View into Blade Construction

[Bruce Pennington]

This broken tip seems to give us a view into how the blade was constructed, right?  On a Yoshiaki blade for sale HERE.

 

 

If so, what method would you call it?

 

At the risk of chase two rabbits at once, I've started wondering about the various methods, the kabuse method triggering my puzzlement.  

 

Would a smith start the blade with one of these stacking patterns and then do the fold/hammer, fold/hammer?  Or is this method of construction it, without folding?  Because if they stack, say Kobuse, then fold & hammer, what difference does it make?  The folding/hammering, multiple times is going to mix it all up in the end.

[John C]

Bruce:

It's too difficult to see in this pic, however under a loupe you can see the kobuse core inside this chip. Blade was polished too thinly I suppose.

 

John C.

[DoTanuki yokai]

At this part of the tip should be only the steel from the edge no matter what construction method was used. 
Also I would put the Diagramm you posted away bruce. 
Some of the construction methods are a real thing but they lack any proof and in the end matters nothing at all in my opinion. Soshu Kitae is the most cringe part of this Diagramm and evolved from Wikipedia and Chinese replica sellers talking s**t.

Also the Makuri technique comes to a similar result as Kobuse but is considered the faster method but is more prone to Mune ware in my opinion. I’m not interested in telling my opinion on this whole Diagramm over and over again i simply hate it and have said it too often already 

I think this info is better http://www.ksky.ne.j...99/construction.html

 

 

John how can you tell that it is not simple ware in the edge steel part ? 

[John C]

1 hour ago, DoTanuki yokai said:

John how can you tell that it is not simple ware in the edge steel part ? 

I can't get a picture of it, however under a loupe the chip looks like a hole with a line of darker steel running under it. Kind of like if you dug a hole and saw the top of a dark pipe running through it. That's what it looks like to me, however I am almost always wrong when it  comes to sword stuff. Could be a ware but having not seen one under steel before (it's the only blade I have with a chip) I'm not sure exactly what I'm looking at. 

 

John C.

 

[ROKUJURO]

As Christian points out, the small portion of the tip should normally be solid steel throughout without any visible layering. Also, the small chips in the cutting edge don't give us a clue as to the blade construction. If it is a WWII SHOWA-TO blade, it is likely a mono-steel blade with no inner build-up of different layers.

But what I think I can see in the picture of the broken-off KISSAKI is a fault in the hardening process which was the reason for the failure of the tip. The inner part of the steel seems to be quite coarse while a small area of the surrounding surface steel is a bit finer in grain structure. This lets me believe that the tip of the blade was accidentally overheated in the YAKIIRE process. The smith was probably aware of this but waited a moment before he quenched the blade.  

To answer Bruce's second question: The smith prepares different steels separately by forging out the respetive kind of TAMAHAGANE, then folding and fire-welding - and repeating this until the steel was homogeneous. These different steels are then stacked as shown in the very much simplified coloured diagram above (or in the drawings of the SUMIE sisters), heated and fire-welded together to form a block which was then drawn out by forging to the final shape of a blade.

In the scientific literature on steel research you can even find microscopic images of Japanese blade sections which prove that the construction of these sword blades was indeed done by these methods.

However, you will find huge differences in the execution of the work depending on who forged the blade. 'Fast and dirty' work (as sometimes done in war times) never produced high quality blades with a regular inner build-up of the steel.

[Bruce Pennington]

8 minutes ago, ROKUJURO said:

The smith prepares different steels separately by forging out the respetive kind of TAMAHAGANE, then folding and fire-welding - and repeating this until the steel was homogeneous. These different steels are then stacked as shown in the very much simplified coloured diagram above (or in the drawings of the SUMIE sisters), heated and fire-welded together to form a block which was then drawn out by forging to the final shape of a blade.

Thanks Jean.  So, am I hearing this right? - The hard steel is heated, folded, hammered, repeat; and the soft steel is heated, folded, repeat; THEN the blocks in desired amounts are placed together in one of the various methods and this combination is drawn out into the proper blade shape?

[ROKUJURO]

Exactly Bruce!

This makes it understandable that a sword blade can be ruined BY ONE WRONG BLOW especially in the final stages when the outer layer thickness of the steel (KAWA GANE) can go down to as little as 1 millimeter.

[John C]

2 hours ago, ROKUJURO said:

Also, the small chips in the cutting edge don't give us a clue as to the blade construction. If it is a WWII SHOWA-TO blade, it is likely a mono-steel blade with no inner build-up of different layers.

In reference to the chips on my blade, it is a star stamped gendaito from Kunimitsu. So not sure which construction method would have been used.

 

John C.

[ROKUJURO]

John,

if it is a GENDAITO, you can be sure that one of the traditional methods was used.

These high quality blades often suffered much hardship after the war when they came into the wrong hands. A hard cutting edge will probably survive a true fight in combat better than being misused for some time by little Joe in the garden....

[Apercus]

I agree with Jean’s assessment of the process but would add that in the process of folding each individual steel type they do not typically continue until the steel is homogeneous. You would not see the visual effects of layering such as Itami if the steel is homogenous. The boundary layer between folds has silicon which distinguishes the layers. The presence of distinct layers adds mechanical advantage by increasing resistance to crack propagation. 
 

There were also other types of construction that are not shown in the chart such as san mai. Close examination of blades by Cyril Stanley Smith have shown that some smiths alternated steel types (carbon content or composition) before repeating the folding process, thereby producing an effect similar to “pattern welded” blades common today. I have one of these in my collection. I would not be surprised to see almost any variation of structure. As mentioned, skill level of the smith is probably the most important variable in how the sword will perform.