Master Bladesmiths · Kyoto, Japan
Steel Shaped
by Centuries
of Mastery
At Abyssal Moon Thread we carry forward the unbroken lineage of traditional Japanese swordsmithing. Every blade we forge — from the ore selection to the final mirror polish — is guided by the same principles that armed the samurai of feudal Japan.
A Living Tradition in the Heart of Kyoto
Founded by master smith Hiroshi Tanaka in 1978, Abyssal Moon Thread has forged its reputation on the same principles as the legendary swordsmiths of the Edo period.
Our workshop sits in the historic Higashiyama district of Kyoto — a neighbourhood that has housed artisans and craftspeople for more than four hundred years. The smell of charcoal and the ring of a hammer on hot tamahagane steel have echoed through our walls for nearly five decades. We are proud to be designated by Japan's Agency for Cultural Affairs as a registered traditional craft studio.
Every blade begins as raw tamahagane, the precious steel smelted in a traditional tatara furnace. It is folded, drawn, shaped, and differentially hardened through a process measured not in hours but in days of careful, attentive labour. The result is a sword that is not merely a weapon — it is a living document of Japanese metallurgical genius.
Learn Our StoryThe Abyssal Moon Thread Difference
Eight pillars of mastery that define each sword we produce — from the first heat of the forge to the final edge geometry check.
Tamahagane Steel
We source exclusively from Shimane Prefecture's Nittoho Tatara — Japan's only remaining traditional steel smelter. The high-carbon tamahagane it produces contains microscopic variations in carbon content that, through skilled folding, become the soul of the blade's strength and flexibility.
Traditional Folding
Our smiths fold the steel between 8 and 16 times, creating up to 65,536 micro-layers. This process expels impurities, distributes carbon evenly, and develops the fine crystalline structure responsible for the blade's legendary cutting ability and resilience under impact.
Clay Differential Hardening
The tsuchioki (clay application) stage is where the hamon — the hallmark temper line — is born. Our smiths apply a precisely formulated clay mixture to control the quench, producing a hard edge capable of extreme sharpness alongside a tough, flexible spine that resists breakage in use.
Hand-Cut Geometry
After hardening, the blade geometry — shinogi (ridge), niku (convex grind), and kissaki (tip) — is shaped entirely by hand using traditional sen scrapers and various grinding stones. Each geometry decision is made by the smith's eye and feel, not a jig or machine template.
Honbazuke Polish
Our in-house togishi (polishing master) works through a progression of increasingly fine Japanese water stones, from the rough nugui to the ultra-fine hazuya fingerstones. The process takes four to seven days and reveals the full visual beauty of the hamon and the steel's inner landscape of nie and nioi.
Koshirae Mountings
The tsuka (handle) is wrapped in genuine same (ray skin) and hand-braided ito (silk cord) in the traditional technique. The tsuba, fuchi, and kashira are either antique fittings sourced by our team or commissioned from partner metalworkers who specialise in traditional iron and shakudo alloy work.
NBTHK Certification
Each sword we produce is submitted to the Society for the Preservation of Japanese Art Swords (NBTHK) for inspection and certification. Papers accompany every commission, providing independent authentication of the blade's quality, school, and construction method — essential for collectors and serious practitioners.
Lifetime Maintenance
We consider the relationship with a sword owner to be lifelong. Every blade we forge qualifies for our maintenance programme: regular inspection, re-polishing when the steel requires it, and replacement of any mounting components that show wear — ensuring your sword remains in peak condition for generations.
The Six Stages of Forging a Katana
A single sword passes through six distinct phases over a minimum of six weeks. Each stage demands its own mastery, and no two blades are ever identical.
Steel Selection
Our master smith hand-selects tamahagane pieces from the tatara bloom, identifying the optimal carbon gradients needed for the kawagane (hard skin) and shingane (soft core) of the specific blade type being commissioned.
Orikaeshi Tanren — Folding
The steel is heated to forging temperature in the charcoal furnace, then hammered, doubled, and folded repeatedly. The fire scale is brushed away between each fold. This laborious stage transforms raw sponge iron into the uniform, purified steel the blade requires.
Sunobe — Blade Shaping
Once the steel billet is prepared, the smith hammers it into the elongated preform called sunobe — establishing the general length, curvature, and mass distribution. The sori (curve) of a katana emerges partly here and partly from the differential hardening that follows.
Tsuchioki — Clay Coating
A specialised clay mixture of pine charcoal, grinding stone powder, and clay is applied in a specific pattern: thick along the spine to insulate it, thin near the edge. When quenched in water, the exposed edge cools rapidly (martensite hardening) while the spine cools slowly, locking in flexibility.
Togi — Polishing
The togishi begins with coarse stones to establish the geometry, then progresses through ten or more grades of finer stones. Final hand-polishing with uchigumori hazuya and jizuya stones creates the characteristic mirror-bright ji-hada and the luminous, cloud-like hamon patterns.
Koshirae — Mounting
The finished blade is fitted into its habaki (blade collar), then mounted in a shirasaya (storage mount) or a full decorative koshirae. The tsuka is assembled, the sageo cord tied, and the completed sword is photographed and submitted for NBTHK certification before delivery.
Commission or Acquire a Blade
We offer a curated selection of sword types, each available as a bespoke commission or from our limited ready-to-ship collection. All pieces include documentation and a lacquered presentation case.
Shinogi-Zukuri Katana
The quintessential samurai sword form — a long curved single-edged blade with a pronounced ridge line (shinogi) that defines its iconic silhouette. Our standard commission runs 68–73 cm in nagasa, forged from folded tamahagane with a suguha or notare hamon. Available with shirasaya or full koshirae. Signed and dated habaki included. NBTHK Hozon papers applied for upon delivery.
Hira-Zukuri Tanto
A flat-ground tanto without a shinogi, presenting the entire ji (body of the blade) as an uninterrupted canvas for the hamon. Blades run 25–30 cm in nagasa. Because of the shorter length, our smith dedicates proportionally more finishing time per centimetre than on a long sword — the result is a breathtaking concentration of metallurgical artistry in a small, intensely focused form. Ideal as a collector's piece or ceremonial gift.
Shinogi-Zukuri Wakizashi
The companion blade worn alongside a katana in the traditional daisho pairing. Running 45–60 cm in nagasa, our wakizashi shares the same tamahagane and folding process as the katana, yet the shorter length allows finer, tighter hamon work and more elaborate kissaki geometry. Daisho commissions (matched katana + wakizashi with harmonised fittings) are available at a combined discount. A set commissioned together carries a unified aesthetic identity from tsuba to sageo.
O-Nodachi Field Sword
The grand field sword of the samurai cavalry — nagasa 90 cm and above, requiring exceptional strength in the smith's arm and absolute mastery of the quench. Because nodachi are quenched in larger water tanks with unique thermal dynamics, the hamon patterns that emerge are unlike those on shorter blades: dramatic, cloud-like, with wild tobiyaki islands appearing spontaneously within the temper zone. Accepts only six commissions per calendar year.
Iaito Practice Sword
Crafted for practitioners of iaido and iaijutsu who require a sword of proper weight, balance, and geometry for cutting practice and kata without the edge of a shinken. Made from a zinc-aluminium alloy with an authentic polish and full traditional koshirae. Each iaito is individually balanced by our smith — not factory-weighted — so the handling characteristics mirror a real tamahagane katana as closely as science allows. Includes a canvas carrying bag and cleaning kit.
Fully Bespoke Commission
Everything designed from the ground up: blade type, length, geometry, hamon style, steel folding pattern, tsuba school, ito colour, lacquer on the saya, and engraved hi (groove) with custom inscription. A consultation session with Master Tanaka is included, typically three to five hours covering metallurgical options, historical references, and aesthetic vision. Lead time is 12–18 months. Price varies with specification — contact us to begin the dialogue.
Selected Blades from Our Workshop
A glimpse at three recent commissions — each one a distinct conversation between our smith's technique and the client's vision.
Commission — 2024
The Autumn Moon — Choji Hamon Katana
Commissioned by a private collector in Munich, this 71 cm shinogi-zukuri katana carries one of the most demanding hamon styles — choji, named for the clove-blossom pattern that erupts along the temper line. The choji pattern requires the clay application to be sculpted into dozens of individual lobes before quenching; a single quench either locks in the pattern or destroys the blade. The ji (body) shows a refined ko-itame grain with chikei lines — dark veins of martensite visible in oblique light. The koshirae uses a rare antique iron tsuba from the Mino school.
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Commission — 2024
The Black Pine — Hira-Zukuri Tanto
A 27 cm hira-zukuri tanto commissioned for presentation to a retiring director of a Kyoto cultural foundation. The steel carries a vivid notare hamon with tobiyaki islands — spontaneous floating patches of hardened steel that appear like stars in a night sky when the blade is examined in strong raking light. The saya is lacquered in matte urushi with a hand-painted pine motif by Kyoto lacquer artist Reiko Mizushima. The ito is braided in deep indigo and charcoal silk. A shirasaya travel mount was also prepared for safe storage and transport.
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Commission — 2023
The River Mist — Suguha Wakizashi
At 52 cm, this wakizashi occupies the upper boundary of its class. The client — a New York-based curator of Japanese antiquities — requested the most austere, classical aesthetic possible: a straight suguha hamon in the tradition of the Yamashiro school, paired with a simple bronze habaki, a plain oval iron tsuba, and a saya of polished plain hinoki cypress with no lacquer. The steel itself carries a remarkable o-hada grain visible through the ji — a legacy of the particular fold sequence our smith selected — and the suguha hamon shows a dense, even nie constellation along its entire length.
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Ownership that Transcends a Purchase
A Abyssal Moon Thread blade is not a product — it is a relationship with a living craft tradition that began centuries before we opened our doors.
Documented Provenance
Each blade comes with a signed certificate from our master smith, NBTHK inspection papers, and a photographic record of every stage from raw steel to finished sword — a complete historical document for future owners.
Guaranteed Authenticity
Every blade is forged on-site in our Kyoto workshop using verifiably traditional materials and methods. We never purchase, re-sell, or re-mount third-party blades. What you receive is entirely our own work, made under one roof.
Secure International Shipping
We manage all Japanese export permits, customs documentation, and destination-country import requirements. Blades are shipped in a padded lacquered presentation case inside a purpose-built wooden crate — fully insured.
Generational Value
Fine nihonto (Japanese swords) made by certified smiths have consistently appreciated in value over decades. Our blades, with NBTHK documentation, are recognized in the art market as legitimate cultural artefacts — not merely decorative items.
Three Clients. Three Journeys.
Behind every blade is a story. Here we share three commission journeys — the brief, the choices made, and the result.
Zurich Museum of Asian Art — Permanent Collection
The museum requested a reference-quality katana representing the mid-Edo period aesthetic for their permanent Japanese arms gallery. Working with their curator, we produced a katana forged in the style of the Bizen-Osafune school — wide hamon, deep sori, prominent bohi groove. The sword is now displayed alongside sixteenth-century originals and educates more than 120,000 visitors per year.
Daisho Commission — Los Angeles, California
A fourth-generation Japanese-American client wished to honour his family's samurai heritage with a matched daisho — the katana and wakizashi pairing that represented a samurai's social status. The fittings were designed around the family's ancestral mon (crest), hand-engraved in shakudo by our partner metalworker. Both blades carry harmonised gunome-midare hamon, creating a visual dialogue between the pair.
Feature Film — Production House, Auckland
A major historical drama required six period-accurate katana for principal cast members — swords that would survive on-set handling, close-up photography, and simulated combat choreography. We produced six functionally identical blades in terms of specification, but each with a subtly unique hamon so they could be individually tracked in continuity. The production designer described the blades as "the only authentic objects on the entire set."
Words from Those Who Carry Our Blades
From martial artists to museum curators, collectors across the world have entrusted us with their most meaningful commissions.
Receiving the blade was one of the most moving experiences of my collecting life. The NBTHK papers confirmed what I already felt the moment I drew it from the shirasaya — this is a work of exceptional quality that speaks directly to the great swords of the Edo period. Master Tanaka's communication throughout the commission process was equally extraordinary.
We display the Abyssal Moon Thread katana alongside sixteenth-century originals, and our curators agreed it holds its own both visually and technically. The documentation package was comprehensive enough to satisfy our acquisitions committee without any additional verification. I recommend them without hesitation to any institution seeking a contemporary reference blade.
Twenty years of iaido practice, and I can say unequivocally that my Abyssal Moon Thread iaito is the finest sword I have ever trained with. The balance is not matched by anything factory-produced. When my teacher picked it up for the first time he asked immediately who made it. That reaction is the only endorsement I need.
The daisho commission we received as a family heirloom piece exceeded every expectation. Watching Master Tanaka work during our studio visit — the economy of movement, the decisiveness at the forge — made it clear we were in the presence of something genuinely rare. The swords now occupy the centrepiece of our family reception room and are the first thing every guest notices.
Everything You Need to Know Before Commissioning
Commissioning a hand-forged Japanese sword is a significant undertaking. We answer the questions we hear most often from prospective clients.
Insights on the Art of Japanese Swordsmithing
Our smiths and scholars share their knowledge — from the metallurgy of tamahagane to the history of Japan's blade-forging traditions.
How the Tatara Furnace Produces the World's Most Remarkable Steel
The tatara smelting process, conducted over three days and nights, transforms iron sand and charcoal into tamahagane — a heterogeneous steel whose internal carbon landscape is the very foundation of the nihonto's unique performance characteristics. We examine the chemistry and the ritual.
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A Field Guide to Hamon: Reading the Temper Line of a Japanese Sword
The hamon is arguably the most visually distinctive element of a Japanese blade — and the most informative. From the straight suguha of the Yamashiro school to the explosive gunome-choji of Bizen, every hamon style carries historical and aesthetic meaning. This illustrated guide decodes the major types.
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The Tsuba as Art Object: Five Centuries of Japanese Sword Guard Design
Often overlooked in favour of the blade itself, the tsuba (sword guard) is a distinct art form with its own schools, techniques, and collecting traditions. We survey the major periods — from the austere iron guards of the Muromachi period to the elaborate shakudo compositions of the Edo — with reference to pieces in our own collection.
Read ArticleVisit Our Workshop in Kyoto
Whether you are ready to begin a commission, wish to arrange a studio visit, or simply have a question about our swords, we welcome every conversation about the craft. Our team responds to all inquiries within two business days.
Higashiyama-ku, Kyoto 605-0074
Japan
Sunday & Public Holidays: Closed
