How Do Liner Locks Fail?

Ironman

Ironman

Joined
Aug 16, 2002
Messages
402
When a linerLock (LL) fails, how does this usually happen? I mean, I can only guess that pressure to the spine of the blade causes the liner to move off the tang and allow the blade to fold. This would be due to poor design or construction. Maybe the liner is very thin, and goes all the way to the right, and slips between the blade and scale allowing the knife to fold. I mean, a LL never really can "break" right? My Benchmade 426 was advertised with "extra thick" Ti LL. Does the extra thick make any difference at all? If it slips off it slips off, thick or thin. Why not make it go all the way to the right to start? It would be more secure right? FYI, my BM 426 locks up perfect and passes a real hard spinewhack with flying colors. Just wondering, seems like LL are not a fav around here, except me. :confused:
 
Most failures are due to poor design or defective materials. I have seen liners bend. slide into the unlocked position when pressure was applied to the back of the blade, and I have seen then actually start folding and bending inside the knife. I have never seen this happen on a good quality liner lock just on $5.00 Chinese gas station knives.
 
I have went out of my way to try and make them fail , the only time I have had one actually fail is when the manufacturer did not give the lock enough of a.... cant think of the word , a bend , I guess.
In other words when the lock does not engage enough , or is not strong enough to withstand medium to heavy finger pressure.

Ready for a surprise ? Two of my failures are a Benchmade App and a CRKT edc M16.

Do not ever assume just because the manufacturer is renowned , that your knife is failsafe. :)
 
rebeltf said:
Ready for a surprise ? Two of my failures are a Benchmade App and a CRKT edc M16.

Do not ever assume just because the manufacturer is renowned , that your knife is failsafe. :)
Click to expand...

I'm not surprised, both my Apparitions, regular and G-10, fail a spine whack test. I sent one in, but it came back the same.

Eric.
 
Another failure mode people report is during twisting motions, as when drilling a hole with the point. Cutting forces make the handle tend to rotate in the hand (even with a tight grip) and the liner can get shifted sideways, allowing it to disengage. This won't happen with a spine whack, but is not so uncommon a motion during actual use.
 
Ironman said:
When a linerLock (LL) fails, how does this usually happen? I mean, I can only guess that pressure to the spine of the blade causes the liner to move off the tang and allow the blade to fold. This would be due to poor design or construction. Maybe the liner is very thin, and goes all the way to the right, and slips between the blade and scale allowing the knife to fold. I mean, a LL never really can "break" right? My Benchmade 426 was advertised with "extra thick" Ti LL. Does the extra thick make any difference at all? If it slips off it slips off, thick or thin. Why not make it go all the way to the right to start? It would be more secure right? FYI, my BM 426 locks up perfect and passes a real hard spinewhack with flying colors. Just wondering, seems like LL are not a fav around here, except me. :confused:
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As the OP deftly states, logic would dictate a well designed liner lock go ' all the way ' to securely stay in that position. From what little I've picked up over the years on the blade fora, the intent of that partial engagement is to make the design self adjusting for wear.

Two faces (at least one angled) sliding into each other for lock engagement and release will wear them down. This is where the idea of allowing only partial engagement when NIB condition came from. That's why you hear people talking about the liner/frame bar 'walking' across the blade portion of the lock as their knives wear in.

My 2¢.
 
I think you described most of it - the liner fails to stay in contact with the tang. Once things start moving around due to the forces exerted on the blade and handle, the ramped intersection either pushes the blade away, or the blade tang moves away from the liner. With any other closing force also on the blade, it does.

Things that seem to contribute to this are thin stainless liners - they are usually too hard and slippery; a steep ramp intersection - which acts to push the two parts away; a short liner - a primary cause of steep ramps; small pivots - which lack area to control side motion; soft pivot washers - which add long term looseness; and a guaranteed low price.

Look for a linerlock with phosphor bronze washers, flat ramp,and long titanium liner, and you will see rock solid reliability and a price to match. It's what it takes to buy quality in this format, something a plastic bucket of knives at the gas station can't touch.

The problem is that the average knife buyer knows less about the subject that they do electronics or automobiles - and makes a decision based on what it looks like, not how it's built. There has been little effort to try to educate the masses.
 
I certainly agree with most of the statements so far. I don't, however, have a problem with liner locks. When a knife is being used as a knife, few liner locks will fail. There is, of course, liner locks that are better than others. In my opinion it's always worth a few extra bucks... or few extra $20 bills to get good quality.

Liner locks probably get far more bad press than they deserve.

:)
 
Of course with all the above mentioned forces conspiring against your lock's solidity, there's the User Induced failure.

Our typical ham fisted user may inadvertently -totally or partially - disengage the lock by application of force in the corect place ie. thick fingers work their way into the notch in the handle and unlock the blade.
 
I think People dislike LL's because they are effectively like a knockoff of a Frame lock which one of or the strongest locking system.
 
i don't think the reliability of a liner lock has much to do with the brand or the price you pay (- though the odds of finding a lemon probably increse as price drops)
my benchmade dejavoo passed every single test that i could think of, but so did my $30 Taiwan made Boker/Magnum Kalashnikov 74
the key is IMO tight engineering & outstanding QC
i guess you have to handle and try for your own if a LL works, which kinda rules out buying online
still, there are LL out there that surely deserve a second chance
 
From above...

"I think People dislike LL's because they are effectively like a knockoff of a Frame lock which one of or the strongest locking system."

I was under the impression that the fram lock was an improvement of the liner lock.
 
hlee said:
From above...

"I think People dislike LL's because they are effectively like a knockoff of a Frame lock which one of or the strongest locking system."

I was under the impression that the fram lock was an improvement of the liner lock.
Click to expand...

While I'm not a historian, I think you are correct. As I understand it Michael Walker was one of the early guys making liner locks. Chris Reeve liked the concept and decided to beef it up by using the full thickness of the scale as a lock.

I simply love the simplicity of the CRK Sebenza.

:)
 
On a knife review I read, a guy got a leatherman charge and showed in a picture that his lock would not engage fully.......... on the day i ordered mine!!! He said he could dissasemble it and fix it. Naturally worried, I messed around with my Kick, and gave my self a nasty blood blister. I guess what i am getting at is that if you aren't buying a garbage knife the issue is design and quality control, in this example the LL would not fully engage, and that is why it failed.

PS. Go to google and type in leatherman charge TI in images and you will eventually see a charge LL with a highlighted circle around the faulty lock
 
Most everytime a liner lock defeats it is directly related to the mating up of the blade and the lock and the angle of the ramp it slides into typically referred to by some makers as the interface or innerface depending on who it is.

A general rule of thumb I follow myself unless its a collector piece of historical value that I don't intend to use is this. If the ramp (interface) looks like a sliding board it probably is.

STR
 
ashtxsniper said:
I have seen them actually start folding and bending inside the knife. I have never seen this happen on a good quality liner lock, just on $5.00 Chinese gas station knives.
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Whew, for a second you had me scared! Luckily I bought me a $7.00 knife at a hardware store. I don't go in for them really cheap knives. I'd rather spend a couple of dollars more and get a dependable knife made in China. None of them Pakistan knives fer me, no sir!

Mine's also got a "surgical stainless," blade, so it's guaranteed sharp. It don't have no springs in it like that slip joint genuine Barlow replica knife that near cut my fingers off!

Anyhoo, CRKT's Lake and Walker Knife Safty seems to be a pretty good, though I've heard of some failures where the shim has bent or fallen out. And I bought a Smith & Wesson PowerGlide for ten bucks, brand new, honest, no joke. The blade comes from the bottom and pops through the top, making for a very secure knife. Unfortunately, even though I got it at a great price, I still don't like it much. It's too much of a hassle to open and close.
 
Oh boy. This could get ugly real fast but here goes.

Its like this. The contact area is the critical part of the lock on a liner lock but with a thinner liner there is less pressure needed to be able to make the lock move back off the blade than there is with a stouter more resistant frame lock. Still if there is a flaw in the design it is the sliding board contact area needed to make it work. Even Walker and Lake recognize this short falling in the design or they would not have felt the need to come up with the LAWKs system to secure the lock up better, which by the way I understand is coming standard on all CRKT knives now.

The longer the blade and handle the more weight you can leverage with use into the contact at the pivot area and this is by pressure on the tip of the blade. Longer blades and handles means more weight on the pivot so a 4" blade with a 5" handle with 50 pounds of downward pressure on the lanyard end is going to translate into more weight at the pivot than a 3" blade and a 4" handle and so on. Again its all about leverage.

On many knives I've personally tested that have had sharply angled contact areas they cannot hold more than 65 pounds of weight at the lanyard end of the knife before the lock slides right off the blade allowing the body to fold in like it does when you want to close it. The heck with how strong the liner may be because it never gets to that point before it starts moving off the blade after a certain amount of weight is at the pivot. Flatter contacts just hold up better before the lock is stressed enough to move or spring back the other way from stress pressure but many makers just don't like flatter contacts because of a belief that it will cause the lock to work its way across the interface to the opposite side faster that way. At least that is my understanding.

Personally, knowing this from testing what I've used and making the locks myself has taught me about the locks and the various schools of thought in making them. It changed the way I felt about them. I don't think I really need to point out that in a heated moment any 12 year old young man can exert 65 pounds of pressure on the tail end of a knife handle.

STR
 
Ironman said:
How Do Liner Locks Fail?
Click to expand...

According to the 3 stitches and nerve damage on my right index finger, by being too thin, being too loose, and having inadequate contact surface with the blade.

I'll admit that my experience has left me with some bias, both against CRKT knives (both pre-LAWKs knives, which left me with the injury above, and current LAWKs knives which require a secondary lock to be "safe"--and therefore I avoid like the plague) and other linerlocks, but construction and reputability matter most. I still own and use a linerlock or two, such as the Microtech LLC or Protech Harkins ATAC, but these have proven their reliability.

One question often asked is how a linerlock is any different than a framelock. A legitimate question as many linerlocks (such as Striders, Spyderco Military, or certain Benchmades) have lockbars every bit as thick and/or strong as many framelocks (like BM Monolock or Kershaw Leek). Construction and quality count for quite a bit of it, but so does the simple nature of the lock. A framelock will nearly always have the added benefit of the hand's pressure applied to the lockbar itself when the knife is gripped tightly.

It's as simple as that. Given the same strength, thickness, and contact area, a framelock will almost invariably be stronger than a linerlock because of the way the knife is gripped.

This fact alone can lead to lack of (often justified) confidence in the linerlock design.
 
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