Blade failure on 8mm thick Condor Heavy Duty Kukri!

T

T1nkerer

Joined
May 24, 2014
Messages
16
Well i never thought this could happen with such a think blade made from a respectable material good for the tasks it would find itself being used for but here i am. The knife is only 4 weeks old and i have been using it for chopping wood, as its intended for. Struck a chopped log to split it and SNAP! Its failed along the thickest part of the blade. I can see a scorch mark on the blade end of the brake where it looks like it was overheated when being ground/shaped. Contributing factor? Any metallurgists on here to give an opinion on this? Now i have a problem. I'm taking it back to the suppliers tomorrow and am expecting an exchange or refund but i really liked this blade. Could mine have been a defective blade or is this the limit for the knife, to be honest ive lost confidence in it now?




 
Weird break. I bet there was an inclusion or flaw in the steel to get a clean break in that spot. When I see a darker area in a break, normally I am thinking there was a micro crack already there?
 
Another example of why I never carry only one knife when "out there". ANY knife can have a heat treat/inclusion/or other undetectable problem. I'm sorry you had this experience, and understand your lack of trust in this knife, even though it is an anomaly from this maker. I'm confident you will be taken care of, but admit I would go for something else since my outlook would never be the same on that model. A real shame, but ca-ca occurs.
 
Wow. That's a thick blade made out of tough steel -- 1075, I think. It should be tough as nails. And I see no obvious stress risers.

Because the edge-side of the break is darkened, I'd guess that it was already cracked there for some reason, and the darkening is weathering or staining. But I don't really know.

Sorry for the broken knife, but thanks for sharing.
 
You'd need a metallurgist and a microscope to know for sure but my guess is a small crack started at the sharp edge, perhaps at an area of bad metallurgy. I am not accusing them of a burned spot, like I said you need an expert to decide. But I think a small crack grew slowly through the darkened area and then got long enough that one final chop caused a crack that ran the length of the brighter area all at once.

If they warrant the blade for chopping they should replace it.
 
I don't know what it means for the grain to blow out, but if you look at the second photo, it looks like you can see the line of the final break starting from the dark spot at the bottom of the stained break near the edge right up to the top of the break at the spine.

I don't think a burnt edge would take on a pattern like that stain. I think there was a defect in this particular blade. If it were just a grain issue, it would have likely broken in a different part of the blade, not at the widest section where there are no stress risers.

I can't imagine that the seller would not replace that blade, and I'd guess that you could wail on the replacement knife till the cows come home and and never see a break like that again.

It would be nice for some metallurgist to give us a photo tutorial on various types of breaks and what to look for to explain them.
 
Im sure they will replace it. Think i will get another as this failure seems so strange and i love the knife. To get around the confidence thing i will put it to work on the same log and do the same thing again to be sure it was a one off problem. I will offer to buy the broken knife back from them if they do it for a reasonable cost. Been toying with what sort of knife i could make out of whats left on the blade. Silver linings and all :)
 
Twindog;13693488]I don't know what it means for the grain to blow out, but if you look at the second photo, it looks like you can see the line of the final break starting from the dark spot at the bottom of the stained break near the edge right up to the top of the break at the spine.

I don't think a burnt edge would take on a pattern like that stain. I think there was a defect in this particular blade. If it were just a grain issue, it would have likely broken in a different part of the blade, not at the widest section where there are no stress risers.

I can't imagine that the seller would not replace that blade, and I'd guess that you could wail on the replacement knife till the cows come home and and never see a break like that again
It would be nice for some metallurgist to give us a photo tutorial on various types of breaks and what to look for to explain them.
Click to expand...
Great idea. :thumbup::thumbup:
 
All right !
The darkest part of the failure is probably an inclusion .That then started a crack around it. This crack then oxidized to cause that 1/4" + dark area. Then you whacked it and it was 'all she wrote ' !! The grain size might be a bit large.
For many years I was a fencer and picked up broken blades .They were poor quality 9260 with lots of large inclusions. Nicks on the edges from parrying, beating or failure at an inclusion were the two modes of failure .
 
This is the 3rd or 4th failure of something from Condor I've seen posted here in the last 2 years or so. I'm not thinking I'd want to buy one anytime soon.
 
mete said:
All right !The darkest part of the failure is probably an inclusion .That then started a crack around it. This crack then oxidized to cause that 1/4" + dark area. Then you whacked it and it was 'all she wrote ' !! The grain size might be a bit large.For many years I was a fencer and picked up broken blades .They were poor quality 9260 with lots of large inclusions. Nicks on the edges from parrying, beating or failure at an inclusion were the two modes of failure .
Click to expand...
Hey Mete:So are the two dark spots in the discolored part of the edge both inclusions? Would they double the chance of creating a crack that would lead to full blade failure?
 
Now that's a freaking blade fail. I was half expecting a couple of small deformations on the tip after you dropped it onto concrete like in the other thread. Holy cow that's some thick steel that some wood got the bettee of.
 
+1.....


Twindog said:
I don't know what it means for the grain to blow out, but if you look at the second photo, it looks like you can see the line of the final break starting from the dark spot at the bottom of the stained break near the edge right up to the top of the break at the spine.

I don't think a burnt edge would take on a pattern like that stain. I think there was a defect in this particular blade. If it were just a grain issue, it would have likely broken in a different part of the blade, not at the widest section where there are no stress risers.

I can't imagine that the seller would not replace that blade, and I'd guess that you could wail on the replacement knife till the cows come home and and never see a break like that again.

It would be nice for some metallurgist to give us a photo tutorial on various types of breaks and what to look for to explain them.
Click to expand...
 
That's an interesting break. I can't really tell from your pictures, but it seems like the black spot doesn't reach the edge, which pretty much excludes the possibilities of it being a scorch mark or oxidation. Scorch marks are caused by your combusting agent depositing carbon on a surface, and there's no way enough oxygen could have diffused through the steel to cause internal oxidation like that.

So it seems to be some sort of inclusion like others have suggested, most likely an impurity of some sort when the steel was smelted. Your blade shows brittle fracture characteristics throughout all that I can see. Look for little surface striations near the black spot. Those are signs of fatigue failure and if you find them, the fracture is probably due to the inclusion being a stress raiser and growing a little crack till failure.

You can try scratching the black spot too, that'll tell us whether it's a surface substance or a 3-dimensional impurity.
 
bronyblacksmith said:
the grain on that kukri is huge.
Click to expand...

Yes it is. I guess....but what do I know.

Anyway. I broke a Nepal kukri at the cho and the grain looked a lot like that. I'm sure no expert but that grain looks cast to me. I caught all kind of hell for batoning with an over 1/4 thick Kuk. I really don't understand why a chunk of steel like that can fail when pounding on a piece of wood. Hell, I've used wedges to split wood that were probably 100 years old and they are still going strong. Beat'em with a sledge too. Wood shouldn't break steel. No way, No how.
 
sirupatespecial said:
Yes it is. I guess....but what do I know.

Anyway. I broke a Nepal kukri at the cho and the grain looked a lot like that. I'm sure no expert but that grain looks cast to me. I caught all kind of hell for batoning with an over 1/4 thick Kuk. I really don't understand why a chunk of steel like that can fail when pounding on a piece of wood. Hell, I've used wedges to split wood that were probably 100 years old and they are still going strong. Beat'em with a sledge too. Wood shouldn't break steel. No way, No how.
Click to expand...

I saw your post and that they where giving you a hard time. wood can break steel, especially if you get it caught in a knot, but most choppers should be able to baton rather large logs especially a 1/4 inch thick or larger kukri.
 
I don't really see any typical fatigue failure but I'd like to examine it much closer . BTW does anyone have a magnifier that plugs into your computer ?
You don't have to have a fracture start on the outside. One of the most spectacular failures I've seen is that of a very large rotator of an electric generating station. It had failed through fatigue from the imperfections in the center . The centrifical forces were enormous !! It tore apart the rotator , the building and every thing nearby !!
 
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