Katana Blazing Sun Kobuse Blade Jojaku Koshirae 炎陽

Clay Tempered Full Tang Shinken (真剣) | Blazing Sun Katana: TangGu (湯谷) Kobuse Blade (甲伏造) + TangGu (湯谷) Hantachi Jojaku Koshirae (常寂拵)

The Hantachi-style koshirae (半太刀拵) combines classical design with functional strength. The blade is forged in Kobuse-zukuri (甲伏造) construction, with a hard steel jacket and softer core, as used in traditional tamahagane blades. The surface shows Ayasugi-hada (綾杉肌) grain and a straight suguha hamon (直刃刃文) created through clay tempering (覆土焼入れ). The saya (鞘) is in hantachi (半太刀) configuration with steel fittings replacing buffalo horn. Palm lacquer (棕櫚塗) gives a textured finish. A golden-brown silk sageo (下緒) is tightly tied. The tsuka (柄) is wrapped in amber silk ito over aged yellow samegawa (鮫皮) with hishigami (菱紙) inserts. Brass menuki feature family crests (家紋). Fuchi-kashira (縁頭) are plain steel with a smooth finish. The tsuba (鍔) is a mokko-gata (木瓜形) guard made of antique-finished brass.

TangGu (湯谷) Kobuse Blade

This blade is hand-forged (Tezukuri / 手作り) from our own refined steel in Kobuse-zukuri (甲伏造) construction. This method reflects the structure of traditional Tamahagane (玉钢) swords, balancing edge hardness and core flexibility for resilience and cutting performance.

Blade Forging Details

• Blade Name: TangGu Traditionally Forged Kobuse Blade (甲伏造)
  

• Forging Method: This blade is forged in Kobuse-zukuri（甲伏造）style, with a hardened outer layer over a softer iron core. It is differentially hardened using clay tempering（覆土焼入れ）, producing a sharp edge, resilient spine, and a visible hamon（刃文).

• Materials: Steel refined in-house using traditional methods（伝統的手法による自家製鋼材）

• Purpose: Designed for Iaido (non-sharpened), Kenjutsu, and Tameshigiri (test cutting) practice, as well as for collection, display, and appreciation by enthusiasts and connoisseurs.

Blade Specifications

• Blade Length (Nagasa刃長): Approx 73 cm
• Tang Length (Nakago 茎長): Approx. 24 cm
• Width at Base (Motohaba 元幅): Approx. 31 mm
• Thickness at Base (Motokasane 元重): Approx. 6 mm
• Width at Tip (Sakihaba 先幅): Approx. 22 mm
• Thickness at Tip (Sakikasane先重): Approx. 4 mm
• Kissaki Length (Tip 切先長): Approx. 40 mm
• Mekugi-ana (Peg Hole 目釘穴): 1

Blade Characteristics

• Shape: Shinogi-zukuri (ridged blade 鎬造), Iori-mune (flat ridged spine 庵棟), Ō-kissaki (Large tip 大切先)

• Forging Pattern (Hada 鍛肌):Ayasugi-hada（綾杉肌）— cedar-grain pattern with alternating waves.
• Hamono (Blade Pattern 刃文): Suguha（直刃刃文）— straight temper line formed by clay tempering.

Special Features and Workmanship

Hi (Groove) Engraving

• Type: Hi-Nashi (樋なし)
• Processing Range: None (No bohi) – Solid blade for added weight and strength

Polishing Work

• TangGu Polishing Levels:
  • Highest-grade shaping polish 最上・成形研磨 
  • Superior rough polish 最上・下研ぎ 
  • Detailed final polish 最上・仕上げ研ぎ 
• Key Features:

  • The blade has refined geometry and balanced weight, with Kobuse (甲伏) construction—a hard outer steel layer around a softer core. Traditional polishing reveals a brightened edge (Hashiro/ 刃白), matte jihada (地肌), and a high-polish ridge line (hōmi / 峰).

Fittings and Mountings

Blade Fittings

• Tsuba (Handguard 鍔): Mokko-gata（木瓜鍔）brass tsuba with aged antique finish, plain surface.
• Fuchi-Kashira (縁頭): Steel with smooth, undecorated surface.
• Menuki (目貫): Brass menuki with traditional kamon (家紋) motifs.
• Habaki (鎺): Hand-forged brass with aged antique finish.
• Samegawa (Ray Skin 柄鮫): Natural ray skin aged to a soft yellow hue.
• Handle Wrapping (Tsuka-maki 柄巻): Yellow cotton ito, tightly wrapped.

Saya and Accessories

• Saya (Scabbard 鞘): Hantai-tachi style (半太刀拵) scabbard with steel fittings at koiguchi, kurigata, and kojiri for durability.
• Saya Lacquer (鞘塗): Palm bark-style lacquer (棕櫚塗) with textured natural pattern and earthy tones.
• Sageo (Cord 下緒): Golden brown cord, tightly woven and tied.

Measurements

• Blade Weight: Approx. 0.65 kg
• Sword Weight (without Saya): Approx. 1.0 kg
• Total Weight: Approx. 1.4 kg
• Overall Length: Approx. 100 mm