Hello everyone. Thank you for reading this article. I’m Shogo from Let’s ask Shogo, the interpreter of the online lessons and owner of this website.

Quite a lot of real katana and most Iaitō training katana have grooves on the blades. The question is, why do they have them? If some katana don’t have grooves, what are the benefits of having them?

The grooves on the katana blades are called Hi or Bōhi in Japanese. It is generally said that there are three main benefits of having them.

1. Weight reduction
2. To make it easier to pull out after thrusting
3. Designability

The most obvious benefit is weight reduction. It is said to be about 10% lighter because of the grooves. It is also said that the grooves in the blade make it easier to pull out the katana when it is thrust into an enemy. This is the same mechanism as a kitchen knife with holes in it. Finally, it is also said to have a positive effect on design. The presence of grooves increases the surface that reflects light, making the katana appear more brilliant.

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