So . . . I Broke My Kershaw Cryo

Giving five examples of failure of a knife in a thread is just bad science. You do know this is a thread about failure of said knife right? Would you expect everyone who had the knife not fail also post? Remember when that Kershaw Mod said they do occasionally fail? Without knowing actual failure rates I think I will go with the Kershaw folks rather than a self selecting bad example.
 
The-Stig said:
I own one, and it has not broken because I do not carry it. I don't like the feeling of assisted knives, and any spring will eventually wear out. It's a ticking time bomb. Of course, you could say that everything wears out, but not nearly as fast as a spring will. I just don't think it's a good design that is built to last. The idea that my knife could suddenly break at any moment does not inspire the confidence I am looking for in a knife. With most knives, you can see warning signs if they are starting to wear out. Things like lock travel and blade play. With a spring assisted knife, there is no such warning.
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If you don't like the feeling of assisted knives or your fear of them failing is too great to overcome you should definitely avoid them. The great thing is we have so many great choices out there and most of us can find the knives with the characteristics to make ourselves happy. I would say I have a couple hundred assisted knives...99% are Kershaw/ZT. I've carried and used many different assisted Kershaw/ZT knives...some for quite some time and I personally have no fear of one failing. If it does....I'll fix it.
 
Karda said:
Obsessive Compulsive flipping of any knife can deform lockfaces and lock bars, destroy stop pins and in the case of assisted knives, also break springs.
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I don't think many realize the damage that can be done by compulsive flipping.
Knives are made to cut with, and not to be constantly played with.
 
Morrow said:
If you don't like the feeling of assisted knives or your fear of them failing is too great to overcome you should definitely avoid them. The great thing is we have so many great choices out there and most of us can find the knives with the characteristics to make ourselves happy. I would say I have a couple hundred assisted knives...99% are Kershaw/ZT. I've carried and used many different assisted Kershaw/ZT knives...some for quite some time and I personally have no fear of one failing. If it does....I'll fix it.
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I agree. But, if I see a possible weakness in a design, especially one that is unnecessary, it ruins the whole thing for me. I know it is trivial to fix, but a lot of the reason why I carry the knives I do is because I have pride and confidence in owning them. If I'm not confident in the product, I lose interest in it.

It may very well be the case that assisted knives are reliable enough for my purposes, but the knowledge that the knife has an Achilles heel just ruins it for me.
 
Morrow said:
If I took the time to read the discussion.......you're only going to get a couple of those before we have a problem. I read the discussion. I said in my earlier post that I've had torsion bars fail prematurely and I've had them last for a very long time. Sometimes they just break. I was addressing your super-duper business suggestion to "overbuild" just to be safe. I was addressing the point that overbuilding could be a waste of money if the failure rate doesn't support it. I was addressing the point Kai knows their business more than YOU do.
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Personal attacks, wonderful.
If you read my posts:
1. I said we don't know how KAI built the Cryo. However they built it, they have a low return rate due to premature broken springs according to the ZT Rep. I would imagine they'd overbuild them for warranty cost reasons. People will expect Kershaw to fix them, whether it was normal use or not.
2. Of course they know their business better than me, or you, or Karda. Yet here Karda seems to have inside information as to how the designers and engineers made the spring. Oh wait, that was just false information to try to prove his point, which is "it's abuse to flip them so often". The spring it self is not going to over travel, ever. It's not going to be forced to be under more stress than it already is. Tell me how you can achieve the two on a knife like the Cryo. Flicking is only going to release the spring's tension.
3. My opinion is simple: The spring bar failed prematurely due to a defective spring.
Given that the OP did not modify the knife's spring, and only flicked it open repeatedly neither of which induced 360+ Fahrenheit in temperature build up (ridiculous to even think that) nor induce the equivalent of 10,000 openings as per specifications nor induce metal fatigue (according to what I read on springs, that would happen maybe at 10,000+ "cycles"). Given the fact a Kershaw representative made a reply regarding that spring bars failing prematurely likely are defective, chances are this is just one occasion of a faulty spring bar.
Again that's my opinion, not fact not anything.

PS: Don't mock someone's idea for improvement as a way to further your point. It's how this forum is a database of information. People give their opinions on products and what they think they should change. In this case it wasn't what they should change, it's what they probably thought of long before I did, because as you said they do indeed know their business far more than me.

Karda said:
What was that you were saying?

Just from this thread alone.....
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How many have been sold? How many returned for broken tension bars, and at what periods.

You speak as if with common sense you can somehow say statement and people will take them as facts.
 
Morrow said:
How many have you owned? How many have failed?
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Many, and all.

Some weeks some years.

And though the spring style changes the way it breaks does not.

I like kai but they really need to address the issue. I've even had customers knives bar break in the hand full of times I need to open a folder to sharpen it. This is far from user error and though covered by kershaw is a complete PITA when it happens.
 
Just to be clear...you're saying you've owned many knives with Speedsafe and they have all failed? Every single one of them?

knifenut1013 said:
Many, and all.

Some weeks some years.

And though the spring style changes the way it breaks does not.

I like kai but they really need to address the issue. I've even had customers knives bar break in the hand full of times I need to open a folder to sharpen it. This is far from user error and though covered by kershaw is a complete PITA when it happens.
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I have a chive I got around 2000 and its been opens countless times, never broke a bar. I'd say they are dependable. To say otherwise is akin to saying "don't trust tires, they get flats", ridiculous.
 
I wouldn't consider this much of a problem in knives where the SpeedSafe mechanism has no effect on the blade detent - if the assisted spring breaks, the knife can just be opened manually. No mechanical failure in the actual the operation of the knife in any way.

However - if they knife depends on the SpeedSafe spring as acting as a partial or full detent, then spring failure is a more serious issue. You'd think they could hire a design engineer or materials engineer that could actually design a reliable spring! :D

(I'd say their spring are too brittle (RC run too hard), but what do I know?)
 
symphonyincminor said:
I wouldn't consider this much of a problem in knives where the SpeedSafe mechanism has no effect on the blade detent - if the assisted spring breaks, the knife can just be opened manually. No mechanical failure in the actual the operation of the knife in any way.

However - if they knife depends on the SpeedSafe spring as acting as a partial or full detent, then spring failure is a more serious issue. You'd think they could hire a design engineer or materials engineer that could actually design a reliable spring! :D

(I'd say their spring are too brittle (RC run too hard), but what do I know?)
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If the heat treat gets the springs too hard - yes they could be more susceptible to brittle fracture. If the springs are designed to 10,000 cycles as mentioned before -designing to a higher cycle count could probably prevent a lot of the failures that happen, however rare they are. But - that could mean that the spring needs a greater cross-sectional area which could in turn mean that there is a lot more resistance to closing the knife or that it fires too hard. It's hard to say anything about the design without knowing the geometry of the spring.

This really seems to be a QC issue on the springs to me. Too hard or too large of cracks/voids in some specimens rather than bad design. I probably have close to 10,000 open/close cycles on a zt0350 - I play with it incessantly - never had an issue at all. I have a friend that had a torsion bar break after 2-3 months but I don't know how many cycles.

But what do I know, I'm just a design engineer. :D
 
I am new here,so take it for what is worth.

I have had no problems with my Cryo, even with repeated unnecessary flicking. Nor have I had any problems with my ZT0301, other than an annoying rattle.Which can be easily fixed with packing the torsion bar in grease, I just haven't gotten around to it yet.

I am sure that broken torsion bars seem more frequent than they really are. People tend to express disappointment more than satisfaction.
 
MIKE1218 said:
This really seems to be a QC issue on the springs to me. Too hard or too large of cracks/voids in some specimens rather than bad design. I probably have close to 10,000 open/close cycles on a zt0350 - I play with it incessantly - never had an issue at all. I have a friend that had a torsion bar break after 2-3 months but I don't know how many cycles.

But what do I know, I'm just a design engineer. :D
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Agreed - unless you get a sizable sample of failures in hand to do a detailed failure analysis, it's hard to make a concise determination of what is a the main mode of spring breakage.

They have multiple suppliers for these springs (look at how many designs they go into, both foreign and domestic) and it's probably more of a supply-side issue than it is with the design. I can bet ya those spring drawings have gone through numerous revisions over time.... I would think they would ease up on the design constraints over the years to make it a more reliably manufacturable.

Maybe they should just start adding in an extra spring (pennies) instead of having to eat the time/resources/headaches on continuous RMA's?


Todd21969 said:
I am sure that broken torsion bars seem more frequent than they really are. People tend to express disappointment more than satisfaction.
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Quoted for some much-needed perspective..... :thumbup:
 
I think they would add extras if it didn't look bad to customers. People want to think they got a dependable tool instead of a gimmicky toy that requires extra care and maint.

Assisted Kershaws breaking springs have to be many times over the most reported folder fail over the years, but always Kershaw's best selling knives regardless.
 
Old thread and old Cryo, but newly broken spring. It didn´t get apart but a crack appeared at the same point as most and the action became weak. I opened it and can see the crack with a loupe. It is the size of half the cross section. Hardly some 300 (edited) actuations cause I almost don´t use it. Sorry to the fans but it´s bad design, cause most of them break at the same point. Probably the cause is that it´s a spring steel cold bent and they come from factory pre-cracked. That kind of steel part should be bent annealed and quenched after bending.
Funny that I managed to make an almost equal spring from a part of a spiral spring and when it was almost exact the final bending broke it!!
I had enlarged the detent hole, so that the ball reaches it and now it became manual.
 
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alex1577 said:
Here's how it happened. I was just sitting down, messing with the cryo as i usually do and then found myself flipping and closing it with my left hand and then *snap* I've heard the sound before from the cryo when closing but this time is was louder. I thought nothing of it but when i tried to flip it again, it dawned on me. I broke my kershaw cryo :(. I took a picture for you guys to see

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So, what do you guys think about this since this is the discussion forum?
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Thank god I expected a blade break.
 
It happened with my Shield. Called them, asked for a spring/torsion, they sent one.
Not a big deal, those are inexpensive models. Kershaw took care of it.
 
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