Katana Boshi Beauty of this little hamon line within the Kissaki


Everything You Need To Know About Boshi

You can't look at a katana and not be struck by its beauty, despite its function as a lethal weapon. The Katana has a complex anatomy, and many components complete it. Among all the essential elements of a Katana, here I share everything you should know about Boshi. 

What Is Boshi?

Boshi refers to the clay tempered part that runs along the Kissaki or the tip of the Katana blade. In simpler words, Boshi refers to the portion of the hamon line in the kissaki which is produced during heat treatment of the katana blade. Blades that haven't been differentially hardened lack the Boshi that makes them so distinctive. 

Boshi translates to hat or cap. This portion of the hamon is called boshi because it sits like a hat on the tip of the blade. It is the hardest part of the hamon to polish. It is said that the time taken to polish just this portion of the blade is the same as polishing the whole blade. And on top of that it’s just there completely for the aesthetics. So, you could say that the boshi is a true labor of love for the sword smith.  

What's The Usage Of Boshi?

The boshi has no particular use besides just looking pretty on the katana. It is an extension of the hamon which is just a byproduct of the clay heat treatment process. This process provides different properties to the edge and body portion of the katana. And this difference also is reflected by their difference in appearance. And thus the hamon is formed. The hamon extends to the tip of the blade. And its portion on the kissaki is called the boshi.

Sword smiths spend a great amount of time accentuating the boshi. But it is mostly for aesthetic purposes. This is something you can request for your custom katana.

What Are the Common Lengths Of Boshi?

The standard length of Boshi is the same as Katana's Kissaki and largely depends on the blade maker. 

The Kissaki can be any size the bladesmith sees fit but most commonly comes in three different sizes - Ko, Chu, or O. These sizes are approximately 3 cm on the small end, 6 cm in the middle, and 7 cm on the large end, respectively. Most mass-produced blades will have a Chu-Kissaki, which is by far the most typical.

Frequently Asked Questions

  1. What are the Most Common Types of Boshi? 

Ans: Common types of Boshi found on katana swords include:

  • Hakikake-Boshi: The primary distinctive feature of this type of Boshi is Hakikake. However, a Boshi with an even greater amount of Hakikake may be called Kaen. 
  • Ichimai-Boshi: This type of Boshi will have a Kissaki that has been tempered fully or almost entirely. 
  • Jizo-Boshi: The type of Boshi that resembles a statue of the Bodhisattva Jiz when viewed from above; it is similar to Midare-Komi, but its Kaeri region is narrowed significantly. A Jizo-Boshi is a common type of Blade among Minoans.
  1. What is the Biggest Flaw of a Boshi You Should Look Out for?

Ans: The most severe problem with Boshi occurs when the temper line comes in contact with the ha or the Blade's edge. The temper line may break off the Blade's edge in a worse situation. If the temper line breaks off the tip, it is no longer regarded as structurally sound and cannot be utilized safely for tip cutting.


If you are buying, selling, or just learning about Katanas, having sufficient knowledge about their anatomy is a must. So today, I share with you all that you must know about one of the essential components of a Katana, Boshi. Thanks for reading!

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