Knife snapped while straightening! (pics)

Magnaminous_G

Magnaminous_G

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Jul 13, 2011
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So I was straightening a friend's J.A. Henckel's utility knife to get it ready for sharpening. It's one of the Solingen-made Twins line, not the lower quality, Brazil-made International line. I've sharpened J.A. Henckels knives for this friend before, and I've had to straighten some of them, too. A little table-edge straightening fixed them all... until this one. I wasn't even putting a lot of weight into it and had just started when *SNAP*. This happened. I took macros of the steel cross section at the two break points. Do you guys see anything that might explain why this knife snapped like that?


QbU5o6S.jpg


N3vzu37.jpg


NOduFQC.jpg
 
have you tried to file that blade, those end shots are telling me its a very hard blade. Can you take one more picture that shows the whole blade.

Richard
 
Tinbasher said:
have you tried to file that blade, those end shots are telling me its a very hard blade. Can you take one more picture that shows the whole blade.

Richard
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Not sure what you mean by "file" the blade or "picture that shows the whole blade."
 
File the blade= just to feel if you can file it or not

The whole blade = I can't see the top or bottom edge of the blade in the pictures

Richard
 
overheated ? the grain looks way too big, thats a lemon imho.

link this to the knifemaker discussion forum and see what the pros say about it.
 
pwet said:
link this to the knifemaker discussion forum and see what the pros say about it.
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I did. Bad idea. They think I'm looking for excuses so I can get out of responsibility. That's what happens when you post something like this in a sub-forum full of professional craftsmen...
 
and no one commented about the pics meanwhile ? :eek: quite stunning.

back to topic this is what x50crwhatever (the steel used by henckels or a close cousin) should look like after a correct HT. pic courtesy of a french maker, its a test sample. hope the pic isnt too large.

dscf3671z.jpg


you can see the grain and the break pattern, the fact that yours snapped straight without any deformation on the bent side means a lot to me. but, as always icould be wrong, its not my job.
 
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How's the edge where the two sections broke off look? Perhaps all the stress caused a snap to occur inline with some damage from the V sharpener
 
Could be a number of things but without Lab testing its just a lot of random guessing. In the end you broke it and will learn from it.

How bent was it?

In your correcting of this bend did you flex less, equal, or more than the angle of set bend that you were trying to correct? (How far did you flex the opposing way?)

Most straightening is typically done on laminated blades, I usually use a hammer on softer steels :)
 
straightening a blade can be a hard thing to do. i have made test blades to see what works to straighten a blade and sometimes you get lucky but most times they break. i have straightened a few by using 3 wooden dowels. do you have access to a rockwell tester? to me it looks like the rc might be real high.
 
knifenut1013 said:
Could be a number of things but without Lab testing its just a lot of random guessing. In the end you broke it and will learn from it.

How bent was it?

In your correcting of this bend did you flex less, equal, or more than the angle of set bend that you were trying to correct? (How far did you flex the opposing way?)

Most straightening is typically done on laminated blades, I usually use a hammer on softer steels :)
Click to expand...

Hi knifenut :) Not very bent, a slight bend but noticeable. I've straightened a lot of knives using the Mark Richmond method on a table, sometimes bending toward the table, but always lightly and incrementally, and my table has rounded edges, over which I place a towel. Never had a break before. I wasn't flexing it much at all. I had just tested it lightly at first and then started to apply a little pressure and *SNAP*. Some of the guys in the knife maker sub-forum think the grain is on the large side, which *might* be the culprit.

It's been too long since your last vid. I think you know what you need to do. :D :D :D
 
The fact that there are two breaks would indicate that hardness was the culprit, rather than a fault in the blade. I broke a M4 blade on an AFCK that I had a knifemaker reharden to 64 HRc. It also broke into three pieces and the grain structure looked similar.

If you can bend a blade to the point where it will hold a new position, you are going to fatigue that metal and leave it weaker. Probably not a big deal for a kitchen knife, but still an issue. It seems odd to me that your friend had so many knives that were bent. Maybe the QC on that batch of knives was lax.
 
Magnaminous_G said:
I did. Bad idea. They think I'm looking for excuses so I can get out of responsibility.
Click to expand...

That's flatly untrue. I don't know where you got that idea. They (including me) are telling you that straightening a cold blade was a bad idea in the first place.
 
Thats a bummer man. I provide the same free service for friends & family. It seems like at least once a week someone brings me an abused kitchen knife or two that need some TLC. More often than not they are warped and need a little straightening. Sometimes it works sometimes it doesn't. The thicker knives usually wont bend with the amount of force that I feel comfortable with and they just stay warped.

I checked out the other thread you started and I cant believe that people are opposed to straightening a cold knife. If you watch Murray Carter's sharpening videos he tells you that the first step is assessing a blade's straightness and correcting it accordingly. I don't remember Murray ever saying anything about heating a blade to a certain temperature before straightening.

Anyway buddy, sorry about the hassle with the knife. Better luck on the next one.
 
Murray Carter? Pfft. He's just a famous, award-winning ABS Master Smith. He doesn't know anything compared to these guys. I'm ashamed at you, Talley!
 
I feel for you who tried to provide such service (free IIRC?).

Learning from your lesson, I'd just sharpen it around and as much as possible without straightening. Even if that means doing it in sections :(.
 
That's not bad advice, Chris, but I'd rather tell someone to give up on a bent knife than continue to use it bent. I'll warn my "customers" (yeah, I do it for free :)) from now on, but no one should be using a bent knife, and I won't sharpen one unless the bend is so slight it doesn't affect the sharpening (and if that were the case, I'd be inclined to fix the bend! :D). If it breaks, it breaks. But I'll give plenty of warning. As I said in the initial post, I've straightened dozens of knives with no incident. This was the first break.
 
Is it worth sending it back to J.A. Henckel? What is their warranty?

The fact that it broke in two places at the same time leads me to believe that there were problems with the heat treat. Add that to the large grain size and it looks like a manufacturing defect.

The only time I ever got a break that looked like that was when I dropped a knife that had been hardened, but not yet tempered. Have you run a file across it to see how hard it is?

JMHO,
Allen
 
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