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Zone hardening
- Thread starter foxjaw
- Start date
- Joined
- Apr 6, 2001
- Messages
- 2,632
I have to reply to this one, Experts please correct me if I am wrong.
The Khukri is your "do everything" knife, it can does and will do anything you put up against it. The "sweet spot" is the hardest part, meant to chop and cut with, the tip can do this but is softer because it is more likely to hit a rock and be dinged, or to be used as a shovel to dig with. The area forward of the cho is soft, cause, well my theory is,
A. It is easy to mess up an edge / blade so close to the hilt if one was to strike something here with bad technique, with the majority of the weight of the blade forward of this point the edge can easily be rolled with a less than perfect strike. If it is soft, all the better to chakuma or hammer out your messed up blade.
b. If the blade was hardened here, the point of the blade where it is the least wide, I think the forward weight of the blade would be more likely to snap off, Although on a thicker model (see AK) I think this would not be a problem, On a Suripati or a Kobra it would be.
... if this isnt correct please correct me, and besides... the kamis have their own reasons.
The Khukri is your "do everything" knife, it can does and will do anything you put up against it. The "sweet spot" is the hardest part, meant to chop and cut with, the tip can do this but is softer because it is more likely to hit a rock and be dinged, or to be used as a shovel to dig with. The area forward of the cho is soft, cause, well my theory is,
A. It is easy to mess up an edge / blade so close to the hilt if one was to strike something here with bad technique, with the majority of the weight of the blade forward of this point the edge can easily be rolled with a less than perfect strike. If it is soft, all the better to chakuma or hammer out your messed up blade.
b. If the blade was hardened here, the point of the blade where it is the least wide, I think the forward weight of the blade would be more likely to snap off, Although on a thicker model (see AK) I think this would not be a problem, On a Suripati or a Kobra it would be.
... if this isnt correct please correct me, and besides... the kamis have their own reasons.
The tip is kept softer for the inevitable strike against a rock or something else that is very chop resistant. My tips have encountered rocks, chain fence post, and the odd nail. Also a softer tip can mean that if it is deformed it is likely repairable.
The area behind the sweet spot is also a tad softer. They do not appear to be as soft as the tip on my khukuri's. I suspect this is for vibration control and strength during prying.
Will
The area behind the sweet spot is also a tad softer. They do not appear to be as soft as the tip on my khukuri's. I suspect this is for vibration control and strength during prying.
Will
- Joined
- Mar 5, 1999
- Messages
- 34,096
There's another reason for the softer area by the cho. This area is often used as a drawbar for various woodworking tasks and for slicing duty, especially meat. It is much easier to sharpen, especially in the field, if it's a little softer.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Leaving part of the blade soft significantly increases the impact toughness of the blade in that area as well as the ductility. In short this means that the knife can be beaten on severely with little or no side effects except cosmetic damage. It also means that it will take a very large degree of flex, and tend to just deform when its limit is exceeded instead of just snapping suddenly.
The downside to not hardening the whole blade is that it reduces the strength. You can really notice this on a 1/4" bowie, as it can cause around a 50% decrease in strength (depends on how soft the soft parts are and how high up the high parts extend). However when you are speaking of 1/2"+ thick khukuris this is not much of a problem as even with the back left not fully hardened the blade is still extremely strong.
To clarify though, I have seen khukuris (not from HI) that were weak enough to bend by hand. The problem here was that the hardening didn't extend high enough on the blade and the part that was hardened was not hard enough. Thus the strength of the blade was too low. I have bent such blades sideways and as well twisted them about the handle producing a swirl like in a candy cane.
-Cliff
The downside to not hardening the whole blade is that it reduces the strength. You can really notice this on a 1/4" bowie, as it can cause around a 50% decrease in strength (depends on how soft the soft parts are and how high up the high parts extend). However when you are speaking of 1/2"+ thick khukuris this is not much of a problem as even with the back left not fully hardened the blade is still extremely strong.
To clarify though, I have seen khukuris (not from HI) that were weak enough to bend by hand. The problem here was that the hardening didn't extend high enough on the blade and the part that was hardened was not hard enough. Thus the strength of the blade was too low. I have bent such blades sideways and as well twisted them about the handle producing a swirl like in a candy cane.
-Cliff
- Joined
- Mar 5, 1999
- Messages
- 34,096
Thanks, Cliff. I've come to believe that differential hardening is an art. The fellow doing it had better know what he's doing or he's looking for trouble.