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Why So Few Hirazukuri Katana?


Ken-Hawaii

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Spotted this http://www.ebay.com/itm/Japanese-Samurai-real-sword-Katana-sharp-steel-blade-Koshirae-hirazukuri-antique-/262731252439, & it looked rather weird with no shinogi. It got me wondering about why there are so few hirazukuri blades longer than wakizashi.

 

Is there something in the forging process that makes it harder to make blades that long?  :dunno:  I've seen one or two of them, including one gorgeous Muramasa on this site, but why so few?

 

Ken

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There's a nice example here:

 

http://www.seiyudo.com/ka-090116.htm

 

I remember reading somewhere that longer hira zukuri blades were more prone to cracking during the quenching process but I can't remember where I got that from. 

 

Best,

John

 I have also heard of them cracking after an apparently successful quench! 

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Hello:

 Might it not be that on a shinogi-zukuri blade the ratio of the width of the surface in contact with the material being cut, that is from the ha to the shinogi line, is perhaps around .7 or so of the width of the entire blade, thus reducing surface drag in comparison with a hira-zukuri blade of the same overall width and therefore increasing cutting efficiency? Niku, which can be readily applied to a shinogi-zukuri blade, might also add some comparative efficiency to the shinogi-zukuri style. Niku could of course also be a surface contour on a hira-zukuri blade, but the effective contact contour would likely be wider. 

 Arnold F.

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Often wondered if their scarcity was related to decreased structural integrity or a lack of popularity.  Perhaps they were never en vogue.  I have seen where modern day cutting competition participants say the Hira-zukuri shape made awesome cutters. Never saw any remarks regarding how they held up long term.

 

Would like to see the Gendai example as well.

 

I have owned a couple of them, but sadly let someone pry one of them away.  Both are pretty long, one with a 28" nagasa and the other is 29".

 

Here is a link to the one I have photos of: http://yakiba.com/Kat_Akihiro.htm

post-10-0-70249800-1479998829_thumb.jpg

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The shinogi being thickest part of the blade allows a greater cross section thickness as opposed to the hirazukuri which is flat from ha to mune and along it's entire length.  The shinogizukuri format also decreases drag when cutting as opposed to the hirazukuri where the entire side of the blade is in contact with the object.  Therefore, you get both increase strength with lower drag.  The shinogizukuri also allows the yokote format of the kisaki which increases strength while allowing shortening the tip of the sword.

 

PS:  I see Arnold posted while I was typing.   

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I have read the same thing many times and in theory I tend to agree with you guys in regards to the shinogi being thicker and producing less drag, less surface area making contact with the target, et..    Also, I have never had the opportunity to cut with a Hira-zukuri blade so I cannot compare them.

 

I have cut with various thickness shinogi-zukuri blades and the thinner the profile the easier they cut.  More niku equals more drag, less efficiency.  

Again, I have not compared them personally, but it makes me wonder if the thinner profile of the HZ would produce much less drag, offsetting the small increase in surface area.

 

I would tend to think the HZ would not be as strong overall as the SZ.  

Which could be a reason they never became as popular as SZ, and are not seen as much.

Just my 2 Yen. 

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The matter is much older than appears in these comments. The Shinogi (ridge) first appeared in China at least during the Han dynasty and entered Japan as soon as the trade allowed it. Shinogi (ridge) is a natural addition to the flat (Hirazukuri) blades in order to obtain a more performing sword and is mainly intended for long and medium blades. It firstly appeared in Kirihazukuri blades. These blades has the advantage in having a thicker and consequently heavier and more resistant body maintaining a thin, hence sharp, edge thru the application of an angle. The result is a 5 sided cross section. This is a very good enhancement for swords that might strike hard objects as armor or bones. A thinner triangular section (Hirazukuri) is sharper but also more prone to break due to the shocks mentioned. More, the beefier upper section of Kirihazukuri gives more weight to the kinetic action, and this possibly remedied to the lesser cutting ability. With time swordsmiths realized that to move up the Shinogi would mean to add sharpness to the edge, in some way mixing the Kirihazukuri (upper part of the blade, above the Shinogi) and Hirazukuri (lower part of the blade, below the Shinogi) maintaining a five sides cross section. This proved to be the more effective cross section for long blades in Japanese history, with a perfect mix of resistance, weight placement and cutting ability.

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Hi 

 

I was under the impression that Hira-zukuri were the sharpest blades. The more acute the angle the sharper the blade.

Shinogi-zukuri reach full thickness at approximately 2/3rds of the way up. Hira-zukuri are not at full thickness until the top the blade.

Like hollow ground (cut throat) razors 

Please fill free to educate me

 

However i believe they are more likely to crack in tempering and in battle.

 

Here mine 27"shinshinto blade, gimei 

post-1770-0-88214100-1480015096_thumb.jpg

post-1770-0-57749900-1480015129_thumb.jpg

post-1770-0-87674100-1480015148_thumb.jpg

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I was under the impression that Hira-zukuri were the sharpest blades. The more acute the angle the sharper the blade.

 

Sure, and that's because they are popular in modern cutting competition. However tatami mat have no armor and doesn't byte back with another sword, the two reasons that made Shinogizukuri blades preferred in wartime periods. When the Pax Tokugawa  covered Japan, they remained the fashionable ones among samurai.

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More niku equals more drag, less efficiency. 

 

Ed, I was under the impression that Niku was introduced exactly to diminish the Surface of the blade in contact with the soft target. A v shaped blade has more Surface in contact with the flesh than one with proper niku. The curvature of niku displaces flesh not allowing it to enter in contact with the upper part of the blade. This of course applies not only to shinogizukuri blades but to Hirazukuri blades with proper niku as well.

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Okay, so the consensus is that hirazukuri blades morphed into shinogizukuri to decrease failure from lateral flexion & stress. Basic physics. So has anyone seen a blade in between what we consider no shinogi & a full shinogi? There must have been quite a few, but I've never seen one. Carlo, have you seen one during your extensive research?

 

Ken

 

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Niku is to provide support for the edge when cutting hard targets such as armor and bone; I notice that many of the competitors in Japanese tameshigiri exhibitions are using very wide thin swords that flex easily when the hasuji is not correct....they have someone onsite to help bend them back :-?  :)

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