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Japanese Blades: Bo-hi or No-hi?

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Navigating the world of Japanese swords and the related terminology can oftentimes be confusing. You may see terms like bo-hi, no-hi, or fatasuji-hi but what do all these mean in terms of sword function and appearance? A “bo-hi” is the Japanese name for the grove that runs along a blade, with the bo-hi being the most common variation. Whether you need this addition depends on a variety of different factors, such as the aesthetic value and how you intend to use the sword. Here we take a closer look at the differences between bo-hi and no-hi, as well as some not-so-common variations.  

What Is Bo-Hi?

A bo-hi, also known as bohi, hi, fuller, or a blood groove, is simply a groove carved into the blade of a sword, just under the spine. Chances are you have heard the myths that this groove existed to allow blood to flow down the blade or reduce the chance of suction and the blade getting stuck in an opponent, however, this is not the case. The idea of the bo-hi works to help reduce the weight of the sword while compromising as little strength as possible. The addition of a bo-hi also shifts the balance point of the blade closer to the wielder. The principle of this groove works very similarly to an I-Beam used in architecture and reduces considerable weight whilst sacrificing minimal durability.

How Is Bo-hi Created?

Traditional bo-hi were created through a process of hand carving, using specialized tools, such as a sen and various chisels. Once the grove is carved out of the steel, the polisher begins the careful work of polishing the bo-hi. As you can imagine, this process takes time and incredible skill, but reveals a unique bo-hi. 

Mass-produced production swords that have a bo-hi do not use this traditional method. Instead, a machine creates the groove, leaving rounded termination points. This is how you can tell if a bo-hi is hand-crafted or made by machine. A hand-crafted bo-hi has termination points that follow the contours of the sword tip.

Different Types of Bo-hi

When talking about the fuller or grove in a sword, most people simply refer to it as the bo-hi, bohi, hi, fuller, or blood groove. However, there are many different variations of these grooves, with very distinct differences. 

  • Bo-hi – a traditional bo-hi runs the full length of the blade, from the yokote to either just before or under the habaki blade collar. 
  • Fatasuji-hi (Double Bo-hi) – Similar to the bo-hi, the fatasuji-hi runs the length of the blade, however, instead of one groove, there are two parallel grooves.
  • Kuichigai-hi – Two very thin groves on the top half of the blade. 
  • Koshi-hi – A short rounded top grove located near the tang.
  • Naginata-hi – A mini bo-hi with the top created opposite of the blade.
  • Shobu-hi – This is a specialized grove shaped like the leaves of an iris.
  • Kakinagashi-hi – this groove extends halfway into the tang of the blade. In some cases, the grove extends to the end of the tang, known as kakitoshi-hi.

Benefits of Bo-hi

For many, the addition of the bo-hi provides the aesthetic appearance of a traditional blade and that is often enough. However, what are the benefits of a blade with a bo-hi, and will it make a difference to you? Let’s take a closer look at what the addition of a bo-hi achieves.

  • Weight Reduction – the main reason for a bo-hi is to reduce the weight of the blade. For example, a Japanese katana with a bo-hi weighs 20-35% lighter than a blade with a no-hi. In battle, this reduced weight increased flexibility and movement with the blade, making for easier and faster strikes on the enemy. 
  • Adjusting Blade Balance – A blade with a bo-hi has a balance that shifts towards the wielder, making movement more controlled and graceful. 
  • Amplified Sound – The sound when a blade moves through the air, known as “Tachi-kaze,” is amplified in blades with a bo-hi. The level of sound, however, still depends on the speed and technique used by the individual wielding the sword. Because of this additional volume, it is an excellent way for students to understand their technique and where improvement may be necessary.

When a Bo-Hi Might Not Be the Best Option

If you are looking for a sword to cut targets such as bamboo, a blade with a bo-hi may not be your best option. Because the bo-hi reduces the weight of the blade and shifts the balance towards the hilt, it produces a less powerful cutting action. While it may feel easier to wield, it offers reduced lateral strength. 

At Kult of Athena, we offer a wide selection of high-quality blades inspired by traditional swordsmith techniques, including the addition of the bo-hi. Browse our selection of beautiful, functional Japanese swords today to find the perfect addition to your collection. 

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