[JohnKSa]

I was watching an old NOVA program on the Samurai sword online yesterday and saw the swordmaker insert the low-carbon steel inside the high-carbon exterior to form the lamination the Samurai sword is famous for.

It didn't hit me until today that most laminated steel these days is formed in just the opposite manner. The tougher steel is on the outside and the harder steel on the inside. Given that the Samurai style lamination came first, I'll call the new style "reverse lamination".

The only advantage I can see to reverse lamination is that you can sharpen the blade until there's just a sliver left and you'll still have hard steel on the edge. A traditional laminated blade can only be sharpened so many times before the tougher steel inside will be exposed and the edge-holding capability is reduced.

Is that really the reason for using the "reverse" lamination approach, or are there other things I'm missing?

[M-Cameron]

ide imagine it would be due to how the 2 blades are used...

on a samurai sword, you have a blade that is subject to hard impacts but still needs to be sharp.....thus the hard outside layer for edge and soft internal layer for cushion.

on a knife, you really only need a knife that will easily take an edge, but still be rigid enough to not deform under use......thus the softer layer outside for easy sharpening, and a harder internal layer for support.


i dunno, just my guess...

[hso]

Different methods of construction were used.
http://encycl.opentopia.com/enimages/17/16860/Katana_core_diagram.png

[JohnKSa]

Still, with one possible exception, all of the designs put the bulk of the hardened steel outside and the tougher,softer steel inside--just the opposite of what we see in laminated steel knives today.

Are there reasons other than extending the life of a knife that is sharpened frequently that drove current laminated steel knives to reverse the lamination?

[hso]

This is from my favorite Japanese sword site.
http://home.earthlink.net/~steinrl/laminate.htm
http://home.earthlink.net/~steinrl/lamin/keycode.gif
http://home.earthlink.net/~steinrl/lamin/maru.gifhttp://home.earthlink.net/~steinrl/lamin/kobuse.gifhttp://home.earthlink.net/~steinrl/lamin/sanmai.gif
http://home.earthlink.net/~steinrl/lamin/soshu.gifhttp://home.earthlink.net/~steinrl/lamin/makuri.gifhttp://home.earthlink.net/~steinrl/lamin/wariha.gifhttp://home.earthlink.net/~steinrl/lamin/orikae.gifhttp://home.earthlink.net/~steinrl/lamin/gomai.gifhttp://home.earthlink.net/~steinrl/lamin/soshu.gif

[ugaarguy]

Still, with one possible exception, all of the designs put the bulk of the hardened steel outside and the tougher,softer steel inside--just the opposite of what we see in laminated steel knives today.
With both styles the harder steel is on the edge, and softer steel is at the spine. The form is different, but the function is the same.

[hso]

In forging, in some cases it is easier to forge a "taco" of hard steel around a soft core instead of trying for forge weld 2 pieces of hard steel around a hard core and getting the edge for weld properly.

Remember that there were several ways in which steels of different hardness were forge welded to form a composite blade structure. The goal was all the same, a hard edges blade with a softer body/spine.

[JohnKSa]

In forging, in some cases it is easier to forge a "taco" of hard steel around a soft core instead of trying for forge weld 2 pieces of hard steel around a hard core and getting the edge for weld properly.I don't do forging, so I don't have a feel for such things. So would it be difficult to do a taco of soft steel around a hard core--with the hard core protruding from the edge side? That would have given an effect similar to modern laminated steel.

Also, some of those designs are quite intricate--requiring a lot of complicated sandwiching--and yet they all seem to favor soft inside, hard outside even though some of them are easily more complicated to implement than a modern laminated blade.

Maybe that's just what worked so they never tried anything different?The form is different, but the function is the same.From a cutting standpoint with a new or relatively fresh blade, yes. From a sharpening standpoint--especially over time, the hard core inside means the functionality is retained no matter how many times you sharpen it.

What I wonder is if there are other benefits/disadvantages to one approach over the other in terms of functionality.

[9mmepiphany]

I'm almost reluctant to post this as my knowledge of blade composition is generously referred to as limited.

However, I am getting the impression that you aren't considering the full function of the blade in use.

The hard metal is to allow it to cut, the soft metal is to give it flexibility so it doesn't break during a cutting stroke. The sides of the blade are used to parry and deflect slashes, a harder metal is more likely to allow the other blade to slide off...as opposed to the soft filet they used to put on the spine of the bowie to catch the other blade

[CWL]

I was watching an old NOVA program on the Samurai sword online yesterday and saw the swordmaker insert the low-carbon steel inside the high-carbon exterior to form the lamination the Samurai sword is famous for.

You heard a narration, right?

My guess is that if it was a narration you heard, there was a mistake made during the translation. Don't expect people who do translation or who work the recording to know anything about Japanese sword manufacture.

[JohnKSa]

My guess is that if it was a narration you heard, there was a mistake made during the translation.Not following you.

There doesn't seem to be any debate that the general approach of the Samurai sword makers was to put a tougher/softer core inside a harder, high-carbon "sheath".The sides of the blade are used to parry and deflect slashes, a harder metal is more likely to allow the other blade to slide off...as opposed to the soft filet they used to put on the spine of the bowie to catch the other bladeVery good! I hadn't thought of that, but it makes sense.

[conw]

Aren't lots of laminates now used for corrosion resistance around a harder less resistant steel?

[hso]

In knives, the use of more corrosion resistant steels as an outer layer is more of a way to use a less expensive material that is more corrosion resistant than a more expensive cutlery material.

[Newb223]

I'm almost reluctant to post this as my knowledge of blade composition is generously referred to as limited.

However, I am getting the impression that you aren't considering the full function of the blade in use.

The hard metal is to allow it to cut, the soft metal is to give it flexibility so it doesn't break during a cutting stroke. The sides of the blade are used to parry and deflect slashes, a harder metal is more likely to allow the other blade to slide off...as opposed to the soft filet they used to put on the spine of the bowie to catch the other blade
This is exactly what my understanding has always been with Samurai Swords.

[CWL]

JohnKSa,

Did you hear this description directly from the swordsmith's mouth, or was there an English translation that you heard/read?

I'm just saying that it may be a simple case of improper translation. Happens all the time.

Could you visually tell which steel was which in the film?

[ugaarguy]

CWL, why do you keep arguing that he heard it or saw it wrong? HSO has posted images and links confirming that the lamination JohnKSa describes is one of several common methods used in making Samurai swords.

[CWL]

Strange, I wasn't arguing anything, I was just asking to understand what JohnKSa saw & heard.

While those lamination techniques are all historically accurate, I was not aware that any living Japanese swordmakers still used the lesser techniques such as the Kobuse. This was a technique common during times of war when it was necessary to equip many conscripts with cheap steel, so inferior swords were "good enough" for them.

In post WWII Japan, anyone who could afford to consign a sword from one of the Japanese "Living Treasures", would not expect a simply laminated sword, but would expect a properly folded sword using the best grade steels. Any living swordmaker in Japan wouldn't be interested in making one of these simple 3-layer swords either, unless it was to recreate the technique for historical study.

[ApacheCoTodd]

I'm almost reluctant to post this as my knowledge of blade composition is generously referred to as limited.

However, I am getting the impression that you aren't considering the full function of the blade in use.

The hard metal is to allow it to cut, the soft metal is to give it flexibility so it doesn't break during a cutting stroke. The sides of the blade are used to parry and deflect slashes, a harder metal is more likely to allow the other blade to slide off...as opposed to the soft filet they used to put on the spine of the bowie to catch the other blade
Samurai-shmamurai... I'm fascinated by the notion of deliberately soft metal to foul another "fighter's" knife. Gotsta re-visit that "Bowie" legend now.

Then there're those 9 different blade compositions in post #5... Never knew the options were so involved. Do those represent trends separated over time or build preferences that a maker or wielder might prefer and chose over others available at the same time.

[JohnKSa]

In post WWII Japan, anyone who could afford to consign a sword from one of the Japanese "Living Treasures", would not expect a simply laminated sword, but would expect a properly folded sword using the best grade steels. Any living swordmaker in Japan wouldn't be interested in making one of these simple 3-layer swords either, unless it was to recreate the technique for historical study.It was an hour long show and I summarized it a bit for my opening post.

The high-carbon harder outer sheath was made from folded steel. It's possible that the softer inner core was as well--they didn't specifically say one way or the other.

So you are correct. It wasn't simply a laminated sword, it was a laminated sword made from (or at least mostly made from) folded steel.

I assume that the same applies to the designs in hso's posts. While the figures represent only the lamination used in the construction, I suspect that the appropriate portions of the laminates are made from folded steel.

[hso]

Folding steel had more to do with homogenizing the materials more than anything else.

Ancient steel making methods produced a mix of steels that had to be sorted. It was not the clean precise methods used today. That meant the steel had to be sorted and then high and low and no and too high (gross simplifications) steels then had to be combined to produce a finished steel with the properties for the implement being made. Need a hammer head, combine different proportions of A and B and C and D to get the right properties. Need a hoe or knife, change the proportions to get a steel suitable for the hoe or knife blades. Much like making a cake, muffins or pancakes you take the recipe components in the right proportions and mix them the right way for different products. For an ancient smith that means your bowl and spoon are a forge and anvil and hammers. Beating the mixture takes on a very different aspect. :D Need a katana? Now you're making fine pastry where you not only mix your components to need different steels to make a composite structure that has hardness and flex so you put hard blade steel in part of the blade and flexible softer steel in the core. It also saves on your highly valuable edge steel to use it sparingly by forge welding it with less valuable steel (kinda like we see today with "super steels" laminated with far less expensive steels).

The objective is to get a smooth/homogenous mixture with the right properties where we want them whether it is a pastry or steel. You have to beat the materials to get it.;)

[heron]

Folding steel had more to do with homogenizing the materials more than anything else. That, and removing impurities. If something like a grain of sand got into the batch -- not unlikely with their methods -- the only way they had to remove it was to beat the piece thin and knock the slag off of it, fold it over and repeat the process. I think this process may also have helped align the grain of the steel.

Modern processes keep things much cleaner and more uniform.

[JohnKSa]

I'm fascinated by the notion of deliberately soft metal to foul another "fighter's" knife. Gotsta re-visit that "Bowie" legend now.The idea was, according to what I've read that either Bowie or the knifemaker didn't want the blade glancing off the guard (and possibly into part of the holder) and that is why it was made of a softer metal that would catch the edge and prevent a glancing blow from causing injury.

I don't recall reading that the original Bowie had a soft spine, but it's possible, I guess, and it would make sense.