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Interesting blade failure on a Sebenza...
- Thread starter Gaston444
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Basically this.
In my mind, any company can have a knife make it through QC that shouldn't have, and I have no problem with that. I think not being ok with that is somewhat of an unrealistic expectation.
Even if the company has great six sigma/ ISO 9000-9001 processes and QC, the possibility still exists that something could make its way through that shouldn't (even if the likelihood is extremely low... like .3% of goods or way, way, way less depending on the standard). This is exactly the reason that companies have warranties, to cover cases like this. And as long as its not a big systemic problem (like suddenly we saw hundreds of sebenzas cracking this same way), and they didn't do anything to fix that process AND they didn't cover it in warranty, I have no problem with it.
In this case it seems to be a one-off problem (at least I haven't seen it before, whatever that's worth), where the company stands behind the product and replaced it free of charge.
Seems fine to me.
Any chance this is a hint about the "rep"/"reputation" system used in other forums?
I'm a longtime forumite (overclock.net.... hence "ocn - logan"), and find that really helps separate the "wheat from the chaff" so to speak. It provides another way for users to "prove" legitimacy/trustworthiness other than just post count, or time on the boards. It doesn't magically fix trolling, but so far in my experience it has helped with it substantially. Users are always trying to be helpful, to increase their reputation rather than just posting a lot.
Anyway, that's my two cents
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Don't worry about it. Everyone will tell you what you did, it's the Internet and it knows best and will let you know it.
It's no big deal, stuff breaks. A material flaw can happen to any knife, even a cheap Schrade. You have no clue what happened to it before you got it, could have been dropped just right and created a weakening crack. I seen a guy drop his motorcycle on the clutch side and it had scratches on the end of the lever. Everything checked out fine. About a mile down the road he pulled the clutch in and it broke where it attaches to the clutch cable. Anyone who's been around metal knows trauma to it can cause the slightest of pressure later on to cause the final break. i abuse the snot out of my Sebenza and it's one the most sturdy built folders I've owned or used.
Have fun with your new blade!
trevitrace
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Hmm. Looks like an old CRK broke for reasons we can only speculate. Looks like CRK replaced it. Id say while its not nearly the norm Im glad to see it was handled swiftly and the owner has a new sebbie after many years of faithful service of the fallen offender. Do I think its shocking? Nope. Is it normal? Nope. Should it be read anymore into it than that? Not in my opinion. Everything that can break will under the right circumstances. I actually think its more impressive that the knife survived as long as it did under the circumstances. And before anyone points a finger at me calling me a fanboy I have only owned one Chris Reeve. So I wouldnt call myself a fanboy. Hell, Im not even a fan really. But for some odd reason I dont see a need to hate things I dont like.
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Yup. And why his consistent and constant trolling is allowed to continue I will never understand.
Blade steel by its nature is somewhat "notch sensitive". Knife blades have various discontinuities that provide stress concentrations and invite fractures to happen, thumb holes and holes for thumb studs are some of the worst.
A LOT of lateral force on a blade could cause a fracture to initiate, lots of ways this could happen. Or a significant lateral force repeated enough times to initiate a fatigue crack and then a little bit more load could then cause a fracture. I'm not sure how this would happen in normal use. This is the closest to the "straw that broke the camel's back" discussion. I'm not sure if there was a way that the material could have had cracks at the hole from manufacturing. You would not see these through x-ray but you could find them with dye penetrant or magnaflux procedures.
In college I tested large bolts in fatigue. Once I had a fatigue crack going 3/4 of the way through a bolt, I could clamp it in a vise and break it by hand, and I'm talking about bolts up to 2" diameter. So having a fatigue crack already there makes a tremendous difference.
A LOT of lateral force on a blade could cause a fracture to initiate, lots of ways this could happen. Or a significant lateral force repeated enough times to initiate a fatigue crack and then a little bit more load could then cause a fracture. I'm not sure how this would happen in normal use. This is the closest to the "straw that broke the camel's back" discussion. I'm not sure if there was a way that the material could have had cracks at the hole from manufacturing. You would not see these through x-ray but you could find them with dye penetrant or magnaflux procedures.
In college I tested large bolts in fatigue. Once I had a fatigue crack going 3/4 of the way through a bolt, I could clamp it in a vise and break it by hand, and I'm talking about bolts up to 2" diameter. So having a fatigue crack already there makes a tremendous difference.
stabman
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Some Spyderco Military's have broken blades too...
Mine hasn't broken, but then again, neither has my Umnumzaan.
The real problem is those damned internet knives.
Internet knives seem to break all the time.
So remember boys and girls, don't go live on the internet...all the knives are brittle, and cats take pictures of themselves with their heads stuck through bread.
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CRK has only had about 100 broken blades since they started making the Sebenza.
That's over a 25 year period, and I don't think any other company could say that.
I don't know, but I have a hard time believing it broke by wiping it on his pants.
That doesn't really matter though since CRK replaced the blade.
Many companies won't replace broken blades even if the knife isn't this old, so kudos to CRK.
Glad they took care of him.
Thank you !
Hopefully he will stop trolling EVERY CRK thread now.
Thanks again.
That's over a 25 year period, and I don't think any other company could say that.
I don't know, but I have a hard time believing it broke by wiping it on his pants.
That doesn't really matter though since CRK replaced the blade.
Many companies won't replace broken blades even if the knife isn't this old, so kudos to CRK.
Glad they took care of him.
Thank you !
Hopefully he will stop trolling EVERY CRK thread now.
Thanks again.
I know of a few that could....
Stress fractures due to the pin pressing on these is a known anomaly. Most of them have cracked out the top of the hole though. I suppose it's possible that this one thoroughly cracked the blade and it went unnoticed. Time and usage took care of the rest. At any rate, CRK took care of the problem, so it's a non issue.
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I'd like to see proof that CRK actually replaced the blade. Sure blades can be broken, often by user misuse, but CRK blades, maybe 1 in a 1,000,000. The warranty is probably more for the pivot and lock mechanism than for broken steel parts. It is an interesting story though. The blade doesn't look it was used or sharpened very much. Again, the story originates in France from what source?
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I had not heard that because I don't pay much attention to CRK knives but it makes sense and could play into this problem. If you have a small defect that begins from something like this in the manufacturing process, it would not take much additional stress from something like lateral bending to cause it to fracture all the way through. Fatigue and fracture each require some form of defect to initiate, and an appropriate level of stress. The thing is that a larger defect will allow fatigue or fracture to initiate at a lower stress level. If you take a piece of metal and reduce its potential defects beyond a certain level, you increase its fatigue life to infinity.
Back to the thumb stud pressing- every hole and every thumb stud will be slightly different- some studs press in easily, some studs press in and break the blade, others might be right on the verge of causing a fracture but not quite enough to cause it to propogate all the way out to the edge. Take one of these and add some stress from lateral bending and that will cause it to fracture the rest of the way.
Yep. That's a broken blade, all right.
That is not a good design for manufacturing something thin out of notch sensitive material. The sharp points in the "M" are especially bad for stress concentrations, and how close one of the points is to the blade hole is apparently a real problem.
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The design of the Tactility, or rather, this version with the cutouts (I have one, by the way) is not really designed for a heavy use case. It seems much more of a gentleman's folder, and I use it as such all the time. It cuts food, open envelopes, cuts string/tape/etc. with no issue. Yes, the "M" stamping appears decorative in design, and if you were to try to do lots of back and forth levering side to side with this knife, I can see how it might be easy to break. However, as long as you understand what this particular knife is supposed to be about, you won't have issues.
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