This webpage shows the swordmaking process
based on valuable photos performed by the late living national
treasure, Miyairi Akihira (1913-1977). He entered the Nihonto Tanren
Denshusho (directed by Kurihara Hikosaburo Akihide) at the age of
10. He made an unbreakable record of five consecutive "Tokusho" winner
in Shinsakuto Gijyutsu Hatpyoukai from 1955 to 1959. In 1960, he became
a Mukansa followed by the second living national treasure in 1963. He
aimed the Shizu Kaneuji and Soshu style during his life.
material: In ancient times,
the resource of the Japanese sword was mainly steel scraps (such as nail,
broken pot, plow, etc.) as well as a tamahagane which was refined from the
tatara, the traditional iron smelter. Currently, the NBTHK supplies
tamahagane to swordsmiths in Japan.
Sumi-wari: Splitting wood
charcoal is the first step for swordmaking, which is called "sumiwari". The
best charcoal comes from the pine tree but chestnut tree is also used. To
make one sword, about 12 - 15 kg of charcoal is consumed. The different size
of charcoals control the forging temperature in the hearth and they provide
the carbon into the steel. About 2 - 3 cm of even size is used at Kitae
(forging) process but smaller size of 1 - 1.5 cm is used in Yakiire
(tempering/quenching) process. This sumiwari process is a very important
step for smith trainee (There was an old saying that the trainee had to
spend 3 years just to learn sumi-wari). Akihira was well known for spending
most of his valueable time in the sumiwari so that he couldn't make more
than two swords per month. In order to learn his craftmanship afterward,
thesedays no more than two swords/month are allowed to produce by a smith in
Aku-zukuri: "Aku" means burnt
straw which is used in forging process. Aku is used broadly in forging steps
e.g. the fixation of tamahagane on takogane in tsumi-wakashi process.
Tsumi-wakashi I: Pieces of
tamahagane are heated in the hearth to be classified. Based on the carbon
content in each piece of tamahagane, they were used for kawagane (skin
steel: brittle, hard, high carbon content) or shingane (core steel: ductile,
soft, low carbon content). At first, kawagane pieces are stacked on the
takogane (flat steel scoop), which also becomes the part of the nakago.
Tsumi-wakashi means stacking process.
Tsumi-wakashi II: After
stacking tamahagane pieces, wetted Chinese drawing paper covers them to fix
the stacked pieces. In addition, clay water is slightly poured on it to
Tsumi-wakashi III: Aku covers
the stacked tamahagane again follwed by another pouring of clay water.
Chinse drawing paper, clay water, and aku play important roles on
maintaining the uniform temperature of tamahagane in the hearth, preventing
the contamination by outer impurities, and stabilizing the carbon content
Shita-kitae I: After
tsumi-wakashi process, the forging begins. By increasing the temperature of
the hearth, stacked tamahagane is heated. This is the beginning of
Shita-kitae (Base forging).
Shita-kitae II: Hammering
onto the tamahagane begins. There are many sizes of hammers used such as o-zuchi
(big hammer) which weighs about 1.1 kg. Hammering is another important step
for smith trainee. Hammer should be hit the exact position at the anvil. The
swordsmith leads the hammering process with his ko-zuchi (small hammer).
During this stage, many vacancies inside the tamahagane are revealed to the
surface and removed.
Orikaeshi Tanren I: "Orikaeshi"
means folding. Forged tamahagane are folded transversely and
longitudinally. At each folding stage, tamahagane is heated and cooled down
by water again and again. This procedure oxidize the steel surface and
removing these oxidated layers greatly reduce the content of impurities
Orikaeshi Tanren II: These
show the transverse folding.
Orikaeshi Tanren III: These
show the longitudinal folding. The difference between these two folding
procedures lies on that the small hammer is used to fold in transverse
folding while the big hammer is used in longitudinal folding. Generally,
about 12-15 folings are repeated.
Age-kitae (Hada-kumi) I:
After shige-kitae which produce kawagane and shingane respectively, another
forging step can be added (Age-kitae). Tamahagane is forged again as a shape
of stick once more and cut uniformly about 7.5cm long. This age-kitae is an
optional step and sometimes omitted. A tight microstrucutre and hada (grain
pattern) can be expected after this step and the uniformity of the carbon
content is improved.
Age-kitae (Hada-kumi) II:
Tamahagane pieces are stacked in cross manner.
Age-kitae (Hada-kumi) III:
Likewise the shita-kitae, tamahagane is heated and folded 7 to 8 times.
Kumi-awase (Honsanmai style):
Kawagane, shingane, and hagane are
combined each other to designate the sword structure. These photos show the
Honsanmai style (Two kawagane, L-shape hagane and shingane connected to
combining each different tamahagane, long stick of sunobe is shaped. This
forging step is called "Hizukuri". By the direction of the smith with the
help of big and small hammers, sunobe becomes the shape of the sword. With a
small hammer, the smith shapes, elaborates, and predicts the dimension of
the sword in his mind.
Kissaki-hizukuri: Kissaki is
shaped at the end of the sunobe. When the kissaki is shaped, the shingane
should not be exposed and the kawagane should not be thick.
Nakago-hizukuri: Nakago is
Shiage: Mune and hiraji are
shaped by chisels. Hamachi and munemachi are also shaped in this step.
Finally, the dimension of the sword (sugata) is completed.
Yakiba-tsuchi: This is the
clay coating to make a hamon. Yakiba-tsuchi is a clay mixture which is high
temperature resistant. At first, sunobe is cleaned to eliminate any oil or
impurities on the surface followed by the coating of Yakiba-tsuchi. The
composition of Yakiba-tsuchi is a top secret to the smith. In general, it's
known as a mixture of clay, (polishing) stone powder, and charcoal powder.
Clay becomes hardended during Yakiire step and sticks to the steel surface
firmly. The thickness of the clay coating determines the cooling rate in
quenching. Stone powder is bigger than clay so that it minimizes the the
compressive stress of clay during drying. On the other hand, the charcoal
powder is burned out in the hearth before quenching and produce a micro-void
inside the clay coating. These numerous micro-voids produce micro-bubbles by
vaporization during quenching and increase the cooling rate.
Tsuchi-oki: The thinner
coating of Yakiba-tsuchi is applied to hiraji and the shingiji is coated in
thick manner. These coating thicknesses result in the different cooling
rate and consequent microstructure of the steel. Yakiire has two styles:
Bizen style in low temperature tempering and Soshu style in high temperature
tempering. Different styles determine even the different kind of clay
Tsuchi-tori I: There are two
kinds of tsuchi-tori exist. In both coatings, basic thin coating is applied
at first. Positive method leaves the thicker clay in hamon area by recoating
the clay with "brush". On the other hand, negative method makes the thinner
clay by eliminating the basic clay coating with "scoop". Left photo shows
the positive method to make a suguha hamon while the right shows the
negative method for a gunome hamon.
Tsuchi-tori II: Another
photos to show various styles. The left produces choji midare with negative
method and the right produces a gunome. Postive method is easier than
negative but hamon is not so dynamic. Negative method is difficult to
success but the taste of hamon is deep and aesthetic. Akihira usually used
the negative hamon coating method.
Boshi tsuchi-tori: Boshi is
being made in kissaki is boshi. Boshi is one of the main characteristics in
the sword appraisal.
Yakiire I: The most important
stage in swordmaking can be the Yakiire (heating-quenching) process. After
coating clays onto the blade, it is heated up to 720 - 780C. Smaller wood
charcoals are used not to peel off the clay coating. If the process
temperature is increased slowly, Nioi-deki of Bizen style can be made. Fast
increase of hearth temperature is necessary for Nie-deki of Soshu style. The
latter is more difficult than the former.
Yakiire II: Once the sword
attains the right temperature, it is quenched into the water box (Mizubune).
The water temperature is another important factor as well as the speed of
quenching. In this stage, the cutting edge bends more because of the
martensite transformation of steel which results in 4.4% volume increase. If
this volume increase and applied tension stress in cutting edge are not
tolerable, the crack (hagire) can be initiated at the cutting edge and
Yakiire III: There are
several factors which determine the success of yakiire. They are mainly a
clay coating thickness and its composition, quenching temperature and
cooling rate, and a sword dimension to endure the tensile stress at the
cutting edge. To relieve the residual tensile stress in cutting edge,
another tempering (Aitori) is applied sometimes.
Sori-naoshi: As mentioned
before, the curvature of the sword increases and the smith corrects this
curvature if needed carefully.
Kaji-togi: Before tossing the
blade to the togishi (polisher), the smith performs a basic togi. Any
defects or problems are examined by smith. It was said that the polishing
skill of Akihira was much better than usual togishi.
Nakago-shitate: Nakago is a
face of the smith in the sword. File mark left by chisels in nakago is
Mekugi-ana drilling: If the
only one machine is used in Japanese swordmaking thesedays, it's the drill
to make a mekugi-ana. In ancient times, it was punched. The poisition of
mekugi-ana is usually 7-8cm below from the hamachi.
Mei-kiri: The last step is to
sign the name of smith on the nakago. Sometiems, the swordsmith signed in
different way according to the quality of the sword he made. The above shows
a Tachi mei.
Copyright 2004, Jinsoo Kim
No part of this webpage can be reproduced
or copied without permission
The text and
images are used with permission of Jinsoo Kim.