liner lock failure

9

9engine

Joined
Nov 15, 2000
Messages
91
I have had my new Kershaw Boa for about two weeks now, and after reading about some lock failures and some people testing the lock strength of their knives, I decided to do a little test myself.I opened the knife, made sure the lock was engaged,and checked for blade play. Then, I turned the knife edge up and held the handle so my fingers were out of the way and I brought the spine of the blade down onto my knee with a fairly hard blow. THE LOCK FAILED!!! I was amazed! I tried it several more times with the same results. I even tried just laying the blade on a table top and pressing down and I got the same result! Is this common with liner locks or do I have a defective knife? Has anyone else experienced this? Ken, If you are out there, please help!
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Hi 9- That does'nt sound too good. I have never had a liner lock fail on me, not even on a production folder, and I would like to think that that's not unusual. I'm not sure what to suggest, I would call the dealer or Kershaw and explain the problem to them, maybe you can obtain a replacement.
Has anyone else had this problem ?
Donald.

[This message has been edited by nowhere fast (edited 11-23-2000).]
 
The famous "spine whack test" did it again
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I have a large CRKT KFF that closes (without the additional LAWKS engaged) constantly after the third whack.
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I think this shows that the delicate geometry of a correctly closing liner lock isn´t that easy to manufacture.

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"Peace is not without conflict; it is the ability to cope with conflict" - Leo Giron
www.messerforum.net - the premier German language knife-related web board
 
Perhaps I'm missing the point but just what does the 'whack' test prove? The reason knives have locks is to prevent them from closing up on your hand when the blade snaps forward as it can when pushing hard with a folding knife. It seems to me that you don't need a lock tough enough to pound nails with the back of your blade, just one strong enough to keep the blade from snapping back and cutting your hand. Is that right? I'm no expert in knife design, if I'm wrong please tell me.

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wdg123

[This message has been edited by wdg123 (edited 11-23-2000).]
 
You are correct that you don't need a knife capable of pounding nails with its spine. The above test is just a method people have developed to try to answer the important quesion, "Is this gonna close on my fingers?"
I tried it out on my MT LCC just now and it stayed open.
The one Kershaw I ever bought is a POS, so it doesn't surprise me to see one more reason here not to buy another.
 
if you have a problem wiht your kershaw,take it back.they will replace or fix it.i find that they are fine knives,even the non open asisst ones (although they arent quite as nice).

but i dont agree with the spine whack test.when you are actually using the knife,how often do you actually bang the blade against the counter? you dont expect your favorite handgun to mix cookie dough,do you?
 
I expect the slide to lock back when the mag's empty.
Thing is, you never know what you might do with your knife, or what awkward position you may be in while doing it. While I do think lock strength is overrated in some respects, I expect any decent lock to pass a simple spine whack test.
One of my lockbacks now fails this test, and has been removed from service until it gets fixed. Gonna send it back one of these days. It is usually used for a work knife, and is used for a variety of tasks. Not worth risking my fingers over.
IMO, a quality product should work as intended. Otherwise it's not a quality product, and I don't want it.
 
Originally posted by wdg123:
Perhaps I'm missing the point but just what does the 'whack' test prove? The reason knives have locks is to prevent them from closing up on your hand when the blade snaps forward as it can when pushing hard with a folding knife. It seems to me that you don't need a lock tough enough to pound nails with the back of your blade, just one strong enough to keep the blade from snapping back and cutting your hand. Is that right? I'm no expert in knife design, if I'm wrong please tell me.

Click to expand...

wdg123,

I said the same thing when I first joined this forum, and was pelted with tirades.

I especially hate the really far-fetched arguments like the one I got about, "What if I'm in a fight and a guy with a baseball bat hits the spine of my knife? It will cut my fingers off!"

I say, if you see a guy with a big bat and you only have a 3.5 inch folder...get the hell outta there!

Don't get me wrong. I'm all for safe products but, like you, I'm pretty sure that locks on knives were designed as a measure of SOME safety (i.e. just in case...); not to give free license for people to use folders as bayonets!

[This message has been edited by Full Tang Clan (edited 11-24-2000).]
 
This is only the start of linerlock problems.

What's often a far more serious matter is to check whether the inside of your forefinger can accidently disengage the lock if you were to "seriously white-knuckle it" while overly excited in a fight.

I was recently pleasantly surprised at the design of several Boker "tactical" linerlocks. They had put the liner release on the rearward edge of the forefinger cutout only. That way, on a hard target stab, your finger will slide up against a nice block designed into the grip to prevent a "slip up" accident and AWAY from the lock release. It had the makings of one of the few "pure linerlocks" I have any respect for, another being a similar concept Steve Ryan uses on the Biohazard - set up the grip so that you can't possibly squeeze the lock release by accident by placing the finger the hell away from the release (versus shrinking the release, an idiot's answer).

Very, VERY few linerlocks are properly engineered this way. And while Boker's praiseworthy linerlock is OK for 3.75" blade lengths, the thin liner itself could never support megafolder blade lengths past 5".

Thanks, REKAT, for a knife with off-scale lock strength that's impossible to accidently trip combined with a 5.45" blade. I'll never carry a linerlock for defense ever again and I'm puzzled as to why people still do.

Jim
 
Originally posted by Jim March:
I was recently pleasantly surprised at the design of several Boker "tactical" linerlocks. They had put the liner release on the rearward edge of the forefinger cutout only. That way, on a hard target stab, your finger will slide up against a nice block designed into the grip to prevent a "slip up" accident and AWAY from the lock release.
Click to expand...
That is an excellent design idea. More secure design than the many liner locks in which the lock release is at the front of the forefinger cutout.

Originally posted by Jim March:
I'll never carry a linerlock for defense ever again and I'm puzzled as to why people still do.
Click to expand...
I usually carry my 710 for defense, but sometimes I'll carry my AFCK, mini-AFCK, or some other liner lock. A well made liner lock is pretty much as secure as you are likely to need a knife to be. I've tested all of mine and they've all passed, so even though there are better locks, I still carry and trust my liner locks. But Axis and Rolling locks are still better.

Reasons for the spine whack test - folding knives come pre-broken from the factory, and, if you try hard enough, you can make them fold up again. You don't want this to happen while your fingers are in the way. No, it's not likely that someone will hit the spine of your blade with a bat, and if they did you'd probably drop the knife anyway. It's a question of how much security you want. If whacking it on a counter is more force than will ever come unto the spine of my blade in actual use, and it survives a counter whack, then I know it will not close on my fingers. I guess it's a matter of testing harder than you will use to make sure it will hold up during use vs testing lightly because you don't expect to use hard. I've read enough accounts of liner locks closing on people's fingers that I test mine so my fingers won't be next.



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Jason aka medusaoblongata
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"I have often laughed at the weaklings who call themselves kind because they have no claws"

- Zarathustra
 
Originally posted by Full Tang Clan:
wdg123,
I especially hate the really far-fetched arguments like the one I got about, "What if I'm in a fight and a guy with a baseball bat hits the spine of my knife? It will cut my fingers off!"
[This message has been edited by Full Tang Clan (edited 11-24-2000).]
Click to expand...

wdg123 & Full Tang Clan, I'm with you.
 
9engine,

I also have a Boa with a lock that fails. The problem with the lock is where the liner contacts the blade (tang?). The angle is so great that the liner simply slides off the tang.
I make mine fail by holding the knife horizontally, with the blade edge up, pinch the blade with right thumb and two fingers and pinch the scales with left hand in the same way then fold it together.
Is your blade ground evenly? The flat part of the blade on mine, along the spine, is longer and wider on one side that the other.
The knife cuts nice and stays sharp but I won't tell anyone to buy this knife. Oh and I had to replace the torsion bar which broke.
 
I think we are discussing individual knives that might not be up to factory specs. I too have a Boa, and it has never failed, but then again, I don't beat on it. We do disservice to items when we knowingly exceed their design limits. I hear the new VW Beetle is a good car; it's good on gas, and it rated highly in crash tests. I don't take a Vee-Dub to the South Dakota National Grasslands for prairie dogs--I take an F-150 with 4-wheel drive. Granted, there's a guy out there who probably will try it, and then complain, "On the first day, I ripped the pan out of this foreign POS climbing a berm..." Further, if a knife has failed, do we complain, or do we return it to the manufacturer for simple repairs?--OKG
 
I'm not a big fan of liner locks either; I don't even trust the good ones as ther is just something about them that does not invite a secure feeling.

I am also not Benchmade's biggest fan. So why is then that I like the AFCK (M2HS) and generally carry it when I reach for a "tactical" (what ever that means) folder? Because I like the knife and generally do not plan on using it for those tough/abusive situations that are generally reserved for fixed blades or the Sebenza.

The best lock is, of course, a fixed blade and uses that approximate the stress of the spine wack test should be reserved for stout fixed blades with a full tang.

Folders offer convenience and, like most conveniences, comes with compromise. With this in mind, I am surprised not to see more small fixed blades with clips and in the pocket sheaths. How about a fixed blade with a (get ready now) ... folding handle?

If you insist on using a folder for para-fixed blade tasks, a mono-lock ala Sebenza is tough to beat.

 
I have , until recently, been carrying a BM 970, and it has seen it's share of abuse, and I have never had the liner lock fail, even when trying the "white knuckle" test. I haven't done the "spine whack" test, mainly because I don't think it's an accurate way to test a linerlock. My 970 is 4 years old, and still locks up just as solid as it did NIB from the factory. I still like, and fully trust the knife, but a recent purchase of a BM 720 with the Axis lock is now my daily carry.
I will still purchase liner locking knives, and continue to trust them, as long as they come from a high quality manufacturer.

Just my 2 cents worth.

[This message has been edited by CODE 3 (edited 11-24-2000).]
 
Perhaps some you of got the wrong impression of my "test". I didn't whack it on a counter or hit it with a baseball bat, I hit the spine on my KNEE, not even hard enough to hurt. Don't you think a knife that cost $125 should withstand this?I think a knife that is deemed "tactical" by it's designer should at least take a little abuse, since it is considered to be a "hard use" tool.The amount of force I used could easily be surpassed if I was field dressing a deer and accidentally hit the ribcage. Anyway the knife is on it's way to Kershaw for repairs. Thanks for your opinions.
 
Yes, spending $125 on a knife should be a guarantee of good quality, no doubt abou that..and your absolutely correct, that knife you have is a danger.

In my opinion, the best "liner lock" I've seen yet is the Micro-bar lock on my Socom elite. I haven't spine wacked it, but I don't think I need to, as it's pretty obvious this lock isn't going to fail that kind of test.

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mikemck@austin.rr.com
 
Maybe I did misunderstand you. I have seen posts where people actually clamp their knives down in a vise, and whack the spine with a hammer. Of course, the majority of knives will fail that test, and I wouldn't be stupid enough to do that anyway. It proves nothing in my book, except how to ruin an expensive knife.
Whacking my 970 on my knee isn't an option, either, because it also proves nothing. I have tried to forcefully fold my 970 up without releasing the lock, and I can't budge it, and the knife has seen hard use over the last 4 years. I'm a Firefighter....you can imagine what it has been used for...and has NOT failed me in any way.
I don't hunt, so field dressing animals isn't something I'll ever do either.

Just for the record...the last Kershaw I owned was a small pocket knife..and it was a pile of junk. the ONLY Kershaw I would even consider buying now is their multi tool.

Remember...thats just my opinion.

[This message has been edited by CODE 3 (edited 11-24-2000).]
 
I own very few liner-lock folders and prefer most other locks including the slipjoint and lock-back to this device. To me it has always seemed that biggest advantage of the liner lock was its low cost and ease of manufacture. Perhaps now we are discovering that we overestimated both of these advantages.

Recently, I have added both a Kershaw Boa, and a Buck Strider to my collection. After reading this thread I decided to test both of them as indicated above. While keeping my fingers clearly away from the path of the blade I hit the back of the blades repeatedly and solidly against my knee. Nether blade unlocked and there was no discernable movement in the position of either liner lock.

The blade lockup performed adequately. It looks like the knives mentioned in the prior posts are examples of quality control issues. Go ahead and buy these models if you like them but check them carefully to ensure proper tolerance.
 
Originally posted by MAURICE:
but i dont agree with the spine whack test.when you are actually using the knife,how often do you actually bang the blade against the counter? you dont expect your favorite handgun to mix cookie dough,do you?
Click to expand...

Maybe not the counter...but I have a scar on my thumb from tapping the lid on a jar of pickles that just wouldn't open. I was using a POS unnamed liner lock folder that I used to keep in the kitchen for opening boxes, bags, etc. I wasn't tapping hard, just enough to loosen the lid a bit.

Needless to say, after stopping the blood that folder got taken outside and smacked with an 8 lb. sledge a couple times.
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My CS Voyager now handles the dead knife's former duties. I figure if the lock can take a ton or so of weight, tapping a jar lid won't stress it overmuch.
 
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