Sunnobi tanto (寸延び短刀) are larger than ordinary tanto, with nagasa (blade length) 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.
An utsushi (写) is a careful and exacting replication of an existing work, undertaken for the purpose of study and further understanding of the process, techniques, and historical mindset of the original craftsman.
This project is an utsushi-type study of one of the kata (forms) made several years ago from the tracings of famous swords. The profile is closely based on the lovely form of an original named Shuhan, forged by Sadamune (相州貞宗), a Kamakura-era (~13th century) master swordsmith. Originally this was planned to be a rustic satoyama style blade but during the process some interesting details of the layered mining-car rail steel appeared and the decision was made to polish the blade more clearly to see the hada better.
A rack of steel kata for study and reference, made from the tracings of famous historical swords, Sadamune third from right.
A kata is a pattern or form used for study or for reference when creating an utsushi blade. The exercise of accurately making kata based on the work of historical smiths is an excellent way to train the eyes, mind, and body to create proper tanto forms. The most important aspect of making kata is to work carefully to be as true to the original lines as possible.
The raw material for this blade spent the last century as a mining-car rail on Vancouver Island.
The steel is very rare and unique in that it is pre-industrial, a form of blister or shear steel that retains layering from the process of refining it under a steam hammer, similar to wrought iron but much harder to find.
This blade was forged from a section of the top piece of the track that the car wheels ran upon. It was prepared for forging by removing any deeply pitted areas which could cause cold shuts.
Sunobe: Forging the Pre-form
Using the large mukozuchi hammer to roughly lay out the sunobe (rectangular pre-form) which allocates the proportions and amounts of steel for the final geometry and establishes the tapers. The tang will be placed once the proper length is determined.
This blade is based on a kata of a famous large Sadamune tanto (lower right). Photographed and graded by Jourdan Causey.
Hizukuri: Forging the Bevels
View of the traditional swordsmithing forge during the forging process. Fuigo bellows supplying air to the charcoal fire. Photographed and graded by Jourdan Causey.
Working closely to a kata requires frequent checking and careful progress.
The kata faithfully reproduces the original’s four or five mounting holes, including one plugged with copper and one with steel. This means the original blade was mounted in at least five different koshirae over the centuries, and it appears to have been shortened at least once as well.
Working on the final adjustments after hizukuri to more closely represent the kata.
The surface is rendered fairly smooth by careful hammer work alone, saving time with a file later.
Getting very close, with the exception of the spine curvature, which will be introduced by yaki-ire (hardening) and must be compensated for in advance with a straighter spine.
As the tip will be hardened on both edges for a short way the curvature is more steep there as well as next to the tang with the aim of matching the rest of the curvature after yaki-ire.
Arashiage: Rough Filing
The machi (notches) are filed in to delineate the tang area.
The outline of the spine, edge, and tang areas are cleaned up–in order and given final adjustments.
Once the profile is complete, the thickness of the spine and edge are corrected and then the blade is placed in a sen-dai (staple vise) to clean up the bevels.
The bevels are first filed down to the lines set around the perimeter and then drawfiled to smooth the bevel geometry.
The blade is ready to be cleaned with ash and water for the application of the clay mixture in preparation for yaki-ire.
Yaki-ire: Hardening the Blade
The light still shows the clay placement after yaki-ire. The hamon placement may or may not follow it exactly depending on the steel and other factors.
After hardening the sori (spine curvature) is continuous from tip to tang and matches the kata.
Another look at the clay line as well as the comparison to the form of the original kata.
Togi: Polishing the Blade
The coarse stages of polishing set the final geometry and make subtle adjustements in the lines.
The hamon has an interesting form and interaction with the layers of the steel.
The difference in rusting rates highlighted the layers of the omote (public/display side) hada very strongly in the earlier stone stages while polishing the ura.
Ura (back/private side) hada showing by rapid oxidization while polishing the omote.
This unique rolling mist artifact of the hada and hamon are definitely one of the highlights of this blade.
The final polishing using natural Japanese waterstones will be done after all the mountings are made and fitted.
The finer the stones the more subtle details of the hada become visible in the right lighting.
The unique interaction between hada and hamon has produced an interesting “rolling mist” artifact.
See the mounting process and more information on the Asagiri tanto.
Specifications
長さ/刃長 Nagasa: 11 sun 1 bu 5 rin (338mm)
元幅 Motohaba: 1 sun 1 bu (34mm)
重ね/元重 Motokasane: 2 bu 5 rin (7.5mm)
反り Sori: 1 bu 2 rin (3.5mm)
中心/茎 Nakago: 3 sun 2 bu 4 rin (98mm)
柄長 Tsuka: 4 sun 8 bu 5 rin (125mm)
拵全長 Koshirae: 20 sun 6 bu (525mm)
形 Katachi: hira-zukuri, iori-mune
刃文 Hamon: suguha, with ubuha
帽子/鋩子 Boshi: ko-maru
中心/茎 Nakago: futsu, kuri-jiri, as-forged, one mekugi-ana
銘 Mei: mumei (unsigned)
拵 Koshirae: chisagatana, issaku (with the addition of nine antique components)
