Frame lock stronger then hidden liner lock?

[Siggyhk]

I just wanted to point out that I recently saw a newer mt socom fail a spine wacking (on a carpeted 4x4) even though it seemed to lock up tightly before and after the test. I also have seen my amphibian close after I threw it into some wood. (abuse or not, it is what it is) The mt locks are significantly thicker than most liner locks. Seeing the recent issue with that knife was pretty much the final straw for my faith in liner type locks. But, as STR pointed out, these locks have been asked to preform beyond thier original intended uses.
Looking at my sng, mini socom elite, and cqc-12, they all only have a small portion of the lock actually in contact with the blade. This would lead me to think that a liner lock could possibly duplicate the contact area of even larger frame locks. But for me, frame locks are a winner simply due to the hand reinforcement you get. A good question may be -how many frame locks would slip off the tang and close if the hand wasn't there to keep them in place?

 

[HoB]

Maybe I am not picturing this right, I still don't see why a shorter leaf would require a steeper ramp?

And I am not concerned about the wear of the leaf face but about deformation due to compression. I have seen it even on steel leafs. The face is easily compressed/deformed even by light impacts on the spine of the blade.

WadeF: Well, ultimate strength is a different issue than reliability, and most people seem to be more concerned about reliability. To avoid pissing contests and inter-company strives, I won't say who tested, but it is a reliable source, nor which knife precisely, but one very well known and regarded framelock was tested to about 400 lbs/in. That is 400 lbs one inch from the pivot. At the length of the blade, it would translate to a bit over 100 lbs at the tip. According to Spyderco's testing, liner lock of the Military has IIRC an ultimate strength of roughly 600 lbs/in (600 lbs applied one inch from the pivot).

As to what you would use such a lock for: I have had to cut open one of those heavy duty cardboard shipping tubes, that I would usually use a saw for. I punched in the tip of my knife and then leveraged the tip against the inside of the tube while pressing down on the handle. It made short work of the tube, but you have to keep in mind that I am bearing with a good part of my bodyweight on the handle, this way you easily apply a few hundred pounds one inch from the pivot. If you push with the ball of you hand about 3 inch from the pivot on the handle with half your bodyweight (in my case a bit over 200 lbs), you are putting a torque of 300 lbs/in on the lock and I can tell you from experience, it will not even seem very much to you.

 

[straitshot]

Consider the geometry. The leaf moving sideways follows a radius based upon the length of the leaf from where it flexes to the tip bearing against the blade base (ramp). If the ramp angle is very close the this radius, wear and security will be enhanced. Longer leaf equals longer radius and lesser ramp angle to allow slippage of the leaf. Also, blade width at the base matters in strength: the farther the bearing part of the ramp is from the center of the pivot pin, the less leverage there is for force to deform parts of the knife. Less leverage equals more inherent strength. Compare a narrow folder with a wide one of similar design and this will be apparent.

 

[DaveH]

the farther the bearing part of the ramp is from the center of the pivot pin, the less leverage there is for force to deform parts of the knife.

Actually I think you have that backwards, the leverage is increased, however the angle in which the leverage is applied is decreased. Lower angle means less likely to slip and deform.

 

[T.K.C.]

Yuppers, a frame lock will always be stronger than a liner lock, for the reasons already mentioned.

 

[straitshot]

Maybe I can further clarify. Linear "closing" force applied to the knife passing from the handle through the pivot to the blade is resisted by lock geometry. A greater distance, measured along a line perpendicular to the line of force, decreases leverage between the leaf bearing point on the ramp and the center of the pivot pin. For example, if the ramp bearing point was very nearly directly in line with the force passing through pivot pin, the lock or other parts would easily fail. I hope this is more descriptive. In this case the stop pin plays no role, but the same geometry matters when "cutting" force is applied to the blade from the handle. This is why I pay as much attention to the stop pin as I do the lock when evaluating potential strength of a frame or liner lock design.

 

[HoB]

Thanks, Staitshot, I've got the picture now. I know what you mean, but I think you are facing a trade-off: Longer leaf -> less bend but longer torque arm, shorter leaf -> more bend, shorter torque arm. You can compare it to bending a 2" nail that is already bend by 10 deg to bending a 2.5" nail that is only pre-bend by 5 deg (I totally made up those numbers, just wanted to illustrate the point). But I see now way you would have a flatter ramp.

TKC: As I mentioned before, your statement is simply incorrect. More reliable maybe, but stronger depends on how linerlock and framelock are executed.

 

[straitshot]

HoB, absolutely correct. Assuming all else is equal, the inherent design strength of the framelock is the greater, but all else is RARELY equal. For example, a thick friction washer that requires the leaf to travel farther sideways onto a relatively thick blade base has the same effect as shortening the leaf radius and increasing the ramp angle to induce slippage.
As Jack O'Conner once observed, it depends on "...so many things it would take two walruses to think of them".

 

[T.K.C.]

I disagree with you HoB! There is nothing that you can say to convince me that a liner lock is stronger than a framelock!! NOTHING! I can agree that we disagree.

 

[straitshot]

Oops, sorry I misspelled your last name, Jack.

 

[HoB]

I disagree with you HoB! There is nothing that you can say to convince me that a liner lock is stronger than a framelock!! NOTHING! I can agree that we disagree.

Mmmh, actually, I would never ask of anyone to value my words so highly. But how about if someone that you respect MEASURED a linerlock stronger than a framelock? This is hardly a case of agreeing or disagreeing. Strength can simply be measured which should among reasonable people curtail the discussion.

 

[T.K.C.]

I would find it hard to believe that anyone could find a liner lock stronger than a framelock.

 

[richardallen]

Compare a Boker Trance [Framelock] to a Strider AR [Linerlock]. Do I need to say more?

Keno

 

[STR]

I would find it hard to believe that anyone could find a liner lock stronger than a framelock.

The only cases I could site would be the ones where a .125 or thicker ti frame lock only came out to barely engage the blade at all for less contact than even a .032 liner lock where the lock face sheared from forces during cutting. As I recall this happened to a Buck Strider or maybe it was a Strider knife that Cliff Stamp tested back when Mick was still active here. I remember quite a feud over it after Cliff posted his results and Mick didn't like what he read. Can't say I recall the knife though.

Anyway, I never understood the logic of building a thick a$$ frame lock only to allow .020 to actually get behind the blade but many guys make them this way. When asked they say that its so it will wear longer, which again only states to me that they recognize they are having wear issues with them. I would suggest that until you break in such a lock of this little contact that you take it easy until you wear it enough to allow more of it to get out there behind the blade to properly support it.

STR

 

[nozh2002]

I disagree with you HoB! There is nothing that you can say to convince me that a liner lock is stronger than a framelock!! NOTHING! I can agree that we disagree.

You defenetely have strong opinion. Initially I asked why it is precived this way - "frame lock stronger then hidden liner lock". I undestand that you are the best person to answer this question - please. Why do you think frame lock so superior to liner lock? So far Joe mentioned really good point, do you have anything to add to this?

Thanks, Vassili.

 

[STR]

Some models of liner locks like the thicker liner locks that are built like the little Strider 881 and larger 880 folder may exceed the frame locks in testing because they have no lock relief cut outs to make the bend in the lock. As I recall going from memory since I sold the only folder I had in that 880 SP the lock was .080 on that first production run folder. So, theoretically one could argue that a .080 liner lock with no relief cut out would be stronger than a .125 frame lock with a .039 lock relief cut out. Then again, and for that matter one could also argue that a .050 liner lock is stronger than a .125 frame lock with a lock relief of .039. Whether its correct or not would be up to whoever really wants to prove it bad enough by purchasing one of each to test to failure.

This strength issue has nothing to do with the reliability factor though which is once again the concern with liner locks for most people that are wary of them. I guess it boils down to what is more important to you, the overall strength potential of the lock itself or the reliability of the lock staying put to actually reach the limits of its strength in the first place.

Looking at it this way brings on the obvious solution to the problem doesn't it?

I mean looking at the Buck Strider 880 that is a ti lock in .080 thickness and yet has no lock relief cut out to make the bend easier in the lock one has to ask why is any lock relief even needed to be taken down to some of the extreme thinnesses that some are taken to? In fact why not take it down to .080, stop there and make the bend?

STR

 

[3Guardsmen]

I, too, have often wondered why the "relief" cut-out on framelocks and some of the larger liner locks are even there. It appears to add to the bend angle of the liner, which I don't like, and it also thins down the amount of material you have backing the lock. I see no reason for them ("relief" cut-outs), especially as ridiculously thin as some are making them. And I don't necessarily agree with Strider's reasoning for putting the cut-out on one side versus the other: http://www.badlandsforums.com/faq/Whyisthelockbarcutoutontheoutside.shtml If stresses on the lock, that could possibly cause failure, depend on which side the cut-out is placed, why have a cut-out at all? I don't think a full thickness frame-lock would be THAT much harder to close without the aid of a cut-out. Heck, it may even serve to help the detent, causing the blade to stay closed a little better.

Yuppers, a frame lock will always be stronger than a liner lock, for the reasons already mentioned.

I disagree with you HoB! There is nothing that you can say to convince me that a liner lock is stronger than a framelock!! NOTHING! I can agree that we disagree.

I would find it hard to believe that anyone could find a liner lock stronger than a framelock.

TKC,
While I understand you have your opinion on this matter, I fail to see where you provided any evidence to refute HoB's. A company that you often post in great praise of has done tests that definatively prove that your opinion on frame-lock vs. liner-lock strength, at least on a certain model, is not necessarily based in fact. The information is out there, you just need to do some searching to find it.

That is not to say that ALL liner-locks are stronger than ALL frame-locks, just that a model of each, tested against each other, came out with different results than even I would have expected. Now, a good question to raise would be whether the frame-lock in question was being gripped at the time it was tested, as manual reinforcement of the lock is one of the strong selling points of the advantage frame-locks have over liner-locks.

Regards,
3G

 

[3Guardsmen]

I would greatly value your opinions on this article, where statements are made that the liner-lock was found to vastly superior to the lock-back, in terms of strength, during testing:

Information found here- http://pweb.netcom.com/~brlevine/liners.txt (bolding and underlining by me)


THE LINERLOCK -- RIGHT FROM THE SOURCE

Michael Walker's invention and development of the LinerlockTM

by Bernard Levine (c)1997 - for Knives Illustrated


The "Linerlock" knife is now so familiar that it is easy to

forget that both the knife and the name are relatively recent

inventions. Michael Walker made the first modern Linerlock in

1980, and he registered the name Linerlock as a trademark in

1989. Since the mid 1980s, dozens of hand knifemakers and factory

knife manufacturers have made locking liner type knives inspired

by Walker's designs, although very few of them fully understand

either the advantages or the limitations of this mechanism. The

best way to understand the Linerlock is to look back at how

Walker developed it.



THE EARLY DAYS

Mike Walker began to make knives early in 1980. One of his

first customers was a collector and dealer in Red River, New

Mexico, named Don Buchanan. Mike made ten fixed blade knives for

Buchanan. Don asked Mike for sheaths to go with these knives.

Mike made those leather scabbards reluctantly, then announced

that he hated making sheaths. So Don said, "Make folders."

Mike did. He made slip joints. He made lockbacks like the

factory folding hunters then on the market. He made mid-locks

with mechanisms copied from antique folders. But he was not

satisfied with any of these. Walker envisioned an improved folder

that would do away with what he saw as the many limitations of

conventional lockbacks.

First, he would design a knife that the user could open and

close safely and easily with one hand, without having to change

one's grip, or rotate the knife in one's hand.

Second, his new knife would do away with the sharp "back

square" of the conventional pocketknife blade. When a

conventional blade is closed, its back corner sticks out, and can

snag the user's clothing. In some folders the back square is

enclosed by extended bolsters, but this can compromise the shape

of the handle. Mike envisioned changing the basic geometry of the

folder, in order to eliminate the problem entirely.

Third, and most subtle, his knife would be self-adjusting

for wear. Other innovative folders of this period, notably the

Paul knife by Paul Poehlmann (patented 1976), were very strong

and very sleek, but they required careful adjustment of set

screws to keep their blades from working loose.



THE LOCKING LINER

Mike was familiar with the old locking liner design patented

by Watson & Chadwick in 1906 for Cattaraugus. Used first on

traditional folding hunters, this mechanism became standard on

electricians' pocketknives, and was also used on Cub Scout

knives. In this design, the liner projects above the handle, and

it is split lengthwise, alongside the pivot pin. The side of its

narrow tip engages the front edge of the tang when the locked

blade is open.

Mike noted that only a thin extension of the liner could be

used as the lock in the Watson & Chadwick design. This was

because most of the liner had to engage the pivot pin, in order

to hold the knife together against the tension of the backspring.

The result is that this type of lock is inherently weak.

Mike went back to first principles. He realized that if

spring tension and lock-up could be provided by a liner alone, he

would be able to dispense with the backspring entirely. With the

back spring gone, he could then have the end of the liner cut-out

engage the bottom end of the tang, making for a much stronger and

more positive lock. Indeed it would be nearly as strong as the

old Marble's Safety folder (patented in 1902), while dispensing

with that knife's long, awkward, and fragile fold-up extension

guard (the folded guard serves as that knife's lock when the

blade is opened).



STRONG AND SECURE

As it worked out, Mike had not anticipated just how strong

his new lock would be. About 1984 I helped to run side-by-side

destruction tests of all the types of locking folders available

at that time. Each test involved securing the handle of the knife

without blocking the movement of its blade or spring; then

sliding a one-foot pipe over the open blade (which was oriented

edge downward), to serve as a lever-arm; and finally hanging

weights from the free end of the pipe until the lock failed.

Name-brand conventional factory lockbacks failed at between

5 and 7 foot pounds (except for one that failed with just the

weight of the pipe). A Paul button-lock knife proved to be more

than twice as strong as the best of the conventional lockbacks.

But a Walker Linerlock was nearly four times as strong as the

lockbacks. What's more, when Walker's Locker did finally fail, it

failed in the open position. Instead of closing suddenly upon

failure, as all the other knives did, it seized up and became a

"fixed" blade.


SELF-ADJUSTMENT

This strength turned out to be a fringe benefit of Walker's

self-adjusting design. He based this design upon the simplest of

all mechanisms, the inclined plane, or wedge. The end of the tang

is slightly beveled. The end of the liner is not (although it can

be, as long as the angles do not match). Both parts must be hard.

When the blade is opened all the way, the liner passes the inner

edge of the tang, but it is stopped before it passes the outer

edge. The liner's leading edge bears on the beveled end of the

tang. If the pivot joint loosens over time, the point of

engagement of the lock-up moves further along the bevel, so it

continues to lock up tight.

In the destruction test, when we applied an extreme load to

the blade of Walker's Linerlock, the free end of the locking

liner moved all the way past the end of the tang, and wedged

itself between the blade and the fixed liner. Mike was later able

to disassemble and repair this test knife, and today it is

(almost) as good as new.

In his first Linerlocks (he was not calling them this yet),

Walker made the liners out of spring-tempered 440-C blade steel

(he did, and still does, his own heat treating). The lock-ups

were not yet the full width of the tang -- Michael changed this

after the destruction tests, to make his knives even stronger.

The thick 440-C liners of those early versions applied so

much spring pressure to the blades that no other mechanism was

required to retain the blades in the closed position. But when

Mike began to experiment with lighter gauge liners, he realized

that a separate element would be needed to perform this function,

which is performed by the backspring in conventional knives. In

1984 Mike began to incorporate a ball detent in the frames of his

Linerlocks, allowing the liner to be dedicated totally to lock-up

in the open position, while the ball detent held the folded blade

closed.



TITANIUM

These new lighter gauge liners were made out of titanium

alloy. Titanium has many features that make it especially

suitable for this application.

- Titanium has a high strength to weight ratio.

- Titanium has superb spring retention qualities, without the

necessity of any heat treatment. A titanium spring will recover

from a severe load that would permanently deform a steel spring

of the same cross-section.

- Titanium galls to other metals -- it seizes to them, rather than

slipping past them, when they are rubbed together under tension.

This makes titanium useless for moving parts, but ideal for parts

that are meant to seize, such as the end of a liner engaging the

end of the tang of a folding knife blade.

- Titanium can be electrolytically toned to a wide range of

attractive colors. Michael and Patricia Walker pioneered the

application of this technique to knives. In fact Patricia Walker

was the first artist to engrave and anodize titanium, both on her

husband's knives, and on her own jewelry and artwork.



ADVANTAGES AND LIMITATIONS

Walker's Linerlock mechanism is flexible and forgiving in

many ways. In the 1980s Mike would go to shows with a box full of

unfinished blades that he had ground freehand in all sorts of

shapes. Customers would pick out ones they liked, and Mike would

then make knives around these blades, without any need for the

precise patterns that burden the makers of conventional lockbacks

and slipjoints.

However, one aspect of the Linerlock is not forgiving at

all. This is the bevel at the end of the tang, on which the end

of the locking liner bears. If this angle is too acute, the liner

will slip and the lock will fail. If the angle is too obtuse, the

liner will stick, and the blade will be difficult or impossible

to close.

Mike emphasizes that there is no single correct angle for

this bevel, as some writers have mistakenly claimed. Rather it

must be determined for each knife. The optimal angle is a

function of the blade and liner materials, of the spring tension

of the liner, and most important of all of the overall length of

the knife. The free end of the liner moves in an arc of a circle,

and the length of the knife determines the radius of this circle.



LINERLOCKS TODAY

Mike Walker rarely makes Linerlocks any more. He has

licensed the name, and various aspects of the mechanism

(including the patented safety latches recently developed jointly

by Walker and Ron Lake), to a few other makers and manufacturers.

On his own current knives he uses some of the dozens of other

locking mechanisms that he has invented over the years.

Mike is flattered that so many makers and manufacturers use

his invention, though he is disappointed that most of them fail

to grasp all the subtleties of the Linerlock mechanism. Because

of this, most of their knives lack the strength and smoothness of

Walker's own.

And Mike is angry at certain pompous Johnny-come-lately

makers who attempt to claim credit for his inventions and his

designs. One shameless maker is today receiving royalties for a

design that Walker created two years before that particular maker

assembled his first knife. But Mike never patented his original

mechanism or his early designs, so this sort of copying is now

water over the dam.

However Walker's trademark rights are another story. Mike

lets his lawyers deal with any makers or manufacturers who have

the temerity to use his "Linerlock" trademark without his formal

written permission.

*** END ***

Regards,
3G

 

[RedEdge77]

Aren't knives meant to cut? Sure I can see using the tip for some work but how much pressure is actually applied to a lock? If you are using a knife for what it is meant for then you should really not have to worry about what type of lock it has as long as it keeps the blade open.

Someone else in this thread we all should learn to use slipjoints and I agree 100%. :thumbup:

 

[STR]

3Guardsman its a neat historic piece that is interesting. My tests don't pan out the same way though. I think anyone that tested those original liner locks against Spyderco or Cold Steel lock backs would find that the results are starkly different than whatever brand of lockback they tested at that time. I believe Cliff Stamp, Joe and others have often stated also that spine whacks can be passed quite well with a number of liner locks but its the twisting torque motion that will suddenly show its weak point in the design. Also, as I've noted myself even on ones I thought were fine that you can spine whack one successfully 500 times and be quite confident in it and then go to show it off to someone as they watch only to have it fail on you suddenly without warning or reason to figure out why.

STR