webpage shows the swordmaking process based on valueable 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.
1. Raw 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.
2. 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 Japan.
3. 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.
4. 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.
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 stabilize them.
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 inside tamahagane.
7. 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
8. 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.
9. 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 inside steel.
10. Orikaeshi Tanren II: These
show the transverse folding.
11. 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.
12. 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
13. Age-kitae (Hada-kumi) II: Tamahagane
pieces are stacked in cross manner.
14. Age-kitae (Hada-kumi) III: Likewise
the shita-kitae, tamahagane is heated and folded 7 to 8 times.
15. 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 takogane).
16. Sunobe-hizukuri: After
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.
17. 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.
18. Nakago-hizukuri: Nakago
19. 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.
20. 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.
21. 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
Different styles determine even the different kind of clay coatings.
22. Tsuchi-tori I: There
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.
23. 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.
24. Boshi tsuchi-tori: Boshi
is being made in kissaki is boshi. Boshi is one of the main characteristics in the
25. Yakiire I: The
most important stage in swordmaking can be the Yakiire (heating-quenching)
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.
26. 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
stress in cutting edge are not tolerable, the crack (hagire) can be initiated
at the cutting edge and propagated.
27. 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
in cutting edge, another tempering (Aitori) is applied sometimes.
28. Sori-naoshi: As
mentioned before, the curvature of the sword increases and the smith corrects
this curvature if needed carefully.
29. 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.
30. Nakago-shitate: Nakago
is a face of the smith in the sword. File mark left by chisels in nakago is
31. 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.
32. 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
2002~2007, Jinsoo Kim
No part of this website can
be reproduced or copied without permission