Optimal position for liner lock

S

Seth Thomas

Joined
Apr 5, 2001
Messages
583
I read Lewis's post about the five EK's he inspected, I noted his mention of liner lock position relative to the blade.

So, I was wondering was, what would be considered the optimal position for a liner to lock against the blade? Near liner side(right), center, or left. Is this a personal preference or a mechanical tolerance? A Commander could be used as a dicussion model.

Seth

[This message has been edited by Seth Thomas (edited 05-08-2001).]

[This message has been edited by Seth Thomas (edited 05-09-2001).]
 
From a pure engineering standpoint, I would say that the strongest position would be on the blade just enough so that the liner is completely on the blade. The reason for this is that the type of stress a liner lock sees in called "Columnar Buckling". It is acting like a column. If you've ever seen a column buckle in slow motion, a column will withstand great amounts of stress[the stringer Z-sections beneath and aircraft's upper wing skin are subjected to a constant buckling load of 64ksi or 64,000 psi] UNTIL it starts to buckle. Once it starts and deviates from a straight line, it buckles very rapidly[that's why when a wing fails, it SNAPS]. Therefore, you would want the liner lock to be in the position where it is as straight as possible. The further "up" the blade tang it travels, the more bend it has and is subject to buckling stress.

The other factor is friction between the liner lock and the blade tang. It must have enough friction that the sideways component of the buckling load doesn't push it off the tang. Therefore, keep your tangs lubricant free!

Hope this helps.

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Brigadier
Beretta 92 FS nut and Wave-aholic
"And for this cause God shall send them stong delusion,that they should believe a lie;" 2 Thessalonians 2:11
"And have no fellowship with the unfruitful works of darkness, but rather reprove[expose] them." Ephesians 5:11

[This message has been edited by Brigadier (edited 05-08-2001).]
 
Uh...yeah, what he said.
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[This message has been edited by Arkham_Drifter (edited 05-08-2001).]
 
My Commander Liner locks just into the second half of the blade. Time for adjustment?

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I would agree with above.

I prefer mine to engage completely, yet still on the left. That also means there is more room for wear over time. (although I do have some liner locks that go all the way to center).
Jim
 
Brigadier-
Yes, your treatise most certainly helped. I can't wait to hang out at my favorite knife shop. I'll causally nudge the conversation toward liner lock alightment and then I'll hit em with your explanation. Yeah Baby -- I learned that on the Emerson Forum!

Perhaps you can explain why Kalifornia can't keep the lights on.

Really, thanks for the detailed information.

Seth

[This message has been edited by Seth Thomas (edited 05-09-2001).]
 
One of the interesting things about failures (I'm talking steel now - hey, what can I say? I'm an architect. This post wheted the appetite
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)is that as a steel column or beam starts to fail it actually gets a bit stronger.It's kind of like a progressive curve towards the failure, with a sudden spike right before the end. Neat, huh?
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OK, maybe I'm the only one who finds it neat.
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Anyway, since the liner lock is acting in compression (like a column) the more "seated" it is on the tang, the better. Now, that isn't to say that, if the liner is over on the right (looking at the kinfe upside down), you should't worry. I prefer mine from center to left of center. What you might want to periodically check for is stress marks at the center of the lock, if you use the knife really hard on a regular basis. When locked, the liner is essentially pinned at the top and the bottom. Forces will try to seek the easiest route out, and in this condition, that is at the center of the lock, since there's nothing there to keep it fixed.

OK, OK, I'll shut up now.
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See - Keep on talkin' If I had this Forum while I was in school, I would have aced Physics. And, my semester project could have titled "Linear force compaction of metal matrix locking structures".

I would have never went into computers.

[This message has been edited by Seth Thomas (edited 05-09-2001).]
 
I am a little bit worried about my new Commander. The lock is just on the left hand side of the blade. Its still strong, i could not force it closed, but my SOCFK locks right in the middle. Anybody think this might be a big problem? Something that should be fixed?
 
Off the top of my head, the liner lock should have as much engagement as possible only to prevent slip. No matter how much or how little engagement there is, the amount of force applied to blade is always the same stress transferred to the lock. Therefore, I don't lose any sleep over engagement, just as long as there is reasonable engagement. See2, as a Nuclear Engineer, I also find it neat. Dick
 
Here's how to adjust your liner lock position:

This is for a right handed model for orientation purposes. Loosen ALL screws on your knife that hold the liners in place including the pivot screw. Loosen, but DO NOT remove. Open your knife, but don't let the lock engage. Hold the knife in your left hand parallel to the ground with the opening pointing up. Your left thumb should be just forward of the clip, your other 4 fingers on the opposite scale. Now, using your left hand only, put pressure fore or aft on the scales in the direction you want the lock to move. For example, if you want your lock to engage LESS, push away from you with your thumb and towards you with your fingers. The opposite is true if you want MORE engagement. Now with your other hand, lock the blade open and see if the liner is where you want it. If it is, keep applying pressure and tighten the screws quickly. Once tightend, open and close the knife a couple times to double check the lock position. If satisfied, remove the pivot screw, Loc-Tite it, and adjust your blade tension. Voila, you've just possibly saved sending your knife to EKI for a lock adjustment.
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Of course, this is only a minor adjustment. Knives in need of major adjustments should be sent back to EKI.

Hope this helps. I've done it to three of my 7B's where the lock had migrated too far to the right, now they are dead center.

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Brigadier
Beretta 92 FS nut and Wave-aholic
"And for this cause God shall send them stong delusion,that they should believe a lie;" 2 Thessalonians 2:11
"And have no fellowship with the unfruitful works of darkness, but rather reprove[expose] them." Ephesians 5:11

[This message has been edited by Brigadier (edited 05-09-2001).]
 
Thanks for the info. Will the lock eventually move over to the middle on its own? If not ill have to try to fix it myself.
 
Hey Brigadier!

Neat tinkering tip, thanks, i'll try that out on my Commanders.
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(edited for spelling)
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Be well!/Jonas aka 2Sharp

"Who want fulfillment? -denial lasts forever"
Total Emerson knives freak!!! Usual Suspect wanna-be...

The coolest bar in the world: http://www.geocities.com/Pentagon/Camp/8373/index.html
My knives!

[This message has been edited by 2Sharp (edited 05-09-2001).]
 
Bob Terzuola's book , The Tactical Folding Knife, addresses liner lock fit in considerable detail.



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Please take your seats gentlemen; oh, and flip 'em if you've got 'em.
 
Got to looking at the lock after reading these responses and a short discussion with John Hollister today. It would appear that having the locking arm engage farther across the blade cam would be better than having it engage too close to the liner lock side.

As John was saying, there doesn’t appear to be enough room for the lock to slip between the blade and the opposite liner. So for the lock to fail, it would have to be a stress failure on the locking arm. The lock can tuck into the liner on the near side and the cam shape on the blade favors that side but the lock wants to spring to the far side.

So is my logic correct to say that as long as the locking lever is solidly onto the blade cam it shouldn’t need adjustment even if it is toward the far liner?

Bob

 
I refer to my original post, if the objective is to prevent failure of the liner lock, than the amount of engagement does not matter. Slip of the liner lock IS dependant on engagement. For me, if there is reasonable engagement and the mechanism operates smoothly, then I forget about how much actual engagement there is. Dick
 
Budrichard-
In regards to your distinction between failure(breakage) and engagement slippage:

Besides wear and unwanted lubrication on the contact surfaces, are there any other factors that can reduce friction and thus increase the possibility of liner slippage?

Should these surfaces be textured to mildly increase friction?

Seth
 
Seth, I am not an expert on liner locks but am a Nuclear Engineer with extensive physics background. If liner lock engagement is dependant on friction, you want the maximum surface area, friction force is equal to the force being applied and the coeficcient of friction. Therfore you want the smoothest possible surface. Texturing will decrease the area available and DECREASE the total force. My opinion is do not modify the manufacture/makers design or finish detail. The maker has a vested interets in his product performing and knows best how to accomplish this. Dick
 
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