..damaged nakago...

[werner]

Hi,

 

I have a koto? katana....a bullet went through the tsuka and damaged the nakago...it hit it exactly where the hole is and cracked it - the nakago has a crack from the middle (hole) to the outside - in other words it is only attached at the bit above the hole....(I will provide a pic later) ...my question is how this can be fixed? I don't want to be killed mentioning welding...but that is the only thing that came to mind...appreciate any opinion...

 

Thanks heaps.

 

Jock

[John A Stuart]

If the sword is in imminent danger of having the nakago break I would have a professional Nihonto polisher/restorer repair it. If it is relatively stable, live with it. John

[werner]

....thanks John - just out of curiosity....how does a professional smith/polisher fix such a problem? Wouldn't that involve certain "heat-treatment" too?

 

Regards,

 

Jock

[Grey Doffin]

If it needs to be fixed, and if it can be fixed, it has to be done by someone with skill & experience. Not just a professional polisher, a classically trained polisher and probably in Japan.

Grey

[werner]

Sorry Grey,

 

That's what I meant...proffessional trained polisher in Japan....sorry for the misunderstanding..

 

Jock

[bluboxer]

Hi Jock,

I would agree with John as to having it repaired.

The only way to fix this without actual welding would be to silver solder.This is a very strong bond similar to brazing and would keep the temperature of the nakago at a relatively moderate heat. The nakago would still have to undergo some re-patination.

Is there a mei present?

If so a proper suriage can be done.As in Orikaeshi mei where the part to be removed is bent around to the opposite side.

[werner]

Hi Jock,

I would agree with John as to having it repaired.

The only way to fix this without actual welding would be to silver solder.This is a very strong bond similar to brazing and would keep the temperature of the nakago at a relatively moderate heat. The nakago would still have to undergo some re-patination.

Is there a mei present?

If so a proper suriage can be done.As in Orikaeshi mei where the part to be removed is bent around to the opposite side.

 

Hi Alan,

 

Thanks for the input....

 

- no mei on this one.

 

Just wondered about: " would keep the temperature of the nakago at a relatively moderate heat." What is the issue with temperage exposure of the nakago?

 

I understand/know about the fact that it is very destructive for the blade if it is exposed to high temperatures...but what would it do to the nakago? To my knowledge the tempering doesn't go along the nakago? Would the problem be the heat "travelling" from the nakago to the blade - other side-effects?

 

Concerning the suriage/Orikaeshi mei procedure....would that not compromise the stability of the blade - considering the mekugi ana and the crack - that leaves us with approx 65% of the original nakago strength...? As far as I'm aware of Orikaesh mei doesn't affect the nakagos strength as it mainly concerns the end of the nakago not the beginning...right?

 

Does anybody know how the proffessionals in Japan would fix such a problem? To my humble knowledge "welding" wasn't practised too much in the traditional ways.....(I could be wrong)

 

Concerning the silver solder - please correct me if I'm wrong - my understanding is that welding "binds" (using existing material) and soldering is more a "filling process" (solder as a filler) - the stability created with soldering would by far not reach the welding - right? - Just trying to get my head around this one....

 

Thanks heaps!

 

Jock

[werner]

...just found the following:

 

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (752 °F).[1] The filler metal used in the process is called solder.

 

Soldering is distinguished from brazing by use of a lower melting-temperature filler metal. The filler metals are typically alloys that have liquidus temperatures below 350°C. It is distinguished from welding by the base metals not being melted during the joining process which may or may not include the addition of a filler metal.[2] In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. Soldering is an ancient technique mentioned in the Bible[3] and there is evidence that it was employed up to 5000 years ago in Mesopotamia.[4]

 

I do understand what you mean with soldering in relation to the much lower temperatures required.....yet stability would be compromised....I really would be interested in how this would be solved by a Japanese proffessional.....

 

Jock

[Turbo storm]

As a welding engineer, I agree with the above statement.

[bluboxer]

Hey Jock,

what I meant by a "moderate heat" is a weld heat is 1000 deg. C and above.This would totally wreck the patina on a nakago.

A 280C heat ( a high tempering heat) can be contained in the nakago by submersing the blade in a cooling bath to prevent further tempering or complete removal of the ha near the nakago.

 

During shortening the hamachi and munemachi are moved further up the blade effectively keeping the nakago of a desired length.

This brings forth another question; would a modern togishi even consider doing this to an antique blade?

 

As you discovered soldering has been practiced for several thousand years and I am sure the Japanese are also adept at it. Perhaps someone with more knowledge can answer that one and whether a togishi has or would consider this process.

 

I used to make custom carbide tipped circular saw blades for special applications and the carbide tips were silver soldered onto the steel blade.this is a very strong bond and failures were rare and only occurred when a saw would encounter a nail or similar object within the wood.

Also; western bladesmiths frequently use this to attach guards and bolsters to their knives after heat treatment.

[John A Stuart]

In fact there are cases of nakago being welded on other blades. The use of copper block heat sinks and water soaked rags. Then the new nakago is filed and re-patinated. John

[Turbo storm]

In fact there are cases of nakago being welded on other blades. The use of copper block heat sinks and water soaked rags. Then the new nakago is filed and re-patinated. John

Copper, and aluminum are excellent conductors of heat. If copper were to be wrapped around the blade, much like a very thich habaki, the heat would not transfer past that point, therefore protecting the temper of the blade. A typical "heat affected zone" from welding extends 1- 1 1/2" from the toe (edge) of the weld. the heat affected zone is the area in which the mechanical properties of the material have been heated to the point where the hardness, ductility, and tensile strength have been altered due to the application of heat. With the right welding process, and heat affected zone control, the affected area could be reduced to as little as 1/2"-1" (12mm-25mm). The heat affected zone is typically characterized by a dark changing of colors, sometimes resembling a rainbow of dark golds, dark reds, and blue/blacks. With this small of an area needing repaired, I see no worries with affecting the surrounding areas. The main question is, should a repair of any type be made. The bullet hole is a part of the history, but that part is better determined by someone with greater knowledge than myself.

[werner]

In fact there are cases of nakago being welded on other blades. The use of copper block heat sinks and water soaked rags. Then the new nakago is filed and re-patinated. John

 

 

Well....that is something I didn't consider....I was aware that some swords had a nakago with a wellknown smiths mei added to (obviously) mislead buyers.....I'm not sure if this is only a recent practise or if that has occured in the "olden days" too....if that would be the case that it has been done in times past then "welding" must have existed for quite some time as "soldering" wouldn't have done the job - tell me if I'm wrong here...I'm just trying to imagine how welding could be achieved in a small area if one doesn't have access to modern day welding equipment.....guess I have reached my limitations here....

 

Jock

 

Thanks heaps for all the input to all of you!

[werner]

Hi Jock,

I would agree with John as to having it repaired.

The only way to fix this without actual welding would be to silver solder.This is a very strong bond similar to brazing and would keep the temperature of the nakago at a relatively moderate heat. The nakago would still have to undergo some re-patination.

Is there a mei present?

If so a proper suriage can be done.As in Orikaeshi mei where the part to be removed is bent around to the opposite side.

 

 

Hi Alan,

 

My apology...the previous statement was wrong...there is a mei....see link:

 

viewtopic.php?f=15&t=9382&p=77755#p77755

 

Jock

[Bugyotsuji]

A repaired Tsuka should provide good reinforcement to a cracked Nakago.

 

Can silver solder really be repatinated?

[bluboxer]

Hey Jock,

I don't see the damage in the pics.

 

Piers,

I meant re-patination of the steel near the repair as it will have to be prepared by cleaning the surface to get bare metal in order to bond with the solder.The solder I have used is 6% silver and 94% tin so I think it can be patinated although I have not tried.I don't think it would be possible to hide the repair anyway.

[Bugyotsuji]

Alan, thanks for the reply. I ask because I had a repair done to the iron/steel firing pan of a matchlock. Maybe it was a type of arc welding. (?) It's a good job and very solid, but it looks silver and different, and it refuses to take patination. Please ignore as necessary. In the meantime I'll try and recall what process they called it in Japanese.