Liner-lock failures...what a shock!

J

Johan

Joined
Oct 12, 1999
Messages
631
Hello all! Just a few minutes ago I got the strange urge to check the strength of my liner locks. I took out a bunch of them and proceded to smack the spine on the carpeted floor of my room (I didn't want to do it on a desk for fear of damaging the spine or scraping off the balck coating on some of my knives). Two or three smacks, re-set the lock repeat. The results surprised me. Keep one thing in mind though, I have NEVER had ANY of these blades fail in REAL use:

MT SOCOM (2 diferent ones)-failed first smack every time, blade did not snap shut though, moved just enough to disengage the lock. At the price of these and the fit and finish I was rather disheartened.

Emerson Commander-passed.

Emerson CQC-7-passed.

Spyderco Starmate-passed.

Spyderco Veile-passed.

Benchmade Sentinel (old model)-passed.

Spyderco Military (old model)-failed every time, first time, closed completely. I wanted to get a new Military in plain edge, but now I've got to wonder. The fact that it closed completly really bothered me.

I also tested a couple of Axis locks as well as a mono-lock. Rock freakin' solid. I gotta say, it really makes me wonder. I always thought liner locks were really safe and while some of them are rock solid, some of them are really weak. That being said, I;ve never had one fail in the real-world. What's more important: Real world failure (which I've had none)? or Possible failure (which I've had several of?

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"Better to reign in Hell, than serve in Heav'n"
John Milton
There are only two types of people; those who understand this, and those who think they do.
 
Spyderco re-vamped the Military a while back and dealt with this spine whack failure issue.
My Military gets tested from time to time and passes every time. The way I test is to start at the base of the spine and medium strength whack, whack, walking out to the tip and back to the base.

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My new bumper sticker:

Let me tell you about my SIFU!
 
King Grinch-the only CS knife I have is a fixed blade so I'm pretty sure that's going to pass
smile.gif


Misque-I'm glad to hear about the new Military, I really want one. The one that hurts the most is still the MT SOCOM; so much money and failed so easily
frown.gif


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"Better to reign in Hell, than serve in Heav'n"
John Milton
There are only two types of people; those who understand this, and those who think they do.
 
You shouldnt be suprised at how the MT's performed. Use the search feature and you'll find that this is common for the first couple spine whacks on a MT. It supposedly "sets" after this and shouldnt fail.
 
I guess I got lucky as my SOCOM passed the first time and hasn't failed yet, as a matter of fact I'm whacking as I type. Well, in between sentences anyway.
BTW, will I go blind if I keep doing this?
smile.gif


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My new bumper sticker:

Let me tell you about my SIFU!
 
Yoda, It is not acceptable that a supposedly hard use knife fails in the beginning. Not all dare to whack over 200$ knife if they think that it may not be a keeper. Light use knife sometimes turn to hard use knife with out time to braking it in. If knife needs a little banging around factory should do it and then repolish etc it before letting people use it. All do not have this knowledge about MTs. I strongly suspect that clerks in cutlery stores do not first start telling potential buyer that MTs lock fails some time in the beginning.

 
Misque:
You will only go blind if you whack it on your desk, and it shoots up and hits you in the eye. So you may want to tone down on your whacking, or at the minimum, whack away from your eyes. And to be fair, you should share the whacking through the rest of your collection too.

Stryver
 
I remember this came up before. I know last year when I bought my SOCOM, I spine whack tested it right away. It passed, no problem or indication of one. I periodically retest all of my liner locks that get carried.

Some seem to think they may break in after awhile. Johan, I think you're right to be disappointed and concerned about the SOCOMs.

That's good news about the newer Military.
 
Stryver,
All my linerlocks get the treatment on a fairly regular basis just to make sure nothing has changed. Especially the ones that see regular carry. I'm an advocate of testing folder lock strength on a regular basis. My fingers are precious and I'm rather attatched to them, don'tchaknow?
smile.gif


------------------
My new bumper sticker:

Let me tell you about my SIFU!
 
I have never had a linerlock fail the spine whack.I also have my doubts as to how practical this test really is.What I usually read is "my knife failed the spine whack so I got rid of it".My question is: does anyone know why exactly the lock failed.Is it a function of the pivot being loose?The lock surface angles?I keep my pivots pretty tight and wonder if this might be why I haven't had any failures.I also wonder about repeated checking of the lock through spine whacking.This seems to me to be a pretty high stress test to do on a regular basis and I wonder if this could do more harm than good.Any thoughts?To me it would be like removing spark plugs on a car to check spark plug gap.A sound pratice if you do it for a routine tune up.But if you did it on a weekly basis you stand to increase the chances of cross threading and in the end it would probably be more risky than the benefits you would get.Is there a more practical test?
troy
 
My "regular basis" is about every 3 months. It is a medium strength test not a full bore power whack. When I get a new knife, I test it a few times over the span of a few weeks just to make sure.
It's all a matter of preference, this spine whacking thing.
If you feel the need to test your knives in this manner, then do it.
It is not a mandatory type of test and should not be construed as such.
I do it for my own peace of mind.
Some may not be as paranoid as me and not feel the need to test in such a manner.
As a matter of fact, in the larger scheme of things, this test doesn't really prove much at all, as the load put on the blade does not come from the spine direction anyway.
I just feel safer knowing if a load is put on the spine for whatever reason, it will hold up and not collapse on my fingers, which, BTW, did I mention are precious to me?
smile.gif


------------------
My new bumper sticker:

Let me tell you about my SIFU!
 
DRAT!! Double post! I hate it when that happens!

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My new bumper sticker:

Let me tell you about my SIFU!

[This message has been edited by misque (edited 02-25-2000).]
 
There's quite a few guys who won't buy liner locks at all anymore -- myself included. There are liner lock knives I actually trust, but so many fail that it does worry me. Even worse, sometimes a knife that passes for years, one day suddenly starts failing. Anyway, take care and test your knives, and don't be surprised when they fail -- you've been warned !!
smile.gif


Joe
 
Good points troy.

My periodic whacking is about equivalent to the spark plug change done for a tuneup. How practical/relevant is the test? Don't know, but I wouldn't be comfortable carrying a knife that failed this test.

I also keep my pivots tightened, and check them regularly. This might be a factor in failures.

How to do the whack test? Carpet doesn't work for me. I like to do more than just 1 flat whack. 1 whack at each end and a flat whack is the minimum test. On carpet, the tip oriented whack will cut the carpet. I use a magazine placed on a solid table or desk top. This is solid enough to get a good whack without doing any damage, other than a little slice into the magazine.

How do you all do your tests? Are they really relevant or are we all deluding ourselves? Don't know. I suppose we could solve the problem by carrying fixed blades, but those folders are so practical and convenient. Better lock - perhaps a good compromise solution.
 
this is one of the things I like about this forum - people here have forgotten things I will learn in twenty years...

can anyone please post a picture of the way you test the lock so I can understand exactly how you do it?? and how it fails??

10x anyway for bringing this to my attention.


 
You might start out with the liner lock test FAQ that AT Barr and I wrote, at: http://www.bladeforums.com/features/faqs.html


Different people use different tests, and have different testing objectives. For me, I'm just trying to test the basic lock integrity, not slam the lock really hard to test its outer limits. Other people slam pretty hard to test outer limits, which is fine, I just choose not to do it that way. Note that it is not at all uncommon to get one failure, then the lock "sets" and doesn't fail again.

I open the knife, then hold it edge-up. With my right hand, I grab the butt-end of the handle between index finger and thumb -- note, NO PART of my hand is in the path of the blade. Remember, lots of lots of liner locks fail, so you'd better make sure no part of your hand is in the path of the blade. Okay, so now I'm pinch-gripping the butt of the handle, still holding the knife edge-up. Now I hit the spine of the blade on a desktop or something. I do not use much force, but I flick my wrist to get a lot of velocity -- the knife is impacting more like a whip than like a crowbar. With this test, I often can fail a lock which has been tested with more of a crowbar-type impact.

Joe
 
I have tested four MT socoms all failed.
a benchmade pinnacle passed lock did slip a little though.
benchmade spike failed
two klotzlis passed
sebenza laughed at the idea.
basic #5 also laughed.
smile.gif
 
Good points, Joe. That is a very good way to test liner locking folders. I've tested a couple of liner locks of mine that way. Only I put a magazine on a table top to provide a good surface, like Bob Irons.

Now, Johan, you ask which is more important. Real world failure or possible failure?

Possible failure translates directly to real world failure if something ever impacts the blade or submits as much force to the blade as in your tests. Bottom line, they're your fingers. I wouldn't carry a folder for medium or heavy use that failed the spine whack test.



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Yeah! Drop the chalupa...
 
When Joe first started preaching about liner-lock failures I really couldn't understand the relevence of spine-whacking on the under side of a desk or table. I guess I couldn't relate to real-world use that would duplicate this.

Not that I'm a highly trained knife fighter, but I found a solution to test my liner locks. I took a small 1/2" or 3/4" wood dowel about a foot or so long, covered it with tape and proceeded to whack my knives...holding it with one hand (ENSURE your fingers do not cover the closing side!), I would whack it on the spine.

My theory was to duplicate someone hitting my blade such as a baton or other like-weapon or even duplicate having something fall onto the blade (that actually happened to me once, a camouflage pole actually fell and hit my wrist as I was cutting some WF-16 wire...knocked the knife out of my hand, but the potential was realized).

The only knife that failed on me was a brand-new MOD Trident. Yes, I should have sent it back, but I was able to take it apart and file down the liner lock to where it would make better contact with the blade...hence fixing the problem. Previouly I could tap the back of the open blade with a pencil and the blade would fly shut:O!

If you have to whack your blades with a baseball bat or two-by-four, then you probably need a fixed-blade.

Dave

[This message has been edited by dp (edited 02-25-2000).]
 
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