Hairdressing Scissor Blade Geometry: Convex, Bevel & Semi-Convex

Steel sets the ceiling. Geometry decides how close to that ceiling the scissor actually gets. The same ATS-314 billet can be ground into a scissor that slide-cuts like silk or one that folds hair like a wet tea-towel — the difference is the blade profile.

The Three Edges That Matter

Convex (Hamaguri-ba)

The Japanese hollow-ground edge. The inside of each blade is slightly concave, and the cutting edge itself is a smooth convex curve meeting at 20-30°. Razor sharp, slices on contact, and absolutely required for slide cutting, point cutting and any modern dry-cutting technique. Every ShearGenius scissor ships with a true convex edge, hand-finished on Japanese water stones.

Semi-Convex

A compromise grind: convex on the outside, bevelled on the inside. Cheaper to manufacture and more forgiving of rough handling, but will not slide cut cleanly. Commonly found on mid-tier European and Korean scissors.

Bevel Edge

The traditional flat-ground edge at 40-50°. Durable, easy to sharpen on a basic machine, but push-cuts rather than slices. You can feel the hair being crushed rather than parted. Fine for blunt-cutting coarse hair; wrong for any modern technique.

Which Geometry for Which Technique

• Slide cutting: Convex only. Bevel and semi-convex will drag and snag.
• Point cutting: Convex preferred. The tip must be razor sharp and unchipped.
• Blunt cutting wet hair: Any of the three will work; convex gives the cleanest line.
• Texturising with a teethed blade: The cutting blade should still be convex — the teeth handle the weight removal.

How to Spot a True Convex Edge

Hold the scissor open under a bright light and sight down the ride line. A true convex edge shows a smooth, continuous curve with no flat facets. A bevel edge shows a distinct angular line. A semi-convex looks convex from the outside only — the inside face is flat.

Related Reading

• Steel guide — ATS-314 vs VG10 vs Cobalt vs 440C
• Handle types — offset, crane, even, swivel
• Complete glossary
• Best scissors for slide cutting