Optimal position of the liner lock

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alan0354

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Hi,

I want people that are experienced in working on liner lock folding knives to comment on this. Below is a picture of 3 knives with the liner lock grind to different position relative to the bottom of the blade.

Linelock position.jpg

1) The one on the right is the most common when one buys a new knife, ALL of them regardless of brand comes like this. The liner lock is on the far left side, some doesn't even go in far enough to flush with the side of the blade.

2) The middle one I grind so the liner is in the middle of the bottom of the blade.

3) The LEFT one I grind more to let the liner lock almost go all the way to the right side.

What is the reason why ALL the knives come looking like (1) on the right? I would think it is safer to have the liner at least like the one in the middle so the blade is LESS LIKELY TO FOLD BACK DURING USE.

Actually I would think the best is the one on the left that the liner is towards the right side. As you can see, even wearing out with time, the liner goes all the way to the right, it will be stopped by the metal plate(frame) on the right to prevent from going off the bottom of the blade. This should be the safest position in my book.

BUT before I make this conclusion, I want to hear from experienced knife people whether my conclusion is correct, also whether I am missing something that I should consider.

If I am right, it would be so easy for manufacturers to grind the liner to look like (3). Why not?

Please comment.

Thanks
 
In my opinion, and experience, it's the actual lock-up, not how far the lock travels across the tang that matters most. As long as the lock fully engages (the lock coming to a stop completely within the tang), as long as the knife was properly made (like the tang ground at the right angle), as long as the lock holds the blade securely in the open position, and as long as the knife is used as a knife, and not a prying tool, there shouldn't be any real risk of it accidentally coming unlocked.

The things that concern me as far as safety go are 1. lock-rock/slippage ( tang ground at the wrong angle causing the lock to disengage with slight pressure, and 2. the lock not fully engaging the tang, just catching on the very edge of the tang.

As far as the lock traveling all the way across the tang, I don't like that at all, and if I received a knife like that I would send it back. I want to be able to use a knife for years, if not decades, and I want the lock to have room to wear in over time and repeated openings and closings. A lock that travels all the way across the tang at the very start of its life of service might wear to the point of loosening and cause lock-play.

The liner lock is my favorite type of lock. I've owned and used many. I've been using them for over 20 years, and I've never had one fail or come unlocked on me during use.

The one bad one I owned was a Gerber Applegate "Combat" folder that had lock- rock right out of the box, and would come unlocked with slight pressure applied to the back or tip of the blade. Fortunately I never actually put it to any use.

In contrast, I once used a liner lock knife (Benchmade Darkstar) to pry open a bathroom door when the door knob broke trapping me inside. To my utter shock the lock didn't fail, and the knife still functions perfectly to this day. Of course I don't recommend using a folding knife in such a manner, but it was a unique situation.
 
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Thanks Killgar,

This is how I grind the liner as shown:



I grind the liner as shown in right that the surface is perpendicular to the frame so when in lock position, the contact is on the right most edge as shown. This will ensure the liner has to be pushed the longest way to the left before it unlock the blade. It should not slip when pushing on the back of the blade.

Even when the contact point wear out, it should not slip, the whole lines just move a little towards the right.

Tell me what you think.

Still, my original question is why manufacturers don't grind it so the liner goes farther to the right. I just think it's a lot safer than how they grind.

Thanks
 
Are you talking about knives that you are making yourself, or existing knives that you are modifying to produce a late lock-up (lock further across the tang)?

I'd have to take a moment and try to count how many liner lock folders I've had, because it's more than a few, but I've never once altered the contact surface of either the lock or the blade tang. That's an easy way to cause problems, or ruin a knife.

I've only had two (I just remembered another one) liner lock knives that I was unhappy with the locks/lock-ups, the Gerber that I mentioned before, and I just remembered a Lone Wolfe T3 that had lock-rock. I got rid of both. All other liner locks I was happy with. I had one Cold Steel Ti-Lite 6 that had a late lock-up that I was not happy with, I fixed that, but I didn't have to alter the contact surfaces to do it.

If a knife locks up tight and secure I don't advocate altering the lock. Aside from the risk of messing it up, you could void the warranty (most definitely if it has a warranty). But it sounds like you and I have a different definition of "secure".

In any event, you're free to do what you want with your knives. I've certainly done my share of modifying knives myself. But if you are making knives to sell, I don't think many buyers would prefer a late lock-up.

Do what makes you happy :) .
 
I am not doing it to sell, just playing around with existing knives specifically Steel Will Cutjack. I am not saying I am right, that's why I run it by experts here. This is just for discussion purpose

I am an engineer(no experience with line lock knives) myself, I just cannot think of one reason that I should not grind to make the liner go a little farther in.

On top, I bend the liner out so it put more pressure towards the right. I make it easy to flip open by rounding out the edge of the hole on the blade that is used by the liner to keep the blade in place in close position. All that is to make the knife more reliable.

I know I can do whatever I like as I am not selling it. I just want this to be a analytical discussion so I learn something.

Ha ha, I am trying to order a few liners so if I am wrong, I can put in new one. I am not insisting that I am right, just want to hear from experts here.

Thanks
 
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alan0354 said:
I am an engineer(no experience with line lock knives) myself, I just cannot think of one reason that I should not grind to make the liner go a little farther in.
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Killgar gave you the obvious reason: You have to allow for wear, and as long as the lock engages properly there is no advantage to making "the liner go a little farther in".
And, not sure if this is an important factor, but the further in the liner goes, the further you have to push it out to disengage the lock.
 
alan0354 said:
Anyone else has opinions?
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Three bad things can happen: (1) you get lock stick, (2) the tang angle is too steep and with pressure on the blade it pushes the lockbar out, (3) in a good lock, the lockbar is harder than the tang, and by grinding it with a machine, you destroy its heat treat and make it soft.

Regarding your OP, like K killgar , I don’t like the lock at 100%. Not only does it not allow to wear, but also, it will make the knife very sensitive to centering adjustments when reassembling (which can change the position a little). Other than that, I have very good knives that I like at, say 20-30% (like Hinderers), or at 50-60% like my CRKs or Spyderco Ti Militaries. (assuming you include the RIL in the discussion).
 
I think most reputable knife manufacturers test and research their products in advance to design the lock to its optimal performance on all the different designs. I’m going to trust them with the design and use them as is until there is a problem then I will send it back to them for warranty. If I try to fix it myself I will probably ruin it and void the warranty so I’ll leave it alone and letthem fix it.
 
I know I need to trust the manufacturers.

I want to get into the mechanical design more, not what is supposed to work, but what is the reason one way or the other.

I want to talk about the analysis of what is good and why.
 
If you are an engineer, look closely at the mechanism on all your liner locks. Pay close attention to the angles on the tang and the lock bar. There is a lot of subtlety in those designs, and as far as I can tell, a lot has to do with not needing tight tolerances, and allowing for wear.
 
gentleman_edc said:
If you are an engineer, look closely at the mechanism on all your liner locks. Pay close attention to the angles on the tang and the lock bar. There is a lot of subtlety in those designs, and as far as I can tell, a lot has to do with not needing tight tolerances, and allowing for wear.
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That's exactly what I am asking here to see anyone actually have experience and knowledge on this. It's hard to think manufacturers not knowing how to grind this. Just what are the reasons?

Well, there's also the possibility they don't know anything!!! From what I see all the knives, I am not sure they really know their stuffs either, a lot of them are really like fashion and people buy for the looks and designers designer for the looks more than anything else. Sorry for this comment if this offends some of them.
 
If a lock has proper lockup and proper contact, it doesn't matter if it engages really early on the tang or really late.

Really late offers no advantage over early, and in fact as mentioned can really shorten the life of the lock, at least as far as tight lockup is concerned.

If you modify a new lock that locks securely early and grind it so it travels all the way to the opposite liner, you will have a loose lock soon, if not immediately.
 
alan0354 said:
That's exactly what I am asking here to see anyone actually have experience and knowledge on this. It's hard to think manufacturers not knowing how to grind this. Just what are the reasons?

Well, there's also the possibility they don't know anything!!! From what I see all the knives, I am not sure they really know their stuffs either, a lot of them are really like fashion and people buy for the looks and designers designer for the looks more than anything else. Sorry for this comment if this offends some of them.
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Maybe they just don’t agree with you.
 
J. Doyle said:
If a lock has proper lockup and proper contact, it doesn't matter if it engages really early on the tang or really late.

Really late offers no advantage over early, and in fact as mentioned can really shorten the life of the lock, at least as far as tight lockup is concerned.

If you modify a new lock that locks securely early and grind it so it travels all the way to the opposite liner, you will have a loose lock soon, if not immediately.
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I am thinking just make it go a little deeper to be secure as shown in this picture.


I just grind so it's slightly pass the left of the bottom of the blade. So there are plenty of room for wearing out.

I just show the extreme in my first post.

Thanks
 
alan0354 said:
OK, don't agree is fine, so what is the right way and why? I want to talk analysis, not just same don't do it. Why?

Anyone actually have experience making knives?
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You’ve been told why, once lock up is achieved more doesn’t matter. Your opinion is then “…just make it go a little deeper to be secure.” Well OK, but why? Why do you feel going in further make it more secure?

If almost all of the liner locks you buy have very early lock up, then knife manufacturers, who arguably have a lot of experience making knives, are telling you their opinion of the right way.

I am not a knife maker, just an engineer, but off the top of my head, the further the liner travels the less spring force it has to hold it in place. Second, the liner and blade in the lock position are not in-line but at an angle. That angle means the normal force has vectors in the X and Y directions. Force in the X will work to push the liner out. Both of these conditions are magnified the further the liner travels, so in these respects early lock up is more secure.
 
Blue Sky said:
You’ve been told why, once lock up is achieved more doesn’t matter. Your opinion is then “…just make it go a little deeper to be secure.” Well OK, but why? Why do you feel going in further make it more secure?

If almost all of the liner locks you buy have very early lock up, then knife manufacturers, who arguably have a lot of experience making knives, are telling you their opinion of the right way.

I am not a knife maker, just an engineer, but off the top of my head, the further the liner travels the less spring force it has to hold it in place. Second, the liner and blade in the lock position are not in-line but at an angle. That angle means the normal force has vectors in the X and Y directions. Force in the X will work to push the liner out. Both of these conditions are magnified the further the liner travels, so in these respects early lock up is more secure.
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Yes, this is what I am hoping to talk, with reasoning.

For the point if the linelock travel more to the right, the spring becomes weaker, this is VALID. I took that into consideration. I actually bend the linelock out more so it put more pressure towards the right in the picture. Of cause that will make it harder to open the knife as the dot on the liner push harder on the hole on the blade that keep the blade from opening.

The fix is I round out the edge of the hole on the blade with a oval diamond drill bit( tip looks like an egg!!). With that, it open just as easy as original but now I put more pressure towards the right than the original knife.

As of the x y, here is my drawing from what I read your explanation.



Do you mean due to the slant on the bottom of the blade as shown in ORANGE, it generate the force in x direction as shown and push the linelock towards the left?

My response is as the linelock move to the left, it will travel to the ORIGINAL SPOT labeled in ORANGE. So that would be no difference as if the linelock was in the original position.

Remember i bend the linelock out more to put more pressure to prevent it from being pushed to the left as easy.


This is what I want to talk, we give our reason and see. I have an open mind, I don't insist on my way. I just want to talk it out like this. If you disagree, let me know.

Thanks for your time.
 
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