Bo-Hi: The Groove on a Katana Blade

The bo-hi is a groove running along the length of the blade. It reduces the weight of the katana without weakening the blade. It also moves the balance point of the katana slightly towards the tsuba. The result is a sword that is a little lighter and quicker in its cuts.

Bo-hi: practical advantages

This groove offers a very practical advantage for those who practise martial arts such as iaido: it produces a distinct sound that helps you recognise a good cut through the air.

Myths and facts about the bo-hi

You may have heard that this groove served a historical purpose as a blood channel, but this is in fact a myth. The bo-hi is mainly there to lighten the blade and improve the balance of the sword.

Bo-hi variants

Several variants of the bo-hi exist. The most classic ends at the habaki, but some grooves extend only to the middle of the blade or just along its first part. These variants serve a visual purpose more than a practical one. The different forms of bo-hi can also influence the sound produced when cutting, giving each sword its own character.

Bo-hi and kissaki: visual harmony

Some craftsmen carve the bo-hi to match the shape of the kissaki to create a perfect visual harmony. This attention to detail is rare today and is generally found on high-end or antique katanas. It adds to the beauty and individuality of each katana, reflecting the skill and passion of the craftsman.

Choosing a katana with or without a bo-hi

When buying a katana, it is important to consider whether it has a bo-hi, according to your preferences and needs. A katana with a bo-hi will be lighter and quicker, while a katana without one will generally be heavier and have a more solid cutting feel. The choice will depend on your aims, whether martial arts practice, cutting tatami mats or simply collecting.