Yari Construction?

[Aiden CC]

I recently have become somewhat interested in yari (as a collector and a bladesmith) and have noticed while looking at pictures of blades in decent polish that it seems like the nakago (if that is the right word) and the base of the blade appears to be made from a coarser material. You can see it fairly well in this photo from eBay:

 

 

I have seen something like this on other examples, to me it looks a lot like the slag inclusions I have seen in old puddled wrought iron (though this would be bloomery iron if that's what it is). Does anyone know how these blades were welded up before final forging? It seems almost analogous to the wrought iron socket welded on to European spear blades, but from images it's very hard to tell where the weld line might be. Since the blade is double sided and shows a hamon on all three faces, it seems like it would be hard to wrap hardenable steel around a core, so my best guess would be a lap weld somewhere, but it's hard to pick out. 

 

Any insights would be appreciated,

 

Aiden CC

[ROKUJURO]

Hi Aiden,

 

welcome to the NMB!

 

There was no "coarse" material used in the construction. If you look at many YARI, you will see that some areas on the surface are polished differently. This may make them perhaps look like another steel. The basic steel used in these weapons is TAMAHAGANE, a bloomery steel which can have different contents of carbon. Usually, different grades are used in a blade depending on the requirements in the use.

 

Japanese smiths will always carefully refine their steel so you will not find slag inclusions in good blades.                 i 

[Baba Yaga]

1 hour ago, Aiden CC said:

I recently have become somewhat interested in yari (as a collector and a bladesmith) and have noticed while looking at pictures of blades in decent polish that it seems like the nakago (if that is the right word) and the base of the blade appears to be made from a coarser material. You can see it fairly well in this photo from eBay:

 

 

I have seen something like this on other examples, to me it looks a lot like the slag inclusions I have seen in old puddled wrought iron (though this would be bloomery iron if that's what it is). Does anyone know how these blades were welded up before final forging? It seems almost analogous to the wrought iron socket welded on to European spear blades, but from images it's very hard to tell where the weld line might be. Since the blade is double sided and shows a hamon on all three faces, it seems like it would be hard to wrap hardenable steel around a core, so my best guess would be a lap weld somewhere, but it's hard to pick out. 

 

Any insights would be appreciated,

 

Aiden CC

 

 

[Baba Yaga]

11 minutes ago, Baba Yaga said:

 

 

Are you interested in what looks like the soft core underneath the polished hard core finish? 

[Aiden CC]

17 minutes ago, Baba Yaga said:

Are you interested in what looks like the soft core underneath the polished hard core finish? 

Essentially yes, and also how the pieces might be welded to get a “core” when you want the jacket of high carbon steel to go all the way around. 
 

Jean, that makes sense. I was confused as to why a piece of steel that looked so well refined would be welded to something that looked much less so. Do you think the black specs are corrosion that happed after polishing? I don’t know how they would be a polishing artifact unless maybe some chemical etching process was employed, which I have found to attack and darken weld lines in my own shop-made steel (sort of like orishigane). That’s the main feature that seemed like it could indicate a less refined material to me as silica inclusions from the smelt take a number of folds to refine/expel. 

[Baba Yaga]

7 minutes ago, Aiden CC said:

Essentially yes, and also how the pieces might be welded to get a “core” when you want the jacket of high carbon steel to go all the way around. 
 

Jean, that makes sense. I was confused as to why a piece of steel that looked so well refined would be welded to something that looked much less so. Do you think the black specs are corrosion that happed after polishing? I don’t know how they would be a polishing artifact unless maybe some chemical etching process was employed, which I have found to attack and darken weld lines in my own shop-made steel (sort of like orishigane). That’s the main feature that seemed like it could indicate a less refined material to me as silica inclusions from the smelt take a number of folds to refine/expel. 

 

Check out a few youtube videos on TAMAHAGANE and sword forging. That may put you into the right direction. 

I think what you're seeing is what we call Kizo but really can't tell because of photos http://www.japaneseswordindex.com/kizu.htm

Here in another on laminations http://www.japaneseswordindex.com/laminate.htm

Read that, so we can understand each other more and get back with any questions. 

[Bugyotsuji]

I think it’s a bit like Kintarō amé or Edinburgh Rock, all extruded and forged from the same material with the pointy end given extra treatment perhaps. (No ‘welding’ anywhere.)

 

Here is a cross-section of a Yari blade, so consistent inside that I cannot see any evidence of sword-blade cross-section construction. Just the faintest whorl perhaps?

 

 

 

 

 

 

PS A long kerakubi neck section is oft said to be an indication of an earlier age.

[Baba Yaga]

16 minutes ago, Bugyotsuji said:

I think it’s a bit like Kintarō amé or Edinburgh Rock, all extruded and forged from the same material with the pointy end given extra treatment perhaps. (No ‘welding’ anywhere.)

 

Here is a cross-section of a Yari blade, so consistent inside that I cannot see any evidence of sword-blade cross-section construction. Just the faintest whorl perhaps?

 

 

 

 

 

 

PS A long kerakubi neck section is oft said to be an indication of an earlier age.

 

Welding is an acronym for bonding AKA melting together. He doesn't mean  Mig tig gas stick plasma.  I hope! 

[Aiden CC]

@Bugyotsuji , that cross section is very helpful, thank you! Do you think the nakago has the same cross section? It seems like a lot of high carbon material to bury inside of the shaft, but there are also a lot  of “luxury” features on nihonto in general so I guess I wouldn’t be surprised. Lap-welding (in a forge) of low carbon material was common for tangs on European swords all the way up toIt the 18th/19th century, IIRC, for material conservation and increased toughness.
 

@Baba Yaga, you are correct about what I mean by welding. I came to nihonto appreciation through bladesmithing, and in that world “welding” primarily refers to bonding two surfaces by forging, so both folding of tamahagane and final construction (kobuse, etc) would be called welding. My day job involves the metallurgy of modern steels (mostly automotive sheet steels), so some of my terminology likely comes from there as well. I have been making my own hearth steel (orishigane in Japan) for the past few years and have made a few tanto, and am now thinking of making a yari. I have made a few hundred other knives but am fairly new to Japanese style swords.
 

As for yari construction, my question is about the blade and how it attaches to the nakago. From the very helpful cross section above it looks like a Maru, Makuri, or maybe Kobuse turned on it’s “side”. The change in color towards the center could also be a gradient in hardening/carbon content from the surface to the interior unrelated to the original construction of the blade. When I talk about a lap weld, I’m talking about a joint like this: 

 

The overlap would be treated more elegantly (scarfed edges etc) to make a good forge weld, but this is the basic principle. This type of joint lets the high hardness material be towards the point and the high toughness material be towards the handle/shaft. European spears (and some yari it seems) use a conical socket with the head inserted and welded and I was wondering if yari had something analogous with a hard blade welded onto a tough nakago. 
 

 

[Brian]

Very probable that when they are forging the yari, the nakago and part of the kerakubi are less refined steel that is forge welded to the better tamahagane used for the tip.
They wouldn't have good tamahagane all the way to the back of the nakago.

[Shugyosha]

As Piers says, the longer kerikubi suggests a koto period spear. Given that spears were in the nature of battlefield consumables and largely supplied to disposable soldiers,  it’s not unlikely that best quality materials weren’t used in (the entirety) of its manufacture. 

[Baba Yaga]

10 hours ago, Aiden CC said:

@Bugyotsuji , that cross section is very helpful, thank you! Do you think the nakago has the same cross section? It seems like a lot of high carbon material to bury inside of the shaft, but there are also a lot  of “luxury” features on nihonto in general so I guess I wouldn’t be surprised. Lap-welding (in a forge) of low carbon material was common for tangs on European swords all the way up toIt the 18th/19th century, IIRC, for material conservation and increased toughness.
 

@Baba Yaga, you are correct about what I mean by welding. I came to nihonto appreciation through bladesmithing, and in that world “welding” primarily refers to bonding two surfaces by forging, so both folding of tamahagane and final construction (kobuse, etc) would be called welding. My day job involves the metallurgy of modern steels (mostly automotive sheet steels), so some of my terminology likely comes from there as well. I have been making my own hearth steel (orishigane in Japan) for the past few years and have made a few tanto, and am now thinking of making a yari. I have made a few hundred other knives but am fairly new to Japanese style swords.
 

As for yari construction, my question is about the blade and how it attaches to the nakago. From the very helpful cross section above it looks like a Maru, Makuri, or maybe Kobuse turned on it’s “side”. The change in color towards the center could also be a gradient in hardening/carbon content from the surface to the interior unrelated to the original construction of the blade. When I talk about a lap weld, I’m talking about a joint like this: 

 

The overlap would be treated more elegantly (scarfed edges etc) to make a good forge weld, but this is the basic principle. This type of joint lets the high hardness material be towards the point and the high toughness material be towards the handle/shaft. European spears (and some yari it seems) use a conical socket with the head inserted and welded and I was wondering if yari had something analogous with a hard blade welded onto a tough nakago. 
 

 

you are correct about what I mean by welding. I came to nihonto appreciation through bladesmithing, and in that world “welding” primarily refers to bonding two surfaces by forging, so both folding of tamahagane and final construction (kobuse, etc) would be called welding.

 

I understood what you were speaking of. I have been involved with fabrication at a very high degree. I'm glad to see you've done the research and understand the processes. 

[IBot]

Prior to the move of the Royal Armouries collection from the Tower of London to Leeds, a yari blade fell behind some boxes in a store room and was not discovered for several years, Being next to te Thames, the room was rather damp and the blade suffered rusting, justifying it being sacrificed for metallurgic analysis. Like that shown above, the blade proved to be made of one homogenous piece of steel. It had however been hardened at the point and down each edge. 

Ian Bottomley

[Aiden CC]

Thank you everyone for the replies, there's a lot of helpful information here. It makes sense that for yari, especially during periods with more conflict, might be made with efficient use of material and larger scale production in mind since, in general, a spear is a more dedicated battlefield weapon and less effective status symbol than a sword since it can't be worn around town. It also makes a weapon 6+ ft long with half the steel of a much shorter sword.

 

Thank you Piers for the point about the kerikubi, I definitely need to study this type of blade more and information about yari seems to be much less abundant than it is for swords. If I recall, Koto swords were often thicker and more "heavily built" in general, could this be part of the same trend, connected to an era with more conflict than others?

 

The cross section being homogenous makes sense to me, it would be tricky to make a composite that had hard steel in the right places without poorly placed weld lines. The only thing it seems could work would be something like a ni-mai kitchen knife, but sharpened on both edges. This would, however, put a weld line parallel to the hamon which seems like it could be unfavorable for aesthetic (and maybe structural) reasons. 

[Bazza]

I'm sure I once read somewhere that Oda Nobunaga reputedly said, referring to his army, that he would rather have 100 yari in good hands than one very expensive sword (except for his own, of course).  I guess this is military 'value for money'!

 

BaZZa.

[Ken-Hawaii]

Aiden, see if this helps:

 

[IBot]

Aiden,  There is an interesting point to be made about the problems in hardening of yari. Like a ken blade, the fact that a yari has a hamon down both sides causes considerable contraction stresses during hardening. When you consider that the stresses generated in hardening a sword are sufficient to cause the blade to curve, the forces generated on both edges of a yari will act so as to cause the point to break off. This could obiously be reduced by quenching from a lower temperature, but I have seen a jumonji blade where the hardening of the central blade terminated about 5cm from the point  and then started again about 2cm further down and continued along the side blades. I can only think this technique employed to reduced the stressing on the point itself.

Ian Bottomley

[Baba Yaga]

The Yari , Ken and other PoleArms were the weapon of choice. I used to see a lot of them years back, but not anymore. They should of outnumbered swords by far. 

The Yanone was another high volume item I rarely see anymore.  I'm quite proficient with a recurve and used to shot at the Archery club, now I walk out my door. 

I "guess" the Yari is like the $2 bill and everyone holds onto them. 

[Bazza]

3 hours ago, IBot said:

Aiden,  There is an interesting point to be made about the problems in hardening of yari. Like a ken blade, the fact that a yari has a hamon down both sides causes considerable contraction stresses during hardening. When you consider that the stresses generated in hardening a sword are sufficient to cause the blade to curve, the forces generated on both edges of a yari will act so as to cause the point to break off. This could obiously be reduced by quenching from a lower temperature, but I have seen a jumonji blade where the hardening of the central blade terminated about 5cm from the point  and then started again about 2cm further down and continued along the side blades. I can only think this technique employed to reduced the stressing on the point itself.

Ian Bottomley

I have mentioned before about seeing an article in my time about "exploding yari",  The gist was exactly as IanB describes, but went further describing (a?) yari where the point had separated 'explosively' from the body of the point due to the stresses.  I have handled a sankaku yari by SAGAMI no KAMI MASATSUNE where the slight curve was  toward the flat side of the body.  Wish I could remember where I read that article with photos...

 

BaZZa.

[Bugyotsuji]

Well, all my Yari have moved on to greener pastures, *save one. Perhaps there has been a sea-change, after years of being cheap, and the poor cousin to swords. (Except for those famous few, the named blades!) Perhaps demand has indeed increased.
 

*Oh, and the one I cut in half for this thread… but only received one ‘like’ for. Maybe I can weld it back together again.