What is Chuumaru Boushi in Japanese Katana terminology?

The term ""中丸帽子"" (Chuumaru Boushi) refers to a type of tempering pattern on a Japanese sword where the tempered edge part is moderate, and from the Yokote line towards the tip, the tip returns drawing a moderate arc along the curvature of the sword. This pattern is often seen in the works of swordsmiths from the middle of the Kamakura period to the early years of the Nanboku-chō period.

On the other hand, the term ""大丸帽子"" (Oomaru Boushi) refers to a type of tempering pattern where the tempered edge part is large, and the tip returns drawing a large arc along the curvature of the sword. This pattern is often seen in older swords and is characterized by its strong impression due to the thin return compared to the tempered blade part.

The term ""小丸帽子"" (Komaru Boushi) refers to a type of tempering pattern where the tempered edge part is normal, and from the Yokote line towards the tip, the tip returns drawing a small arc. This pattern is often seen in the works of swordsmiths from the late Kamakura period to the early years of the Nanboku-chō period.

These tempering patterns are not just for aesthetics, but they also reinforce the important tip of the sword. The creation of these return patterns is a difficult task that reveals the skill of the swordsmith.