Frame lock or liner lock strength

[Cotherion]

Basically I am of the impression that the strength of a frame or liner type lock is the ability of the lockbar (lock piece) to resist buckling (bending) and crushing at the contact point and maybe some kind of failure (combination crushing/buckling at relief/bend) at the bent area of the lock.

Can I get some input cause I've been looking at my ZT0301 and I saw a picture of a Hinderer XM-18 (I am not sure of the code) and I begun to pay attention to the relief area.

Am I wrong to assume that at high closing force then the relief area crushes/buckles assuming the lockbar is sufficiently thick enough to avoid buckling by itself? Then is the relief area the weak part of a framelock? In the Airkat series the framelock is mega thick but the relief is as thick as my ZT0301 and does that mean that the Airkat's lock not significantly stronger than my ZT0301 even with an almost 2 times thicker lockbar?

If that is the case is it a good idea to 'cut' the titanium scale so that the relief although thin has a larger width than what is currently adopted? Basically I'm thinking of a lockbar that the 'cut' is not parallel to the handle but as you cut to the relief area the cut is closer to the backspacer direction in order to increase material at the relief. If any makers are reading this please let me know how good/stupid this sounds.

-keep in mind the compromise between the loss in handle strength vs. the increase in lock strength must be balanced-

I'm not too good at putting my point/points across so please bear with me. It's just that I've been looking at many locks recently and been wondering if the relief area of the lock can be improved or not.

Thanks

 

[Ozy]

The single one way to improve the lock strength of a liner or frame lock is to fold them up, put them in your pocket, and use a fixed blade.

Right tool, right job?

 

[kwackster]

@ Cotherion;

You're not the only one thinking about possible improvements on framelocks, Strider for instance already does what you are describing, by broadening the relief as much as possible.

But there is another concept that got my attention, and that's the way it's done on the older Benchmade Pinnacle, not by thinning down the relief, but by hollowing the lockbar out from the inside.
This effectively creates a u-shape which, in my opinion, should withstand buckling forces better than the standard lockbar reliefs which have been thinned down from the outside or inside.

Take a look at the last picture;

 

[Cotherion]

The single one way to improve the lock strength of a liner or frame lock is to fold them up, put them in your pocket, and use a fixed blade.

Right tool, right job?

I was wondering how long before I'd get 'use a fixed blade' but I'd never expected the 1st post.

Thanks a lot for the pic kwackster that is definitely along the lines of what I wanted to see. But I have seen a lot of Strider folders in the net and I don't recall an enlarged relief area, or maybe what is done now constitutes that?

The relief definitely withstands localized buckling better than existing cut out reliefs. Basically the idea is to weaken that section so that the lock can bend easier. I'm more along the idea of making the total cross sectional area of the relief to be the same as the lockbar's cross sectional area. But this is the first time i'm seeing this type of relief. How does this type of lock relief feel like? Harder or softer than typical locks in closing?

 

[kwackster]

Using the lockbar on the Benchmade Pinnacle feels like using a current Strider SNG with an extra bent lockbar, so it's stiff but not too stiff.
It's a little less stiff than the first generations of SNG's and SMF's which i used also.

I would like to see this type of lockrelief tried on the SNG and SMF models, as well as on the Sebenza's, as i think it's a better concept than just thinning down the relief on either side.
Used in conjuction with the Hinderer lockbar stabilizer it would make for an overall stronger framelock IMHO.

 

[orthogonal1]

I looked at the issue some after dealing with some failures and I figure the bar/blade engagement should result in a small amount of "into the handle" force and that there should be some bearing surface that prevents the bar from moving into the handle, similar to the Hinderer stabilizer, relatively close to the blade.

I have seen where some makers put a ledge on the blade to partially accomplish the same structure as described, unfortunately this surface pivots away.

Of course you can simply shorten the lockbar portion and increase its thickness and width, but there are limits due to being a "pocket knife".

The Hinderer patent may be suffuciently broad to preclude development along these lines as far as putting an additional bearing surface on the knife.

http://www.google.com/patents?id=Y-ydAAAAEBAJ&dq=hinderer+knife

 

[Cotherion]

These are questions which appear if we look into the design deeper. Like the Hinderer lock tab thing is a brilliant and simple approach, there must be something that will enable the full utilization of the strength of the lockbar. No point making a lockbar thicker if the strength is the same in the end.

 

[STR]

Even thinned down they remain strong enough to hold up to even a lot of extreme uses. The lock cuts where it is milled out thin is the weak link in the chain so to speak though and some seem to be taken to real extremes compared to others. I tend to look at the Sebenza models and judge all others based on those which have been using a similar 'stepped' pattern deeper in the middle than toward the sides, done twice and also with a pattern to it where it is incorporating some of what your picture shows BenchMade doing.

If you were to own a Caswell EDC you could take that lock side scale off and see another stepped pattern idea that also works and I've seen a few others from conical shaped cuts where its milled deeper toward the long cut but left thicker toward to the bottom of the lock and so on.

Some liner locks hold more weight before defeat than frame locks when tested with free weights hanging on the lanyard end of the folder by cable with the blade clamped firmly in a vice and its related to the thinner area lock cuts and lock thickness along with other factors like the length of the blade and body. The weak areas tend to give first. However, in the hand the frame lock gets aid from the hand helping to absorb shock with it and although hard to prove it stands to reason that the hand can cushion that force and maybe even help to distribute it along the length of the lock for how it translates down the body to the contact and due to the fact that your hand is there to block travel by your fingers being firmly wrapped around a frame lock it makes up for any loss of strength by the lock cuts in the fact that its much more reliable in the hand during hard uses than a liner lock can be, particularly when twisting lateral torques are applied to the folder body with the blade locked open.

Lastly, even though the frame lock is not the strongest lock type available its perhaps the best suited for hard uses due to the extreme reliability that is inherent in the design and the fact that very little can go wrong with one. When a blade develops vertical movement or even slop from lock wear or use its still usable in many cases and even if one were pushed to the limits where the lock cut area was tweaked enough to kink or fold during a hard use or abuse situation these are not the most catastrophic defeats that can happen in folding knives even when they fold under load in a vice. Usually the blade remains locked open in the same position in these defeat situations. In the hand its even more likely the lock would still be engaged and the blade still opened enough to not have allowed as serious an injury as other knives equipped with a different type of lock.

STR

 

[jmckaig]

Just get an axis lock!

 

[Cotherion]

Just get an axis lock!

I personally am neutral regarding axis locks. I dislike the springs and secondly the wear of the axis bar as time goes by is detrimental to the knife. That combined with thin stop pins I'm not too excited.

I would say:-


1) Get the lock like the Pocket Bushman (truly secure lock and I have not felt this way for quite some time),
2) Get the Tri-ad lock (Cold Steel),
3) Get the super thick button lock of the MOD Mark series (really thick Button lock diameter),
4) Get the Ultra Lock (Cold Steel. Like Axis but improves over time/wear and lock contributed to resisting colsing as well as opening forces unlike Axis which only resist closing forces),
5) Get a custom framelock (many variations and some actually excite me. See STR's take on a framelock in his BUSTR folder),

In order of reduced strength by my view/assumption/opinion. Not verified by tests but by theoretical estimates. If it wasn't for the fact I overall dislike the Extrema Ratio Rao, it's lock plus secondary screw bolt safety is my number 1 no doubt.

 

[SIFU1A]

Just get an axis lock!

not a bad suggestion, but what if ya are like me and a lotta the new BM designs dont "grab" ya, and the ones which do "grab" ya are made by EKI, or spyderco, or?? if thats the case then a liner lock, frame lock or compresssion lock might be in your future lol,