Framelock strength question

Sal and others,
I could be wrong but I was always under the impression that one of the reasons that liner locks are less reliable than integral locks because sudden force applied to the spine of the blade (spine wack) causes the thin liner in a liner lock to flex and wobble, changing the angles in which it engages the tange of the blade causing slippage. The thick liners on integral locks do not flex in this manner so it is less prone to slippage. I don't know how true all of this is, so some insight would be appreciated.

However, I do find that the intergral locks being made today such as the Camillus EDC, Kershaw Leek, Buck Mayo, etc fail spine wack tests far less than liner locks both in my testing and from reports on the forums. In fact, I dont even remember hearing about one failure. Now granted, reports of liner lock failures seem less common these days, probably because far less are being made so it is hard to compare.

As far as lock strength, I'm not particularly worried about it. I can't imagine doing anything that would cause a lock to break, even in emergency situations.
 
Sal Glesser said:
Hi Joe. Pardon my ignorance, but why do you believe the Reeve Integral linerlock (TM) is more reliable than a 0riginal Walker linerlock (TM)?

I have found that I usually agree with your findings, but this has me confused.

In our testing, we have found that when a linerlock fails (defeats, not breaks), the failure is a slippage at the interface between the lock and the tang. When an Integral Linerlock fails (defeats, not breaks), the failure is a result of slippage at the interface between the lock and the tang. The same, though causes may differ.
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Hi Sal,

In the end, the biggest reason I think framelocks are more reliable than linerlocks is because, after handling and testing both, I find I can make linerlocks fail in alarming quantities, but framelocks fail much more rarely. In the end, that's what I'm after -- a lock format that can be made to be reliably, and consistently so, even if it's not executed by maestros like Reeves.

That said, I'm aware that, in theory, the framelock could be susceptible to everything the linerlock is. It's just that I can't get it to happen nearly as often, especially if I do the tests "fairly" -- that is, with my hand wrapped around the lock. Granted, I don't have as many framelocks in my collection, but I've tested enough to feel pretty good about them. The framelock, of course, is susceptible to counterclockwise torquing in a way the linerlock isn't -- if your hand slips but you keep your grip tight, you can catch the lock and disengage it. That may be worrying me more, recently.

Now as to the physical reasons why, I have a few guesses. When squeezing a liner lock hard, the best case is that your hand doesn't interact with the lock at all, and worst case is that your hand interferes with the lock-up. With a framelock, your hand usually reinforces the lockup. By which I mean, unless the clip is in the way, after a firm squeeze, the lock will be jammed further right some. That seems to help. I'm also not so sure you need a gorilla grip to keep the lock in place -- maybe a little fundamental reinforcement is all that's required to shore things up. And perhaps the bigger lock face helps as well.

Be that as it may, the bottom line is, what can I get to fail? What gets more failure stories around the web (unscientific, I just use it as a touchstone)?

Sal, despite the "pardon my ignorance" prologue, I'm quite certain you've tested extensively and are extremely knowledgeable, and wouldn't be pointing this out if you weren't getting different results than I am. Let's accept the idea that framelocks could be susceptible to everything a liner lock is susceptible to, so framelocks could fail on light spinewhacks and torques. Are you seeing them fail in the same percentages as liner locks? What if you re-do the tests with your hand wrapped around the handle (and proper safety preparations in place -- dulled or protected blade, kevlar glove, etc.), have you tried that? My experience is that liner locks fail more often when your hand is white-knuckling the handle, framelocks less often.

Joe
 
Thank you Joe. I like the way you think.

We spine wack a lot. We hold it so that we don't get in the way of the blade. (You'd be amazed at how easily one of our serrated knives will divide a kevlar glove).

We also get to see slips when we test strength.

Causes of slippage are quite varied from twist to surface finish.

We currently make two Walker linerlocks and two Reeve Integral framelocks. We test every piece. Defeats are rare for both, but they are analyzed for exact cause.

sal
 
Which two Reeve Integral framelocks Sal?

I assume one is the Cricket? And the other is?.....
 
Well, my opinion on this won't amount to a hill of beans cause I only own 1 folder a large classic Sebenza. I got this just because 1. I wanted a quality folder, that 2. Didn't freak out the sheeple as much as the fixed blade Busse I also carry EDC. (It's funny, they will freak out at a Mean Street with pretty much the same length blade as the Sebbie, but not the Sebbie) Mostly though I carry a Badger Attack and don't like that to be shown at all.

There have been no lock issues, and indeed it is a very tight lock-up. It's going to HI this week to be Mayonized, but I don't know if he tweaks the lock-up interface or not. It really doesn't matter too much, cause in 'white knuckle' situations I would probably reach for the Busse first. Fixed blade=no lock to fail. But then again, most people don't carry both a folder and a fixed blade.

Rob
 
Over the past few years I've gradually worked my way up from Gerber Ez-out to the Benchmade/Spyderco level as well as a few William Henrys. Today I traded a Calypso and Military for a Sebenza small Classic. I could have saved a lot of money if I'd just bought one of these way back then!
 
Sal Glesser said:
IMO, I do not think that the "squeezing of the lock" with the hand is strong enough to stop a defeat, except for a very small amount of force.
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The current world record for compressive hand strength is 116 kg (one hand). Now of course an average man isn't this strong, but it isn't unreasonable to expect a healthy and active physical person to have half this ability, thus a compressive strength of ~125 lbs. This is easily enough to greatly effect the security of the lock.

In particular, the dynamics of liner locks have this force applied to move the lock to disengage, and on liner locks it usually acts the other way, so the disparity in the force is about double the applied load, and thus a difference of ~250 lbs for an average, active and physical person. More for some, less for others, but somewhere around there.

Aside from this issue, liner locks have a much greater contact area and thus they are more sensitive to small changes in movement. If they disengage at half their width it can leave just a small fraction of a mm supporting the entire load, this will lead to a shear failure quickly. I have seen this directly under small loads.

In general though, frame locks like the Sebenza and others are still subject to the same types of failures as liner locks, in particular torques and such. So they are not a complete solution to the problem, just a slightly more robust design. The compression lock does much the same, and I would prefer it over the frame lock as I have seen jamming failures on a Sebenza in heavy use.

-Cliff
 
The second CUDA MAXX I got failed a moderate whack test. The lock bar just slipped right off the tang (and overlap was a good 50%). Camillus quickly replaced it, of course, but it illustrates that they need to be made right to be reliable. On the one that failed the amount of spring tension in the lock bar was noticeably lower than on other MAXX's I've handled. Also, the slant of the tang seemed to be steeper, and ended with a rounded edge. I don't know whether it was one or the other or both that caused the failure.
 
Cliff Stamp said:
The current world record for compressive hand strength is 116 kg (one hand). Now of course an average man isn't this strong, but it isn't unreasonable to expect a healthy and active physical person to have half this ability, thus a compressive strength of ~125 lbs. This is easily enough to greatly effect the security of the lock.

In particular, the dynamics of liner locks have this force applied to move the lock to disengage, and on liner locks it usually acts the other way, so the disparity in the force is about double the applied load, and thus a difference of ~250 lbs for an average, active and physical person. More for some, less for others, but somewhere around there.

Aside from this issue, liner locks have a much greater contact area and thus they are more sensitive to small changes in movement. If they disengage at half their width it can leave just a small fraction of a mm supporting the entire load, this will lead to a shear failure quickly. I have seen this directly under small loads.

In general though, frame locks like the Sebenza and others are still subject to the same types of failures as liner locks, in particular torques and such. So they are not a complete solution to the problem, just a slightly more robust design. The compression lock does much the same, and I would prefer it over the frame lock as I have seen jamming failures on a Sebenza in heavy use.

-Cliff
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It really doesn't matter how strong your hand or grip is, all human hands are spongey and have some give. Just try and hold down the spring on a slipjoint and close the blade. Now yes you can press the frame lock to tighten the lock up but you can do the same thing with a linerlock. Also you can try and hold down the spring with your thumb on a lockback. But in my opinion if a lock fails your hand will do just about nothing to prevent it from failling frame lock or any other lock. The small amount the lock needs to move to fail is smaller than the give in the flesh of the strongest grip on the handle.
 
db said:
Now yes you can press the frame lock to tighten the lock up but you can do the same thing with a linerlock.
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The forces naturally act in opposite directions.

The small amount the lock needs to move to fail is smaller than the give in the flesh of the strongest grip on the handle.
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You are ignoring the fact that your grips tightens as it compresses, and continues to do so until the compressability is maximized, thus you should be looking at the compressability at the point of maximal load.

At high levels of applied force your skin resists further deformation quite strongly. The responce is highly nonlinear in this regard, taking just a little force to induce a lot of compression (a few lbs is a few mm), but then it takes massive loads to induce it to move further which isn't close to the distance it takes to move a integral from full engagement to not touching the lock face which can be several mm.

A little common sense could be applied here. Take a grocery bag and hold it in your hands with only a few cans, your skin will compress 1-2 mm. Now load up the bag the maximum amount you can carry, this could be as much as 500 lbs if you are really strong (Hugo Girard), obviously at the point of maximum strain the compression can't be much more than the previous 1-2 mm, because if it was the bone would be flattened out, the tendons would all be cut, etc. .

You flesh will only compress a very small amount and then it will stop, in order for it to compress any more the skin has to rupture or all the tissues underneath burst and thus excape from under the load or otherwise suffer permanent damage via plastic deformation. This typically can't happen via direct compression (well it can but it needs a much smaller contact area than the handle of a frame lock), and is only mainly an issue with shear ripping which comes generally when you lose control and the object starts to slip and thus pull your flesh sideways and it can't resist this nearly as strongly as it can being simply squat.

To really nitpick, you can get the bursting effect under high loads - but this is only an issue if your strength gains were so rapid that they out jumped your bodies ability to compensate by increasing the internal strength of the connective tissues and such. This is generally only an issue for heavy drug users - or someone who has massive potential for strength but was *really* inactive.

Of course, once the lock moves even a little (a fraction of a mm), the blade will develop some play as the lock faces are slanted and thus any movement laterally can unduce vertical play. However for the lock to actually fail, the bar must move out of the way of the lock enough for the blade to fold down and reach the fingers. For this to happen the movement is typically quite large, unless of course the lock bar just barely engages the face at full engangement - but this I would argue is a subptimal design in the first place.

-Cliff
 
Cliff...
"You are ignoring the fact that your grips tightens as it compresses, and continues to do so until the compressability is maximized, thus you should be looking"

I'm not ignoring anything. grab a slip joint and press as hard as you can on the spring, then try and close the blade. Your skin will not rip and the spring will raise up. it's not really the same thing but is a better exsample than your bag and can idea. flesh has give and that is just a fact.
 
All of this is very informative but, IMHO, it just illustrates why the liner-lock AND the frame-lock are not the best locks available.

I'll stick with the Axis-lock for now.

Allen.
 
With framelocks IMO it's more an issue of how easily the lock can be manipulated during use. My only framelock is a Kershaw Leek, and the clip can be placed both tip-up and tip-down. It comes tip-down out of the box. I switched it to tip-up, but the lock was easily manipulated during use, which worried me. In the tip-down placement the clip gets in the way of the lock when gripped normally and feels safer. I've only handled a Sebenza (small), but the lock was much more difficult to disengage due to the stronger titanium. I can't comment on possible accidental disengagement during typical use of a Sebenza.

The thing common to both frame and liner locks is that they evenetually will wear out. Metal rubbing against metal will over time wear down. But on a quality knife like a Sebenza, this'll take quite a long time.
 
To me this all gets down to the issue of quality. A knife that is expertly designed, made of top drawer materials and manufactured to a high standard re: fit/finish is going to be much, much less likely to fail. You can put a framelock, such as a Sebbie or Mayo TNT, or a Walker lock, such as one found on a Spydie, through a rigorous torture test and they will come out just fine 99.9% of the time. However, if you put a cheap knockoff through the same test it will most likely fail despite the fact that it has the same dimensions or surface area for the lock/blade mactchup as the more expensive knives because it is a POC. The bottom line is if you want a safe knife you are going to have to pay for it but in the long-run such an investment is well worth the piece of mind and confidence it provides.
 
trane fan said:
To me this all gets down to the issue of quality. A knife that is expertly designed, made of top drawer materials and manufactured to a high standard re: fit/finish is going to be much, much less likely to fail.
Click to expand...

Yes compared to a cheap one, but the problems are inherent in the design. Well I should not say all of them, Joe has described particular custom liner locks which are *very* robust, but I have seen liner locks release on multiple occasions on high end production knives far too often to be 0.1% of the time. You can also get manufactuers to state this is the expected behavior of the locks under twisting and torquing.

Some locks are inherently more robust under certain conditions, lock backs for example are less prone to white knuckling, twisting and prying than liner locks. Integerals are more stable than liners, but still have similar problems. Spyderco's compression lock is better than all of them in regards to that type of release, but can have problems more readily if something sticky gets around the lock.

Db, here is an example of the problem with your compressability argument :

http://www.physics.mun.ca/~sstamp/images/potato_penetrated.jpg

This shows an index finger clearly penetrating a raw potato. Yes flesh is *MUCH* softer than a potato, however the force exerted on the skin is increased it stops being compressable and eventually becomes harder than the potato and then readily penetrates it.

The same thing is what allows people to bend six inch solid steel nails for example. Yes the skin initially gives under the force of the nail, but then it quickly stops compressing and becomes rigid. This only takes a very light amount of force, a small percentage of maximum.

It is also trivial to refute your arguement because it what you are saying was true, it would be impossible to white knuckle a liner lock open because obviously the skin would just give instead of being able to move the liner. This is readily known to be false as it is a common disengagement problem with the liner lock.

Now obviously if you can move the lock in one direction, which shows an application of force, this same application of force in another direction can resist the lock from disengaging.

-Cliff
 
Denix said:
Hi guys!

I've got a question that's been burning me for a while. It has to do with the real (vs. perceived) strength of a framelock, especially compared to locks that wedge metal into the tang (axis, compression, rollock, etc)....
Guy
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Denix, let me throw something else into this one.

Failure due to strength issues during use has happened very, very rarely in my experience, regardless of lock configuration. I probably don't stress my folders as much as some.

However, I have experienced lock failures due to non-strength issues. Gunk in the lock area is the primary cause. So far, the Axis and "Integral-Liner Lock", have proved the least problematic in that regard (most robust). I happen to like the William Henry button lock, but it is susceptible to be disabled by the most minor particle infiltration.

In comparing literally hundreds of liner and integral-liner (framelock) models, I would agree with what is said above, the framelocks are much more forgiving to quality control issues than liner locks. Very few companies or individuals make a really reliable liner lock, IMO. I am convinced that in the "production" category, that Klotzli consistently exectutes the best liner locks.
 
spyken said:
my large regular sebbie is easy to disassemble and clean and smooth as glass. then again, it's a mayonised version. why don't you get a sebbie on the aftermarket, then spend another 85-100 (incl. shipping) and send it to Tom Mayo for some loving. You'll be surprised what you get...
Click to expand...

Sadly, Tom Mayo has announced in the CRK forum that because of carpal tunnel and arthritis, he has to cut back his workload and will no longer be doing Sebenza mods.

Johnny
 
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