What is the curve on a katana? Sori

What Is “Sori”?

“Sori” means the curve of a katana. If you draw a straight line from the tip of the blade to the bottom of the back edge, the distance from that line to the deepest part of the curve on the spine is called the “sori.” By measuring it, you can tell how curved the sword is.

As you can see in the picture, there’s a dashed line going from the tip of the blade down to the bottom. The solid part in the middle of that line shows the deepest curve — that’s where the sori is.

What Types of Sori Are There?

You might think the curve is always in the middle of the blade — but that’s not always true. Depending on where the curve is the strongest, the sori has different names and shapes. Keep in mind, when we measure sori, we don’t include the tang (the part that goes into the handle).

• Saki-zori – Curve Near the Tip. When the deepest part of the curve is closer to the tip, it’s called sakizori. That means the front part of the blade has the biggest curve.
• Torii-zori – Curve in the Middle. When the curve is right in the middle of the blade, it’s called torii-zori. The curve looks a bit like the shape of a torii, the traditional Japanese gate you see at shrines.
• Koshi-zori – Curve Near the Base. If the curve is closer to the base of the blade, near the handle, it’s called koshizori. It’s the opposite of sakizori. Here, the deepest part of the curve is toward the back of the sword.