Lockback failure

J

Joel McNamara

Joined
Oct 28, 1998
Messages
119
With the numerous discussions regarding linerlock failures, has anyone ever experienced an open lockback blade disengaging during use?

Not from mechanical failure, but from some part of the hand accidentally depressing the locking spring.

In the The Firing Line gun forum, Harry Humphries states a preference for linerlocks because of this - based on experience from classes. (Don't know if he's heard about the slap test.)

I personally have never had a lockback fail on me, and was curious if anyone else had.

Joel
 
I haven't and I'm not concerned about it either...I avoid the junk that is out there and to be perfectly honest I don't think I will ever be in a situation where I will have to have the meanest, strongest and tightest lock out there be it liner or lockback. All I want is a good locking mechanism and the knives I do own are plenty strong enough.

Has anyone's Genesis, Voyager or Military failed?

Just my $0.02

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~Greg~
 
I'm shocked about the Ascent failures, and haven't been able to duplicate it with my 4" Ascent. But enough people have that it's worth some concern.

Accidental release failures are the one failure I really watch out for on lockbacks. The trend of going to mid-locks (like Spyderco, Benchmade, et. al. use) has made the risk of accidental unlocking much higher -- the old Buck-style rearlock was harder to hit by accident, at least for me. The midlock puts the lock release right under your palm.

I've never had a white knuckle failure of a lockback in use, the way I've had failures of liner locks, but I have heard of them occurring. I always test to make sure the release is nice and stiff, and to make sure that some quirk of ergonomics doesn't place the lock somewhere it's easy for my palm to hit. It's worth a white knuckle test, too.

Joe
jat@cup.hp.com
 
If you use a Saber grip on a Buck 110-style "rear release" lockback it puts the edge of your palm right on the release. Bet you dollars to donuts that's what Harry saw...methinks I'll ask him. I've had no problems at all with my Cold Steel mid-release piece.

Jim March
 
I have had locks let go from prying. Never fromn my pushing it accidentally, they just let go. I cannot find the root of my Ascent's failures. I pulled it apart, the lock tang fits snugly in the the notch in the tang, and I modified the spring to get more tension, nothing works as of yet. I went so far as to dremel the lock so the lock tang would fit further into the blade notch. No Avail. My guess it it has something to do with the lock geometry and is not readily fixable.


**UPDATE**
As of last night my knife folded up like a slipjoint with little effort. Now it won't. I have No Idea what has caused this sudden willingness to work. The only thing I have done since last night's test is to add a little oil (outers gun oil) to the lock. Needless to say this sudden change of character has caused me to question the reliablility of the lock, so I am still going to replace it with something that I can put a bit more faith in. My Ascent WILL NOT FOLD NOW no matter how hard I hit it. Perhaps tomorrow it might.

Will Someone HElp me out here?@?!

YeK



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"No, it's a Vaquero Grande in my pocket, but I am happy to see you!"
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I've been thinking a little about what might make a lockback fail the spinal tap test, but not fail under pressure. Maybe . . . with a sharp blow spine-first on a hard surface, the blade and handle would stop suddenly, while the locking lug would keep going briefly against spring tension, loosening and bouncing back. If it keeps going far enough, it might releast the lock. I'm not sure how real use could duplicate that effect.

------------------
- JKM
www.chaicutlery.com
 
Since reading this thread I have whacked the backs of the blades on both my Ascent and my Goddard Lightweight as hard as possible to try and make them fail but they are both as solid as rock. I have also white knuckled the knives in various grips and and the only way I can put pressure on the locking bars are in grips that are very uncomfortable and I am sure that in even extreme use I would not hold the knife this way.
With regard to my Ascent, it was very hard to open and close even after I loosened the pivot pin. I applied metal polish to the back of the blade where it meets the lock and opened and closed it NUMEROUS times. I then cleaned it and applied a drop of oil and it is much easier now. My Goddard Lightweight is still the easier of the two to open though.
Maybe I was just lucky with the quality of the knives I received.
 
Alrighty then,

I re-tested my Ascent, and it will not fail now. I am still at a loss as to why it is passing now. As I have said before, as of last nightm it would fail with little effort, even after I took somewhat drastic measures to try and fix it. All I have done since last night was to add a little oil to the lock because it felt gritty and rough. Wait...I did take the claw part of the hammer and tap the lock into the notch, but I had done that before I did the Dremel Mods, and it did not work than. Ugh.

I did get my Girlfriend's Goddard Lightweight. Pass. Real tough knife.

YeK


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"No, it's a Vaquero Grande in my pocket, but I am happy to see you!"
yekimak@hotmail.com
MegaFolderians Unite!!




P.S.

Well I am in hot water now. After I did the spine whack test on My GF's Lightweight, I found that the pin that holds the toggle lock bent, and the whole lock has shifted forward slightly. The pin material is extremely soft and malleable, and has deformed enough to allow vertical blade play..I think I have some pins running around here that will suffice, and they ar eprobably hardened, and hopefully will work better than the original pin material. I will keep you posted as things progress.

[This message has been edited by Yekim (edited 16 February 1999).]
 
Once I had found that the Pin in the toggle lock on the Goddard was malleable, I decided to see how much force it would take for total catastrophic failure. I did not have a scale handy, but when I locked the knife blade down and forced the handle, it did not take too much to make the lock completely break loose. The rivet that held the toggle was completely bent, and nearly sheared, and possibly would have it the lock tab did not pop out of the tang notch. My guess is that much more than 35-40 ponds of force would easily make the lock fail.

Gees, I just destroyed my girlfriend's knife. I think I may be in deep doo-doo.

I think I may live another day, but I will probably have to get another knife for my Girlfriend just to make me feel better.

Graphic Unadulterated gruesome knife surgery content ahead, parental guidance suggested...

I pryed the zytel slabs apart far enough to get the Dremel's cutting wheel in between the toggle and the slab so as to cut the now mangled rivet and remove the toggle. After removing the old (it was really soft, I thought it was aluminum at first) rivet, I drilled out the hole in the lock to a full 1/8", along with the corresponding holes in the zytel handle. For a replacement pin I used the shaft of an old dremel bit that had broken. I cut it to length, and rounded the ends to look like the original rivet.

My Conclusions are that the Goddard Lightweight, is truly a light weight. The removed rivet was made of a soft steel, and is approx. 2mm in diameter. It showed that it had nearly sheared from being torqued on. You may ask "why not send it back?", if I were, they would just stick another cheap ass rivet in the thing, and I do not know if I violated the warranty by doing the test. My fix is an upgrade. My personal feelings are that this knife would have failed sooner or later in my use. I believe that the knife is tougher now that the weak link has been eliminated. I think my next trick will be to replace the RIVET that holds the blade with a Benchmade style pin. This will be after I replace this knife for my girlfriend.

I am at a loss. One minute my Ascent fails, the next it passes, and the Goddard just self destructs. I am begining to think that the lockback is not as reliable as I once thought it was.

YeK

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"No, it's a Vaquero Grande in my pocket, but I am happy to see you!"
yekimak@hotmail.com
MegaFolderians Unite!!




 
Yekim
It may not be relevant, But I have seen lockbacks fail to actually lock properly because of pocket lint.
Sometimes it doesn't take much....and it can clear itsself.
Happens with liner lokers, too. I have a BM Perdue 350 (or is it 3500...anyway, the manual one)....that is particularly prone to lint clogging.
Just a thought.

------------------
Brian W E
ICQ #21525343
If I am a figment of your imagination.....please stop it, NOW.

 
Brian,

Trust me, I have had lockbacks fail from pocket lint too(sometimes Ifeel as if I am the nexus where all lint has its origin), and I try to clean the actions in my knives (and guns) weekly. The Ascent did not have any lint in it. It is just weird that the line between failure and Passing is such an unclear, and thin one. It seems that my impression that lockbacks are more reliable, or at least more predictable, was wrong. I still prefer tham to liner locks, but I have just lost a little faith in the past few days.


YeK

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"No, it's a Vaquero Grande in my pocket, but I am happy to see you!"
yekimak@hotmail.com
MegaFolderians Unite!!




 
Oh yeah guys?? Well, uh, I remember throwing a Buck-lite lockback knife at a tree and the lock failed!!!! How's THAT for a KNIFE TEST??
 
Out of curiosity, How many people encounter situations on a daily or even once a month basis where 35-40 lbs. of force is exerted on the back of their folders(excluding testing)?

I personally don't do torturous tests on every one of my knives, only the one's that I carry often and need to feel a certain comfort level with. I always try to avoid a situation where one of my knives would be used as a prybar or lever, especially against the spine.

My main concern with lock strength of any kind has been against impacts, because they occur fast and usually unexpectedly(disarming attempts). If I felt a wrenching or prying force being applied to the spine of a folder in my hand my instinct would be to "cut 'er loose!", move with the force or let it go.

Not trying to put down peoples testing, just needing to know what activities would require such back applied lock strength for my own future reference, maybe I'm missing something?

NOTE: I'm not addressing the reliability and solidity of lock-up! Just the resistance to back applied force.

Thanks,
Ken
 
It is easy for a knife to experience thirty, fourty or more pounds of force. I can easily exert that much on a knife by cutting resistant material. Heavy rubber hoses, whittling tough wood, not to mention emergency situations. On liner locks, the stop pin is what the blade rests on when open, and is what keeps the blade from opening further. On a lockback, the toggle lock has a dual purpose role, to keep the knife from closing, and to keep the knife from opening further. All of that force is on the little pin that holds the toggle lock in place on the handle. With a lockback, if the toggle pin fails easily from closing forces, it can be assumed that opening forces could cause the same damage.

I do use my knives hard. Testing in this manner helps weed out the weak. I was not extreme in my testing. I do not expect to use my knife as a lever to lift my truck, but I do expect it to not let me down when I need it. Sarcastic remarks just prove one's ignorance on the subject. Testing my knives has been an enlightening experience. The last thing I want to do is loose a finger, I have already come close, and it is no fun. With something as precious as one's digits at stake, I would expect everyone to be a little concerned about wether their folder is reliable, or if it is a pocket guillotine. This goes double for knives being carried for self defense. If you are going to bet your LIFE on your knife, you better be dang sure that it will not fold from impact or hitting a hard target.

YeK

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"No, it's a Vaquero Grande in my pocket, but I am happy to see you!"
yekimak@hotmail.com
MegaFolderians Unite!!




 
Once while I was at Kunsan AB, Korea, we were ripping open old sandbags and dumping them out. I was using my Endura to cut them open, and had a bad grip. The knife tried to close once or twice, so I altered my grip alittle and didn't have any more problems. My Delica might have almost closed on me once, but it was from the way I was gripping it.
Blades
 
Well I was doing something dumb at the time with it, but because of a very tight grip on a Case "Sharktooth" I had caused the lock to release on my left index finger...7 stitches,and the loss of feeling in the tip of it as a result.
Live and Learn I guess....

~Keith~
 
Yekim,

I appreciate the insight. I don't work in an environment where heavy-duty use of a knife is necessary everyday. Only 2 of my past carry lockbacks have had to do 'heavy' cutting during recreational activities. Other than basic spine whacks and gorilla grip and torque, I haven't pushed testing beyond that and was simply needing examples of situations I might not have considered that would push me to retest my daily carry lockbacks.

My question was presented strictly in sincerity, not out of sarcasm. If you percieved it as such, it was not my intention and apologize. I don't feel that I am ignorant regarding the subject of knife locking performance and my safety, if I didn't care, I wouldn't have questioned what everyone was saying and kept living in my own fantasy. My personal 'concern' is what motivated me to post, not an attempt to ridicule. Again, if this is the way it was
seen by you and/or anyone else, I apologize.

For what its worth, I've decided to not carry three folders I own based on past forum member testing results. If I'm not supporting/contributing to a particular point of view, I'm likely asking sincere questions. I'm here to 'learn' first and foremost.

Thanks,
Ken
 
Yekim; I didn't take Ken's post as being sarcastic; in fact, he specifically states:

"Not trying to put down peoples testing, just needing to know what activities would require such back applied lock strength for my own future reference, maybe I'm missing something?"

Remember, Yek, that we are all ignorant to some degree or the other. That is why we come here to learn. Being ignorant is perfectly acceptable. Being stupid is another matter. I confess, that at times, I have been both.

I am not trying to harrass you, Yek, just say that I didn't see any offense where you did. Walt
 


I apologize, and digress a little, but I must mention that it was not Ken who I was refering to. I do my best to get my shots in
smile.gif
, but I guess sometimes my aim is off
redface.gif
.

I think I am still in shock from testing my nives.

YeK


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"No, it's a Vaquero Grande in my pocket, but I am happy to see you!"
yekimak@hotmail.com
MegaFolderians Unite!!




 
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