Question for Bill or Dan...Heat treating Kukris

S

shane justice

Joined
May 12, 2003
Messages
1,606
I really like this part of the forum. Has a nice feel.

Bill or Dan or anybody who has some first hand knowledge ...I have read the HI web site...I was interested to find out that the kamis use water (boiling) to quench the kukri. I have been thinking about it...the pictures aren't really clear... Do they pour the water on the blade flat? Or do they quench with the blade edge upward?
On another tangent...do they face north when they perform the quench?

I posted a long time ago that I was going to forgew a kukri style blade...I did...it came out pretty nice...ready to begin stock removal...normally I heat treat 5160 in oil...but am considering a more traditional approach.

Thanks for any advice.
All knowledge is good.
Shane
 
Limited experience here, but it seems that the rate, positions, distribution of the water is how the hardening is controlled. Unless taught, I'd guess it'd take quite a while to come up with just the right technique.
 
They hold the edge and point somewhat downward and pour water on the edge to quench it faster than the spine. They look for color which helps indicate the proper hardness. This allows the tip, spine and tang to stay softer and less brittle.
 
Uncle once told me that Bura flips the blade over three times as he's setting the "pine" (temper) with the kettle. He also told me Bura looks for something like seven different colors, which must show up in the right place and time or he won't let that blade pass. Bura's mastery of heat treatment explains much as to how he's able to produce those thin, tough, edges he does so well.

Sarge
 
The thing that amazes me is that everyone else quenches then draws down the hardness in two or more separate steps. The kamis quench and draw IN ONE STEP!!! Paul Bos, where are you to explain this to us?
 
why would this make a difference?

BTW, the North is an unlucky direction to many asian cultures, who prefer the more lucky direction South.

I'm a circumpolar guy, so I think north is lucky.

Bill Martina has seen the quench done, I bet he's the guy to talk to. We have had a personn or 2 perform blowtorch heat treats as well, but that's not what the Kamis do.

Keith
 
There's an old wives tale that if you don't have the blade facing north and south when annealing(or heat treating, can't remember which) the magnetic forces of the earth will pull on the blade and twist/warp it.

Had a really fun discussion of this over in sohp talk if you search for it. :)
 
I think I posted somewhere about Bura giving me the demo of hardening the blade but don't have the foggiest notion as to where that might be. Sarge hit the essence of it, though. Ambient temperature water from kettle on red edge at proper flow rate gets the job done.
 
The following does nothing to detract form the Kamis efforts.
What they do
In the time they do it
For the use of the tool
is excellent for its use! Match to match.
If we are making just a few we can spend the time.



Shane
Why not settle for a superior product?
Anneal, triple normalize to insure uniform grain, soak at temperature, then.......
Fully quench the edge in oil
and then temper three times.
If you want even better
Fully quench the edge and the body then draw back the spine to a spring temper with the resultant colors going to a deep brown in the body. This type of knife will bend to a 90 deg and spring back. Second option is to use clay (Japanese style) which is what I do.

Anyway, any blade you do this process with will out-perform the best the Kamis ever made. They would NEVER spend that much time on a tool. And no one can blame them. To them that would be stupid. However, you can and should.
If you are going to try to learn or mimmick a process that will take you years to learn why not make it the best process. Not an indigenous cultures mass-produced production tool making process. You can spend the time -they cannot.

There is another problem you have with pouring as a quench and that is "popping". Most people do not understand why the Japanese made a VERY thin slurry coat of clay and placed it on their actual edges then used thick coats for the sides. The common question is why not use NO clay on the edge?
The reason is that water-in contact with superheated steel- will skin and form a bubble. The result is anything less then uniform hardening.
The results can be visualy interesting in a hamon as you get some pretty "yo" and other interesting features. The very thin clay coating does not prohibit the transfer to martensite- it aids it in doing so in a uniformed process. Make sense?
The thick layers prohibit it-thus resulting in the hamon.
As for watching the colors reduce through their ranges from deep blue to violet to dark brown to light yellow? That gives you spring temper (blue) to about a 60C (yellow) But letting the colors reduce is dicey and non-uniform and are just a fast way to do things.
Quench!
As for sweet spots and things.....

Use of Kukri go way beyond hitting trees and clearing brush with a sweet spot.
If you harden the edge-the whole edge-you can use them for draw knives to square-off and make trapes or shelters or even crude furniture. You can also use it for a fully functional utility tool. I use mine every year slammed into a landscape tie then use the stood up edge to cut landscape cloth as I draw the long lengths across the edge. My wife thought it was magic.
A spring tempered flat spine will be hand friendly and will pound well also. This can be done with the softer steel that they wind up with but you are making _one_ not hundreds. Make it the best IT can be.



cheers
Dan
 
I honestly wonder if the real reason the kamis edge quench with water is because it is easier.

Consider the alternative - fully quench a long, heavy blade in hot oil and "BAM" you got a nice flame/mess/whatever. Then you have to go back and draw back at least 90% of what you just hardened.

Or, you try to edge quench. Anybody ever tried to edge quench a khukuri (or any strongly recurved knife)? What a pain-in-the-rear. The cake pan method would be nearly impossible this way. You'd whack the cho part of the blade against the pan before fully treating just the sweet spot.


Next, consider the cost of oil, compared to the cost of water. Fortunately, for the kamis and for us, 5160 is a very forgiving steel and doesn't mind being carefully water-quenched.


If I understand you right, you want to mimic their process. I assume you already know how to read the colors when heat-treating, so you should be ok. Doesn't hurt to try again if you screw it up - again, 5160 is forgiving.

The water is at boiling temp to not "shock" the steel too bad.

The tea kettle is used to provide a controlled rate of water flow.

The blade is held edge down, and IIRC, quenching starts at the sweet spot and moves outward. (Uncle Bill - any comment on this part?)

I am also assuming you have a forge large enough to handle the entire khukuri (since you did make it there).

The only part I'm not 100% clear of is the amount of time between quenching and tempering (in the kamis process). Couldn't find info on that.
 
I agree with Dan on the reasons that he states for the way/how the khukuri are water quenched the way they are.As far as doing a clay coat then a quench I would try on a couple of thick pieces of scrap that are roughly the same size sahpe and mass as your almost finished khukuri. You could get some...interesting warpage in the blade.I have done alot of reading on heat treating swords and clay in oil almost always leads to the blade being curved in a reverse katana fashion (like a sickle) and water give the upward curve that you see in a traditional katana. I do not know how that would translate in a much shorter stouter blade but it might be something to consider.
 
Thanks to everybody who responded....

I apprecdiate the time you took to answer my question. My own experiments tell me that the the blade must be held point down slightly...water pouring "evenly " from the edge, over both flats...a tricky deal at best.

Dan, I suspect there might be few folks on this thread who would object to your use of the word superior and inferior. As to your proscribed heat treat...I use much the same with my forged blades... The kuk we are working on is 52100...it seems to enjoy multiple heat treat cycles.

I have always found that understanding and respecting the old schools allows a greater depth of current methods.

In the future I may very well start a mid-tech line using CPM steel and Paul Bos Heat Treating. But this will never replace the joy I find hammering steel in my little shop.

Thanks again for your help.
Shane
 
You guys were too fast for me...By the time I sent my first reponse...there were two more answers...

Pendentive...Really...they quench the spine first..hmmm?
The purpose of this question was a greater understanding of craft. I haven't decided what to do...

If I read all the clues this is not much different than the interupted water quench that Charlie Ochs uses.
As to the colors of change during the quench...learning as I go.

If I use the oil method..I use a deeper quench tank so the angle is no problem...neither is the size of my forge.

Point of interest...my first forge was homemade...I used real honest to god charcoal...spent hours chopping it...not because it was easy but because a man has to pay his dues.

Shane
 
Pix I've seen of kamis show them pouring room-temp water through teapot to hit about at top of the edge grind; water then runs down to edge. The teapot gives them a steady, predictable flow of water. Lots of steam to fog your glasses.

Kamis with 30+ years' experience probably don't want to try new untested (to them) methods with their livelihood at stake.

Charlie Ochs uses an interrupted quench in water, but is also careful to have only the edge portion (about 3/4"?) up to austenizing temp. The rest of the blade is a darker red and is not converted to martensite; it's not as hard and brittle as the edge.
 
Exactly what Art said. (you put it very nicely, Art)

I didn't mean pouring over the spine, but rather, holding the blade edge down, at a 45 degree angle and then trickling the water starting at the top of the edge bevel. You start at the sweet spot first because there is so much edge to quench, by the time you do a few inches of it, the rest is starting to cool already.

Good luck with it! Be sure to post pics.
 
"time betwen quenching and tempering"

Someone explained here previously that because the water is only poured on the edge, the residual heat in the great slab of steel does the tempering. If that was correct, it's all done in one step. Poor Bros. If everyone did it this way, they'd be out of business. Of course, this leaves the spine dead soft instead of spring tempered. That probably explains the dings in the spines of some old village khuks I have - dented while being batoned through something.
 
Originally posted by Thomas Linton
Of course, this leaves the spine dead soft instead of spring tempered.
Click to expand...
In the Knife Talk books by Ed Fowler;
he mentions at some point (haven't found it again)
how his edges are hardened to around 60,
but dropping quicky to 40 toward the spine,
with the spine itself 30 or less.

I'd really like to find that again to check the specifics of
which steel, if he still does this or if it was only
during a certain period of his knifemaking, etc.
 
Ddean, posts that I read only a month ago from Ed show that he is using certified runs of 52100 for his blade material. In the past he was using large ball bearings made of 52100, and John Deere load shafts that are made from 5160 that has tighter specs than that used for leaf springs. From what I read he is still using differential hardening in his blades. I believe that Shane is a friend or acquiantance of Ed's and could clarify this for sure though.

Hope this helps, stevo:)

PS~ The way the kamis heat treat the khuks is the first way I was taught to heat treat a chisel (using residual heat to temper that is, not using a tea pot).
 
Steve and Ddean,
Ed has used a number of steels during his career. JD Load shafts are a very high quality source of 5160. He has used 52100 in ball bearing form and now exclusivley uses 52100 from Rex Walter.

The kamis use spring steel from Mercedes' I can surmise that this means also 5160 steel of high quality. 5160, while considered a no brainer among smiths is also the most readily availble steel in the world. Honestly I would put a load shaft against a Mercedes spring anyday. But I do't think they have many John Deere tractors in Nepal.

As to the remarks about the rockwell points on Ed's blades...don't remember any quotes or claims recently...all I know is they cut, very well ...for a long time...and then sharpen very easily. If you want specific info from Ed...just start a new thread and ask. I think he still comes to this site. He is always willing to help out anybody who has questions.
Thanks guys, Shane
 
You must log in or register to reply here.
Back
Top