Newbie question about testing a knife

Mandragore

Mandragore

Joined
May 4, 2001
Messages
65
I'm french and my english-speaking is not very good, especially with technical words.
I read a lot on the Net about the "spine-whack" test for locking systems. The problem is that i don't understand very well what it means. I searched on Internet in order to fine a featured and detailed explanation but i did not find...
 
Spine whacking is when you tap the back of the blade, or spine, of a folding knife against some hard object to see if it will cause the locking mechanism to disengage or otherwise fail. Some people just test the knife by tapping it against their palm or leg with a moderate amount of force, while others tape the knife to a long pole and beat it against a fence post, etc. Others feel the test has no value whatsoever as folding knives are not designed to function in that manner. If you do decide to spine whack your knives, make sure that your fingers are out of the way so that you don't get cut if the blade closes.
--Josh
 
Step 1:
swt-1.jpg

Important: Fingers should be not in the path of the closing blade should it close.

Step 2:
swt-2.jpg


Your knife should not unlock or fold.
 
If something is worth doing, it is worth doing right. ;)

View



It all depends on the knife though. No sense in stick-testing a 2.5" pocket folder.
 
I've just tried that on my Boker gemini and the lock released. I'm gonna get rid of that poor knife
 
Steve, what kind of wood is that stick? Looks nice and might make a good knife handle...
 
Bamboo? I didn't know bamboo looked that slick or shiny and had all those swirls and stuff...
 
That's a rattan stick that has been fire hardened and varnished. Commonly used as training weapons for stick fighting. Rattan is not dense enough to make a good knife handle.

Before you get rid of your Gemini, remember that not very many knife models can pass a severe whack test. If the lock holds under light impacts, you might think about exactly what you are expecting from the knife, and how much you like the Gemini design.
 
Shucks, Steve, thought it was maybe some kind of maple I hadn't seen before. Looks pretty cool.
 
Mmmh, Boker seems to me to be a good manufacturer...
And not many knives will resist such harsh treatment.
Not to mention that you could easily damage your knife this way.
A Liner lock has not been made to withstand such use.
The only downward pressure the blade will ever get is when using the point of the knife.
If you fix the blade in a vise (with lead liners so not to mar it) and apply increasing weight you'll see exactly when the lock fails.
Consider that the weight you apply has a leverage which is 10-20 times what you get when forcing the point thru some material.
So, if you apply 10 Kgs and see that it holds, it means you may safely exert a pressure of 100 Kgs on the point without problem.
How many times do you think to be able to apply such pressure to your knife???:eek:
Realism...
Whacking a knife with a huge pole like you did is like using a tank launched at 60 Mph for crash test evaluation of small city cars :)
 
Originally posted by Alarion
...A Liner lock has not been made to withstand such use...
Click to expand...

Agreed.

...The only downward pressure the blade will ever get is when using the point of the knife....
Click to expand...

That depends a lot on the user. Several injuries have been reported when users hit the backs of their locking folders against solid objects accidentally.

...If you fix the blade in a vise (with lead liners so not to mar it) and apply increasing weight you'll see exactly when the lock fails.....
Click to expand...

Gradual force and sudden impact are two drasticly different tests.

...Realism...
Click to expand...

That is the whole point of the stick test. If you don't need a folder lock that will withstand at least medium impact from a blunt weapon, you don't need to do the test.

...Whacking a knife with a huge pole like you did...
Click to expand...

If you think that is a huge pole, you should see my [censored]. ;)
 
In addition to what Steve noted about accidental impacts directly against the back of the blade, consider that even on a stab there will be a significant amount of force perpendicular to the back of the blade. The amount of which depends on the skill of the user and the motion of the target.

I have stab failed several cheap liner locks similar to the way Steve has mentioned doing whack tests. I attach them to a short stick and stab holding onto the stick. This is a bit worse than doing the stab with the actual knife as you can get a better grip on the knife handle usually (you would hope so anyway) so the stab would be more controlled. However for obvious reasons it isn't practical to do so.

-Cliff
 
Steve: ROTFL! I wouldnt use THAT for testing knives, though... :p
Anyway, yes, impact and progressive force are very different, but I was just considering normal tool use (and this pretty answers Cliff too). I carry my knife as a tool, not for personal defense. I could beat most of my friends at knife duels using harmless rubber props, but I never had any formal training and I have no false hopes about getting out of a REAL knifefight in good health :(
Anyway, should I carry a knife with self defense in mind, I wouldn't rely on a liner lock. Too easy to mishandle the knife and release the lock, IMHO, but then, maybe it's just because, as I said, I have no training in knifefighting :)
 
Yes that's true direct impact and progressive pressure are two different things.
But I remarked that my knife is potentially dangerous even in a progressive pressure situation; let me explain:
On my knife (i don't know if it's a manufacuring problem) the back of the spine, where the liner piece engages after opening the blade is made steeply which means that the metal liner can slide and disengage easily. This is especially dangerous when the knife is in a wet context because water makes it easier to disengage.
 
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