Sunnobi Mountain Tanto

Sunnobi tanto (寸延び短刀) are larger than ordinary tanto, with nagasa a sun or two above 1 shaku (sun nobi, “a sun longer”, from nobiru, to stretch or lengthen). Though there is some area of crossover with hira-zukuri ko-wakizashi and they may have sori similar to ko-wakizashi, the simplified difference would be that they are still designed with tanto geometry rather than wakizashi proportions and form. This is the first hammer-finished sunnobi tanto and also the first mounted in kura style, using reclaimed sword parts.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

The core of this project is a charcoal-forged blade, water quenched with clay and sharpened with waterstones, an outdoor knife that has the foundation of the Japanese sword. The aikuchi style mounting is in the rustic kura (蔵, storehouse) style and includes antique fittings from swords carried generations ago and bearing the patina of the ages.

Satoyama are the managed forest areas that border the cultivated fields and the mountain wilds in Japan. Historically they provided soil nutrients, firewood, edible plants, mushrooms, fish, and game, and supported many local industries and crafts such as farming, timber construction, and charcoal making. The interaction of forest, arable land, wetlands, and streams are an important component of the satoyama landscape.

The subtle appearance of hammer marks and file teeth on the blade, the rustic carved and lacquered wooden mountings, paired with reclaimed sword fittings—treasures from the kura storehouse. A hand crafted tool for adventure that would be very much at home in the field, forest, or mountain landscape.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

Forged from an antique chisel that was forged from an older file decades ago, the blade profile of the mountain style tanto is based on a classical sunnobi tanto and has a wide blade with subtle sori (curvature) that is accentuated by the mounting. The temper of this high carbon steel blade has been left relatively hard, a particular combination of steel and heat treatment that is well suited to users who require a good edge and are willing to take care of it.

The tang is constructed in a similar manner to a Japanese sword requiring only a single bamboo peg to hold the knife assembly together. In addition to the sense of beautiful simplicity, this design allows the knife to be taken apart for cleaning and sharpening work.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

This tanto was specifically forged to fit a large antique Edo period copper katana habaki. Reclaimed brass sword fittings form the ferrule and koiguchi (scabbard mouth) and the seppa (blade washer) came from a Showa era gunto mounting. The handle is carved from Magnolia and reinforced with polished and lacquered rayskin in a spiral wrap. The kurikata (cord loop) is carved from buffalo horn and lacquered, and the mekugi (removable peg) carved from susudake smoked bamboo, darkened from serving many decades as part of a ceiling above the hearth in a kominka farmhouse. The scabbard is carved from Magnolia and lacquered in a dark chocolate wine colour made from natural urushi, black urushi, and ground red crimson lake stone pigment.

The blade is 11.5″ long with an overall length of 17.25″ and just under 18.5″ when sheathed. The spine at the munemachi is 7mm thick.

Specifications

長さ/刃長 Nagasa (blade length): 292mm
重ね/元重 Motokasane (spine thickness): 7mm
元幅 Motohaba (blade width): 34mm
反り Sori (spine curve): 3mm
中心/茎 Nakago (tang length): 100mm
柄長 Tsuka (handle length): 123mm
拵全長 Koshirae (overall): 473mm

形 Katachi (geometry): hira-zukuri, iori-mune, with ubuha
刃文 Hamon (edge pattern): rising suguha
帽子/鋩子 Boshi (tip pattern): ko-maru
中心/茎 Nakago (tang): futsu, kuri-jiri, one mekugi-ana
銘 Mei (signature): mumei (unsigned)
拵 Koshirae (mounting): satoyama kura style aikuchi, issaku (sole authorship) plus 4 reclaimed/antique parts

Materials: antique file steel, Magnolia, buffalo horn, samegawa, reclaimed/antique fittings, natural urushi lacquer, crimson lake

This piece is available online.

Island Blacksmith: Charcoal forged knives from reclaimed steel.


Process

This blade was forged and yaki-ire performed at the museum forge. It began as an old chisel that was hand forged from an even older file decades or perhaps generations ago. The remaining piece of the steel billet became the Koi-oshidori Field Kotanto.

Island Blacksmith: Charcoal forged knives from reclaimed steel.
The large two-handed mukozuchi sledge was used as a one-handed bench hammer for initial drawing out of the billet.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
Only hammer work up to this point, the forged profile and bevels before filing in the final details.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
After filing the notches and cleaning up the profile.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
A small amount of filing was required to adjust the tang to the reclaimed Edo period katana habaki.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
The fit is very close and will be taken the rest of the way after hardening.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
A view of the peaked spine, called iori-mune.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
After adjusting the bevels by drawfiling the steel is normalized by thermal cycling to relieve stresses.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
Applying the clay for yaki-ire, it will delay the cooling effect and produce a hardened edge with a tough spine.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
After successfully surviving the stress of yaki-ire the steel has now become a blade, and gained some sori.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
Reclaimed sheet brass is cut and formed into a kashira (pommel) with a punch and die.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
The edges are filed clean but the fire patina is preserved on the exterior of the kashira.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
Magnolia wood handle carved and prepared for samegawa (ray skin).
Island Blacksmith: Charcoal forged knives from reclaimed steel.
This samegawa was over-polished by a student in the past, but is a precious material that can still provide strength and beauty to a handle.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
Several layers of natural tree source urushi lacquer are selectively polished and cured. The kashira, koiguchi, and kurikata are attached using nikawa (hide glue).
Island Blacksmith: Charcoal forged knives from reclaimed steel.
All parts of the koshirae fit and finished, prepared for final assembly.
Island Blacksmith: Charcoal forged knives from reclaimed steel.
Fully assembled for the first time.

Island Blacksmith: Charcoal forged knives from reclaimed steel.

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