Important technical thread on Shop Talk...

The carbon content in the steel can be modified during forging. In a reducing atmosphere carbon is added to the steel. This is what most likely happens in charcoal fires. In an oxidizing atmosphere carbon is removed from the steel.

The number 5 in 5160 states it is a chrominum steel, where chrome is the major alloying component (about 1%).

Will

[This message has been edited by Will Kwan (edited 22 November 1999).]
 
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Another interesting property of the steels Dan mentioned is that when they are highly polished they become much more corrosion resistant.

I saw about 5 or 6 of the old Cattaragus Q-225 knives like the one I got at the G & K show and although a couple of them had been badly mistreated the blades had no evidence of pitting.These old knives were made from 1095,highly polished,and issued to troops in every theatre of WW II.
I had to reread the article because I thought these knives had a surface coating like the "Kabars."

The Kamis using the water for hardening isn't the only thing I find interesting about thier method of hardening.

Has anybody considered that the Khukuris are _Not Drawn_ after the hardening process?
Perhaps the toughening we get from drawing steels back after hardening in the western tradition is automatically added with the water hardening?
Or is it the differentially heat treatment that does it?

Maybe another interesting question for the technical thread?

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>>>>---¥vsa---->®

If you mix milk of magnesia with vodka and orange juice do you get a phillips screwdriver?

Khukuri FAQ


 
Yvsa, this is why I say our blades are hardened and not tempered. I try to show the difference.

I think it is the differential heat treat that does the job. The kamis get the edge -- maybe a half inch or a little more -- to the color they want and then pour the water. The back of the blade although plenty hot is not red so stays softer.

If they had a controlled oven, of course, the easy way would be to stick the blade in the oven, get it to the right temp. and then quench it in some nice forgiving medium like transmission oil. And THEN draw it. But the kamis don't have the equipment and do the heat treat the old fashioned way.

My great grandfather didn't have anything except water in his shop for quenching. He made and repaired mining equipment, including gears, in addition to horse shoes and wagon wheels and never used anything except water for quenching. And the stuff he made and repaired held up. If you know your stuff you can get a good job done with water. As somebody pointed out blacksmiths have been using water for quenching for thousands of years with pretty good success.

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Uncle Bill
Himalayan Imports Website
Khukuri FAQ

 
Uncle Bill,

Please, by all means, tell the kamis to stick to the old method for heat treating. It just make the Khukuris as Khukuris. A time proven success!

I think saying that Khukuris are not tempered "maybe" wrong. Of cause I am not sure. But as I've said in the "Shop talk" thread, if the kamis is pouring water on the edge to harden to knives. No matter how much water they pour on it, the spine of the knives still retained much heat, and it will go down to the edge and just temper the edge a bit.I don't know to what extend this effect will be. But I guess that is experience determined.

And the uneven evaporation of the water on the edge will result in deferent hardness on even one side of the blade, and that maybe a plus as to prevent chipping.

I would suggest a test on different spots on the hardened edge if our members have access to a hardness tester. It is non destructive, and we may know more.I would suggest one indentation every 1 cm on the hardened area.

I maybe wrong, but I see knives beautiful as it is both art and science. It's romantic to make a knife with traditional method and yet it can be proved to be good with science and modern technology! I really think that it can be proved scientifically.

Joe Leung

P.S. HI has changed my view on Khukuris completely. I didn't see Khukuris as a good knife until I owned a HI Sirupati.
 
Many thanks, Joe.

Maybe Yvsa can give us a little information regarding the difference between tempering and hardening.

An old knife maker told me that tempering was really drawing the blade after hardening and I have stuck with that definition. Maybe he was wrong and so am I.

Yvsa, can you shed a little light on this from your shop experience?

Somewhere, Joe, we have a a thread on the hamon (is that the right term, Jim?) of a khukuri. It was hardened exactly as it should be. The hardest part of the blade is the chopping area and usually comes in at 58 to 60 Rc. Tip will be softer and area above bolster will be softer, sometimes dropping to as low as 50 Rc. Each khukuri will test differently but generally not much.

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Uncle Bill
Himalayan Imports Website
Khukuri FAQ

 
Yep, "hamon". Known in English as a "temper line". The Japanese prized hamons that had nice pretty waves or curliques in the hamon itself, and had names for each that translated to things like "turbulent seas" or whatever. My opinion is they got a wee bit anal about it, BUT there are good reasons for not having a dead straight hamon either.

Basically, if the hamon is a "flatline" it forms a single "seam" between the harder and softer zones. Under extreme use it can part right at the seam, you end up holding the spine and handle and the cutting edge is still embedded in the wood.

This is considered suboptimal
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By making the line "waver" you increase the strength of the inevitable seam.

I've been doing a bit of thunking as to how this relates to Khukuris. I've got a sneaking suspicion I know why nobody's seen a Khuk split at the hamon. What I think is, because they pour water on one side and then the other, the hamon isn't quite at the same place on each side. I think if we took a "cat scan slice" of a khuk and did Rockwells, we'd find that the hard part of one side continues a bit further up the side than the other, and that there'd be some softer steel left in a "V-notch" internally near the hamon. If I'm right, it means there's really TWO hamons, one at each side and since each hamon is a "seam" that doesn't quite line up with each other, each seam is reinforced by NON-seam steel on the other side.

If I'm right, the hamon line on each side of a khukuri will be slightly different. If we cared about pretty hamons this might be seen as a downside; as is, it may be a key reason these suckers don't spit their edges.

Jim
 
Joe has it right -- I posted in detail in the other thread. Steel doesn't care how it's cooled or how it's heated; when it's cooled at the right rate it hardens; when it warms to the critical temperature it tempers. It's all a matter of temperatures and rates of cooling and the phase of the moon is immaterial.
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-Cougar Allen :{)
 
Gunhou, did you get that spring to a cherry red heat? If not that's why it wasn't annealed ... you can't do that with a propane torch, btw.

The work-hardening theory ... if you get it to the critical temperature and anneal it that will cancel out any work-hardening, and also any brittleness it may have acquired in twenty years of bending back and forth ... after a good thorough annealing it might as well be new steel fresh from the mill.

I also wonder if maybe you did anneal it but weren't familiar with what annealed 5160 is like ... it won't file as easily as mild steel. You can file it, though; if you couldn't file it at all you not only didn't get it hot enough to anneal it; you didn't even get it hot enough to temper it much.

-Cougar Allen :{)
 
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I have to do some more thinkin on this subject.Joe an Jim brought up some things I hadn't considered,but one of them,the hamon line,I may be able to check now that I have my toolbox at home.

I have to agree with what's been said already and yet like you Uncle I have seen a couple of old Smiths work and they used water,actually one used the accumalated gatherings of horse urine.It smelled to high heaven but it done a wonderous job of hardening steel.
Then there were also the two old hands in the machine shop that done the actual "Heat Treatment" as well as hardening things by "eye."
D.K. could harden a die punch by eye as well or better than most could with expensive equipment.It saved a lot of time sometimes when things didn't have to be documented.

We have family in from all points at the moment and I am stealing some time at the TV to post this.I will get me a small TV soon,17" and hook up my system to it.That way I won't interfere with the kids cartoons.
smile.gif



------------------
>>>>---¥vsa---->®

If you mix milk of magnesia with vodka and orange juice do you get a phillips screwdriver?

Khukuri FAQ


 
Yvsa, I had an old shop hand who could make and harden tools using the eye only and this guy almost never missed. Was it D-2 he was using? It has been too long and letters and numbers don't last in what I have left of my memory banks.

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Uncle Bill
Himalayan Imports Website
Khukuri FAQ

 
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