Broken Recon Tanto pics--finally

What blows me away is the clean, sweeping curves in the fracture path. Can anyone explain this?
 
Yes , thanks for the photo. Fine grained for sure , brittle fracture . There would have to be some tests made but I wonder if there was not enough temper [ not enough time or temperature for the temper]. If it failed as you explained lack of temper would be my conclusion.
 
mete said:
Yes , thanks for the photo. Fine grained for sure , brittle fracture . There would have to be some tests made but I wonder if there was not enough temper [ not enough time or temperature for the temper]. If it failed as you explained lack of temper would be my conclusion.
Mete,that would make sense it not having a proper temper but can you explain why these Cold Steel knives seem to be breaking in the same general area?
Scott
 
Rat Finkenstein said:
Pounding on the spine of the knife to drive it through the material, usually to split wood. mostly using a stick to pound with. Definitely not an abusive exercise for a good knife.


Thank you Rat. That is what I thought it was but I wanted to make sure. I am here to learn too and don't mind asking questions.
 
Personally, I gave up on CS after receiving a AUS8 Master Hunter a few years ago that you could simply slip the handle on and off of. Regardless, this is the cleanest, most odd fracture I think I've ever personally seen. It was just too weird to me not to comment on it.
 
Razorback - Knives said:
...why these Cold Steel knives seem to be breaking in the same general area?

When you load an object at two ends, the strain is highest in the middle. When batoning you hit one end and press down on the other and thus the point of maximum strain is inbetween them and the break won't go through the choil as there is too much steel, so it goes through the tang very close to it.

For plain carbon steels (and similar low alloy steels) there is a zone of embrittlement at 500F which gives a torsional toughness *minimum* at a hardness of 60 HRC (sound familiar) this zone is usually associated with the precipitation of cementite along austenite grain boundries and usually avoided if you want resistance to impact.

This may be the case with carbon V, you would need to check the tempering responce data to be sure, but even then, though the toughness decreases a lot, it still won't go as far as high carbon stainless and even that won't break by hitting it with a piece of wood.

-Cliff
 
2katana said:
I am strongly suggesting that you call Cold Steel. I have been dealing with them for 25 years and they stand behind their product. When you call you need to speak to the head honcho, his name is Miguel and he's in charge of the customer service department. He has the power to help you. ....:
This to me is the oddest part of this entire thread. There's actually someone at Cold Steel who gives a rat's rear about customer service? Thankfully, I haven't had a need to call anyone there for more than ten years, but was convinced prior to that that no one could hire people as rude as the ones they had on their 800 line, without actually recruiting them. I'm not discounting your expeience with them-it is what it is, but to me, Cold Steel has always epitomized what crappy customer service is all about: disinterested, rude, and abrupt. :thumbdn:
 
When a file breaks it can have that kind of glasslike curved fracture. Files are not tempered at all....
 
I was always taught to baton with a light grip on the handle- just to make sure that it does not move the handle up too much to loose the force that you are applying, and to hit the knife as close to the piece being split as possible. By the way- what were you batonning- could you have hit a knot with your knife. Also where on the knife were you hitting. Not saying that you are at fault- just wanted a bit more of the picture
 
Looks like the knfe was brittle. I had a buck knife (10 years ago) that did the same thing. The blade on the buck broke exacly like the CS. Smooth and with a curve. Buck claimed that the heat treat was bad and the knife had become brittle. Send it back to CS.

Jansen
 
I was batoning through a piece of birch... didn't see any knots nearby. Since the blade wasn't entirely embedded in the log yet, I was hitting the spine of the knife directly over the log. I was holding the handle lightly, mostly to make sure the log didn't fall over.
 
Those who are wondering about the shape of the fracture surface obviously have never seen the thousands of fractures that I have . Failure analysis was a big part of my job !! .....Can they forget to temper ? I had a gravers chisel and when I used it for the first time I had a problem .The very tip chipped off.This was on fairly hard steel so I tried it on soft brass , the same thing happened. After thinking about it I wondered if it had been tempered .After I tempered it it worked fine !!
 
Cougar Allen said:
When a file breaks it can have that kind of glasslike curved fracture. Files are not tempered at all....

So not tempering at all can produce the same sort of failure as improper tempering?
 
Thomas Linton said:
So not tempering at all can produce the same sort of failure as improper tempering?

If you do not temper, the steel will be very hard and brittle. It will fracture much more easily.
 
Files are tempered, files are usually made from high carbon steels similar to 1095 and there is a hardness peak after tempering which increases the hardness and strength slightly and the toughness significantly. Tempering doesn't have to soften the steel.

If cutlery steels are not tempered they are most likely going to be untempered martensite which is unstable, high stressed and can crack on its own. There are other heat treats which don't require tempering and form other products like bainite, but most knives are martensite based.

This could be a case of too long a period after quenching and before tempering which could induce self-cracking and or number of other defects. Since the blade is wrote off anyway I would see if the rest of the blade is that brittle or was it a localized defect.

However if you do that you might get refused a replacement.

-Cliff
 
Keith Montgomery said:
If you do not temper, the steel will be very hard and brittle. It will fracture much more easily.

I thought I knew that. was trying to understand the application of the quoted comment about files.
 
I took a 1/8" wore out file and used sections of birch hardwood flooring about two feel long as a baton. I took a role of paper towel, put the end of the file in side and doubled the roll over then used a heavy work glove on my off hand so I could press doen very hard on the end of the handle. I batoned the file into sections of small wood hard enough to drive the blunt face of the file into the wood and crack off the birch flooring. The file would not break. Note the tangs of files are much softer than the actual file itself. It seems more than a little ridiculus that a tactical or heavy use knife would not greatly exceed the durability of a 1/8" file. I then did a test impact by turing the file so the wide part was on the wood and it was trivial to break though it failed through passing the yield point not from impact. The file is about 10 times stronger through its width than its thickness so that isn't surprising.

-Cliff
 
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