Hollow Grind (Urasuki)

Hollow Grind (裏スキ, Urasuki)

Quick look

• What it is: A concave surface machined into the inner face of each blade
• Purpose: Reduces blade-to-blade contact area, lowering friction
• Lifespan: Gets shallower with each sharpening; eventually needs re-machining
• Quality marker: Deeper, more precise hollows indicate higher manufacturing quality

Why it matters

Run your finger along the inside of a professional scissor blade and you’ll feel a subtle scoop. That’s the urasuki (裏スキ), the hollow grind. It’s there for a practical reason: by reducing the surface area where the two blades touch, it dramatically cuts down on friction. This is a big part of why professional scissors feel so much smoother than the household kind.

The hollow also creates a tiny gap between the blades that allows hair to sit properly before being cut. Without it, hair tends to get pushed or pinched between flat surfaces.

The sharpening problem

Here’s the thing most people don’t realize: every time your scissors get sharpened, a thin layer of metal is removed from the inner face. This means the hollow gets shallower over time. After 20 to 30 sharpenings (depending on the original depth), the hollow can become too shallow to function properly. At that point, the blades need re-hollowing, which is a specialist job that not every sharpener can do.

This is one reason why cheaper scissors with shallow factory hollows don’t last as long. The hollow runs out faster.

Related guide: Maintenance: Sharpening Blueprint

Sources

1. Scissors Yamato technical documentation on urasuki depth
2. Toginon sharpening service documentation