Zero Tolerance Liner Lock Closures?

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klute said:
I worked on a Ferrari once. Had a leak at the gearbox case. Why would a $200,000 car leak oil? Shouldn't it not ever leak anywhere always? Isnt that a reasonable expectation based on the cost of that car?
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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?"
 
tried a light tap on a rubber pad on a table edge
630,562,909 all lightly used and broken in
all stayed locked

620 brand new, was the only one that failed
 
MSchott said:
Thanks. I just checked every liner and framelock folder I own, from a Kershaw Al Mar to 3 CRK's. None had any movement at all when I firmly pushed on the spine of the blades to force them closed.

It's understandable that standards are variable among knife owners. But I will stick to my point that some have expectations that are unreasonable in use. Rock6's post 233 sums it up well IMO.
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I don't do spine whacks, even though I think they aren't an unreasonable test if done appropriately. I'm talking about locks disengaging doing what I just told you. I've had very high end folding knives, including ZTs and Microtechs, exhibit this issue.
 
ROCK6 said:
Maybe I just don't get it. I don't hold my knife loosely and whack on the spine of the blade...it's a test, but I question the validity from a user's perspective. I'm not giving ZT a pass as they should have tighter tolerances to avoid loose lockup, but try and replicate it by actually holding the blade as you normally would. For the flipper actions, the blade doesn't collapse on your and for the frame-locks, I can't get the locking bar to "jump" off. The video is like limp-wristing a pistol; it's going to cause a malfunction because you're not using it properly. There are a lot of hypothetical, "what if" scenarios, but I just can't buy the OP's post of that video. I've carried folders for almost 30 years in the military, deployments around the world, and four combat tours, and I'm using several here in Afghanistan right now.

And...I...Have...Never...Seen...A...Knife...Whacked...Like...That...Ever...During...Normal...Hard...Use

Again, I'm not giving an excuse to the poor execution from ZT, but those that think this is such a crisis have likely never used their knives in an abusive environment and are seriously over-reacting to a nonsensical test to induce lock failure. If you fear hard use will result in lock-failure, put your folders up and stick with fixed blades. Sorry, but I'm not very sympathetic to the outrage and fear...and yes, I've used ZTs pretty hard over here and I'm still counting all ten digits.

I actually don't mind the analysis from the guy in the video, but the testing method is simply absurd from a real-use perspective.

Follow up...so I beat on the spine of the opened blade while holding in my hand like a normal person. The only one I was concerned about was the ZT 0630. I used a roll of 100mph tape and beat on it as hard as the video. No failure (thank goodness). I even did a couple "accidental" whacks on the underside of the table in my room.



So, I call B.S. on the pansy method of testing lock failure. Limp wristing isn't a valid testing method. I will say that the flipper knives do offer an extra measure of security by using your finger to secure the blade open even if "whacked" on the spine disengages the liner/frame lock. I think many are really over-analyzing the failure without addressing actual application.

ROCK6
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Cool, good for you. But often you don't need to smack them on anything to get them to fold. I don't even do spine whacking tests, but I've had some high end folders where I could force the lock to shift or close with my bare hands, so now I always check every knife this way. Sounds like you haven't, but you should keep in mind that it does happen to other people.

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.
 
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klute said:
I worked on a Ferrari once. Had a leak at the gearbox case. Why would a $200,000 car leak oil? Shouldn't it not ever leak anywhere always? Isnt that a reasonable expectation based on the cost of that car?
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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.
 
marrenmiller said:
Cool, good for you. But often you don't need to smack them on anything to get them to fold. I don't even do spine whacking tests, but I've had some high end folders where I could force the lock to shift or close with my bare hands, so now I always check every knife this way. Sounds like you haven't, but you should keep in mind that it does happen to other people.

As for your point about hands reinforcing the lock, I disagree. 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.
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I found the same thing. Depending on the knife and shape of a person’s hand the lockbar receives very little inward pressure from gripping the framelock. Usually the lockbar sits in the crook of my fingers and is barely touched.

I noticed that i seem to get the most pressure on the lockbar when I use sabre grip and less when I use hammer grip.

Also I tend to agree that people generally aren’t gorilla gripping their knives.
 
marrenmiller said:
I don't do spine whacks, even though I think they aren't an unreasonable test if done appropriately. I'm talking about locks disengaging doing what I just told you. I've had very high end folding knives, including ZTs and Microtechs, exhibit this issue.
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To clarify, I did not do spine wacks. I pushed with a lot of force on the back of the blade with the palm of my hand. I assume that’s how you tested. None budged. I may not me Schwarzenegger but I’m strong enough.
 
MSchott said:
To clarify, I did not do spine wacks. I pushed with a lot of force on the back of the blade with the palm of my hand. I assume that’s how you tested. None budged. I may not me Schwarzenegger but I’m strong enough.
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Actually if you read some of Jill’s posts above she mentions how even with great force pushed on the spine the lock wouldn’t fail.

However a light tap on the spine would cause the lock to skip off the tang and fail.
 
MSchott said:
To clarify, I did not do spine wacks. I pushed with a lot of force on the back of the blade with the palm of my hand. I assume that’s how you tested. None budged. I may not me Schwarzenegger but I’m strong enough.
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No, that's all I'm referring to. If yours don't shift, then you're probably golden. Tons of knives don't come that way from the factory, nor do many people check for that before reselling a knife.
 
Lapedog said:
Actually if you read some of Jill’s posts above she mentions how even with great force pushed on the spine the lock wouldn’t fail.

However a light tap on the spine would cause the lock to skip off the tang and fail.
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Yeah, it varies. A tap might cause the lock to come loose due to vibrations transmitted through the lock bar. I generally only test by static force, as hard as my hands can go.
 
Lapedog said:
Actually if you read some of Jill’s posts above she mentions how even with great force pushed on the spine the lock wouldn’t fail.

However a light tap on the spine would cause the lock to skip off the tang and fail.
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I’m trying to understand where in daily use such a tap would occur.
 
MSchott said:
I’m trying to understand where in daily use such a tap would occur.
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When stabbing generally. Like stabbing a tree trunk or anything really. It's not unreasonable to do in your every day. I mean in the office I doubt you'll have an issue. Most people keep there zt's locked up or light use cause they cost alot and they want resale value more than anything.
 
MSchott said:
I’m trying to understand where in daily use such a tap would occur.
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It probably wouldn't, but it could in a self- defense situation. I do enjoy carrying some of my knives hiking for self defense mostly ones I never use, as I carry two then. One for use and one for protection. It seems I'm giving the unused knife a purpose then, however unlikely I'd ever have to use it. Last thing I want is a knife for that , that folds up with a tap on the spine.
 
Lapedog said:
Actually if you read some of Jill’s posts above she mentions how even with great force pushed on the spine the lock wouldn’t fail.

However a light tap on the spine would cause the lock to skip off the tang and fail.
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I get exactly this pattern in a lot of my ZTs when I tried it. Hard pressure on the spine, even very hard, no movement. A light but sharp whack on some folded up paper towels on my kitchen table and they pop open. There are a few that didn't pop open, but after I got the minimum pressure required to do it down almost all of them popped open on the first or second whack. There were some clear trends:

  1. That almost all of my ZTs pop open, regardless of whether they are frame locks or liner locks (there are exceptions, my 0454 and 0450cfzdp wouldn't, for example).
  2. Both of my 0452 knives pop open easily, but my very similar 0454 does not
  3. That no other brand's liner or frame locks that I tried popped open with any consistency (I also whacked three or four Olamics, a few Bucks, and about a dozen Spydercos, and a half dozen CKFs) but there were a few fliers here and there (e.g. one CKF model, the Ratata pops open as well, as does my Kizer Guru)
  4. None of the Buck liner locks that I tried, despite having the thinnest, flimsiest looking lock bars, would pop open
  5. Unless I missed something, none of the knives that had titanium to steel lock contacts failed--none. Every knife that failed had either a steel insert or steel sub-frame lock or whatever.
  6. I also tried with a Medford (it wouldn't pop open) but it destroyed the table and I had to halt my testing ;)
For those who think I'm a lunatic for doing this, it really doesn't take a very hard whack at all. As far as I can tell, lockup position is unchanged on all of them afterwards and there appears to be no lock bar deformation of any sort. It seems like the lock bars just skitter out of position momentarily.

I don't have any particular concern about using any of the knives that popped open, but it does seem curious that the ZTs pretty much all fail where most other brands it's the reverse, with only one or two failing here and there and all the rest staying locked.

For most folks I expect this failure mode will be ignored the same way the Sebenza's poor performance in the CS weight hang test (where the Sebenza failed at a ridiculously small amount of weight compared to other knives they've tested) generally is.

Just don't go whacking the spine sharply on things if you carry a ZT and don't put to much pressure on the spine if you have a CRK and you'll be fine. I think both issues are pretty unlikely to happen in real use, though the unexpected whack on the spine is probably the more likely of the two. I tried simulating handling issues (e.g. banging up on the bottom of a table) and really had to go out of my way to get even the easiest knives (e.g. ZT 0630) to pop open. It takes a pretty sharp crack to jolt them open.

EDIT to add: this experiment did give me a use for the kevlar cut-resistant gloves I never use, though. I bought them when I took up whittling again, intending to use just the left hand to hold whatever I was carving but it turned out that first, it made my left hand sweat and second, I don't cut myself, so it was pointless. I dug them out for this little spinewhackstravaganza, though, so there's that.
 
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MSchott said:
I’m trying to understand where in daily use such a tap would occur.
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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.
 
MSchott said:
I’m trying to understand where in daily use such a tap would occur.
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Plus it doesn't matter to me because it's not like there are no locking folders that won't have lockup defeated by spine whacking. If all of them would come out of lockup from tapping or whacking that would be one thing. The fact that many won't is another matter.
 
I don't doubt, having watched the videos, that I could spinewhack to fail every last one of my ZTs relatively easy. Again, can anybody explain to me how it would benefit me to do so?
 
BigKurtHaze said:
I don't doubt, having watched the videos, that I could spinewhack to fail every last one of my ZTs relatively easy. Again, can anybody explain to me how it would benefit me to do so?
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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).
 
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