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Koa isshin fabrication


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#1 Raphael Pauli

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Posted 30 June 2020 - 12:19 AM

Hi all,

I'm trying to find out how exactly the Koua isshin swords were produced.

Beside vagues explanations of english-speaking authors and the more exhaustive explanations of ohmura-study.net, I can't figure out, how the soft steel pipe was inserted in the hard one.

Furthermore, it seems that all (or almost) Koua Isshin swords have a suguha hamon. Can somebody explain me why?

Sources by answering would be very appreciated, since through my different readings, only Ohmura methodically quoted his sources.

Thank you very much in advance.

#2 Hamfish

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Posted 30 June 2020 - 12:52 AM

The ohmura essay is good, maybe read it again.

With The main focus of researching MORO ZUTSUMI. Then focus on how older laminate rail track was made.
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#3 Raphael Pauli

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Posted 30 June 2020 - 01:09 AM

Thank you for your answer. In the Japanese version that someone translated for me, it is said - as in the english version - that a 500kg steel piece was forged in a rotary kiln (btw if somebody could explain me what a rotary kiln I'd appreciate it too) and streched / enlongated in the shape of a pipe with a mechanical hammer. Then the shingane was inserted in it. Finally, the pipe was cut in lenght corresponding to the weight of the sword, heaten and forged one by one. Here my question, very technically, is: how does this process looks like? How can the shingane get inserted in a 500kg pipe and be cut at the right weight? Physically, I guesse we're talking of a huge pipe and I can't figure myself out how it could be done...

#4 Bruce Pennington

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Posted 30 June 2020 - 01:58 AM

Honestly Raphael, I don't know of anyone that knows. If you can find out, there are a lot of us who would love to hear about it. I watched a "Forged in Fire" episode where the guy replicated a Mantetsu by freezing the soft-steel rod to machine press it into the hard-steel pipe. But we have no knowledge of how the Mantetsu operation did it.
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#5 Hamfish

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Posted 30 June 2020 - 02:45 AM

I don't think that creating such a fit would be necessary.

Because any air pockets would be worked out from one end to the other by mechanical hammering starting at one end and continuing to the other.

The size and length of the swords are such that imho they were in short uniform sections, rather then a long, mass continuous rod, that then was cut into length.


Because we do need just jacket steel for the kissaki, so I would imagine that the core steel would have to be set shorter??

Ps, at the park with the kids so could be talking out my ass
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#6 David Flynn

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Posted 30 June 2020 - 03:32 AM

Does not explain the different Ji Hada.


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#7 Hamfish

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Posted 30 June 2020 - 06:12 AM

That's a good point,
all the ones iv inspected have nothing of any note. But they were all in original polish.

And I suspect the ones that have been polished occurred outside of Japan??

Just for the can of worms, wootz!!!
No known folding, but heaps of structure
So some food for thought.

But that's a tangent, on top of a tangent dav
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#8 PNSSHOGUN

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Posted 30 June 2020 - 07:16 AM

It could be related to various types/batches of Kawagane material used that produced Hada. Considering the long development process there must've been many experiments making them from Mantetsu steel in somewhat traditional methods before a sound method was finalized and adapted to widescale production.
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#9 David Flynn

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Posted 30 June 2020 - 09:48 AM

Koa Isshin, have been seen with Itame, Mokume and Masame.  To get these hada patterns, this is done during forging.


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#10 16k

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Posted 30 June 2020 - 10:07 PM

My belief is that the steel was laminated (by hand or machine) then, when still malleable it was probably formed into a pipe with just one opening. Then the iron rod was inserted into the pipe and, I quote, soldered through an electrical process, then the whole must have been heated again and shaped thanks to a power hammer delivering blows with an equal pressure. Of course, that’s the way I understand the process, and I could be 100% wrong.


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#11 David Flynn

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Posted 01 July 2020 - 03:50 AM

Still doesn't explain the different Hada? Also, if this was the case, all the swords would be completely uniform.


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#12 16k

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Posted 01 July 2020 - 08:24 AM

It could explain the Hada. We don’t know what the steel used was or where it came from. We only know its chemical contents, something which could be achieved by a combination of different steels. Everything I’ve read seems to point out that the inner rod was Manchurian iron, but it says nothing of the jacket origin. Over the years, some people have said it was Manchurian, Chinese, Swedish steel but what if it were a combination of those? The molten, then laminated steel could produce Hada, and the different people or machines laminating it would result in different Hada, more or less emphasized by the war time polish.

 

As for the lack of uniformity, even if a power hammer deals uniform blows, it is still a manual process, guided by a person who shapes the sword as he sees fit, provided it sticks to established requirements.

 

Again, this is all conjecture from my part. What we know (and that I’ll try to sum up in a few sentences later as I’m off to work right now) is scarce. We have the different stages, not how they were achieved. And we also have pictures of the machines they used. When Mantetsu published their book about their sword, they were careful to give just enough without betraying industrial secrets.


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#13 IJASWORDS

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Posted 01 July 2020 - 08:41 AM

From all the articles I have read, most translated from Japanese, rail steel was not used to make swords. But the research was done in the railway facility. 

A rich iron ore of Manchurian origin, was converted at low temperature into an iron sponge. A Doctor Kazuhara Kusaka, studied Swedish steel and Tamahagane with the express purpose of making a sword steel in an electric furnace. A similar process to making malleable iron. 

This sponge was forged and folded to expel trapped gases, slag and impurities. It was formed into a long donut, a soft iron core inserted, then formed by hammer forging into a sword. 

Due to the fact that the outer sponge steel was forged, this sword exhibited a Masame Jihada. In fact, because of its appearance performance and hada, it was appraised as a Koto Hizen Tadayoshi. 

So this trial sword and it's method of production was the basis for subsequent swords, though mechanization would have certainly been used. 

The issue of the Hamon is interesting. In one article it states that an "electric furnace" was used to heat the sword prior to quenching. No mention of clay either. So it is possible that the sword edge was heated in an induction furnace, and quenched, hence a straight Hamon. That's how hacksaw blades are edge hardened, while retaining a flexible back. 


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#14 16k

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Posted 01 July 2020 - 05:33 PM

That is exactly what Neil says, although it seems that the first hundred swords didn’t exactly use this process. They were produced with that soft sponge iron but made not by swordsmiths but by regular employees. Those swords were offered to the army in a sort of publicity stunt occasion.
 

with this success in hand, they hired at least two "real" swordsmiths to teach the employees and devise a cost effective and sure proof method that ended up being our Mantetsu swords.

 

Interestingly enough, the whole idea of the perfectly centered iron core encased in a steel jacket came from the observation of the train wheels and axles which where made this way. A soft core to absorb shocks and an steel rim for durability. It was then transposed to the sword forging method, but so far, we’re still unsure of the exact methods.

 

I have a diagram somewhere where the insertion of the iron rod int a steel casing is shown, but I have no idea if this drawing is original or if it was done by an amateur like us. I don’t know in whic file I’ve put it, but if I can find it, I’ll post it in this thread.


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#15 Raphael Pauli

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Posted 01 July 2020 - 06:05 PM

I'm glad to see that, although we still don't have a positive answer, my question generates such a debate. @Neil: Regarding the clay. In the translation of the Ohmura-site I have, it is cleary mentionned that earth of the region of Dairen was used as yakibatsuchi for yakiire: 炉温八○○~八三○度、焼入水温二五度を保ち、焼刃土は大連神社裏山に良質のものを発見したので之を用いた。 置土は自然乾燥が間に合わないので己(や)むなく瓦斯(がす)※2を用いた。※2 こ れが、焼入れにガスを用いたという誤解を生んだ 刀身焼戻しは、二○○度の熱油中に約三○分間投入したる後空気中に放冷し、歪取り、反り合せ、第二仕上げ、研ぎ等各分業で加工した。 (see:http://ohmura-study.net/223.html) Unfortunately, my translation is in French so I can only recommend you to use online translator deepl.com to translate this quote. @Jean-Pierre (je me permets de répondre en anglais, afin que tout le monde comprenne): What you say, as many other in this chat, is interesting. As your explanations seem to be founded on sources, can you please mention them? That way everybody may consult the hole text.
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#16 16k

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Posted 01 July 2020 - 06:48 PM

Ah! Good question. I have gathered more than 100 pages about Mantetsu for varying sources: Ohmura, this site, everything I can find. There is a lot of redundancy and I’m still trying to make sense of some translations I have from the Japanese and that don’t seem to mean anything in English, so, I know I’ve read it, probably in Ohmura, but where?...


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#17 Bruce Pennington

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Posted 01 July 2020 - 07:56 PM

Ah! Good question. I have gathered more than 100 pages about Mantetsu for varying sources: Ohmura, this site, everything I can find. There is a lot of redundancy and I’m still trying to make sense of some translations I have from the Japanese and that don’t seem to mean anything in English, so, I know I’ve read it, probably in Ohmura, but where?...


Yes, your last post is from the Ohmura site.
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#18 16k

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Posted 01 July 2020 - 08:34 PM

I’m not so sure Bruce. Yes, it is in the part of the article I gave you, but it is one of several things I added and borrowed from another source I think. Then again, I may have added it from another source and yet it could be in one of his articles I have overlooked. Actually, I wonder if this wasn’t part of a post by Kipu or Banbangsan.


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#19 DoTanuki yokai

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Posted 06 July 2020 - 04:33 PM

From "Modern Japanese swords and swordsmiths"  i know the Japanese imported old railroads from europe that already had something like a hada visible in the steel and it was used for showato in seki. I dont know if there could be some connections ?

Maybe also from the book im not sure is mentioned that in yasukuni the smiths should make suguha hamon because its simply faster done. This could be the reason for the suguha for the koa isshin too.


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Posted 06 July 2020 - 04:47 PM

Christian,

 

So far, everything that has been found seems to show that the conception that railroad tracks were used was wrong. It seems this idea was born from the name Mantetsu itself and because, among other things, they managed the railways in Manchuria. However, some swordsmiths seem to have used railroad tracks to create artificial Hada. But all those I’ve seen seem to create a very conspicuous Hada, very different from Mantetsu swords where the most prominent are still very subtle.

 

As for the Suguha Hamon, I don’t know. I’ve always read it was the most hazardous one to make as the stress during yakiire is the one most likely to produce hagiri. Maybe they had found a way, through a constant temperature, to overcome this hazard.


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#21 Dave R

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Posted 06 July 2020 - 05:22 PM

 Railtrack blades are well documented, but are more something done in Seki, rather than by Mantetsu.

 

Regarding Sugaha Hamon, I have not seen anything about problems during yakiiri before, but that traditionaly it made for a tougher sword, interestingly modern neutron imaging has confirmed this....

 

http://www.militaria...apanese-swords/

 

 

 

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#22 16k

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Posted 06 July 2020 - 05:28 PM

Suguha is more dangerous to perform because a Hamon like Choji has more ashi to release the stress points during yakiire. At least, that is what I have come to understand. Maybe I got it wrong.


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#23 Raphael Pauli

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Posted 06 July 2020 - 06:38 PM

Hello Dave, Thanks for the link you posted. I'm going read that carefully, since it seems to provide an interesting hint on the reason of the hamon-shape of Koua isshin tou. Regarding the book Modern Japanese Swords and Swordsmiths that you and Christian mentionned, especially the part you posted, these are informations I'd really take carefully because - as I can see - the authors don't mention any source. This could lead to such statements as the one we find on Mantetsu tou in Fuller & Gregory, Military Swords of Japan 1968-1945, The Bath Press: 1997, p. 78: "These blades were forged by inserting [...] into a Manchurian-made or western steel (often scrap railway lines)." Ohmura, based on original sources, seems clearly to say that this is wrong... My point is: if the methodology of the authors is bad, the informations can't be checked but just be taken for granted.
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#24 Dave R

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Posted 06 July 2020 - 06:57 PM

 Regarding the Seki forges, the writer references an individual Fujiwara Kanafusa aka Kato Takao who worked there. The problem with orginal research is that you cannot reference another work!

 

 

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