. Hair slides along the curved surfaces with minimal resistance. - **Danba (段刃)** — Stepped cross-section. The blade face has a distinct flat section that transitions abruptly to the bevel near the cutting edge, creating a visible "step" or shoulder. This is the standard beveled-edge profile. The step provides the deliberate grip characteristic of beveled-edge scissors. - **Kenba (剣刃):** Sword cross-section. The blade rises to a ridge in the middle, like a sword, so the section is thicker and stiffer. It can carry a convex or flat edge, on one blade (kata-kenba) or both (ryo-kenba). Understanding that hasen and hakei are independent variables is the key insight. A scissor described simply as "convex edge" conflates the cross-section (hakei = hamaguri) with the edge curve (hasen = unspecified). A complete description requires both dimensions: "yanagiba hamaguri" or "suguha danba." This precision in terminology is standard among Japanese sharpeners but rare in Western scissor marketing.