Zero Tolerance Liner Lock Closures?

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BigKurtHaze

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It could be entertaining--I admit, I was amused when I tried it with mine. If you do, don't mess up that one I like best of yours, I like seeing it pop up on your instagram every now and again.

That said, one of the ZTs I carry most, my 0770cf, fails the test casually and I've used that knife a ton. Used it to cut up boxes, pop wire ties, cut carpet, you name it, and it's never failed me, so it's mostly a theoretical problem (much like the Sebenza's poor spine weight performance--unless you plan to hammer it into a tree and stand on it, you'll probably never see it fail in action).
Thanks, Greg! I think I've had enough entertainment value from following along with this thread, will keep coddling my 0909 so it will be making IG appearances for years to come. :thumbsup:
 
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As for your point about hands reinforcing the lock, I disagree. I'm a mechanical engineer and I did some analysis on liner and frame locking mechanisms. It is true that the locks are aided significantly even by small amounts of force applied normal to the locking bars. However, not everyone holds a knife in a hammer grip (a lot of my EDC tasks involve pinch grips or draw cutting), nor do they hold it securely with a death grip, and most damning of all is that not all frame lock knives are designed in such such a way to even put much of your fingers on the lock bar in a hammer grip. My hands wrap around most knife frames and barely touch the lockbar. For liner locks, there's obviously no reinforcing action either. To test this very point, I've held some frame locks in a normal grip and found that, using a wooden dowel or rod to push over the lockbar while being gripped, there was basically no difference in force required to open a knife being gripped and the same one not being gripped

At least with a recoil driven handgun you have to try to limp wrist it to get it to fail. I'm telling you that your grip very well may do nothing to prevent lock failure in the event of pulling a stuck knife out of a firm piece of cutting medium or accidentally knocking the knife on something.

I will agree that you should just use a fixed blade, but that's not how these knives are marketed. Hell, even CRK advertises or once did advertise their Umnumzaan as being a virtual fixed blade.

Yeah, you have to gorilla-grip a frame-lock to have any influence on the lock (even if minimal to none). My reinforcement is really aimed at the flipper "appendage". For normal saber grips, your finger keeps the blade locked-out pretty well. Again, I only mentioned a hammer-style grip as that was the concern (self-defense and failure). If I'm using a pinch-grip or holding it lightly, I'm likely not doing anything (at least that I can conceive of) that would put pressure on the spine of my blade.

My point about limp-wristing is spot on with respect to the test that was being conducted. I would certainly have to hold my handgun in a way that caused it to fail...much like the holding a knife in a pinch grip and whacking the spine on a roll of tape. If I'm holding my knife properly for harder-cutting tasks, the likelihood of inducing that kind of failure is close to zero. Still, I think there are some issues with ZT's design, the steel lockbar inserts, and potentially their mechanical tolerances, so one can't be naïve about thinking a heavy duty folder is designed for fixed blade tasks regardless of the advertisement. My whole disagreement is that the video testing is a poor example of real-world use and a lot of "what-if" hypothetical scenarios are irrelevant. Just because I can purposely induce a failure to feed in my handguns doesn't mean it's a design-flaw, it's an end-user error and improper handling of the handgun. In my world, you mitigate "what-if's" by reinforcing proper planning, training, and using gear properly and purposefully. Again, the real world where I live beats table-top tests everyday...labs are and table tops are great ways to show potential design issues (which I can appreciate), but they don't often represent reality from a user's perspective. Just my humble opinion.

ROCK6
 
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Wow, I kind of lit a fire with this thread.
Anyway, I got my 0909 today. First thing, pressed the back of the blade with my hand, then wacked on my palm, and the then busted it on my knee cap. No failures, no metalic sound. The lock up looks more secure than say Jill's. Her's looks like it locks up more on the corner of the lockbar.
I'm keeping it. Before I got it I did entertain notions of sending it back problem or no and replacing it with an Adamas 275 just because this whole lock failure thing has been kind of disillusioning, but I have to say that I already like it. not often you see an "overbuilt," thick bladed folder like this have a good, high hollow grind that comes to having a suprisingly small amount of material behind the edge. That's exactly what I want because I won't be busting this through cinder blocks but will be gutting things and doing tasks I appreciate a good, sharp edge for. The Adamas on the other hand has an even thicker blade with a saber grind that seems like it would cut more like a wedge. It's is also 65 bucks more expensive, has a blade steel I don't prefer for this application, and appears even bulkier.
I think this will work out just fine and will give updates if it does anything interesting.
 

evilgreg

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My whole disagreement is that the video testing is a poor example of real-world use and a lot of "what-if" hypothetical scenarios are irrelevant.

I love my ZTs and have no plans to dump them. That said, an obvious counter argument to your "it's an unrealistic test unlikely ever to occur in real use" is that many other folding knives don't suffer this failure mode at all. For example, I spine-whacked a few Southards and none of them failed, so why not carry one of them in place of any ZT I'd carry, just to rule out this potential issue, however unlikely it might be?

ust because I can purposely induce a failure to feed in my handguns doesn't mean it's a design-flaw, it's an end-user error and improper handling of the handgun.

Be careful using this argument around revolver fans; they're awfully likely to cackle about this being one more reason that wheel guns are superior to your new-fangled automatic trash--they're not sensitive at all to your wrist's limpness or lack thereof. ;)

I sometimes pocket carry an awful craptastical little miniature 9mm that has not failed me once in 600+ rounds, but if I hand it to someone who doesn't keep a firm grip on it they're likely to find it failing to cycle properly.

Of course I'm not advocating folks go out and limp wrist their revolvers, whether they cycle properly or not--anyone operating a firearm without a firm grip on it isn't likely to hit whatever they're aiming at in the first place, as how can you actuate a trigger without altering where the firearm is pointing if you don't have a solid grip on it?
 
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Be careful using this argument around revolver fans; they're awfully likely to cackle about this being one more reason that wheel guns are superior to your new-fangled automatic trash--they're not sensitive at all to your wrist's limpness or lack thereof. ;)

There is that, but speaking from a combat zone environment where I work with more than a dozen different countries...you won't find a single revolver in use:D That's not to say they're not as reliable or functional, just not popular these days in modern armies. But while limp-wristing a revolver may not induce a malfunction, it does make control and follow-up shots extremely more difficult by needing more time to get control of the revolver. Again, loosely holding a folder and whacking the back of it just doesn't compute with my use of folders I've used for over 30 years in/around the military...and I'm a knife-guy who uses them at every opportunity (or even making up opportunities:D). Show me a systemic, real-world-use problem, even with corrected operator error, and I'll pay more attention. Until then, it's an academic, controlled test, that is artificially manufactured to identify a design flaw that is irrelevant in normal use...However, ZT should take a serious look at their designs regarding this as I think it's either an issue with the steel-on-steel locking insert, or simply poor tolerance (especially for a $200+knife).

ROCK6
 
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Also, I presume you fixed the car? Or did you just send it back to the owner saying, "your expectation that this car not leak is unreasonable?"
We told em not to worry about it. Gearbox Oil level gets checked periodically and the leak was real small. Lots of supercars and others do this shit and it'll be big money to bring about a 100% non leaking component. Part of the game, cars not broken, car is being a car.
 
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My bad for not explaining how small of a leak it was in my original post. I'm not necessarily opposed to your position I'm just giving a perspective.
 
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Yeah, you have to gorilla-grip a frame-lock to have any influence on the lock (even if minimal to none). My reinforcement is really aimed at the flipper "appendage". For normal saber grips, your finger keeps the blade locked-out pretty well. Again, I only mentioned a hammer-style grip as that was the concern (self-defense and failure). If I'm using a pinch-grip or holding it lightly, I'm likely not doing anything (at least that I can conceive of) that would put pressure on the spine of my blade.

My point about limp-wristing is spot on with respect to the test that was being conducted. I would certainly have to hold my handgun in a way that caused it to fail...much like the holding a knife in a pinch grip and whacking the spine on a roll of tape. If I'm holding my knife properly for harder-cutting tasks, the likelihood of inducing that kind of failure is close to zero. Still, I think there are some issues with ZT's design, the steel lockbar inserts, and potentially their mechanical tolerances, so one can't be naïve about thinking a heavy duty folder is designed for fixed blade tasks regardless of the advertisement. My whole disagreement is that the video testing is a poor example of real-world use and a lot of "what-if" hypothetical scenarios are irrelevant. Just because I can purposely induce a failure to feed in my handguns doesn't mean it's a design-flaw, it's an end-user error and improper handling of the handgun. In my world, you mitigate "what-if's" by reinforcing proper planning, training, and using gear properly and purposefully. Again, the real world where I live beats table-top tests everyday...labs are and table tops are great ways to show potential design issues (which I can appreciate), but they don't often represent reality from a user's perspective. Just my humble opinion.

ROCK6

I don’t want a folder that doesn’t fail because of a flipper tab hitting my finger. That feature is supposed to be a secondary safety to the lock’s primary saftey.

I’m not satisfied with a lock that fails but “its no big deal” cause my finger will catch the flipper tab. Sorry not good enough.
 

SpySmasher

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In my world, you mitigate "what-if's" by reinforcing proper planning, training, and using gear properly and purposefully.
Mitigating "what ifs" is a great policy if you have no choice but to accept the uncertainty. When you have the opportunity to remove the "what if" completely by designing it right out of the appliance, that's an objectively better solution.
 
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I doubt it was delivered brand new leaking oil. Anything mechanical can wear out. It's another matter when brand new they aren't up to standard.
The car had a typical very low amount of miles on it, like 4,500 I believe, cars can leak in the way this one leaked right from the assembly line, you hardly ever see it bcz QC is so awesome, especially nowdays, but it's a thing. Anyway, Ferrari is a special case so maybe I'm using a bad example and all of what I'm talking about may relate more to who I am vs what is right, lol. You have a right to a tight lockup, for sure and that knife ain't cheap. Here's snoanot quick example I got a new Taurus PT 92, about a $400 gun, it needed tweaking right out of the box to get everything right. I didn't send it back to Taurus, I needed that gun and saw what to do on it. Anyway, good luck to you
 
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My 0630 spine wacks fine all day but on the other hand it's one of the ones that's really hard to open the knife. Technique and it opens fine. I'm very taken w ZT Emersons and in my mind it's a perfect knife where someone else wouldn't tolerate the very stiff detent. I know there's a fix for it but it's fine with me.
 
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I don’t want a folder that doesn’t fail because of a flipper tab hitting my finger. That feature is supposed to be a secondary safety to the lock’s primary saftey.

I’m not satisfied with a lock that fails but “its no big deal” cause my finger will catch the flipper tab. Sorry not good enough.

Sure, but inducing irrational failure is simply ignorant in my mind. I simply don't chop with the spine of my folder or whack the back of it while holding it upside down and loosely. I just don't accept ignorant use of a product as a means to decry failure. Again, it's an issue ZT should address, but is not indicative of normal use failure. We can all "what-if" every mechanical product we use...some prudence is needed while understanding the limitations. I'm utterly confident in those folders I have for the environment I'm in and the uses I rely on. For those that fear failure, while I think it's irrational and founded in ignorant testing, there are plenty of other options. What is ignorant is to tell everyone that you're "spine whack" away from becoming a member of the nine-digit club.

Mitigating "what ifs" is a great policy if you have no choice but to accept the uncertainty. When you have the opportunity to remove the "what if" completely by designing it right out of the appliance, that's an objectively better solution.

My career deals with a high level of uncertainty even with extensive risk assessments and control measures to reduce or mitigate much of that risk. Accepting a product to compensate for an operator's ignorant use who intentionally tries to induce failure is not the product's fault. Every mechanical device will fail to some degree if misused, abused, or not used as intended. I just don't buy that whacking on the back of a folding knife with a loose grip while upside down is an acceptable demonstration of real-world failure. Sure, it can highlight design flaws, but not against normal use. Have we had an high number of actual lock-failures during real-world use? And then, how many of those were from misuse of the folder?

ROCK6
 
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Yeah, you have to gorilla-grip a frame-lock to have any influence on the lock (even if minimal to none). My reinforcement is really aimed at the flipper "appendage". For normal saber grips, your finger keeps the blade locked-out pretty well. Again, I only mentioned a hammer-style grip as that was the concern (self-defense and failure). If I'm using a pinch-grip or holding it lightly, I'm likely not doing anything (at least that I can conceive of) that would put pressure on the spine of my blade.

My point about limp-wristing is spot on with respect to the test that was being conducted. I would certainly have to hold my handgun in a way that caused it to fail...much like the holding a knife in a pinch grip and whacking the spine on a roll of tape. If I'm holding my knife properly for harder-cutting tasks, the likelihood of inducing that kind of failure is close to zero. Still, I think there are some issues with ZT's design, the steel lockbar inserts, and potentially their mechanical tolerances, so one can't be naïve about thinking a heavy duty folder is designed for fixed blade tasks regardless of the advertisement. My whole disagreement is that the video testing is a poor example of real-world use and a lot of "what-if" hypothetical scenarios are irrelevant. Just because I can purposely induce a failure to feed in my handguns doesn't mean it's a design-flaw, it's an end-user error and improper handling of the handgun. In my world, you mitigate "what-if's" by reinforcing proper planning, training, and using gear properly and purposefully. Again, the real world where I live beats table-top tests everyday...labs are and table tops are great ways to show potential design issues (which I can appreciate), but they don't often represent reality from a user's perspective. Just my humble opinion.

ROCK6
I agree with you, really. I just think this video highlights an issue that people don't like to or refuse to acknowledge, regardless of whether the specific test used to demonstrate it is realistic. Pulling a stuck knife out of something could have caused failure on knives I've actually owned. That shouldn't happen, period. But it does, because some companies don't care about lock geometry. Whatever we think about this video specifically, ZT should look at their design practices that lead to these failures. If, as an engineer, I signed off on a safety device design that I knew occasionally wouldn't work properly, there could be criminal charges associated with it.
 
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I agree with you, really. I just think this video highlights an issue that people don't like to or refuse to acknowledge, regardless of whether the specific test used to demonstrate it is realistic. Pulling a stuck knife out of something could have caused failure on knives I've actually owned. That shouldn't happen, period. But it does, because some companies don't care about lock geometry. Whatever we think about this video specifically, ZT should look at their design practices that lead to these failures. If, as an engineer, I signed off on a safety device design that I knew occasionally wouldn't work properly, there could be criminal charges associated with it.

I won't disagree with your take on it; it's a valid point as well. There is a design flaw, even if I think it's a non-issue for my own needs...

ROCK6
 

bflying

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Ok, I wasn't going to play. But with a cabinet full of ZT's, I couldn't resist any longer. I decided to test most of mine, just for fun. None failed. I used a roll of tape to attempt similar environment. Whacked 1-2 dozen times per knife, probably at least 3 times harder than I would on my knee. I have had knives fail similar to this before, all were inexpensive imports. Some Schrades, mantis comes to mind, and bunch of no-names.

One point to note, I am an ADD/OCD fidgeter. So most of my ZT's are well broken in and seated. The only one that has a like new lock is my 804cf. Models tested were.... 0456, 0850, 0350, 0561, 0562cf, 0450, 0452cf, 0055, 0770cf, 804cf, 0801, 0808.
 

metsfan

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I’ve used my ZT’s for plenty of heavy applications and haven’t had one fail during my use yet. Batoning, prying, whatever...I know the limitations of a locking knife and if I push it beyond those limitations that my fault. Design flaw? Well it’s a locking knife so it closing when force is applied in the direction it closes seems about right, lock engaged or not.

There is no reason to spine whack a knife, aside from making YouTube videos to point out how flawed a lock design/mechanism is. You’ll be just fine with your locking knives folks...well, unless you’re hanging off a cliff while holding onto your knife that’s dug in deep into the face of that cliff, and let’s just hope you’ve got a Cold Steel on you that day.
 

palonej

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I cut inside enclosed spaces quite a bit. Not every time I use my knife but often enough to mention. IF I slip and hit something, I want the lock to keep my hand safe. That's why I use a locking knife.

I also work in some ridiculously tight spots cutting hard rubber tubing.
Have hit knives many times on their spines, usually when extricating my ass out of those tight spots.......I do not want that blade shutting on my fingers.
Most carried work knives??? Spydie Advocate, PM2, Manix, serrated Salt and a Pro Tech TR3. Spine hammered all, absolutely no change in lock up.
I EDC a 450 and 452 a lot. Both lock bars will move over if I push them, but neither failed spine smashes.......but after hearing about this issue for some time, I won’t carry either for work.
Just my $0.02.
 
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I have had a good number of ZT knives. I don't recall them having this issue. I only have one currently, the 0561, and it definitely doesn't have this issue. It has a lock insert and doesn't have any lock rock and doesn't slip.


Here's the thing:

Frame locks and liner locks are not as secure or reliable as a back lock. Or a compression lock. Or a caged ball bearing lock. Or, probably but maybe not, an axis lock.
 
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