Spine Whack Test

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pedder2226

Joined
Dec 11, 2000
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I think I understand what this is...but could someone explain in detail please? I'm still a little lost...
 
Different people do it differently. Here's what I do.

Open the knife, and turn it upside down so the edge is facing up (and the spine is facing down). Grab the knife between the thumb and my curled-up index finger, at the very end of the handle. Make triple sure that my hand is positioned so that if the lock fails and the blade closes, it won't close on any part of my hand. Now whack the back of the blade using a light whippy snap (my choice; other people do a hard hammer-like whack). I often start on something soft like my leg, which causes failure in a surprising number of knives. If the knife holds up, I move to the edge of a workbench.

Joe
 
Hey Joe,
Thanks for the info on this subject, after reading an earlier post on this subject I pulled out my slippery locked EDI and tapped it on the edge of a piece of masonite for a while. Released easily.
Gradually after about 10-20 whacks, not very hard, the lock started to put up more of a fight.
I snapped it open a couple of times as well and ended up tapping pretty hard on the spine with the lock holding.
Now I would be more confident in carying it where for the last year I have considered it unsafe to use.
I would have considered sending it back as defective if they were still in business.
Someone suggested that liner locks are designed to "wear in" and I agree with this suggestion. A strong liner lock, especially a titanium one will hold its machining marks well. And these may not be ideal for lock up. By tapping the spine the lock and blade and forced to wear on the bearing surface and I can easily imagine it taking a set after some mechanical wear of this type.
This was a very helpful tip.
 
Hey Joe,
Thanks for the info on this subject, after reading an earlier post on this subject I pulled out my slippery locked EDI and tapped it on the edge of a piece of masonite for a while. Released easily.
Gradually after about 10-20 whacks, not very hard, the lock started to put up more of a fight.
I snapped it open a couple of times as well and ended up tapping pretty hard on the spine with the lock holding.
Now I would be more confident in carying it where for the last year I have considered it unsafe to use.
I would have considered sending it back as defective if they were still in business.
Someone suggested that liner locks are designed to "wear in" and I agree with this suggestion. A strong liner lock, especially a titanium one will hold its machining marks well. And these may not be ideal for lock up. By tapping the spine the lock and blade and forced to wear on the bearing surface and I can easily imagine it taking a set after some mechanical wear of this type.
This was a very helpful tip.
 
Ok, thats what i thought it was. Thanks.

Now onto my next question:

Whats the point? I heard sometimes it will "fix" a bad lock, but wailing on my knives is not something i practice.

Im asking because i just ordered a CRKT M16, its my first liner lock thats actually worth using, I've use an axis lock for a while, and lost it.

Being only 15, a 40 dollar knife is a pretty good size investment, it isnt like a 300 dollar custom, no, but i want my knives to perform the best, no matter what they cost.

Any more help on this subject would be very helpful.
 
pedder2226--some people think that the spine whack test is silly, but personally, I don't want to use a knife that is going to close up and chop off my fingers. In a recent thread on this topic, Joe Talmadge pointed out that there have been a number of reports of liner locks failing during use, sometimes resulting in injury. While these events are rare, I would rather that it not happen to me. Many people argue that if you are using a knife properly, you shouldn't have to worry about the lock.
Many "tactical" folders have a liner lock. I think most of these knives are intended at least in part for self defense, which might, god forbid, involve stabbing someone-- hardly the time when you want your knife to fold closed on your fingers; you might need them to defend yourself. Granted, stabbing people is pretty low on the list of uses my knives see on a daily basis, so this is just hypothetical. I have a large Applegate-Fairbairn that fails the spine whack every time, even with very moderate pressure. Even though it sounds like a bank vault slamming when it opens, I don't trust it, and it usually ends up sitting in a drawer while knives that pass the spine whack go in my pocket. Besides, just because a liner lock passes the spine whack test once doesn't mean it will continue to pass; it can fail at any time. No lock is perfect, but there are other options besides the liner lock. You might want to look into the axis lock available on a variety of Benchmade knives. Also, certain CRKT models have the LAWKS, an additional locking mechanism that helps insure that the liner won't slide off the blade tang. My CRKT KFF passes the spine whack with and without the LAWKS, though others have reported lock failures with this particular model. Doing a search for spine whack will probably turn up more information than you want.

--Josh
 
You don't have to have a knife that passes the spine whack test if you don't want it to. For example, I carry around a Benchmade 812HS frequently, becuase I like the little knife a lot, even though it is a liner lock. But I don't expect the 812 to be reliable to destruction, in other words, I don't expect the lock to hold until something breaks. I don't expect it to take a blow on the blade spine from a blunt weapon without closing on my fingers, and I don't do any forcefull poking (i.e. thrusting) with it. And it works great as a cutting tool, just as countless slip joint folders have over the years. I almost always carry a 710 or an Apogee in addition to my 812 though, becuase those knives have more reliable locks on them.

It is only when you expect a folding knife to function as an extreme use cutting tool, or even as a self-defense weapon, that your expectations might be a little higher. The existence of more reliable locks on the market today has raised the bar for extreme use, "tactical" folders.

You M16 should be a great knife. Just don't expect 100% reliability from the lock. Use it as a folding knife that may possibly fold in use if you do not take care.
 
Thanks for the info guys, its appriciated.

The knife wont be used too hard, hunting fishing and camping mostly, and the other odds and ends I need to cut. I will have it on me as a EDC. Although its 1/4 inch longer than the legal limit, I live in a TINY town and know every cop here, and have talked to every one on this subject, I will have no problems with the law. It wont be taken to school if thats what you're thinking, I am one of the few teens with a half wit brain these days:)

In the odd, very odd case it is used in self defense (I do carry a kubotan and know various martial arts to ESCAPE and attacker) there is a slight possibilty I need to DISABLE and attacker, if I'm in THAT big of a jam, cutting my fingers is no biggie, as at that point its sliced knuckles or death. The M-16 should be a fine knife for me. Cant wait for it to come:)
 
I spine whack every folder I consider carrying. If the thing is gonna fold up on me, I'd rather leave it in the closet at home. I will never carry a knife I can't depend on. That's why here lately I've been carrying more and more small to medium fixed blades.

They pass the spine whack test every time! yuk yuk yuk. :p
 
Josh Feltman wrote:
pedder2226--some people think that the spine whack test is silly, but personally, I don't want to use a knife that is going to close up and chop off my fingers. In a recent thread on this topic, Joe Talmadge pointed out that there have been a number of reports of liner locks failing during use, sometimes resulting in injury.
Click to expand...

I'm one of those who got injured using a liner lock that failed.
It was only a minor cut across the back of my right index finger thankfully.
It happened with a Boker Gemini series "Angler" model. I was cutting flowers from our Saucer Magnolia. I raised the blade to lightly chop the woody flower stem and the blade spine hit a branch above, which caused the paper thin blade liner to bend enough to fail and snap shut on my finger. All my liner locks get the Spine Whack and there are no paper thin linerlocks allowed in my collection anymore.

Oh, BTW, this knife passed the SW test the first time I tried it, so I blame the thinness of the liner and my clumsiness.:D
 
A question for all you "whackers". What use of a folding knife does the spine whacking test simulate?

In Cub Scouts they taught me to cut away from your body and keep pressure on the blade against the blade stop.

Having owned and operated my fair share of liner locks, I have never had one close on my hands while using the knife PROPERLY!

If you are doing something that will make the blade close, then you are not using the folder for it's intended purpose. Time to check into a fixed blade for what ever it is that you are doing that would make a blade close on your hand.

Remember the liner lock, like the lock back were put into use by manufactures to reduce their liability in law suits. They were not intended to keep a blade from closing while doing something you would not normally do with a knife.

Millions of knives have been made with lock backs. Of course there will be failures, as with any manufactured item. Even the space shuttle has problems now and then. If a study could be done, Im sure more people cut themselves daily in the US with kitchen knives than with liner locks that fail.

Unfortunately, there is no "idiot" test for these knives. Most times when people cut themselves with a knife it is "Operator Head Space and Timing"! Remember you must be smarter than the piece of equipment you are operating.

Don't get sucked into this "Whack" test. This is generally sponsored by the same people who slam open every folder blade they can lay their hands on. Then complain when the lock is almost impossible to release (remember titanium will flex).

Guys, if your using the knife in a manner it was unintended to be used in, it is only a matter of time before you will get cut.

By the way, you guys don't pound the hammer of a loaded pistol on a table top to make sure you won't get an "accidential" discharge do you?

If your doing that, please stop.
 
THERE IS A GOD!

Thank goodness there is somebody who has similar feelings to me about the much-vaunted "spine-whack" test.

To be fair, however, I do not feel it should be disregarded. It is, IMHO, but a part of a series of tests that can be used to evaluate the integrity of a folder's lock-up.

I still feel that slow, twisting motions are much more typical of the types of movements that are much more likely encountered in daily use situations.

Just my opinion. :)
 
Wow, I thought was the only one that wasn't crazy on the idea of the spine whack test! I usually do a stabbing twisting test also.
Mr. Robertson summed it up rather well......the right tool for the right job!
 
Wholly Brethren and Cistern, I hate to think of all the ignorant heathen who blithely trust they will always be able to use their choilless liner lock knives in the way some false prophet told them his false gods "intended" knives to be used and who are afraid to find out if their knives lock at all -- many of them don't. Including high-buck knives, and especially when they're brand new and especially when they're opened gently instead of with violent slamming inertial openings as the True Knife Gods intend all folders to be opened. Verily I say unto you: hard to unlock is good! (Impossible to unlock would be better.)

Verily I say unto you: no one in the history of the world has ever managed to use folding knives for a lifetime and always avoid having any closing force applied to the knife. What the false prophets demand of you cannot be done! In olden times that was not a problem: folding knives had choils whether they had locks or not, and as long as the user had enough sense to grip it with his forefinger on the choil he kept his forefinger. If harkers after false prophets of the present day still have all their fingers intact for now it is only because they have been lucky so far.

Have I alarmed you sufficiently yet? I could go on to quote posts from good honest knife knuts just like you who bitterly regret having listened to false prophets ... some of them sustained injuries beyond the power of mortal surgeons to restore. Get out a liner lock knife and open it gently like a little old lady who thinks blades and stop pins are made of spun glass instead of tempered steel. Hold it so your fingers are out of the way and give it a little tap, again like an old lady who thinks knives are made of spun glass. You might find it folds at the slightest touch. If it doesn't ... are you satisfied? Or do you value your fingers enough to try tapping that spine a little harder -- even hard enough so it would break if it were indeed made of spun glass?

Brethren and Cistern, you cannot break anything that deserves to be called a knife by whacking the spine on a telephone book. You cannot break anything that deserves to be called a knife by opening it in a manner unlike a little old lady handling her precious gold-filigreed china, either. You can get severely hurt if you put your trust in false prophets who tell you your liner lock is safe and never test it to see for yourself.

Only a Benighted Heathen would use a knife with a stoopid joint in the middle in the first place, but if you must use a knife with a stoopid joint at least find out if it works. We of the Wholly Brethren and Cistern do not hate our Heathen brothers ... we pity them ... and we hope they will at least preserve their fingers until one day they may see the Light.

-Cougar :{)
Wholly Brotherhood and Cisternity of Voracious Truth FAQ
 
Les' views come from years of experience, and I never miss a chance to learn from him. So I don't disagree with him lightly, but in this case, I do disagree with him.

Let's be clear on what the spine whack test does. It puts impulse forces perpendicular to the spine of the blade. That force directly stresses the tang/liner junction. You don't have to do a spine whack to simulate this kind of stress -- if a particular action has any force component into the spine, and does so quickly enough to be more of an impulse, it will effectively do the same thing as a spine whack. Thrust your knife point-first into something hard? If you control the thrust perfectly, no problem. But if the point dips even a tiny bit, you'll get a spine force. Thrust your knife into something soft, but hit something hard, like thrusting into a rib? Spine force. In a defensive situation, if your opponent targets and hits the blade spine at all? Spine force. Knife gets stuck, but when you pull it out the spine hits something?

There are any number of reasonable theoretical reasons a hard-use knife might see some force component perpendicular to the spine. The spine whack is just a bit more extreme -- it isolates that spine force, and the impulse is fast. Spine whacking seems unreasonable if you believe it only tests isolated spine forces; if you realize that any spine force component is enough to test the tang/liner junction, the number of situations where you might see this increases.

In the end, if liner locks were seeing a disproportionate number of spine whack test failures, but not a disproportionate number of failures in real use, I too would throw out the spine whack test. But my sense is that the disproportionate number of spine whack failures is matched by a disproportionate number of real failures, which further convinces me that the spine whack test is a reasonable test of the tang/liner geometry, and that several actions can generate forces with some impulse spine-facing component.

I also am not willing to dismiss real failures to "user error". These knives are being designed, manufactured, and advertised as hard-use and defensive knives. As such, they had better expect to be subjected to hard-use and defensive level tests. It's unreasonable to think a real user will never torque or see spine force in hard use or, even more absurdly, in a defensive situation. These are uses where by definition perfect technique cannot reasonably be expected.

I do agree that if your liner lock fails, it's time to look elsewhere. I just don't think you necessarily need to look to a fixed blade. Chances are, if you want to stick with a folder, an axis lock, or arc lock, or compression lock, or any other number of lock formats that are easier to consistently manufacture to be reliable is all you need to step up to.


Joe
 
Cougar and Joe,

Agreed. After nearly losing my trigger finger to a defective liner lock on an early BM mini-AFCK under normal use, and after BM returned it with a "Nope, nuthin' wrong here, musta been you" note, my blood went cold and my balls sucked up, and all my liner locks were sold for scrap...

Folks, if yer gonna carry a knife that folds in the middle, ya better damn well test the thing...but be careful when ya do. :eek:

You can listen to experience, or you can listen to the hype....it's your fingers, you decide.
 
I have rather moderate position as to spine whacking.

Sure, Les pointed very good idea - use your knife as God commanded and nothing wrong will occur. Rely on your common sense more than on mechanical device and your fingers will always be in complete and healthy.

On the other hand some moderate spine whacking can display you how good or bad is this knife executed. Just example: at this year IWA trade show (March, Nuremberg, Germany) I have caused lock failure on new Schrade Lake & Walker production folder whacking blade spine against my palm! Excuse me, but I don't want this knife even for free, no matter will I use it properly or not.

Les,
What use of a folding knife does the spine whacking test simulate?
Click to expand...
The negative impulse load spine whacking could simulate is when hard stabbing with folder is done, for ex. in self defense situation. Here is a lot of tactical folders and a lot of guys who are going to use them for self defense. Luckily no one does but all are speaking about this matter, so this topic is endless :)
 
No one complains that SAK's are junk because they won't pass the spine whack test. Why not? Because they are understood to be non-locking folders. There are two types of folding knives: locking and non-locking. There's nothing wrong with either, but they should be what they say they are. A locking folder should do just that - lock! Lock means lock open, i.e., not close (unless the lock release is intentionally triggered). Non-locking folders are great. I own a few, carry one daily, and carry others sometimes, and there's no mistake about what they are. There is a problem when a knife is sold as a locking folder and it doesn't lock. I'll repeat that because some people don't seem to understand it: There is a problem when a knife is sold as a locking folder and it doesn't lock. It is either false advertising or poor QC, but either way, a locking folder that doesn't lock isn't right, it's wrong, it's broken, it's a bad one. I don't beat on knives for fun and I don't expect a folding knife to be strong enough to jack up a car, but if I buy a locking folder, I expect it to lock. The spine whack test is one way of testing whether or not a "locking" folder actually "locks." For those of you who don't want to damage your knives by whacking the back of the blade, and $60 or $600 is a lot for you to spend on a knife so you don't want to damage it, think about it this way~ that knife cost that much money because it was that well made, and if it's as high quality as it should be, that won't damage it. I used to baby my knives because they were expensive and important to me, but now I see that they were expensive because they're high quality and they're important because they're good quality. One of the things this means to me is that a little spine whack won't break them. Another is that some are actually suited to hard use and won't be damaged by it. No, I don't pound nails in with the spines of my folding knives (I use my closed LM Supertool for that, and it pounds paint cans closed well too), but I do trust that they will stay locked open because I have tested them. If you're using your folder for a task or in such a manner that a non-locking knife would be safe and sufficient, then spine whacking your knives is totally unnecessary. If, however, you bought a locking folder because you wanted one that would stay locked, it might be a good idea to find out for sure whether or not the lock is functioning properly, especially if you value your fingers. And if there's any chance that that knife in your pocket will be used as a last-ditch self defense weapon, a lock failure in that circumstance could mean your death. Would you carry a gun you haven't fired? Or load it with ammunition you have never used? Would you carry a knife as a weapon without having checked to see if it is at all sharp?
 
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