construction

[paulb]

The current thread on Shinsakuto vs Iato has generated a number of different sub-topics. I am concerned that because of the various directions and tangents being taken in that thread that some important discussions and views as well as the opportunity to explore some of these points might be lost. Because of this I have started a new thread where I hope we the construction element begun in the Shinsakuto debate can be further explored. if the moderators would prefer to keep this in the original plaese feel free to move it.

 

Chris Bowen said

One piece construction, if well forged of good materials and properly heat treated can produce an excellent blade.

 

 

John S I think suggested that the ressilience and toughness of a blade was the result of combining hard and soft steel in the jigane and not because of the presence of a soft core (John if I have misunderstood please correct me)

 

These are important ideas to explore further.

 

It has been previously stated that work of the kyo smiths, Sanjo, Awataguchi and Rai together with ko-Bizen and ko-Ichimonji produced swords in single piece construction up until the mid Kamakura period. I think this is a generally accepted point of view.

In the recently posted article I put together about the Awataguchi School I mentioned that I thought the sword in question was made in this manner. I have seen a number of Awataguchi blades (not many, but some) in varying states of ware. Regardless of the amount of metal lost none showed any evidence of core steel showing through. Admittedly most of these were tanto so a single piece construction might be expected. But even the few daito examples showed no tiredness.

Kyo blades are regarded by many as amongst the best ever produced. One of Munchika's swords has been counted amongst the three greatest swords made for more than 450 years.

When you look at early Kyo work it bears little or no resemblance to anything else. It is beautiful but so are many other works. What stands out is the incredible quality of the material, the tightness of the forging and the uniformity of the nie both ji-nie and nie within the hamon resulting from skillful hardening. Nothing else looks like it.

So if it is possible to produce such high quality work in single piece construction what were the motives to change? Can I suggest the following:

1. To make acceptable swords in one piece construction requires excellent material great skill and time. The resulting work would be expensive

2. If demand outstripped supply shortcuts were required. Was it less demanding to produce a blade with a lower grade core? Is a blade made in this way more forgiving of lesser skill?

3. Was it purely a commercial decision. It would be cheaper to wrap a lower cost material with a layer of the more expensive jigane.

4. Alternatively did the change in methods of fighting expose weakness in single piece construction which resulted in experimenting with multi piece construction in an attempt to overcome identified weaknesses?

 

Possibly it was simply a fact that there was insufficient production of high enough quality steel to meet demand and too few good smiths to meet the demand using this very difficult technique.

The basic question is "does multi piece construction create a better product?"

I would suggest that if a single piece blade is produced by a top smith in good material the answer is probably no. Once the quality of either mateerial or smith falls below this top tire multi piece manufature overcomes some of the resultant short comings.

I would appreciate others thoughts on this

Best Regards

paul

[runagmc]

In my opinion, calling the early koto "single piece construction" could be misleading. Instead of a construction of soft core and hard edge, we are talking about a method where the different quality steels were folded together in layers and then the billet was drawn out to length, making the whole sword a layering of softer and harder steels. Which is better? I have no idea, but some seem to indicate the "single piece construction" is, at least when done the way some of the great koto kaji did it.

 

Also, I think it's hard to make nice neat categories, specially for earlier swords, since the methods of material production and sword construction were only limited by the different smith's imaginations or ideas. We have to remember, there have been thousands of smiths who all took different paths, and no doubt tried many different things. Many of our questions will never be fully answerable, leaving things open to opinion and specualtion.

[Eric H]

There is a theory that in Koto times the Tatara operation resulted in low quality tamahagane and it depended entirely on the swordsmiths skill to manage that material to make a sword of high quality, but time consuming. This is in full accordance with the maru-gitae technique formerly specified by Chris B. and Adam L., proven with the sectioned micrograph from a blade by Rai Kunitoshi (there are nenki from 1289-1321).

 

One historical record states that advanced steelmaking processes were employed on a large scale beginning in the Oei era (1394-1428) allowing an increased production of swords. During the late Muromachi period, older methods of swordmaking (maru-gitae?) were abandoned and at the same time new methods of sword making were invented, such as ko-buse and makuri. But why?

 

It is said, that after the Muromachi period a great progress in the manufacture of iron was accomplished, and the smith‘s were able to produce high quality steel. Shinto smiths profited by the improvements in the transportation system having a better access to steel of consistently high quality. It is also said, that a hard type of tamahagane, mass produced, appeared in Keicho (1596-1615).

 

It is perhaps this heightening of the quality of tamahagane, and supposedly at the same time increasing cost of this higher quality tamahagane, that the methods of ko-buse and makuri and other lamination techniques were favored.

 

Interestingliy Suishinshi Masahide initiated a move back to a revival of Koto like swords...did this include the forging in maru-gitae? Naotane has been mentioned.

 

1) yes

2) ambivalent

3) I think yes

4) Swords have been tested in Shinto and Shinshinto time by experienced swordsmen. I refer to the list by Yamada Asaemon and others. Koto swords were tested, if at all rarely, their effectiveness, perhaps superiority, in combat has been taken as proven.

 

Eric

[cabowen]

As said in the other thread, it was time consuming for a smith to refine the steel through forging. In addition, there is a considerable loss of material. Early smiths had to do all of this refining on their own. It was both time consuming and costly. Later, tamahagane came to be made in large quantities, centrally, and distributed to smiths. It was still an expensive material.

 

Using relatively unrefined steel in the core and much less (quantity-wise) highly refined steel for the skin and edge undoubtedly saved both time and material (money).

 

As far as laminating soft and hard steels together, please review the information I posted regarding carbon migration. After 8-10 foldings, the layers would be thin enough that the carbon would equalize between the layers and you would have the same hardness throughout.

 

Koto blades are usually though to be softer than later blades. Shinto and shinshinto are often said to be brittle because of the higher carbon content and resulting hardness.

[runagmc]

http://www.k3.dion.ne.jp/~j-gunto/gunto_147.htm

 

Chris, I thought about the effect of carbon diffusion in marugitae as well, but if you read the Nagayama article, he repeatedly talks about steels of different qualities being folded together to form a tougher sword. I don't know if carbon content is the only difference or not. Mabey they had some way of stopping a complete homogenization. Or mabey Nagayama has a romantic opinion of these older works and his ideas aren't completely supported by fact.

There is the style "Hitatsura of a Sosyu style" in the Period of the Northern and Southern Dynasties. That is the Hamon which a ground metal has a device and was so produced. The steel with which character differs is mixed variously and there is also a portion in which hardening is not contained in the edge. Even if the blade is whole hardening , it does not interfere.

A Kokan Nagayama polisher says, "Therefore a Ko-to is made by the childish sword making using the steel materials which mixed different steel, consequently the beauty of the grain of a blade can be expressed".

The hardness of the edge of a Ko-to is almost the same as the core steel of a Shin-to.Although the quality of the blade of a Ko-to was soft, there was a toughness. Compared with the Ko-to, the Shin-to was hard, the Shin-Shin-to became still harder, and the grain of the blade became monotonous with minerals.

The beauty and the excellent performance (it is pliant and strong) of a blade was realized in combining steel materials of a different kind.

The combination forging of the hard and soft steel which is in others in some numbers excelled this in practical use.

Steel materials of a different kind are combined skillfully, and it also turns out in the battle that the old noted sword of the one-piece forging which elaborated the hardening was excellent. The spring sword of an one-piece forging was excellent in the arms performance with the toughness and hardness of steel materials.

[cabowen]

Most likely hard and soft steels were indeed combined. A smith I know often does this and told me it was a soshu technique. We know now from modern analysis that after a certain number of foldings that the carbon content tends to homogenize....Perhaps the hanten of WWII was an effort to retain some of the hard/soft qualities of the steels to make a more pliable blade....

[ROKUJURO]

....1. To make acceptable swords in one piece construction requires excellent material, great skill and time. The resulting work would be expensive

2. If demand outstripped supply shortcuts were required. Was it less demanding to produce a blade with a lower grade core? Is a blade made in this way more forgiving of lesser skill?

3. Was it purely a commercial decision? It would be cheaper to wrap a lower cost material with a layer of the more expensive jigane......

As we already stated in the TSUBA section and as Chris has pointed out above, construction, carbon migration and the potential hardness of steel depends of it's carbon content. Heating steel to a temperature above 900°C in an oxidizing atmosphere leads to a loss of carbon on it's surface. At the same temperature carbon will start to migrate within the steel package to layers with less carbon content. As we said, time of exposure, temperature, and thickness of layers are the facts to count with. (In a specially created, highly carbon saturated atmosphere steel can as well increase it's carbon content which was a method of old times to make steel from soft malleable iron). In KATANA the carbon content in the cutting edge is often found to be about 0.7 to 0.8 % while other sources mention as much as 1% C.

 

Theoretically, a sandwich-construction with high-quality KAWAGANE (refined with up to 15 foldings/weldings) and a SHINGANE core (with about 10 foldings) has the same properties as a mono-material of the same KAWAGANE quality. The core in such a construction is - theoretically - 'passive' when the blade is being used in slashing while the KAWAGANE skin is 'active' and has to withstand all material stress. But it is evident that this depends on the internal quality of the blade, eg. even layers on both sides and no flaws.

 

In practice the mono-material is suitable for long blades

 

if it is perfectly homogenous with no voids or uneven carbon dispersion, and

if it is differentially hardened with a hard edge (with about 60 HRC found on many blades) and a soft back (roughly 50 HRC)

 

The sandwich construction requires the same meticulous process and hard work with the advance of less high-quality material being needed in the KAWAGANE. Nevertheless the 'marriage' of core steel and skin steel was always critical (depending on the construction of the blade) as it was easy to close in small particles of carbon or to produce tiny gaps in places where the welding was imperfect, causing FUKURE at later stages of polishing.

 

The quality of both constructions would depend on a perfect hardening process.

 

If we compare these Japanese techniques with those in early Europe we find fire-welded blades in Celtic swords of 500 B.C. as a necessary process to homogenize the steel. We do not know if these blades were etched or specially polished as to produce a Damascus pattern but the early Vikings (500 to 1000 AD) started their sword forging with a Damascus-type of steel. Later after 800 AD the Francs succeeded in making very good mono-material steel being as good as Damascus but proved to be less work. This made the Vikings import large amounts of sword blades from the Francs.

 

Going back to Japan we hear about many inferior blades in times of war which were mass-produced under unfavorable conditions or by less qualified smiths. Even today many swords with KIZU are on the market which would not have withstood a severe blow (HAGIRE!). In the same time we have very good swords being preserved to our days, and these were often made by renowned KAJI. In this context we must not forget that many SHINTO and later swords were never tested or used in combat.

 

It is evident that long blades made for slashing are very demanding in construction, but both types of construction - mono-material and composite/sandwich - could be made to the requirements of those days' warfare if the material was good enough and the skills of the smith as well.

[runagmc]

I remember reading somewhere, that in some marugitae koto, they would refine plates of harder steel to a greater degree by folding them like 10 times, and then they would make softer plates with softer material and less refining folds. Then they would forge these together into a single billet and do like 2-3 more folds. It said this process is what creates a blade with kohada and Ohada mixture, and that it was done to add a tougher quality to the sword.

 

Mabey since most of the refining would have been done before the low carbon and high carbon plates were put together, it allowed for less homogenization.

[paulb]

Gentlemen,

Thank you for the comments and ideas which help to clarify a number of points but as always stimulate more questions.

Adam,

I had not heard or thought of the combination of O-hada and ko-itame and ko mokume being the result of forging hard and soft steel in a monostructure blade. Now that you have mentioned it it seems a very credible point of view. Sanjo school work which is believed to be single piece construction exhibits this combination of O-hada and ko-itame. Awataguchi does so to a lesser extent from examples and illustrations seen.

Jean suggests the function and performance of the blade is attributable to the jigane and quenching and not effected by the presence of a softer core ( I understand that is what you are saying but please correct me if I have misunderstood) and that the level of skill required to forge a blade with a soft core is equal to that required to make a monostructure blade. If this is the case then the only reason for using a soft core is commercial. I have no doubt that many of the different stuctures and combinations tried were an attempt to improve performance. But those such as kobuse exist in far too great a quantity to be solely the result of experimentation. I would therefore suggest that such changes in construction were an attempt to a) work faster and b) to reduce cost in time and material.

The reason I am labouring this a bit is that for many years I have believed, based on what was the commonly held view in the 70s and 80s that the soft core of the blade played a major role in the Japanese swords performance, effectively absorbing impact shock when a blade struck. Because of this I could not understand how those swords which seem to be regarded as the best (Munechika, ko-ichimonji etc) could be regarded as such if they lacked this shock absorbing core. I had concluded that these blades were more a status symbol than a weapon and not intended for combat. Based on the debate here and on the earlier thread it appears this was not or at least may not have been the case.

 

Thanks again to all who have contributed to the debate.

[Eric H]

The sandwich construction requires the same meticulous process and hard work with the advance of less high-quality material being needed in the KAWAGANE

SHINGANE...

 

The smith will choose the best pieces of tamahagane when preparing the material for kawagane.

 

Eric

[ROKUJURO]

....SHINGANE...

 

The smith will choose the best pieces of tamahagane when preparing the material for kawagane.....

Did I really choose the wrong terms? I wanted to express that in composite blades less high-end material was needed for the skin steel (which I know as KAWAGANE) in comparison to mono-material blades which were made entirely from this kind of steel.

 

By the way, construction principles like these are to be found from the European Iron Ages to the end of the Middle Ages in knives and tools as well, and the reason was always to save expensive material while obtaining good cutting performance.