Spine whack test?

[jill jackson]

Isn't some of the folding of a spine whacked knife to do with it jarring, or bouncing?
I had a Kershaw Whirlwind that locked up very well but would fail even when I tapped it on my arm. It seemed like it jarred or bounced the liner out of lock-up, as otherwise it was very tight and could not be defeated with hand pressure alone.
What causes the liner-lock to give, when whacked? Is it not grippy enough, or tight enough?

 

[Sep]

Reading Sal's advice, he says 5 lbs is enough of a test for the consumer. Well, in my mind 5 lbs is more of a "tap" than a "whack", and it's entirely appropriate. If the lock can withstand 100 lbs of static load, 5 lbs worth of shocks shouldn't hurt.

Now, this is a question and not a criticism: how can the average consumer perform a 5 lbs test without precise lab instruments? How can he prevent himself from performing a 15 lbs destructive test instead?

 

[Reeek]

I have never whacked a spine in my knife life. Never will either.

 

[allenC]

I have never whacked a spine in my knife life. Never will either.

Then you will never know if the lock is truely reliable or not.
And if you don't care if the lock is reliable, then why not just use a slip-joint folder?

 

[gunmike1]

Reading Sal's advice, he says 5 lbs is enough of a test for the consumer. Well, in my mind 5 lbs is more of a "tap" than a "whack", and it's entirely appropriate. If the lock can withstand 100 lbs of static load, 5 lbs worth of shocks shouldn't hurt.

Now, this is a question and not a criticism: how can the average consumer perform a 5 lbs test without precise lab instruments? How can he prevent himself from performing a 15 lbs destructive test instead?

On my spine taps I use enough force to feel it in my hand but not really hurt bad, I can't really say it's 5 lbs., but considering how it is just a wrist filck I doubt my spine taps are near 15 lbs. I guess I should find a scale and try out one of my spine taps and see what kind of force they are measuring. Like it was said above a spine tap (and all but the most brutal spine whacks) are more for testing the lock under a sudden shock (kind of like bumping the spine into something during real world use) rather than an all out strength test like hanging a few hundred pounds off the handle of a folder. After seeing those posts from Sal years ago I have done it to all of my knives, but always with the thought in mind that wailing away at the spine would just damage the lock rather than tell me anything meaningful.

Mike

 

[pvicenzi]

Then you will never know if the lock is truely reliable or not.
And if you don't care if the lock is reliable, then why not just use a slip-joint folder?

Yes he will, no lock is completely reliable.

 

[Reeek]

Then you will never know if the lock is truely reliable or not.
And if you don't care if the lock is reliable, then why not just use a slip-joint folder?

I carry my Urban quite a bit actually

 

[stabman]

most people who don't like the test don't like it because their choice knife will not pass.

No, most people who don't like the test like their knives, and don't want to beat them apart with a test that really does not test actual, real life usage. I have a goodly number of knives that I KNOW would pass; I trust them to stab wood HARD, but I'll not stupidly abuse them with nonsense tests.

 

[stabman]

Why is it that revolver companies can make a cylinder that can withstand 20,000-40,000 psi and more without exploding in your hand, yet cannot be made so that it can be flipped closed without damaging the gun?

Forces which go in other directions, directions which are not necessary for proper usage of the firearm.
Think of which parts resist which forces in which direction, and you'll have your answer.

 

[stabman]

Well, in my mind 5 lbs is more of a "tap" than a "whack", and it's entirely appropriate. If the lock can withstand 100 lbs of static load, 5 lbs worth of shocks shouldn't hurt.

Such a light tap is a TAP, not a WHACK.
Light taps against the back of the hand to "feel" the engagement is okay.
Beating it like some folks would have you do is silly.

 

[udtjim]

There must be something wrong with me. To me the lock on a lock back is to keep it from closing on your hand by accident while performing normal cutting duties. I am not about to do the whacko test on any of my locking folders.

 

[Angus McGunnigl]

I have a Gerber Yari(the original) that has passed the spine whack test many times.

 

[StretchNM]

If a man is going to perform the spine whack test, the wisdom of thousands of years of knifeknowledge (passed on to us NOT so we can pontificate the whackability of spines) dictates that a man just do it and be done with it!

The spinal tap has nothing to do with knives.

Just something I have learned and I pass it on to all of you.....

 

[mnyshrpknvs]

If you go to YouTube and check out "nutnfancy" videos - I believe he has come up with a good way to test the strength of a lock. He duct tapes a folding knife to a broom handle and repeatedly jabs it into a 6"-7" thick stack of cardboard that is taped taped to a 100 lb punching bag.

I have never had a lock fail on me yet, and I have liners, axis, compression, frame and spine locks. I have tried the whack test on knives that are known to have weak locks and could not get them to fail. I guess I wasn't hitting them hard enough!!

Those are great vids! I watched those and bought my Protech based on his recommendations.:thumbup:

 

[3Guardsmen]

I think someone needs to clearly define the terms "spine-whack" and "spine-tap," then we can really debate the issue. For my own purposes, I consider a spine-whack to be a full strength, full arm's swing of a folding knife's blade's spine into a hard (ideally wood) object. I consider a spine-tap to be a half strength, half arm's swing (no shoulder motion) of a folding knife's blade's spine into a bit softer of an object (ideally the tip of a boot).

If you accept my definitions of those terms, I'll tell you flat out that I've had several well known, well made knives that have failed the spine-tap, including two Spyderco Manixes, the main blade of every Leatherman Wave and Charge model that has passed through my hands, and I've had a few of 'em, a Spyderco Stretch (the original version), two Boker Subcoms, a SOG Twitch, a CRKT Pointguard, and a CRKT M-16 "big dog" tanto. I think that anybody who keeps a knife with even the idea of ever possibly having to use it in a rescue, survival, or God Forbid, a last ditch SD situation is a complete and utter moron if they don't at the very least give that knife an occasional spine-tap!

Most people don't plan on accidents happening, like bumping the spine of the blade on a hard object (table, car door, tree, toolbox, you name it) while withdrawing the blade from an object being cut, but guess what, accidents like that happen every single day! Let me give you a scenario. A Firefighter wants to cut a vehicle collision victim free from his seatbelt, so out comes the rescue folder. The Firefighter shreds the seatbelt apart with his blade, but while pulling the knife back towards him, inadvertantly smacks the spine of the blade on the inside of the wrecked car's door, causing the lock, which should have held up, to fail. Best possible outcome, the Firefighter was wearing great quality gloves and his knife's blade is fairly dull, resulting in a cut glove and a minor injury to his index finger. Worst possible outcome, the Firefighter had crappy gloves, or didn't have them on, had a scary-sharp edge on his knife, is now minus a finger or two, and is on his way to the ER with the collision victim!

For those who say that spine-taps are abusive, I certainly hope you never find yourself in a situation where the integrity of your folding knife's lock is less than stellar and is inadvertantly tested! Luckily, I'll never be in that group.:thumbup:

Regards,
3G

 

[3Guardsmen]

most people who don't like the test don't like it because their choice knife will not pass.

No, most people who don't like the test like their knives, and don't want to beat them apart with a test that really does not test actual, real life usage. I have a goodly number of knives that I KNOW would pass; I trust them to stab wood HARD, but I'll not stupidly abuse them with nonsense tests.

If any of the knives you're speaking of have the Tri-Ad lock, you can thank the guy you're arguing with, as he designed it.

Regards,
3G

 

[3Guardsmen]

Such a light tap is a TAP, not a WHACK.
Light taps against the back of the hand to "feel" the engagement is okay.
Beating it like some folks would have you do is silly.

I think using words like "silly" is just plain silly

Regards,
3G

 

[Mikel_24]

I guess that all folders should be treated as such, regardless of the lock. If you want to stab stuff or smack stuff with the spine, get a fixex blade. Slipjoints are ok in my book and I treat all my folders as such.
Mikel

 

[3Guardsmen]

I guess that all folders should be treated as such, regardless of the lock. If you want to stab stuff or smack stuff with the spine, get a fixex blade. Slipjoints are ok in my book and I treat all my folders as such.
Mikel

You're right. Absolutely no good reason to own a locking folder.

Regards,
3G

 

[pvicenzi]

I stand by my earlier statement that if a lock fails, it is more likely the fault of the user than the manufacturer. If you want to whack a knife into a desk, get a large fixed blade. I cut things every day and in 41 years of using knives, I still have all my fingers, and I've never had a lock fail. Use folders only for cutting. If you need to stab or chop, get out the fixed blade.