GREAT SERVICE

Joined
May 24, 2012
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690
So one thing to note before hand. I am getting a replacement and Yangdu have seen the pics of the failure. She is replacing the blade. But I feel that us as users still need to mention when this happens.

I have been using only knives to split my wood, have never used a axe and have never broken a knife doing so.

About 3 weeks ago I broke my CAK splitting wood, it broke of completely inside the bolster. From what I can see the grain structure is finer than what it should be but not fine enough to be fully hardened. The tang should be soft. The tang where it broke is only about 2.5- 3mm thick same as my mora and there seems to be square and rough cut outs to fit the bolster. ( this design is not as strong as the hidden tangs imo)

I do not want to post any pictures as I have already sent them to Yangdu, I feel its unnecessary to have pics floating the internet. If you really want to see it I will email it to you. The khuk was made by Kumar same as my other AK and feel like he needs to know about this. The way the tang was finished just looks bad. I have a VLUK on the way and also use a 18.5" AK. Love the blades and will buy more close to September and probably for years to come. But I am slightly worried. Kumar is the best Kami HI have and its not he's first failure.

Atleast we are using them besides none of mine are not being used.
 
This is why I advocate proof testing.

I do test all my stuff... the problem is this broke after testing.

And just found a crack at the Cho on my 18 AK... as far as I can see this wont affect anything. Its on that little piece in the middle. Still I will send pictures to Yangdu... I think they are doing something wrong
 
Very interesting. Usually a brittle tang will break under the first hard blows. I test with hard impacts from all directions.

What kind of use did the knife see before it broke, and for how long was it in use? What were you doing when it broke? Was it different from what you were doing before?

How did you do your initial testing?
 
Very interesting. Usually a brittle tang will break under the first hard blows. I test with hard impacts from all directions.

What kind of use did the knife see before it broke, and for how long was it in use? What were you doing when it broke? Was it different from what you were doing before?

How did you do your initial testing?

Batoning wood (sekelbos) it's a dry hard african wood. But should be no problem for these knives. The CAK broke on my 4th session of wood prepping. I did nothing different. Knives won't always fail in testing. It might fail at a later stage. If you give me a email address I will happily send you pics Howard.
 
I put a post up on your profile with my email. Can’t figure out how to do PMs now. Maybe that function disappeared? Would appreciate the pictures although I’m not enough of a metallurgist to interpret them well.

I’m still very interested in your initial testing. Did it include blows to the back and side of the blade? The forces in battoning are directed differently than those in regular chopping and if the initial tests were just chopping they may have failed to stress the flaw.

I will admit that proof testing does not preclude the possibility of a later failure. It does reduce that probability to a small enough value that I have confidence later relying on the blade surviving the same types of forces that it endured in the testing. I try to make it see harder forces in the testing than it will see in use by swinging and impacting the front, back, and each side of the blade against hard wood. Of course, reason must be used. Anything can be broken using levers and mechanical advantage. The idea is to test a bit harder than what the blade will see in anticipated use. One must also consider safety and which direction a broken blade might fly if a failure does occur.

I had a tang failure a number of years back. It manifested immediately in the testing. In 30 years using HI blades that is the one time it happened to me. Of course, Bill replaced the knife immediately, no questions asked. You will find discussions of proof testing in the archives. Bill (a former aerospace engineer) made some runs at getting it incorporated in a formal manner into HI processes but ran into some challenges. The kamis have an old and traditional culture.
 
I put a post up on your profile with my email. Can’t figure out how to do PMs now. Maybe that function disappeared? Would appreciate the pictures although I’m not enough of a metallurgist to interpret them well.

I’m still very interested in your initial testing. Did it include blows to the back and side of the blade? The forces in battoning are directed differently than those in regular chopping and if the initial tests were just chopping they may have failed to stress the flaw.

I will admit that proof testing does not preclude the possibility of a later failure. It does reduce that probability to a small enough value that I have confidence later relying on the blade surviving the same types of forces that it endured in the testing. I try to make it see harder forces in the testing than it will see in use by swinging and impacting the front, back, and each side of the blade against hard wood. Of course, reason must be used. Anything can be broken using levers and mechanical advantage. The idea is to test a bit harder than what the blade will see in anticipated use. One must also consider safety and which direction a broken blade might fly if a failure does occur.

I had a tang failure a number of years back. It manifested immediately in the testing. In 30 years using HI blades that is the one time it happened to me. Of course, Bill replaced the knife immediately, no questions asked. You will find discussions of proof testing in the archives. Bill (a former aerospace engineer) made some runs at getting it incorporated in a formal manner into HI processes but ran into some challenges. The kamis have an old and traditional culture.

Email sent
 
Very interesting! That’s a big chunk of steel to fail. Still interested in your answers to the questions in my last post. Know it’s getting late now in SA. Sleep well. I look forward to learning more later.
 
Very interesting! That’s a big chunk is steel to fail. Still interested in your answers to the questions in my last post. Know it’s getting late now in SA. Sleep well. I look forward to learning more later.

I got the knife middle December both my CAK and AK when my wife returned from Nepal.
The first day of using it was the same as the day it broke... I usually split 2 big bags of sekelbos wood and it broke on the 4th session. I split wood as I usually do Striking the front part of the spine very seldom towards the rear part but occasionally. Nowhere near the handle though.I have never needed to strike from the sides ever with any knife. I am just as confused about this breakage... I have never broken any knife and have used much thinner knives. The CAK should laugh at any force from any direction.
 
I used to process firewood with my khukuris regularly, back when I heated with wood. Didn’t batton too often, but sometimes the knife would get stuck and I would either knock it loose or knock it on through.

The reason for stressing the knife in all directions during proof testing is not because one anticipates hitting things frequently with the flat of the blade, but rather to stress any cracks or flaws, no matter which way they may be directed. In an activity like battonning where the knife is stuck in a hard piece of wood and being struck, shock waves are propagating and reflecting in difficult to predict directions through the metal. Best to have discovered any flaws regardless of their directionality.

By the way, the things I say here are my own thoughts rather than an official HI position. I do proof test my equipment prior to taking it out where I need to rely on it. Of course, proofing a fillet knife would look quite different from proofing a khukuri, based on different anticipated use.
 
I used to process firewood with my khukuris regularly, back when I heated with wood. Didn’t batton too often, but sometimes the knife would get stuck and I would either knock it loose or knock it on through.

The reason for stressing the knife in all directions during proof testing is not because one anticipates hitting things frequently with the flat of the blade, but rather to stress any cracks or flaws, no matter which way they may be directed. In an activity like battonning where the knife is stuck in a hard piece of wood and being struck, shock waves are propagating and reflecting in difficult to predict directions through the metal. Best to have discovered any flaws regardless of their directionality.

By the way, the things I say here are my own thoughts rather than an official HI position. I do proof test my equipment prior to taking it out where I need to rely on it. Of course, proofing a fillet knife would look quite different from proofing a khukuri, based on different anticipated use.

Ok.. I get what you are saying about testing before hand. I misunderstood. Thanks
 
About 3 weeks ago I broke my CAK splitting wood, it broke of completely inside the bolster. From what I can see the grain structure is finer than what it should be but not fine enough to be fully hardened. The tang should be soft. The tang where it broke is only about 2.5- 3mm thick same as my mora and there seems to be square and rough cut outs to fit the bolster.....

Did the break occur at the square/rough cutouts under the bolster? If there's no other obvious reason for the breakage that would be my suspect. The place where the tang joins the blade is a high stress area, and sharp angles can propagate stress forces.

Also, 3mm seems awfully thin for the part of the tang under the bolster. I just checked one of my CAKs. The spine thickness just behind the bolster is more than 6mm, and since the tang tapers toward the butt it would be even thicker under the bolster, which is the part I can't measure because it's hidden. My CAK is a fairly small size for that model, only 15.5" overall length.
 
Did the break occur at the square/rough cutouts under the bolster? If there's no other obvious reason for the breakage that would be my suspect. The place where the tang joins the blade is a high stress area, and sharp angles can propagate stress forces...

In this case, the fracture was substantially below the squared cuts and didn’t come near to touching them.
 
Did the break occur at the square/rough cutouts under the bolster? If there's no other obvious reason for the breakage that would be my suspect. The place where the tang joins the blade is a high stress area, and sharp angles can propagate stress forces.

Also, 3mm seems awfully thin for the part of the tang under the bolster. I just checked one of my CAKs. The spine thickness just behind the bolster is more than 6mm, and since the tang tapers toward the butt it would be even thicker under the bolster, which is the part I can't measure because it's hidden. My CAK is a fairly small size for that model, only 15.5" overall length.

It broke inside the bolster. Yes its very thin... the bottom part of the tang behind the bolster I think is where the problem started... its about 2.5mm thick where it broke and the thinnest part only 2mm.
 
Did the break occur at the square/rough cutouts under the bolster? If there's no other obvious reason for the breakage that would be my suspect. The place where the tang joins the blade is a high stress area, and sharp angles can propagate stress forces.

Also, 3mm seems awfully thin for the part of the tang under the bolster. I just checked one of my CAKs. The spine thickness just behind the bolster is more than 6mm, and since the tang tapers toward the butt it would be even thicker under the bolster, which is the part I can't measure because it's hidden. My CAK is a fairly small size for that model, only 15.5" overall length.

The blade is 11.5" long 10mm thick with the tang only being 2mm thick at the thinnest point. That puts a lot of stress on the tang... I don't think any knife that big with such a thin tang will hold up thinking about it. And thats why I asked for a normal AK as a replacement which Yangdu agreed to as I feel hidden tangs are stronger as they have much thicker tangs. I thought the 2mm thickness was normal
 
Now and then we have few blade failure. I will send replacement knife when COVID-19 gets under
control. Until then all of us have to be patience
 
Now and then we have few blade failure. I will send replacement knife when COVID-19 gets under
control. Until then all of us have to be patience

And that is why you buy from a company with a solid warranty.. thank you.
 
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