Kershaw Spine Whack Fail

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These threads have convinced me to avoid buying used knives completely.

As for whether spine whacks damage a lock over time (as they indeed do), check out what STR has to say about it. Quite instructive observations from someone who has seen ALOT of liner and frame-locks...and made them as well.
 
presz said:
Send in the 2 that aren't Blems. Problem solved. You may get charge $10 for a new blade for the Needswork, but the Piston will be fixed for free. You are SOL on that Blem though. That's why I don't buy them any more. Not worth the risk to save 20%. The only Kershaw that I have ever had lock problems is a Blem........You think that could be why it was a Blem? Kershaw has the best warranty department that there is, give them chance to make it right. Lock this thread until then.......then make a new video.
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Why should a manufacturer cover abusive behavior?
This fallacy is why good warranties go bad, because people do stupid things with their product and expect them to cover it.



gwebb said:
The whole point of the liner lock (or any knife lock for that matter) is to keep the knife edge from coming down on your hand. The only situation that would cause this to happen would be for you to have some kind of pressure on the spine of the blade, which actually CAN happen in real world situations. Much like the situation the previous poster described. It's not like the OP used the knife like a hammer. He was using the weight of his hand. That is pretty ridiculous. The knife in the video is hopefully a lemon and does not reflect the quality of the model as a whole. When i pay the kind of money that we all pay for knives, I expect more. Period. I do not agree with abusing knives but if you think the video shows a knife owner abusing his knife then you probably arent using yours hard enough. That seems to be pretty typical around here though.
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It shouldn't happen if the user is using the knife as intended and is paying attention like he should be (Situational Awareness). I do use my knives hard, but I also use them carefully and I watch what i'm doing. I also take time to maintain them and I don't abuse them.


stabman said:
These threads have convinced me to avoid buying used knives completely.

As for whether spine whacks damage a lock over time (as they indeed do), check out what STR has to say about it. Quite instructive observations from someone who has seen ALOT of liner and frame-locks...and made them as well.
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Me too.....
For those interested in an opinion from a guy with more experience than most anybody posting in this thread:
http://www.bladeforums.com/forums/showthread.php/633521-Spine-whack-test?p=6663589#post6663589
 
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My Kershaw Blackout did not fail in the open position. The blade tang slid off of the edge of the peened lock face and the lock disengaged causing the blade to close. Not lock open and become a fixed blade. It was a gross failure of the walker lock through no abuse of the knife.
 
My ZT0200 fail a "Piston" strength spine-whack. I reground the lock mating surface on the blade side to be curved instead of flat and now it won't fail even with huge force in spine whacking.

My conclusion in my situation, a flat contact surface can result in the lockbar slipping away under force. A curved contact surface (if ground properly) will result in a surface that under hard spine-whack there will be no forces that "push" out the lockbar but compresses the lockbar due to the "perpendicularity" of the contact surface.

If I could post a vid (If i i knew how) then i'd show you guys that my modded ZT0200 spine whack will shock you and I'm very very sure that if you use a normal zt0200 then it WILL fail spine whacks.
 
Well, look to the experts, not the internet savants.

I bought an ACTF from Bob Terzuola. A thirty year old liner lock design. He said the knife should and it did stay open with pressure and/or impact on the spine. Say what you want, but who in this 7 page thread has more expertice than Bob Terzuola?
 
Karda said:
Why should a manufacturer cover abusive behavior?
This fallacy is why good warranties go bad, because people do stupid things with their product and expect them to cover it.





It shouldn't happen if the user is using the knife as intended and is paying attention like he should be (Situational Awareness). I do use my knives hard, but I also use them carefully and I watch what i'm doing. I also take time to maintain them and I don't abuse them.



Me too.....
For those interested in an opinion from a guy with more experience than most anybody posting in this thread:
http://www.bladeforums.com/forums/showthread.php/633521-Spine-whack-test?p=6663589#post6663589
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Karda, it would be nice if accidents didnt exist. Accidents happen, that is why the liner lock is there. I dont care how thoroughly you analyze a situation and how well you maintain your knives. Accidents will still happen.
 
I think something important to remember when it comes this test, is that if its going to be done, it should be done by the maker, not the end user. Before the knife is in the hands of the end user. This may provide useful information during R&D and testing, when the knife is going to be destroyed or abused anyway. But not during regular use. As STR has pointed out, it is damaging to the components of the knife. Damage that cant be undone. A human in good condition should be able to survive a fall of 20 feet. That is also something that could feasibly happen to you. But its going to take a toll on you if it does, and I doubt anyone would want to volunteer for it so that they could find out. Either way, you'll probably never be the same again.

With the spine whacking, a good knife should be able to take some impact to the spine without the the lock failing, but that would be incidental to its use, not something thats part of regular use. Ask cutom makers what they think of people performing this test on their knives, and if they'll warrant the damage it causes. Two makers already weighed in in the thread Karda posted. Again, a big difference in doing some of these tests while the knife is being developed, and is going to be abused to test the durability, and doing it as part of daily use and expecting no damage to the knife.
 
brownshoe said:
Well, look to the experts, not the internet savants.

I bought an ACTF from Bob Terzuola. A thirty year old liner lock design. He said the knife should and it did stay open with pressure and/or impact on the spine. Say what you want, but who in this 7 page thread has more expertice than Bob Terzuola?
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Completely agree.

You can spine whack the crap out of a Spyderco Military and it doesn't budge. Some companies know how to make a liner lock properly and some don't. It's not some stuff you just throw together for sure. I think many companies think the liner lock is cheap to make and easy so they use it. Problem is, if you don't do it right then you take a good lock and make it look like garbage. I have a 5 year old Spyderco Military that I have, in fact, whacked pretty hard on the spine against a wooden bench. It was fine. No movement at all or anything. It's not a safe queen either it's a user and has been used. The lockup hasn't moved in about 3 years. It settled in right in the middle of the lock ramp.

Lots of people in this thread just being sarcastic ***holes just to post something. Why bother?
 
HiFirst, let me say that the spine-whack-test is NOT a test of the lock's strength.
The spine-whack-test does NOT determine how strong a lock is or how many pounds of force a lock can withstand.

It is a test to check lock geometry and lock function.

And it does not take much force for a defective lock to fail the spine-whack-test.
You don't have to tape it to a broom handle and beat the daylights out of it.
All you need to do is give the spine of the blade a firm hit on something solid.


I have had only three knives fail the spine-whack:
One was a CRKT Mirage....it was the first one and it occurred before I had even heard about the spine-whack-test....
Years ago, I was hiking through some woods and carrying my CRKT Mirage.
I stopped for a break and decided to clean the mud off my boots.
After using my knife to scrape off most of the dried mud, I then decided to get some of the dried mud out of the tread of my boots by tapping the tread with the back of the knife blade.

On the first tap the blade folded as if it had no lock what-so-ever, and it cut the back of my thumb.
I thought that I had just failed to lock the blade open properly.
But later, I read about the spine-whack-test on this very forum.
So I decided to test the Mirage again (in a safe manner this time)....
And sure enough, the lock failed every time I tapped it on the carpeted floor.
And again, it didn't take much force at all: not even a full arm swing....just a little wrist snap.

My experience with that CRKT Mirage made me a believer in the spine-whack-test, and I have since tested every locking knife that I have ever owned or considered buying.
I typically just grasp the knife (with my fingers safely out of the blades closing path) and give the spine of the blade a firm hit on the sole of my shoe.
Besides the CRKT Mirage, the other knives that failed the spine-whack-test were a Benchmade Crawford Leopard and a Lone Wolf Harsey T2 folder.

I will not carry any folder that fails the spine-whack-test.

Take it from one who has been bitten by a folder that failed....
The test is not destructive at all, and it is 100% valid for checking the reliability of any given lock.


Sal, the owner of Spyderco Knives, also recommends the spine-whack-test.
In fact, Spyderco does this very test on their folders.
From this thread:
http://www.bladeforums.com/forums/showthread.php?t=366883&highlight=whack
And here's another quote from Sal, from this thread:
http://www.bladeforums.com/forums/showthread.php?t=145078&highlight=whack
Ignore the spine-whack-test at your own peril....but don't say you weren't warned. ;)




Allen


This is a post from the other thread involving STR. I would agree that a light tap on a cardboard box corner or such is useful and not abusive, but just a way to check function. Also, new Tapatalk Beta really sucks.
 
I wonder who will crawl out of the woodwork and call this "knife abuse" "

"After using my knife to scrape off most of the dried mud, I then decided to get some of the dried mud out of the tread of my boots by tapping the tread with the back of the knife blade. On the first tap the blade folded as if it had no lock what-so-ever, and it cut the back of my thumb."
 
First off that's a pretty pis poor looking design, second if I had a folding knife of my design sold and it did that i would recall and fix or refund any customer with one. Because in my opinion my product is a faulty design because it is said to lock up when that's not true, which to me makes me feel like I failed as the designer.
Also i've used the back of folders before because sometimes the edge is not very useful well the spine is. Thou lucky for me my common folder was a CS AK-47 (lock mechanism fixes into the blade thus is extremely secure) which I used to break down cardboard at the store I worked at since some boxs were just to much of a pain to do by hand.
 
I'm seeing a whole new niche here, the "Slip Lock" knife. These can be used to convert traditionalists to modern folders.
 
If Sal says some light spine taps are a good idea, I can roll with that. He said periodically do them to male sure the lock is still doing its job. The knife in the video appears to be failing this test too easily. Something is probably wrong. Testing is not necessarily synonymous with abuse.
 
TriviaMonster said:
If Sal says some light spine taps are a good idea, I can roll with that. He said periodically do them to male sure the lock is still doing its job. The knife in the video appears to be failing this test too easily. Something is probably wrong. Testing is not necessarily synonymous with abuse.
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Exactly. Sal knows how to make a liner lock. Joe Talmadge does as well. If these two guys state that spine whacks are OK then they are. If you choose to believe that your knife is solid even though it fails spine whacks then you are fooling yourself. Plain and simple. It's not acceptable.

It would be different if the guy was whacking it hard as heck on the end of a 2 x 4 but he's not. It's a light whack with a human hand. No big deal. Any good knife will pass that.
 
Well, I have a knife which passes spine-whacks...but fails under steady hand pressure on the spine of the blade (which is why I decided to give it the useless whack "test").

But hey, everyone go out and do whatever the heck you want with your knives...they're yours. :)
 
stabman said:
Well, I have a knife which passes spine-whacks...but fails under steady hand pressure on the spine of the blade (which is why I decided to give it the useless whack "test").

But hey, everyone go out and do whatever the heck you want with your knives...they're yours. :)
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It seems like several experts have stated striking the spine can give you useful information and is a valid test, even STR advocated testing the lock, he just pointed out he advocated a tap rather than a whack and seemed concerned there were some who would do it too hard and potentially damage the knife. Although, even if it does damage the knife that hardly makes the test itself invalid.

My issue really isn't with people who consider spine whacking abusive, as it obviously can be, but the statement that it's a useless test. I view a lock as a mechanism designed to resist closure due to pressure or impact that would normally force a knife closed. Spine whacking or tapping is something that fairly obviously falls into that category. Now, you can obviously make any knife, even fixed blades, fold if you strike with enough force on a hard enough surface, but if you apply a consistent level of force and knife A fails and knife B doesn't there are some obvious conclusions you can draw. People may put too much weight on those conclusions, or even extrapolate fallacious conclusions from the test, but that doesn't speak to the validity of the test itself.

TL;DR Version: A lock that passes a spine whack is superior in at least one way to a lock that fails it. Other factors may determine the knife that fails to be better in the long run, but it ain't better at resisting impact and since that's part of what a lock is designed to do, it's good info to have.
 
Insipid Moniker said:
My issue really isn't with people who consider spine whacking abusive, as it obviously can be, but the statement that it's a useless test.
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It was absolutely useless as regards that knife.
The "test" would say it was safe, yet it failed under rather slight pressure applied by hand.
 
stabman said:
It was absolutely useless as regards that knife.
The "test" would say it was safe, yet it failed under rather slight pressure applied by hand.
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I would argue that's an inaccurate conclusion. The test only showed that the lock could stay open in the face of sharp impact, not that it was safe. Again, I don't think it's the end-all-beat-all of safety tests and I acutally think the hand pressure test is more important, but the fact that it fails one and not the other gives some really interesting information about the lock on that knife.
 
I see the benefit of actually testing the lock strength ourselves. The alternative is just blind trust or faith. I cannot fault a person who wanted additional assurance regarding their folders.
 
I have the benefit of living in the same city as Sidney "Pete" Moon a respected custom maker who makes some high end folders. I have also known mr moon since i was a little boy as we went to the same church. Brought him a frame lock i was having problems with and guess what he did. Spine tap test by lightly tapping the spine several times on the edge of a hardwood table. I'm not talking about overhand strikes but just a few light taps so he could test the lock to see if it functioned as designed or failed. Take it for what's its worth.
 
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