Overextending an integral lock

CPP

CPP

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Some integral/frame lock knives have a feature to prevent the lock arm from extending too far past the stationary part of the scale. For example, Lionsteel has the Rotoblock system one purpose of which is to prevent this from happening. Since most frame locks are made of titanium which I understand has memory, how common, under ordinary circumstances, is it for the lockbar to overextend to the point where it can no longer lock the blade in place when activated?
 
Under normal use? Not that common. But to be fair with so many folders now having some form of overtravel stop i no longer am very careful when closing a knife. So for me the chances of it happening on a knife without such a feature is actually more likely than before.
 
It's very uncommon, almost to the point I'd say it's never happened on a properly built knife. We had this discussion a couple years ago, and I proved it by over extending the lockbar on my large classic sebenza to the point of prying it out further than I was able to push it with my thumb. It did no harm to it at all. Pictures below, and Ill reference the old thread if you'd like to read through it.

Since that older thread, I got into knife making for a little while, and I've set and fixed a lot of lockbars. It would be almost impossible to push the lockbar far enough out past the frame to the point of reversing it - On accident. The only way that would happen is if the lockbar was extremely too thin, and it didn't have enough inward tension to begin with.



It locks back exactly where it always has. not one bit less, and still solid as ever




I post these above pictures on the third page of that thread -

http://www.bladeforums.com/forums/s...verextended-a-lockbar?highlight=over+extended
 
I've had the reverse problem with a couple linerlocks. I guess it could happen with frame locks also. That is over-locking - the liner lock goes too far, actually past the blade tang and hangs on the opposite side making it nearly impossible to unlock and close the blade. Fixed a couple by radically adjusting the pivot pins, but had two that ended up in the trash. Of course this was happening with a couple cheapies.
Rich
 
It's extremely rare that I've seen or heard of it. I suppose I can see it happening under extreme stress or maybe a strong gloved hand not having the tactile sensation to sense an overextension.

Let me insert here what a fan I am of Lionsteel's Roto-lock insert--prevents overextension AND locks the blade open. I use it all the time and it does inspire a bit more confidence in the solidity of the lockup. I wish more folders had such a great feature.​

The Sebenza test doesn't surprised me--it's a Sebenza. (Fun to see those pics, egally.)

In that regard the only other thing I can think of is that apparently, like steels, a lot of mystery-numbers and prefaces (e.g. "Spacecraft Grade" or "Aviation Quality," etc.) seem to be applied to titanium now, implying that there is titanium and then there is "Titanium." Maybe some of the lessers overextend and memorize it more than the better "blends" of the metal. Maybe I'm wrong too. :)

And maybe an expert will come along and go into this a little bit....
 
Typically, frame locks that have the stop, have it, because they need it.

I have owned some that did not have a stop that should have had one. They were way to easy to open. I sold them. I have pretty big strong hands and was afraid of bending the lock bar.

I have many CRKs and I have NO worry about over extending the lock bar. The amount of tension required to even unlock it is quite surprising. The above test on over extending a Sebenza probably would be close to impossible without something to pry it open like the user above used.
 
A frame lock stop is a solution looking for a problem. A properly designed frame lock doesn't need it.

In the old days it was called "bells and whistles" you add them to a design not for function, but to discriminate your product in a market that has too many similar designs. In the case of the frame lock stop, they ingeniously invented a problem that the "bell and whistle" solves, thus making it a design requirement for some buyers.

But hey, we all know the old man under stress can lift the car off his dying son, so your adrenaline pumped muscles will ruin that frame lock w/o the stop when the stuff hits the fan... :)
 
brownshoe said:
A frame lock stop is a solution looking for a problem. A properly designed frame lock doesn't need it.

In the old days it was called "bells and whistles" you add them to a design not for function, but to discriminate your product in a market that has too many similar designs. In the case of the frame lock stop, they ingeniously invented a problem that the "bell and whistle" solves, thus making it a design requirement for some buyers.

But hey, we all know the old man under stress can lift the car off his dying son, so your adrenaline pumped muscles will ruin that frame lock w/o the stop when the stuff hits the fan... :)
Click to expand...

Rick Hinderer came up with the idea of a lock stabilizer because he overextended a lock for exactly the reason you say, adrenaline.

Lock stick is another reason you could overextend a lock, but then that goes to bad design as well.
 
Lost Cosmonaut said:
Rick Hinderer came up with the idea of a lock stabilizer because he overextended a lock for exactly the reason you say, adrenaline.

Lock stick is another reason you could overextend a lock, but then that goes to bad design as well.
Click to expand...


Like BrownShoe noted, it could have been added for mere aesthetics, and to differentiate from other similar designs. I don't know if I necessarily believe the story of Rick breaking his knife, and if he did, than I believe it was flawed to begin with.

Look at the cutout of my Classic Sebenza - It's relatively thin compared to a lot of other knives. Pushing the inside edge a half inch out past the outer edge, and it didn't even affect the tension. You'd have to move it a lot further out to - A) reverse the inward spring that it already has and B) Move it even further out so it brings the lock the other way after tension is released.

I've been in a lot of high stress situations(with or without a knife doesn't matter), and I've never forgotten how to use something as basic as a hand tool. It's all muscle memory - I don't think you'd just apply 75lbs of force with your thumb unintentionally.
 
egally08 said:
........Look at the cutout of my Classic Sebenza - It's relatively thin compared to a lot of other knives. Pushing the inside edge a half inch out past the outer edge, and it didn't even affect the tension. You'd have to move it a lot further out to - A) reverse the inward spring that it already has and B) Move it even further out so it brings the lock the other way after tension is released.
Click to expand...

My Grayman Dua is the same way, thinner cutout but will overextend and not affect tension at all.

egally08 said:
I've been in a lot of high stress situations(with or without a knife doesn't matter), and I've never forgotten how to use something as basic as a hand tool. It's all muscle memory - I don't think you'd just apply 75lbs of force with your thumb unintentionally.
Click to expand...

Have to disagree with this part though. I can see an overextension being possible in a high-stress/panic situation....maybe especially with gloved hands with limited feel under stress. I think I could bend some of them too far if I just tried too, also.

You should be able to apply your "never forgotten" theory to shooting 'muscle memory' as well...but we all know what happens to accuracy under extreme stress--that barrel is shaking all over the place. I've encountered it and in that split second you aren't likely to, say, empty a magazine or cylinder as accurately as casual target shooting. I certainly can see it vis-a-vis lockbar overextension too (without a lock stablizer of course) under stress.
 
Lost Cosmonaut said:
Rick Hinderer came up with the idea of a lock stabilizer because he overextended a lock for exactly the reason you say, adrenaline.

Lock stick is another reason you could overextend a lock, but then that goes to bad design as well.
Click to expand...

lock stabilizer also prevents lock bar pressed into the back of the knife with a strong grip. Is that also a "invented problem"? I don't have an opinion, just want to take a poll of yours.
 
CPP said:
Some integral/frame lock knives have a feature to prevent the lock arm from extending too far past the stationary part of the scale. For example, Lionsteel has the Rotoblock system one purpose of which is to prevent this from happening. Since most frame locks are made of titanium which I understand has memory, how common, under ordinary circumstances, is it for the lockbar to overextend to the point where it can no longer lock the blade in place when activated?
Click to expand...

I have never had an issue.
 
Over travel stops are an extra do dad people can look at and admire, I have never seen anybody here post a problem detailing an over extension on a frame lock. The only over travel stops that actually have any benefit is the Lionsteel roto block that locks the knife in the open position, even if it is uncomfortable as hell in use.
 
I decided to do a couple more tests, because I still think it would be impossible to break a lockbar because you disengaged it while under stress. My opinion does not apply to knives that are not correctly and proportionally built - Meaning extremely thin cutout or a lockup that is stuck to the point of having to use a tool to release it.


In this picture, I am using all my strength and forcing the lockbar out as far as I can with one hand, just like I would do if I was unlocking it. I measured the distance the lockbar travels - Measuring from flush - and I was able to move it 4.21mm past the frame.


jRllLDz.jpg




QUiEb5c.jpg



http://imgur.com/lUD1DYi


I used a scrap knife I never finished to wedge between the frame and pry the lockbar much further than I could extend it. I measured it at 8.25mm. That's 4mm further than I could do it when putting as much force as possible while using the same technique I would be using if unlocking it. Next photo shows the knife back to normal, with no discernible differences. Feels to be the same amount of tension as there was before.

0estIei.jpg



I know that each knife is different, and each person is different. Could it happen? Sure, but with a properly built knife, I doubt that it will ever happen. Like I said in an earlier, I moved it a lot further than I could one handed, and I didn't even begin to reverse the inward spring it already has, much less bend it so far that it breaks it. From my experience setting and fixing lockbars, someones thumb doesn't have enough travel in that grip to break it.
 
Thanks for the testing. You've proven its a solution looking for a problem :)
 
brownshoe said:
Thanks for the testing. You've proven its a solution looking for a problem :)
Click to expand...

I would only interject to say that he proved it is a solution looking for a problem on well-built knives without any issue to stat with. When buying a knife blindly, or becoming subject to the rule that no two knives can be 100% the same in production, there certainly is a possibility that the issue could be real in some knives, and possibly in some particular instances of knives that are, as a whole, very well-made. There are issues in QC at some level or another for all knife manufacturers, even if those issues are very VERY minor in the case of CRK or similar quality products.

The simple version of what I'm trying to say is that this test proves 2 things in theory:
1. A well-built and executed knife will not likely need an over-travel stop for the lockbar.
2. The particular knives tested in both instances are (by this criteria) well-built and executed examples of those models.

That is not to say that absolutely every Sebenza is without the need for an over-travel stop given the same test were to be performed on each example (though I personally beliave that the Sebenza does NOT need one myself), or that all Dauntless models are completely without the need for one either (again, I believe it is a safe bet that they don't need one personally).

The other main point of this is that not all manufacturers built their knives to even nearly the same level of consistency, precision, or care that these two examples and their respective brands are known to be. Take a ZT knife for an example (I am not picking on ZT). I can almost guarantee that is I went and tested the actual numerical tension in the lockbars of 50 ZTs of the same model, even from the same serial number grouping, I would find a MUCH higher level of deviation in those figures than I would in doing the same with 50 Sebenza models, though a variation would still exist.
I would also be willing to bet that there are many companies that are not as good at making a knife that has a stable and sufficiently thick lockbar cut to support both a strong lockbar and a proper lock engagement, meaning that problems could feasibly arise from the absence of an over-travel prevention system.

Now, should this be a really big issue for someone who takes care when using their knives? Generally, I would personally think not, but then the argument of extreme situations does become relevant, as well as the debate over how much a company would like to rely on the sensible action of those who buy its products...
I think the second debate kind of proves the point I'm about to make:

If it makes the manufacturer's job easier, and it makes the product more stable, consistent (in theory), and gives the customer (or at least a portion of the customer base) feel more comfortable with trusting the product, while not significantly increasing the monetary or time costs in the product itself, then it does seem to be solving a problem, whether or not that is really the problem it was originally designed to resolve.
Basically, it might not be needed on all knives, but the fact that it could be needed on some knives gives manufacturers and customers good enough reason for it to be warranted. And if it creates a feature that makes products more competitive without harming the actual use or cost of the product significantly, then is it really a significant issue?

Just my...long-winded...thoughts on the matter, and the tests provided. Certainly don't intend to start an argument with anyone, but just wanted to chime in on this point. Anyone who has a countering argument, I'd really like to hear it with all honesty too :)

And I really hope I didn't make that confusing...I tried to be as exact as I could while keeping it understandable, so if I just started blabbing, someone please let me know.
 
Rich S said:
I've had the reverse problem with a couple linerlocks. I guess it could happen with frame locks also. That is over-locking - the liner lock goes too far, actually past the blade tang and hangs on the opposite side making it nearly impossible to unlock and close the blade. Fixed a couple by radically adjusting the pivot pins, but had two that ended up in the trash. Of course this was happening with a couple cheapies.
Rich
Click to expand...

FYI the fix for that is a larger stop pin, which can easily be made out of a drill bit cut to length and sanded to diameter. You can even use a nail if you're in a hurry but they tend to dent. Most knife maker supply shops also sell blade stops in various sizes.

Adjusting a pivot shouldn't fix that in a well fit knife.
 
EricV said:
FYI the fix for that is a larger stop pin, which can easily be made out of a drill bit cut to length and sanded to diameter. You can even use a nail if you're in a hurry but they tend to dent. Most knife maker supply shops also sell blade stops in various sizes.

Adjusting a pivot shouldn't fix that in a well fit knife.
Click to expand...

Replacing the stop pin on a folder can present another issue though. Many (not all but many) folders use the same stop pin in which the blade rests in the open and closed position. If you increase the diameter of the stop pin he blade will no longer rest at the same point when closed. In some cases the detent wont line up with the hole in the blade.
 
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