Zero Tolerance Liner Lock Closures?

[midnight flyer]

ROCK 6, great post!

So true... no matter the situation, there will always be unhappy folks. Like you, I am not ditching my ZTs, but as posted earlier my newest work knife as of about 2 weeks ago is a CS Ultimate Hunter.

Everyone that has doubts about ANY product should simply stay away. Wayyyy to many high quality work knives out there at better prices than ZT like the CS Ultimate Hunter. I truly hope they get all of this straightened out, from top to bottom, but it's kind of looking like it might be a slow roll.

Robert

 

[JeremiahWeaver09]

i had a brand new zt 0550 that would easily close with just a bit of pressure on the back of the blade, the lock would just immediately slip

personally, im trying to steer away from liner and framelocks in general, im going to mostly stick to backlocks and axis locks, i just have no confidence in liner and framelocks

 

[marrenmiller]

I think many have theories about looser tolerances (to avoid lock-stick), poor geometry, and even the lock-bars being steel-on-steel, which can create less friction for the lock. I actually think the locking bar should be titanium...since it can be replaced, let the lock stick a little more for security reasons (then people would bitch about how hard the locking bar is to disengage). Again, I'm not seeing a significant issue with lock failures on my ZTs, and I think the OP's video is a poor example of how to test lock failure. It would be similar to using your knife upside down with a loose pinch-grip, tapping on the spine...should that cause your knife lock to fail? No it shouldn't, but that's not a realistic test from my perspective. I've held my blades over a table, in my hand, both firmly and loosely, and whacked (harder than the video) on the back of the blades; no failures. I'm buying into the theory that the locking bars don't have enough friction and if the geometry or tolerances are off, a loosely held knife will vibrate the locking bar loose. That can be a concern and one ZT should take seriously, if only because they tout their designs as hard-use folders and we have a lot of spine-whackers in the knife community.

I know Cold Steel touts their Triad lock as one of the strongest, and I don't disagree. A minor complaint is that the lock can be a beast to disengage. Too many people want a smooth, fluid action folder when opening AND closing, with the strength of a fixed blade. ZT has part of that, but won't win a consensus on the latter until they figure out how to find the balance of a more secure locking bar that doesn't vibrate loose but doesn't stick so hard it takes two hands to unlock.

ROCK6

Why is the OP's method poor just because it doesn't work for you? As I believe we already went over ad nauseum, if your knives work properly than this doesn't apply to you. Congrats.

Meanwhile, recognize that: A) some people's knives, for whatever reason, absolutely don't lock securely, and B) that holding a frame lock may not do anything to secure it, depending on hand size/method of grip/knife frame design. Again, myself and others here have gripped knives hard and unlocked them just about as easily with a dowel slipped in between our fingers as without gripping it. I invite you to do the same test with a bunch of framelocks before you keep posting that.

You are right on the ultimate cause; there's not enough friction in the lock interface. A properly designed lock is like a self-locking brake: entirely dependent on friction to work, not on externally applied forces. They need to work on making their lock geometry and tension consistently correct to fix this.

 

[ROCK6]

Why is the OP's method poor just because it doesn't work for you?

I invite you to do the same test with a bunch of framelocks before you keep posting that.

Just simply my opinion, nothing more. Holding a knife loosely like that with the blade open isn't a technique I've ever used or seen used, and can't see the practicality of it outside of proving something that may or may not be relevant for real-world use. Relevance shouldn't be based on hypotheticals; however, it does show a potential flaw which I recognize. While I don't think that flaw affects me or my uses, I also don't think ZT should tout their folders are "hard-use" when people point out the flaw despite the controversy over the severity of the locking failure.

As to testing, I do, but I use my knives normally, even somewhat roughly. I just think too many knife enthusiast induce failure with abnormal practices to prove or disprove what they consider a design flaw. I'm in no way defending ZT's locking bar slips...the issue is there, I just don't think it's the end of the world or my fingers are forfeit because of it. Using a folder is more about technique than reliance on a locking design; even slip joints can be used extremely hard if handled properly.

ROCK6

 

[Lapedog]

I think many have theories about looser tolerances (to avoid lock-stick), poor geometry, and even the lock-bars being steel-on-steel, which can create less friction for the lock. I actually think the locking bar should be titanium...since it can be replaced, let the lock stick a little more for security reasons (then people would bitch about how hard the locking bar is to disengage). Again, I'm not seeing a significant issue with lock failures on my ZTs, and I think the OP's video is a poor example of how to test lock failure. It would be similar to using your knife upside down with a loose pinch-grip, tapping on the spine...should that cause your knife lock to fail? No it shouldn't, but that's not a realistic test from my perspective. I've held my blades over a table, in my hand, both firmly and loosely, and whacked (harder than the video) on the back of the blades; no failures. I'm buying into the theory that the locking bars don't have enough friction and if the geometry or tolerances are off, a loosely held knife will vibrate the locking bar loose. That can be a concern and one ZT should take seriously, if only because they tout their designs as hard-use folders and we have a lot of spine-whackers in the knife community.

I know Cold Steel touts their Triad lock as one of the strongest, and I don't disagree. A minor complaint is that the lock can be a beast to disengage. Too many people want a smooth, fluid action folder when opening AND closing, with the strength of a fixed blade. ZT has part of that, but won't win a consensus on the latter until they figure out how to find the balance of a more secure locking bar that doesn't vibrate loose but doesn't stick so hard it takes two hands to unlock.

ROCK6

A proper functioning liner/framelock should not be relying on friction to prevent failure.

What if abit of oil from the pivot gets on a lockface? Or what if the titanium wears and leaves a layer on a lockface? That can also cause the lock to slip if the geometry is not correct.

 

[ROCK6]

A proper functioning liner/framelock should not be relying on friction to prevent failure.

What if abit of oil from the pivot gets on a lockface? Or what if the titanium wears and leaves a layer on a lockface? That can also cause the lock to slip if the geometry is not correct.

Oh, I agree, the locking should be strong enough (especially the thicker ones) to withstand slippage on it's own, but I've seen some almost "polished" locking faces which baffles me. Having more than a few titanium face locking bars provides that extra friction to prevent it from jumping off if tapped hard. I do agree, geometry is a critical factor which is what I think contributes to the poor lock-ups. I think there are several factors which create the locking failures...

 

[Steely_Gunz]

I think many have theories about looser tolerances (to avoid lock-stick), poor geometry, and even the lock-bars being steel-on-steel, which can create less friction for the lock. I actually think the locking bar should be titanium...since it can be replaced, let the lock stick a little more for security reasons (then people would bitch about how hard the locking bar is to disengage). Again, I'm not seeing a significant issue with lock failures on my ZTs, and I think the OP's video is a poor example of how to test lock failure. It would be similar to using your knife upside down with a loose pinch-grip, tapping on the spine...should that cause your knife lock to fail? No it shouldn't, but that's not a realistic test from my perspective. I've held my blades over a table, in my hand, both firmly and loosely, and whacked (harder than the video) on the back of the blades; no failures. I'm buying into the theory that the locking bars don't have enough friction and if the geometry or tolerances are off, a loosely held knife will vibrate the locking bar loose. That can be a concern and one ZT should take seriously, if only because they tout their designs as hard-use folders and we have a lot of spine-whackers in the knife community.

I know Cold Steel touts their Triad lock as one of the strongest, and I don't disagree. A minor complaint is that the lock can be a beast to disengage. Too many people want a smooth, fluid action folder when opening AND closing, with the strength of a fixed blade. ZT has part of that, but won't win a consensus on the latter until they figure out how to find the balance of a more secure locking bar that doesn't vibrate loose but doesn't stick so hard it takes two hands to unlock.

ROCK6

I totally agree. Maybe ZT needs to either move away from the whole hard use folder thing if they are going to keep making more artistic and aesthetic designs. I don't doubt my fancier specimens could hold up to hard use, but I do agree that by either adjusting their marketing to be more about smooth refinement or going back to the old school tough as nails hard use tactical folders they are maybe not going to have so many confused people as to why their knives are slipping off the lock.

I think I need to clarify one of the reasons why this type of lock failure bothers me. As unrealistic as it seems to be, I was literally cutting at this angle with a weird grip a couple weeks ago. The only difference was that I was doing it blindly.

I was installing a piece of interface with a pump. The bezel was set, but when I went to reach in to pull the plug I found it had a factory zip tie holding it back. Instead of redoing 45 minutes of work, I elected to reach in with my 920 and do a quick snap cut.

I flicked and banged at that zip tie 5 or 6 times before i snapped it. Had i banged the back of the spine on the frame, i could have easily had it fold on my hand.

I would much rather deal with sticky difficult locks than worry about how smooth the action is.

 

[Lapedog]

I totally agree. Maybe ZT needs to either move away from the whole hard use folder thing if they are going to keep making more artistic and aesthetic designs. I don't doubt my fancier specimens could hold up to hard use, but I do agree that by either adjusting their marketing to be more about smooth refinement or going back to the old school tough as nails hard use tactical folders they are maybe not going to have so many confused people as to why their knives are slipping off the lock.

I think I need to clarify one of the reasons why this type of lock failure bothers me. As unrealistic as it seems to be, I was literally cutting at this angle with a weird grip a couple weeks ago. The only difference was that I was doing it blindly.

I was installing a piece of interface with a pump. The bezel was set, but when I went to reach in to pull the plug I found it had a factory zip tie holding it back. Instead of redoing 45 minutes of work, I elected to reach in with my 920 and do a quick snap cut.

I flicked and banged at that zip tie 5 or 6 times before i snapped it. Had i banged the back of the spine on the frame, i could have easily had it fold on my hand.

I would much rather deal with sticky difficult locks than worry about how smooth the action is.

A litte lockstick never really bothered me as long as it isn’t too severe. Infact the original Walker liner lock design considered lockstick a feature.

My biggest issue with lockstick is it tends to wear out the lock faster.

 

[rogatsby]

I was thinking of buying a ZT at some point, but there is enough evidence out there that I don't think I will pay $200 plus for any ZT. I can understand folks chiming in and saying that their ZT's are fine, but those who are so vociferous in defending ZT no matter what, to the point of accusing those Youtubers of fabrication or fraud, are going too far. Most ZT's are too big and heavy for my liking anyway. And even if only a small percentage of their knives are affected by this problem, the refusal or inability to fix the knives sent back is inexcusable.

 

[Goose 7279]

I still love my ZT knives 300 ,303 , 3x 350 , 2x392. I feel that the 350s that I have and have dealt with are all the most stout liner locks I have handled. I understand to each their own.

I have cut 2 inch thick belt and poly panels etc with a absolutely no lock failures or even the slightest hint of play. I work in a mine so my knife gets used and abused. Used for things most people here would not do.

The recurve on the 350 makes it a cutting demon for conveyor belts drive belts etc. I have atoned 2x4 wedge s for screen siderails multiple times still no play and solid as ever. This is my experience and may not be the same for others.

Even though I abuse my knives I still use common sense and in my few years on this earth have never felt the need to spine wack any knife. I have inadvertently hit the spine of many of my k Ives and the only one that ever happened more than once was an Ontario rat 1 in D2 carbon fiber.

To me ZT makes a great knife as does spyderco and benchmade and many more I have owned cold steel but Lynn Thompson is a pretty lousy person in my opinion that I refuse to buy from. Cold steel has had multiple issues with their locks and knives especially the 4 max etc. My point is every manufacturer has its issues and I know ZT is a company that will work on it. Benchmade has had issues with the 940axis lock breaking excessive omega springs. Spyderco dodo and first gen manix 2s and the tuff folder had lock issues. Emerson liner lock problems. With all this said I own a knife from all these brands and some I own are the very models that I listed. None have failed on me but as stated i don't spine whack or baton with a 4lb.

Like I said I know my experience is not the only one just putting my 2 cents in.

 

[marrenmiller]

Just simply my opinion, nothing more. Holding a knife loosely like that with the blade open isn't a technique I've ever used or seen used, and can't see the practicality of it outside of proving something that may or may not be relevant for real-world use. Relevance shouldn't be based on hypotheticals; however, it does show a potential flaw which I recognize. While I don't think that flaw affects me or my uses, I also don't think ZT should tout their folders are "hard-use" when people point out the flaw despite the controversy over the severity of the locking failure.

As to testing, I do, but I use my knives normally, even somewhat roughly. I just think too many knife enthusiast induce failure with abnormal practices to prove or disprove what they consider a design flaw. I'm in no way defending ZT's locking bar slips...the issue is there, I just don't think it's the end of the world or my fingers are forfeit because of it. Using a folder is more about technique than reliance on a locking design; even slip joints can be used extremely hard if handled properly.

ROCK6

You don't have to hold a knife loosely to have virtually no pressure on the lockbar, as we've alluded to numerous times by now. I'm going to stop bringing this up now but I really think you should try it for yourself, because it sounds like you think that has something to do with this problem when it really doesn't.

The point isn't that it need affect you in your uses. It's that if someone has a folder like this and they make an error in judgment or aren't as careful as you, or they have an accident and knock the open knife into something, that it won't punish them by closing on them. That's the expectation that tons of other good knives meet, and that some ZT knives have issues with.

 

[rogatsby]

The guy who made the video in the OP posted another video where he gives a rebuttal to those who have criticized his spine whacking of the ZT's as being unrealistic and impractical. I think he has a pretty good point. Take a look. His point starts at about 1:55 of the video.

 

[bambam99]

I was thinking of buying a ZT at some point, but there is enough evidence out there that I don't think I will pay $200 plus for any ZT. I can understand folks chiming in and saying that their ZT's are fine, but those who are so vociferous in defending ZT no matter what, to the point of accusing those Youtubers of fabrication or fraud, are going too far. Most ZT's are too big and heavy for my liking anyway. And even if only a small percentage of their knives are affected by this problem, the refusal or inability to fix the knives sent back is inexcusable.

I wouldn't steer away from ZT because of this.
If its not your flavour that's one thing.
I have 10 plus... love them, no issues with my locks all hold up.

I have yet to see anyone send theirs in with proof to say it wasnt fixed.

 

[not2sharp]

This is the good old USA. If there were an actual risk, a lawsuit brought by a herd of vicious ambulance chasers, would wipe out the company in short order. Until then it is safe to assume that ZT is safe to use. Consumer product safety is a benefit of buying US made products.

n2s

 

[ROCK6]

A litte lockstick never really bothered me as long as it isn’t too severe. Infact the original Walker liner lock design considered lockstick a feature.

My biggest issue with lockstick is it tends to wear out the lock faster.

This is why I'm just curious why the locking inserts can't simply be titanium? Again, there's concern about wear on titanium locking bars, which I can understand, but if the insert is replaceable, you get some lock-stick that will wear on the insert but can be replaced. It does sound pretty sad that you need to engineer a solution to what is obviously either poor geometry or simply looser tolerances for the sake of a smoother opening/closing knife. Again, not a bad thing unless your marketing your knife as a heavy-duty folder.

You don't have to hold a knife loosely to have virtually no pressure on the lockbar, as we've alluded to numerous times by now. I'm going to stop bringing this up now but I really think you should try it for yourself, because it sounds like you think that has something to do with this problem when it really doesn't.

The point isn't that it need affect you in your uses. It's that if someone has a folder like this and they make an error in judgment or aren't as careful as you, or they have an accident and knock the open knife into something, that it won't punish them by closing on them. That's the expectation that tons of other good knives meet, and that some ZT knives have issues with.

I tried on five different ZT models and couldn't induce failure. I'm not saying it's not a potential problem with some ZT knives as some do seem to have failures; my only criticism was with the actual testing method of the OP, not necessarily the outcome. There's obviously some inconsistencies with ZT's production, but it's not affecting my folders, as much as a I try. At the end of the day, ZT really should address the issue even if only for their reputation than just safety concerns.

ROCK6

 

[firefighterguy]

I wouldn't steer away from ZT because of this.
If its not your flavour that's one thing.
I have 10 plus... love them, no issues with my locks all hold up.

I have yet to see anyone send theirs in with proof to say it wasnt fixed.

What proof do you need? I sent mine in and it wasn’t fixed. As have others.

 

[Lapedog]

This is why I'm just curious why the locking inserts can't simply be titanium? Again, there's concern about wear on titanium locking bars, which I can understand, but if the insert is replaceable, you get some lock-stick that will wear on the insert but can be replaced. It does sound pretty sad that you need to engineer a solution to what is obviously either poor geometry or simply looser tolerances for the sake of a smoother opening/closing knife. Again, not a bad thing unless your marketing your knife as a heavy-duty folder.



I tried on five different ZT models and couldn't induce failure. I'm not saying it's not a potential problem with some ZT knives as some do seem to have failures; my only criticism was with the actual testing method of the OP, not necessarily the outcome. There's obviously some inconsistencies with ZT's production, but it's not affecting my folders, as much as a I try. At the end of the day, ZT really should address the issue even if only for their reputation than just safety concerns.

ROCK6

The point of putting a steel lockbar insert in is probably more for its longer wearing properties than the fact it can be swapped out for a new one when the lockbar wears out.

Actually so far I have never heard of someone replacing a worn out steel lockbar insert.

Friction, titanium, or whatevee, that’s not the solution. The solution is for them to fix their damn lock geometries.

 

[firefighterguy]

Curious on everyone’s thoughts on the role of lube in this? If a knife is over lubed, and oil is on the tang, could that cause these knives to fail?

I don’t understand lock geometry and designs enough to know if a properly made frame lock should be affected by lube.

 

[bambam99]

What proof do you need? I sent mine in and it wasn’t fixed. As have others.

Well you are the first person I've heard of sending it in.
What did ZT say ? Email or letter saying why it wasnt fixed ?

 

[marrenmiller]

Curious on everyone’s thoughts on the role of lube in this? If a knife is over lubed, and oil is on the tang, could that cause these knives to fail?

I don’t understand lock geometry and designs enough to know if a properly made frame lock should be affected by lube.

With proper lock geometry, it shouldn't.