Spine whacking (and other knife tests): Realistic?

F

Full Tang Clan

Joined
Jul 22, 2000
Messages
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I’m wondering if some of these tests that some manufacturers use to promote their knives (as well people in these forums use to determine whether a knife is worthy) – like spine whacking – are overkill? Do these tests reflect “real life” situations?

Now let me be the first to say that I support the underlying principle of evolving products to make them better. I’m also against cheap products that are dangerous to consumers.

However, how often are you going to find yourself in a situation when the spine of your knife blade is getting 200 lbs of pressure put on it? Obviously Jones, you’re using your knife upside down!

Even in the case of exerting force on the tip: Forget 200 lbs. If it's even 100 lbs of force, it seems to me that you are in more of a danger of your blade snapping, or losing your grip and running your hand up the blade of your knife (ouch!). No extra thick 410 SS liners, or a safety Axis lock is going to save you then.

In addition, you’re not going to be using a $300 folding knife as a chisel, or a slotted screwdriver. If you’re doing that, may I suggest that you save yourself a few bucks and pick up a $50 tool-kit from Wal-mart. This brings me to another point: Warranty is void if knife is misused.

Many of these manufacturers build and advertise their knives as being able to survive a confrontation with a Sherman tank. However, they’ll void the warranty if you so much as use your knife as a scraper to take frost off your car window!


NOTE: This post is not to "flame". It's just a commentary. I just bought a BM 710 but I question how often I'd use the Axis lock.

 
It never hurts to kick harder than you have to. I have, on at least one occasion, been cut when a nonlocking folder closed unexpectedly. I was cutting a thick sheet of plastic and only had a Victorinox Super Tinker on me. The blade bound in the material and despite careful attempts to remove it gently and by flexing the plastic, when it did come out it closed. Fortunately the cutting had dulled the edge a little and it did not close too quickly. The cut was minor. Now would a lock that could withstand 25lbs have been enough? Probably. Would I prefer that it be able to take 100 or even 200lbs? Definately. It is not as if you pay more per pound of protection and even if you had too, I would.

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Tang,

Twice you used the phrase, "how often . . . ?" How often is often enough? I have a fire extinguisher in my kitchen. How often do I use it? Never. I also have a first aid kit and a jack in the trunk of my car. Never use 'em.

The spine whack test is legitimate. True, you don't normally place that kind of stress on a knife when cutting things, but it is quite possible in a fight to have the spine whacked by your opponent's weapon, or you could whack it inadvertently against a wall or door frame. Even normal folks in everyday life could bring the spine in contact with the bottom of a table or other inanimate object. When I was young and stupid I used to break duck and pheasant wing bones by whacking them with the spine of a knife-- fixed blade, lock-back folder, whatever. I just assumed the lock would hold. Good thing it did.

Even if your knife doesn't have to be "that" strong or "that" reliable, given a choice it might as well be. Just like having a car that can go faster than 65 mph.

David Rock

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AKTI Member # A000846
Stop when you get to bone.

[This message has been edited by David Rock (edited 07-26-2000).]
 
Considering the drastic consequences of a lock failing during vigorous use, the spine whack test is legitimate and appropriate.

A T Barr is the knife maker who devloped this test, and his knives are built extremely well; he knows knife making thoroughly, and I believe his test to be an excellent test of a lock's safety.

Walt
 
A good example of a realistic combat situation that could equal a spine whack test is when you hold a knife in reverse grip ("icepick grip") with the edge away from your arm and use the spine of your knife to trap an attackers limb between spine and arm. I wouldn´t want the knife lock to fail in this situation.

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"Peace is not without conflict; it is the ability to cope with conflict" - Leo Giron

[This message has been edited by judge (edited 07-26-2000).]
 
It is true that the spine of a folding knife will not often get "whacked" during normal use. But under abnormal use anything could happen. As long as the lock is as strong as the hand holding the knife, it is as strong as it will ever need to be, so the difference between a lock rated at 300 lbs and one rated at 500 lbs is inconsequential, but the difference between 20 lbs and 200 lbs is a different story and an important difference. It all depends on how much extra security you want...

You say you just bought a BM 710 but you're not sure how often you'll use the axis lock??- how about every time you open the knife?

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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
 
I've always said that it's up to the user to decide which tests are relevant to him -- after all, it's his fingers. However, I also caution against deciding against spine whacks too quickly. First, a brief comment on hard-testing overall:

In addition, you’re not going to be using a $300 folding knife as a chisel, or a slotted screwdriver.
Click to expand...

Maybe not. But if this is a hard-use knife or tactical knife, it often happens that the knife gets fairly stuck in the object, and has to be torqued and twisted out -- this puts several bizarre stresses on the lock. Now listen, if the maker says that this is a gents' folder, suitable only for opening envelopes and cleaning nails, I'm okay with skipping the spine whack test. But if he's going to call his knife "tactical", "utility", "hard-use", etc., I'm certainly going to judge it that way.

Okay, first some history. I (and A.T. Barr) use the spine whack test as a basic test of lock geometry. As such, I do a moderate whippy spine whack. Others use the spine whack test as a fundamental test of lock security, and do hard-power spine whacks. Neither of us is especially right or wrong, we've just come to different conclusions about what the test is and how useful it is.

There are certainly reasons to be concerned about a knife surviving the spine whack test. There are the theoretical concerns about someone hitting the spine of your knife with a stick or whatever -- seems like a reasonable concern, standard defang-the-snake type doctrine. For all I know, this is a completely theoretical concern -- I do not know whether or not a folder has ever folded on someone during a real fight due to this. 'course, if it had, the owner would probably not be around to take about it anyway. On the utility side, it is definitely a less-theoretical concern. Getting the knife stuck, yanking it out, and hitting something when the knife finally releases, is actually something people have talked about firsthand. Knowing all the above, it's hard to see how you could simply dismiss the spine whack test.

Of course, having been one of the folks who popularized this test, I sometimes become concerned that it's considered by some to be the alpha and omega of lock testing. A test in which white-knuckling and torquing of the handle is done is really critical, and probably even a more important test than spine whacking. Even the worst detractors of the spine-whack test all seem to agree that white knuckling and torquing failures are serious real-world issues. And I see many reviews these days where the reviewer talks about the knife failing/passing the spine whack test, and there's no indication that he's tried the arguably more-important white-knuckling and torquing tests.


Joe Talmadge

PS Ironically, one thing the spine whack test can do is "set" the lock geometry. Many knives fail the spine whack test exactly once, then never fail it again. Why? Because the first whack helped the lock settle in, so the geometry is correct and the lock slips no more. Even knives that fail due to slow spine pressure, rather than impulse pressure, can often be "fixed" this way.
 
I carry a penknife nearly all the time and have done as bfm several times.
My knife collection has grown and I have a few liner lockers. I don't trust them that much, and think of them as one step up from a slip lock. Most of the ones I use are the smaller models with thin blades. Getting the job done relies on a fine edge and thought.
For medium folders I still prefer a backlock and will give them a fairly hard time. My Al Mar Sere Attack is as about as good as it gets for hard work, but even then I wouldn't hammer it.
After that then its fixed.

Spine wacking is a good test. When you mess up a cutting job its usually when you are forcing the issue. Stresses go all over the place. You lose control and anything can happen from snapping the blade, to prying denting the edge, to over the top which places stain on the lock.
I say test them every which way posible. You will if you use a knife over a long time.
 
If I worried about my lock that much I would just use my butterfly-knife all the time, I am 110% confident that it will hold.
 
You know, in hind-sight, I think I asked a really redundant question regarding spine whacks and secondary locks. It's almost like asking whether air-bags are necessary in a car to survive a crash. The answer is "no". Is it advantageous to have? In most circumstances, "yes". A safety of margin is always better.

I guess I'm more concerned that these stringent (I use that term rather than "unrealistic") tests, and secondary locks are going to override other important factors like the blade, or how the knife feels in one's hand, etc. I hope people don't start to ignore other factors.

Case in point: Of all my knives, I prefer carrying the SOG Magnadot. It's a good knife IMO: a mean-looking thick blade, 3.6" edge, snaps open quickly, nice balance, good factory sharpening job, etc. In addition, it feels right.

However, by those stringent testing definitions, it would be considered a hazardous knife -- lockback, Zytel handle with no steel liners, no safety lock -- and may cause people to avoid it like the plague.

In other words, I don't want people to think that axis locks, and frames which can survive a hammer blow are the "end all, be all" of knives.

Anyways, thanks for everyone's responses.
 
Tang - Accidentally hitting the tip of a 4" knife while lifting your arm...Arm weight (say 25 lbs) + force to lift (maybe 10 lbs) = 35 lbs times 4" leverage arm = 140 inch/lbs of force. It doesn't take as much as you'd think to develop some force.

Two opposing, conflicting male arms could easily generate 100 lbs of force times 4" of blade (leverage arm) = 400 Inch/lbs. Could you imagine a serrated Spyderco closing up on your hand? even once? How often is not an issue.

Walt, FWIW - Spyderco has been spine wacking all folders since 1981. We've rejected entire runs over lock defeat. We also have minimum lock strength standards that we use for each model.

sal
 
However, by those stringent testing definitions, it would be considered a hazardous knife -- lockback, Zytel handle with no steel liners, no safety lock -- and may cause people to avoid it like the plague.
Click to expand...

Full Tang --

While I understand your concern about people focusing on this one particular test and ignoring the other parts of the knife, I don't believe I see that happening here. A secure lock is a necessary but not sufficient requirement for a good folder -- I think everyone understands that.

As far as requiring liners, safety locks, particular handle materials, etc., who says? Certainly not me -- I carry either a Calypso Jr. (micarta handle, no liners, lockback) or Endura (zytel handles, no liners, lockback) almost every day. That endura is my beater knife, and it's been through a whole lot.

I still spine whack every folder that I own. Just because it's lightweight doesn't mean I'll accept an unsafe lock.

Joe
 
Sal Glesser said:

Walt, FWIW - Spyderco has been spine wacking all folders since 1981. We've rejected entire runs over lock defeat. We also have minimum lock strength standards that we use for each model.
Click to expand...

I am amazed at this. It speaks volumes about the integrity and concern for the customer of Spyderco. It also answers definitively whether or not a spine whack test is 'overkill.' My compliments to you and your company, Mr. Glesser.

Walt
 
A test I'd find much more interesting would involve the folder to be opened, force applied the way you do when you cut -- at perhaps 200% the force one would normally use -- then moderate bending and twisting force applied perhaps every fifth time and occasionally some pressure against the lock, then closed ten thousand times. All without developing any sort of play.

Any manufacturer do something of the kind?

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Urban Fredriksson
www.canit.se/%7Egriffon/
Latest update: A Russian hand made hunting knife

"I've always been fascinated by Scandinavian knives [...] they're simple, in an advanced way".
- Bob Loveless
 
I second the concern over twisting/gripping type tests. Tripping the linerlock release while holding the grip "white knuckle style" is a serious concern. Especially when a fight is more likely to produce such a fierce grip.

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To me, it all boils down to this:

If faced with multiple lunatics armed with clubs/knives/whatever, I want to be able to utterly trust the bit of steel I pull. I don't want "this thing is supposed to be pretty good" running through my head I want "Well, at least I've got the best in the world" there. I think that translates all the way to my face, gives just a tiny extra measure of resolve, raises the odds they'll rabbit and I'll face no legal/medical/emotional consequences at all.

I've "been there, done that" twice now, in over 18 years of constant carry. Both times the goblin(s) ran. Not too indicative of a crazy lifestyle, I don't think.

I now carry a Sifu. If I was limited by law to 4" I'd probably carry a Carnivore, though there's other worthy choices in that size range I'd ponder (Sebenza, or it's Mission derivative with the same lock).

BUT: special kudos to CRKT for making the KFF that "the masses" can afford (sub-$40 from Mike) and will probably do as well as anything in it's size range in a hairball fight. If I needed to buy cutlery for multiple friends or something, and was on a budget, it's a hell of a good "starter streetfighter".

Jim
 
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