Spine Whack Test

I'm confused now about what the issues really are.

I think maybe the confusion arises from the fact that there appear to be assumptions made by the different posters as to what an "extreme" or "hard" use knife is intended for. It appears that to some, "extreme" use is when the knife is being used in a tactical situation, other than viciously opening envelopes and cardboard boxes :). To others, "extreme" use might be of the sort that one would find in the wilderness, i.e., chopping, slicing, etc.

IMO, this kind of debate could be well served if we were to state up front the intended purpose of our knives. Otherwise, I believe we run the risk of painting an entire category of locks as unsuitable for anything but opening envelopes and, in turn, do a grave disservice to those manufacturers who have dedicated precious time, money, and effort to building the best examples of that particular type of lock with the end user's safety in mind.

Just my $0.02,

Matthew
 
In 1982, with all my worldly possesions in some guy's van in the mountains of Colorado (*really* a long story), a plan was devised to get into the van.

I would use my trusted Al Mar Falcon lockback (easily passing the spine whack test) to pry up the little wing window lock, thus gaining entry. Putting the top edge of the knife under the lock, pressure was applied with both hands upwards to try and rotate the wing window lock. Upon hearing the "Snap" and with arms now above head level (and seeing the blade was still open!) I assumed the window was ready to be opened!

But no.

Upon inspection of the now-profusely bleeding hand; the lock had given way, closing on two fingers of the right hand with sufficient force to cut down to the bone. On hitting the bone the blade then ricocheted back open. Net result; window still closed, stiches needed on both fingers (but you guessed it, if the condition was such that all wordly possesions are in some guy's van, 1:30am in Steamboat Springs, CO a hospital bill was not an option) and a better understanding of the love-hate relationship of man and tempered steel.

The lock's fault? Passed the spine whack test. And a liner lock?...just a matter of degree.

The moral of this story? Cut with the blade.

-Michael
 
Locks are put on Folding Knives as a Safety Device to prevent the knife from accidently closing and cutting the user's fingers. (If experience did not show that it is not uncommon for closing pressure to come to bear during routine use of Folding Knives Locks would not be developed and employed.)

No matter what the application is an Unreliable Safety Device is worse than No Safety Device at all.

Locks are Mechanical Devices and are therefore subject to Limitations or Failures.

It is only prudent for anyone using a Folding Knife to understand the limitations of the mechanism preventing the Blade from closing during use.

The Spine Whack test is one way of safely putting a predictable force on the lock.

Depending on the person performing the test it may be as benign as lightly striking the heel of the hand or as extreme as a full swing of a stick with the knife clamped in a vice.

The point on both ends of the spectrum is to apply closing force against the lock in a situation where failure will not result in injury.

The spine whack test is not perfect in that it cannot always predict failure. However, it should not be discounted or reviled.
 
Gah! I knew this would happen.

I wanted to know what it is, and how its done, not an essay long post on what you think of it. Opinions are welcome, but I had ti skim through those last posts cause I was bored:)

Anyway, how hard are you supposed to wack the things? I was trying it on some of my cheap folders (one i bought for 5 bucks like 3 years ago) and as hard as I pounded, it wouldnt close. I was sure this China cheapie would fail. All 5 of my cheap liner locks passed, all together they couldnt have costed more than 70 bucks.
 
pedder: sorry, but there's no such thing as a spine whack discussion that doesn't included long-winded diatribes about why spine whacking either is the spawn of satan or is the one true path.

About how hard you should spine whack, there's no consensus on that at all. How hard do you think it should be? I tend to use not much force at all, but I do a light whippy snap -- I'm going for speed, not force. I can often fail a liner lock with a light whippy snap, that someone else might not be able to fail with a heavier shot to the spine. Which means that the speed of the impulse force to the spine is more important than the actual force used in the, uh, whack.

If your cheapies aren't failing, they aren't failing. You should also try torque-testing them. The spine whack isn't the end-all of lock testing. I always white-knuckle test, and do a slow, higher-power torque test.

Joe
 
Originally posted by Les Robertson
A question for all you "whackers". What use of a folding knife does the spine whacking test simulate?
Click to expand...

Les,

No one could buy and sell thousands of "tactical" liner-lock folding knives and completely miss one of the primary uses they are being designed, built, and marketed for, so I will just conclude that you are being disingenuous. But lets just pretend, for the benefit of others, that I am the first person to ever conceive of using a "tactical" folder for self-defense(imagine that). The first thing I did was start training with one. This includes gripping the knife firmly and regularly thrusting the knife into foam covered training targets. Guess what happened? I started getting lock releases. I was talking this over with Ernie Mayer one time, years ago, and he said when they started training with some currently popular liner lock "tactical" folders against common street weapons like sticks and chains, that the locks on their knives were releasing frequently on impact as well. So I started whacking the spines of all the liner lock folders I had with sticks. They all failed at least part of the time. Other than button release autos, there was no alternative at the time, so I just went forward with a higher awareness of the limits of my knives.

Then Chris Reeve came out with the Sebenza, REKAT came out with the Rolling Lock Pioneer, and eventually Benchmade came out with the Axis lock. Looking for a better self-defense folder, I stick-tested these knives as well. Guess what? They didn't fail! I not only discovered a revolutionary new use for folding knives, but I found a way to determine how suitable a knife was for this new use as well.

So if anybody is considering following in my pioneering footsteps, and carrying a folding knife for the purpose of self-defense, they can either take my word for it, or they can test their folders for themselves. Hopefully, if enough of us start carrying folding knives for self-defense, knife makers will begin making knives intended for this purpose some day. ;)

I don't actually do much stick-testing any more. All the knives that I intend for defensive use have been tested and the ones that didn't pass the test are long gone. It is not like I am out there whacking the spines of my knives on a daily basis. I still treat a folding knife like a folding knife, but I have a realistic level of confidence in the folders that I carry with the notion that they can be used as a last-ditch self-defense weapon.
 
Steve,

If you can block the attack of an assaliants stick with back side of your folding knife, that means, in most cases, you are close enough to either re-direct the blow or trap the arm of your assaliant. Most trained knife fighters would opt for the re-direction or trap, allowing them to explore the options given to their free hand which is holding the knife.

Steve, for most, a stick is not near as lethal as a knife. This is not to say that stick in the hands of a highly trained individual cannot be lethal. However, I would much rather have an assaliant come at me with a stick than a knife.

Steve, Im glad you have found a folder that meets your needs for blocking clubs and chains. However, most of us, and I suspect even you. Seldom, if ever use our knives to protect us from a strike made by an assaliant with a stick.

New locks were developed primarly for either ease of manufacture (the frame lock by Reeve) or the rolling and axis locks are primarly developed for commercial purposes. Steve, you really don't belive that these locks were developed for the purpose of building a superior "self-defense" knife. Holy Civil Litigation Batman! Speaking of lititgation, I suspect you would find you would not have grounds for any if you tried to sue a manufacturer for lock failure while conducting your stick whacking test. As this would not fall in the realm of reasonable expectation.

Steve, a question for you? If the axis lock is such a superior lock. Wouldn't it follow that Benchmade would put this lock on every knife that comes out of the factory? I will admit I really don't follow factory knives, so for all I know Benchmade is currently making all of it's knives with this wonder lock! If that is the case, Im sure Steve, you will correct me. If not, could you explain to me why this superior lock is not on every knife Benchmade makes.

Steve if you are finding your locks failing on you, I would suggest you are using the knife for a purpose it was unintended for (such as using the back of the blade to block an attack from a stick or chain, there by making it collapse. I suspect if you checked with the manufacture of said knife, you would find that you have in some way violated the warranty of that folding knife).

For Steve and others who feel it necessary to whack the back of a blade on a table to check the lock up. I would caution you doing this at a knife show. As those standing on my side of the table will take exception to you doing that.

I will say with frankness and candor, that I agree with Joe Talmadge and his white knuckle test. As gripping the handle of a folder as hard as you can, should not release the lock.

I have handled knives that have failed this test. Generally, this is attributed to the wrong angle either put on the lock, the blade or in some cases both. This is a legitmate concern and should not be overlooked. As the chances of an encounter with a stick wielding assaliant on a daily basis are slim and none. The chances that you will use your knife with a firm or even "extra-firm" grip is a realistic possibility on a daily basis.

So no, I am not being disingenuous (I feel I write with nothing but candor and frankness). I guess I just remember the lessons of my youth better than some. Always cut away with a knife and I remember my father smacking me in the head as he saw me using a knife in lieu of a screwdriver. He handed me and said "right tool for the right job".
 
Originally posted by Joe Talmadge
I tend to use not much force at all, but I do a light whippy snap -- I'm going for speed, not force. I can often fail a liner lock with a light whippy snap, that someone else might not be able to fail with a heavier shot to the spine. Which means that the speed of the impulse force to the spine is more important than the actual force used in the, uh, whack. Joe
Click to expand...

Joe,
If I remember my college physics correctly, force varies with the square of the velocity; i.e., force = mass x velocity squared. So, perhaps your "whippy" snap actually has more force than another person's slow, hard whack?
 
Dave,
If I remember my college physics correctly, force varies with the square of the velocity; i.e., force = mass x velocity squared. So, perhaps your "whippy" snap actually has more force than another person's slow, hard whack?
Click to expand...
No, the kinetic energy = 1/2 mass x velocity squared and it has nothing to do with discussion subject.

The locking liner is loaded along its plane and takes some kind of deformation what I don't know how to name properly in English, sorry. To understand try this simulation. Take a straight plastic or metal ruler (about 10" long) put it vertically on the desktop and start to compress it along its length with your hand. After certain point of force increase it will loss stability and will be bent despite you are applying the force in compression direction only. When it will start to bend it will cause the dramatic decrease of the force necessary for further deformation comparing with the force required for any compression.

This is the way locking liner is loaded.
And now try to apply impulse force with your hand compressing ruler and releasing it violently with different frequencies. You should notice that your ruler makes some kind of micro-jump on matching surface (for the liner it would be blade tang) when load violently disappear. With certain frequency of even light taps it can start to "dance away" from its proper position causing lock failure. Or it can make one large jump out of its place in single hard tap. Generally this is the random matter how it can behave if it will behave improperly.
This is only one way to make thing properly, thousands ways are to screw it up.

Each device can fail. So I'm always rely on my common sense more than on any device. Exactly as Les advised.
 
Originally posted by dsvirsky


Joe,
If I remember my college physics correctly, force varies with the square of the velocity; i.e., force = mass x velocity squared. So, perhaps your "whippy" snap actually has more force than another person's slow, hard whack?
Click to expand...

Dave, I think the bottom line is: If I did my light whippy snap on your kneecap, it wouldn't hurt. Other testers might do a harder hammer-type blow, and that would hurt. So I'm sure I'm imparting less energy and force.

E=.5mv^2 F=ma But I think there's more going on than the simplicity of the equations suggests. I do a light whippy snap, I snap my wrist then relax, and it's nothing but the blade coming around. When I see someone doing a more hammer-like blow, I can see there's follow-through which continues to drive the drive, so it's hitting much harder.

Joe
 
Originally posted by Sergiusz Mitin
Dave,

No, the kinetic energy = 1/2 mass x velocity squared and it has nothing to do with discussion subject.
Click to expand...

:o Apparently they're right when they say that the mind is the first thing to go. :o
 
Really guys, you MUST do a spine whack test on a folding knife.

I like to start with about 5 lbs. of whack pressure, at a medium velocity. I whack on a professionally made "Spine Whacker" covered with special 10-12 oz. whacking leather. (www.spinewhack.com)

After 30 reps at 5 lbs, I go to 6 lbs. of whack pressure, at a medium velocity , of course.

I repeat the 30 rep test at 1 lb. increments up to 28 lbs of whack pressure, at a medium velocity.

To test for metal fatigue, I don't let the knife rest during any part of the procedure. Rest will cure fatigue. Keep that knife in constant motion.

If I experience a spine whack failue at any point in the process, I throw the knife immediantly away into the "Spine Whack Test Failure Bin". The Bin is currently is filled to the size of a cord of wood.

I then start another test with another knife of the same make and model.

I have performed this test on examples of the same make and model knife for the past three years. No knife has passed the test to date. I'm $15K in the hole, but it will be worth it if I can find one that passes. It is my life we're talking about, ya know?

JD :D :D
 
JDWairr--I love it when a good smarta$$ shows up on one of these "groaner" threads. Do you think .45 is better than 9mm? Do Emersons suck?
 
Originally posted by Wirebender
JDWairr--I love it when a good smarta$$ shows up on one of these "groaner" threads. Do you think .45 is better than 9mm? Do Emersons suck?
Click to expand...

Yes and Yes.....in no particular order.

JD
 
Steve, good points all, and thanks for the honesty! So, here goes nothing...

Ye verily,

I propose that all ye disbelievers of the "Spinewhack" test not do spinewhack tests, moreover, I propose that you continue to buy whatever the great gods of advertising, and the greater gods (not all gods are created equal), of "custom" tactical folders recommend that you buy.

Furthermore, I highly recommend that you believe these unproven claims of blade lock strength, and "know" that should the time come when the lock may fail, (whose time "will" come), know that said lock will not fail...and it will not fail because, and only because, "someone" told you that it wouldn't...

Sleep well my brothers, you keepers of the true faith, those that believe the truth according to the good book of "Someone said so", and don't come crying to me just cuz you cut your fingers off, you true believers you.

btw, I "carry" an old style Spyderco lockback Endura, which WILL close up on fingers when used in Anger, and a Spyderco BS Military, which WILL do the same...I recognize these limitations, and I treat the knives accordingly...they are tools, nothing more, nothing less, and I carry them because I "know" what they are.

On a more serious note...

If you are carrying a tactical folder, if you think it's a weapon, and if YOU haven't personally "proofed" it as a weapon...and I mean get enraged and cut, punch, and slash the hell out of hard targets with it, then you DESERVE to lose your fingers!

These knives are not "toys", and if you treat it as a toy, you're going to get hurt! I know, I have the scars. I laid out nearly 100 knives for cleaning today...I have four (4) folders, and one of them is a SAK.

That should give you a bit of a clue about how I feel about folders....my feelings come from the memory of my balls sucking up into my gut when I nearly severed my trigger finger....twice, two styles of folders, two years apart....learn from my experience friends, avoid repeating it if possible, and test your knife YOURSELF!

"You only get what you pay for"...that's my two cents worth!

(I've got to say this, and for those of you that take offense because I'm hitting close to home here...."I don't give a good goddamn if you feed your family selling knives or not. If you have crossed over to the dark side, deliberately or not, and are selling tactical folders as reliable, dependable, and failsafe, with the exception of those very few truly "bullet proof" models, then you sir(s) suck butt, and I hope to god that you cut yourself deeply and painfully with one of your "failsafe" knives, on a daily basis, until you "get it"...Got it?).

*laughs* Hell, we'll even know who you are, based on your reply(s)...lol
 
Melvin-Purvis:

Oh, oh my. :eek:

Les:

Just a couple of comments so that others won't get confused. You don't have to be blocking to get your weapon hand, or your weapon, hit by a stick or other blunt weapon. If your weapon hand ain't in your hip pocket, it is a primary target for attack.

In Kalifornia where sticks are outlawed, only outlaws carry sticks. The rest of us are limited to folding knives for concealed carry, so a folding knife is what I am most likely to have to defend myself against whatever weapon I am attacked with. And most people who have trained with sticks, including myself, would prefer to have a stick against someone with a knife because of the greater range. A solid, heavy stick is quite deadly. Anybody who has watched any Dog Brothers tapes has seen men go down after a single shot to the side of the head, through a heavy fencing mask. Without armor, those shots would most likely have been deadly or permanently disabling.

As far as what type of locks Benchmade is making, you know better than anyone that what is selling is what gets made, so as long as people are buying liner locks, knife makers will continue to make them. But that just obfuscates the issue. What Benchmade makes is completely out of my control and beside the point. If I controlled Benchmade, I certainly wouldn't make any new models with liner locks that even remotely suggested themselves as tactical, which may actually be the case except for the Model 690. I certainly have not bought any, so I can say that I have done the only thing I can to discourage the production of any new liner lock tactical folders.

I don't believe that the liner lock is useless or evil, I only believe that it is not the best, or even second best, for a "tactical" folding knife. But I think I have said that already, so I will apologize to the general readership for repeating myself and shut up on the issue...until next time. ;)
 
ROTFLMAO @ Melvin-Purvis!

That was a great post!
To the point and funny as all Hell to boot.:D

Melvin-Purvis wrote:
(I've got to say this, and for those of you that take offense because I'm hitting close to home here...."I don't give a good goddamn if you feed your family selling knives or not. If you have crossed over to the dark side, deliberately or not, and are selling tactical folders as reliable, dependable, and failsafe, with the exception of
those very few truly "bullet proof" models, then you sir(s) suck butt, and I hope to god that you cut yourself deeply and painfully with one of your "failsafe" knives, on a daily basis, until you "get it"...Got it?).
Click to expand...

I agree.:p
 
All I know (personally) is you <i> will </i> be asked to leave the table if you do this on used knives at a gun show.
 
If you are choosing between two knives that are identical in every respect except one has a Lock and the other is a Slipjoint which one will you choose?

If you choose the Slipjoint, I have no argument against your stance that the Spine Whack is unnecessary.

On the other hand if you choose a blade with a lock on it, I must ask "Why?".

Could it be that you chose a Folding Knife with a Lock over a Slipjoint because you know deep in your heart that no matter how careful you are you may very well end up with pressure on the back of the blade during use?

If you acknowledge as millions of other Knife Users who purchase Locking Folders that at some point the Lock may be called upon to resist closing forces to protect your fingers, Why do you begrudge anyone testing the reliability of that lock?
 
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