Part of the MoonSwords Steel Guide series. See the full matrix to compare every steel we forge.
Quick answer: Sanmai ("three layers") is a laminated blade construction: a hard, high-carbon steel core sandwiched between two tougher outer layers. Kobuse is its two-piece cousin, a hard jacket wrapped around a softer core. Both aim for the same balance, a keen edge on a resilient body. Typical core hardness for a clay-tempered sanmai blade is 58–61 HRC. Our sanmai katana is the Kafuu ($659).
Why Smiths Laminate a Blade
A single steel has to compromise: harder means a better edge but less resilience. Lamination lets the smith use two steels where each works best. The hard core forms the edge, while the softer outer layers absorb stress and protect it. Japanese smiths developed several such constructions over centuries, and sanmai and kobuse are two of the best known. See our samurai sword-making traditions guide for the wider history.
Sanmai vs Kobuse
- Sanmai: three layers. A hard core runs through the middle and is exposed along the edge; tougher steel forms each side.
- Kobuse: two pieces. A U-shaped jacket of hard steel wraps a softer core, so the hard steel forms both the edge and the outer surface.
Both are differentially structured by design, and clay tempering adds a second layer of differentiation on top.
Sanmai at a Glance
- Typical core hardness: 58–61 HRC
- Toughness: high, thanks to the outer layers
- Edge retention: high
- Surface: clay-tempered hamon; the lamination line may be visible after polishing
- Rust care: high
The Kafuu Katana
The Kafuu is our clay-tempered sanmai katana in the high-end tier. Lamination and clay tempering together give it a hard edge, a resilient body and a true hamon. If you like the idea of a layered blade but want a visible pattern across the whole surface, compare it with our Damascus katana. For laminated Chinese construction, see the Qianqing Sword in our Master Collection steel guide.
FAQ
Is sanmai better than a single steel?
It balances edge and resilience structurally rather than through heat treatment alone. A well clay-tempered single steel can achieve a similar balance; sanmai adds the layered construction on top.
Do you make kobuse blades?
Our current laminated katana is sanmai. For a specific construction, ask about a custom blade.
Are your HRC figures measured?
The 58–61 range is typical for a sanmai core. Where a product page lists a figure, that figure applies to that sword.