Been busy - Forged Kodzuka "Tactical ?"

J

Jason Cutter

Joined
Oct 9, 2002
Messages
1,419
Another custom-ordered Kodzuka. This one has a hand-forged to shape blade of 1095 steel, 4.5inches of edge, 9.5inches OAL. I’ve used my clay-backed hardening technique this time focusing on developing a “bainite ??” spine for added toughness, rather than for the various added details in the hamon, like ashi and utsuri. My one-sided version of a yoroi-toshi reinforced tip design. Tapered tang with Mr Loveless’ favourite Olive green canvas & stainless fittings. Its all a very simple design with a simple pouch leather sheath.

You can see the larger grain structure above the hamon in the pictures. I think it actually looks cool. Its done by first completely hardening the blade, then performing the differential edge hardening. In testing, I’ve found such a knife to be more resistant to bending than one with a completely soft spine. Its sort of a spring temper on steroids ! I believe other knife & sword makers are also doing this now in an attempt to reduce the tendency of Japanese style blades to bend under extreme stress.

Thanks for looking. Constructive comments of all types welcomed. Should be flying to its new owner right now... Jason.

Additional Pics
Detailed shot of the hamon
http://www.fototime.com/18A878D4D2E4178/orig.jpg

With sheath.
http://www.fototime.com/AD9FA156B437C07/orig.jpg

orig.jpg

orig.jpg

orig.jpg
 
Jason, ....looks great...and you took a fantastic pic of the green canvas handle..... mine come out some what dark most of the time;)
 
WOW :eek: that is awesome, I love all the detail and the simple utility of it. I have to get a blade from you soon, the problem is you have done so many great knives it will be hard to choose one.
 
Why am I droolin' that way ???... Can you tell me, Jason ???!!!!..... Why ???!!!.... As usual, a GGRREEAATT job !!!!
 
Man, that thing is sweet lookin'. Could you explain the purpose of the upper grind on the spine. Is this designed for decoration, or as a chopping surface? Love the temper line.

Lagarto
 
That is really my new favorite knife. The wave temper line combined with the almost western style sheath. good God. that is a work of art.
 
Very cool, Jason.

When you harden it the second time, do you bring the entire blade up to critical temp or just the edge?
 
Oh wow ! My thread is back from "the dead." Thanks guys, Much appreciated.

Lagarto, the spine profile is my own version of what I believe is called a "yoroi-toshi" spine. Generally meant as "reinforced" or "armour piercing" because the spine thins down like a false edge, then returns to full thickness nearer the tip for added strength. I'm sure it works, but I do it because I like the appearance of it. I also generally grind it on the left side, because some people (who are mostly right handed) who use my knives in a practical way, turn the knife edge up in the hand to scrape something (eg.- firestarter / magnesium block / de-barking wood) with the spine. Hope that answers your question.

Wulf, the second time I harden, the spine is covered with clay in the desired pattern. At the time the edge is "soaked" long enough above critical and ready to quench, I don't think the area covered by clay really gets above critical. Probably not even at normalising temp. Its a dark red that glows under the clay. I have to say, there's nothing very scientific about how I do it. Its a combination of "thats simply how my forge works" and a bit of accidental discovery. Most metallugical concepts go right over my head.

In response to your question, I'll also quote a work colleague who is a wanne-be metallurgist. "I think it may be unnecessary to do the double quench method to get the bainite type spine. If you cover the spine in clay, then ensure that the entire blade gets to critical before quenching, it is likely that the clay, acting as a quench resist will in effect create a mar-quenching / mar-tempering process by preventing rapid cooling of the spine. Bainite structure in the spine will be achieved in a single procedure."

However, in my forge, I run the risk of overheating the edge and causing grain growth if I heat long enough to get the entire blade to critical. So the first way is how I do it. There you go. I hope this makes sense. :o

Thanks again. Jason.
 
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