Hammer Mark? Bullet Deflection?

[Blazeaglory]

Could this be a one in a million hit by an old round? Does anyone know what this is? Looks like an indentation of some sort.

[Ted Tenold]

Significant "fukure".  Fukure are delamination blisters.  In Western smith terminology they're called  "cold shuts".

[DavidF]

I agree with Ted.  It's a delamination blister.

[Guest]

Hi Dwain.,

 

Here's a thread concerning Battle damage:

 

http://www.militaria.co.za/nmb/topic/23378-any-shin-gunto-with-battle-scars/

[Blazeaglory]

So it's just a big fukure? Air pocket that opened? I thought that at first but noticed that above and below it looks like the steel actually warped as well. You can see the circle that dents in and what looks like shockwaves around it. Would a air blister that big be over looked? I'm not denying(I would think it's more likely fukure than bullet dent) but it just seems really large

 

It's too bad because otherwise this would be a nice sword.

 

What are your thoughts on this? A big problem or no big deal? To me it kinda detracts from the over all beauty of this blade. Its koto as well so I was thinking cap and ball (black powder) but that's just my wild imagination lol

[Ted Tenold]

Not at all insignificant.  The buckling is because the metal is becoming foil thin, and due to it not being fused with the sub-structure, it is essentially "floating" in this region.  This could be a problem originating at the seam/juncture of the kawagane with the shingane, which in turn could mean that the kawagane is getting very thin throughout much or all of the blade.  It doesn't mean the metal will "erupt" like this throughout, but instead the shingane will just become exposed as the kawagane is worn away.  Here's an example of a cold shut between shingane and kawagane made visable in a cross section. It's the black gap seen to the left with the lighter color to the outside showing the kawagane, and the darker core metal being the shingane.

 

 

Sometimes they can be repaired with "umegane" or filler metal obtained from a donor blade.  This is essentially sword surgery, in that the metal in the region is carved out, and a small slab of replacemet metal is installed with a mechanical fit, then the sword polished either in that place or in whole.  The best of these procedures will be nearly invisible, and the least attentive are small rectangular pieces that are quite conspicuous, but do afford some measure of repair.  Blisters in the yakiba cannot be repaired with umegane as the hardened steel isn't ammenable to the process.     

[ROKUJURO]

Dwain,

a FUKURE is not an 'air-pocket', it is filled with iron oxide which prevented a tight weld in the forging process. It is a welding fault which comes to light when a blade is polished a number of times until the KAWAGANE becomes thin. Ted describes that perfectly.

The main problem is that FUKURE present a weak spot in the blade. If they break from a hard blow, it will be in this spot.   

[Blazeaglory]

  On 10/23/2018 at 5:33 PM, ROKUJURO said:

Dwain,

 

a FUKURE is not an 'air-pocket', it is filled with iron oxide which prevented a tight weld in the forging process. It is a welding fault which comes to light when a blade is polished a number of times until the KAWAGANE becomes thin. Ted describes that perfectly.

 

The main problem is that FUKURE present a weak spot in the blade. If they break from a hard blow, it will be in this spot.  

 

Oh Im Sorry. I was just quoting Nagayama from "The connoisseurs book of Japanese swords" where he says "a pocket of air that wasn't forced out during the forging process". But what does he know right? lol (I kid I kid) Hes a polisher not a metallurgist

[Blazeaglory]

  On 10/23/2018 at 4:12 PM, Ted Tenold said:

Not at all insignificant. The buckling is because the metal is becoming foil thin, and due to it not being fused with the sub-structure, it is essentially "floating" in this region. This could be a problem originating at the seam/juncture of the kawagane with the shingane, which in turn could mean that the kawagane is getting very thin throughout much or all of the blade. It doesn't mean the metal will "erupt" like this throughout, but instead the shingane will just become exposed as the kawagane is worn away. Here's an example of a cold shut between shingane and kawagane made visable in a cross section. It's the black gap seen to the left with the lighter color to the outside showing the kawagane, and the darker core metal being the shingane.

 

sample26.jpg

 

Sometimes they can be repaired with "umegane" or filler metal obtained from a donor blade. This is essentially sword surgery, in that the metal in the region is carved out, and a small slab of replacemet metal is installed with a mechanical fit, then the sword polished either in that place or in whole. The best of these procedures will be nearly invisible, and the least attentive are small rectangular pieces that are quite conspicuous, but do afford some measure of repair. Blisters in the yakiba cannot be repaired with umegane as the hardened steel isn't ammenable to the process.

Thanks! Thats pretty much what I thought it was and was trying to say but I like the way you put it better

 

And Im assuming there are different levels of Fukure? Such as, I have a couple "tired" blades that have seen some polishes and the hada looks worn away (in a similar oval shape) but doesnt look as deep as the one pictured at all(or technically what it will soon become with more polishes). On my current blades it's maybe just a tiny micro layer oval or area that you can't even feel.

 

I guess what Im thinking is that fukure could be "polsihed away" or "polished open" to reveal a very deep pit or just a thin layer correct? But it looks like it could be pretty deep to me

[Carlo Giuseppe Tacchini]

  On 10/24/2018 at 1:40 AM, Blazeaglory said:

Oh Im Sorry. I was just quoting Nagayama from "The connoisseurs book of Japanese swords" where he says "a pocket of air that wasn't forced out during the forging process". But what does he know right? lol (I kid I kid) Hes a polisher not a metallurgist

 

I wish I was a metallurgist with the metal knowledge of Nagayama-Sama...

[Blazeaglory]

  On 10/24/2018 at 4:07 PM, Carlo Giuseppe Tacchini said:

I wish I was a metallurgist with the metal knowledge of Nagayama-Sama...

Haha I agree

[ROKUJURO]

  On 10/24/2018 at 1:40 AM, Blazeaglory said:

Oh Im Sorry. I was just quoting Nagayama from "The connoisseurs book of Japanese swords" where he says "a pocket of air that wasn't forced out during the forging process". But what does he know right? lol (I kid I kid) Hes a polisher not a metallurgist

I admittedly admire the Japanese experts for their practical knowledge, derived from longterm experience. However, metallurgy is a modern 'western' science, and it often approaches the technical questions differently. In addition to that, translation difficulties can lead to expressions that are not correct. 

 

One of my daily works as a blade-smith is fire welding steel so I know what I am talking about. I could explain at length why and how FUKURE happen, but this may not be necessary in this context.   

[Blazeaglory]

  On 10/24/2018 at 6:25 PM, ROKUJURO said:

I admittedly admire the Japanese experts for their practical knowledge, derived from longterm experience. However, metallurgy is a modern 'western' science, and it often approaches the technical questions differently. In addition to that, translation difficulties can lead to expressions that are not correct.

 

One of my daily works as a blade-smith is fire welding steel so I know what I am talking about. I could explain at length why and how FUKURE happen, but this may not be necessary in this context.

No you did good in your earlier response. I was just joking with you????????

 

I understand what fukure are and how they form. I just didn't think this was one but I can see it now.