The bohi (bo-hi) refers to one or more grooves that are cut into the blade of the sword, running along the blade from the base to the tip. This feature was originally intended to help balance the weapon and make it easier to control in combat. However, it also had the added benefit of making the sword more aerodynamic, which helped increase its cutting power.
What is the bohi for
This groove serves several purposes:
The beliefs say that the bohi help to prevent blood from clogging the blade and making it difficult to wield. They also provided a place for the blood to drain so that it would not drip down and make the sword handle slippery. In reality, from a functional standpoint, the bohi helped to reduce the weight of the sword by removing some material from the blade.
The bo-hi groove also helps to prevent the blade from breaking at the point where it is thinnest (the "edge").
Finally, it makes the katana more aerodynamic, which can help increase the speed and power of swings.
From an aesthetic standpoint, katana bohi added visual interest to the sword and made it appear more menacing. They also served as a way to identify the swordsmith who made the sword, as each swordsmith had their own distinctive bohi patterns.
Bo hi types
There are three main types of katana sword grooves: the bo-hi, soe-bi, and futatsu hi.
1. The bo-hi is the most basic type of katana sword groove and is simply a single channel running down the length of the blade. This type of groove does not significantly affect the weight or balance of the sword and is mainly used for aesthetic purposes. There are three main types of katana bohi: kiri (切), maru (丸), and kaku (角).
- Kiri bohi are the most common type of katana bohi. They have a straight, angled cut that runs along the length of the blade.
- Maru bohi are katana bohi that have a rounded cut. They are less common than kiri bohi, but are still seen occasionally.
- Kaku bohi are katana bohi that have a square or rectangular cut. They are the least common type of katana bohi and are rarely seen.
2. The soe-bi is a more complex katana sword groove that consists of two channels, one running down the length of the blade, and the other running along the back edge of the blade. This type of groove is designed to help balance the weight of the sword and can also be used for aesthetic purposes.
3. The futatsu hi is the most complex katana sword groove and consists of two channels, one running down the length of the blade, and the other running along the back edge of the blade. Unlike the soe-bi, however, these two channels are not connected at the base of the blade. This type of groove is designed to help balance the weight of the sword and can also be used for aesthetic purposes.