Merits of the spine-whack test

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Brutus013

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So, a lot of people seem to bring up a knife, be it liner lock, lockback, or whathave you, as having a bad lock if it fails a spine whack test. That is, a short, sharp applied force in the opposite direction of the force cutting would apply. They say that means the knife could easily fail if you are cutting with the knife. Me, I say the test is pointless. When is that kind of force going to be applied when using a knife how it's supposed to be used? If you are using proper cutting technique, I don't possibly see how the spine whack test is applicable.
 
It's a bad test, my knuckle will tell you that, under any normal conditions a lock with any decent rep WILL not fail. If you expect to use the knife in extreme conditions look into a fixed blade or knife with lockfailsafes.
 
Which is exactly why a large number of older microtech socom leaf locks fail easily with the slightest spine tap 3 or 4 times before they're reliable. It's a valid test, you need not smash the spine like you were using it like a hammer. A firm tap on a solid object will suffice.
 
imho it should be called a spine tap not a whack, ya dont have to whack the heck outta it to tell if its locking right, a lite tap on your palm or on a carpeted floor will tell ya what ya need to know and not mess anything up, i can whack anything on a workbench hard enough to make it fail, which isnt neccesary nor a good thing.

but a lite tap to ensure its locking up right wont hurt anything and is a good idea with liner locks as they can wear and get outta adjustment fairly easy.

its hardly "pointless" imho.

i want a lock to hold the blade open myself so when my cutting technique is a little off for whatever reason it wont fold up on me, i have -0- desire to go back to "slippies" myself.
 
Here is a pretty good explanation as to why a light spine tap is not a bad idea. The link points to a single post by Sal Glesser discussing the merits of a light spine tap test. It's brief and well worth reading.
 
SIFU1A said:
imho it should be called a spine tap not a whack, ya dont have to whack the heck outta it to tell if its locking right, a lite tap on your palm or on a carpeted floor will tell ya what ya need to know and not mess anything up, i can whack anything on a workbench hard enough to make it fail, which isnt neccesary nor a good thing.
Click to expand...

What he said. :thumbup::cool:
 
Brutus013 said:
So, a lot of people seem to bring up a knife, be it liner lock, lockback, or whathave you, as having a bad lock if it fails a spine whack test. That is, a short, sharp applied force in the opposite direction of the force cutting would apply. They say that means the knife could easily fail if you are cutting with the knife. Me, I say the test is pointless. When is that kind of force going to be applied when using a knife how it's supposed to be used? If you are using proper cutting technique, I don't possibly see how the spine whack test is applicable.
Click to expand...

It happens, with the sh in front of it :D You could be in a tight spot and have to stab something, whether it be a wild animal (bear, alligator, even deer) or a person in defense. That was always my complain with most of emerson knives, they all (with the exception of two) have liner locks. If I have a "tactical" knife, it better not fail when I need it most.

You could also be working in a tight spot, pull out your knife and accidentally "whack" it against something and that's all it takes to lose a finger.

I agree with Sal, a slight tap should do :thumbup:
 
Define "whack" :D

But seriously, that's the problem w/ advocating or rejecting this test, isn't it?

For me, it's a valid test as long as I keep the following, "real life" scenario in mind: what if I'm using my knife and I unexpectedly hit something immovable with the spine of the blade. For me, that scenario defines a reasonable "whack" that the lock should be able to withstand, one that can be simulated with a table edge and a firm hand movement of about 12" down onto the edge. That's it--anything more is knife abuse and may actually *promote* failures in the future!
 
Very bad test. When I tried it, my buddy's back never recovered after my third blow which was the hardest.
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Ho, wait a minute. . . you mean the back of the blade?!?
 
The spine-tap-test is 100% valid.

How can anyone call their lock safe and secure when it folds with just a firm tap on the spine of the open blade?

And for anyone who says, "you shouldn't hit your knife on the spine", I ask of them, why have a locking folder at all....why not just go with a slip-joint?

I've had several knife that have failed, and all it took was a firm tap on the spine of the open blade and the folder closed as if it didn't have a lock at all.
And all of those knives were liner-locks too (a CRKT, two Benchmades, and one Lone Wolf)....it's now hard for me to have confidence in any liner-lock folder.
 
There are no merits to whacking your folder regardless of the lock type.

A light tap, key word "LIGHT" is all that is needed. You are better off paying close attention to the lock and how it works, how it sounds, how it engages and if debris or deformation is evident than you are whacking it or tapping it routinely.

It is my belief that routinely tapping the locking mechanism with needless sudden sharp taps weakens the lock contact interface area more and more as you do it and this by putting undue pressure on it's nice crisp edges causing indents and dings that are not necessary.

I am now cautious even to promote taps because what some call a "light" tap may in fact be whacking in others eyes and vice a versa. I call a 40 pound bag of bird seed heavy. Some call that light. You just can't predict. My advise anymore is this. Make sure your folder lock is working when you buy it so in normal use it stays put. If its a liner lock allow the lock to break in before tapping or especially whacking it. You can see with liner locks/compression locks that typically many manufacturers and makers create the locks so very little connects when new but just enough to lock the folder open. I just bought a new CQC7A on ebay new from Emerson and the lock is barely engaging the folder. This is not a very assuring connection but it works fine in normal use. Is it fine for heavy? Probably but I'd rather not tap or whack it now at this precarious stage because quite frankly. Its not smart!

To tap or whack it now is a good way to shear off a part of the lock but even if its connecting good when opened right out of the box this changes with some uses and eventually they all move in further after a while. Some like my Emerson are not even covering .025" of a .050" lock thickness but move in and fully get behind the blade in short order from normal uses. Give the lock time to do that from real use just being cautious and aware of it at first. Lockbacks are usually good to go, axis locks, ball locks and arch locks also. Compression locks fall in the same category to me for break in as the liner lock but generally speaking use the err on the side of safety, cautious and aware approach regardless of any lock until you get to know the folder.

After that occurs for you maintain it and keep it that way so its clean and nothing is blocking travel or connection and then let those dings and indents develop from actual use instead of doing it needlessly when you know the lock functions as it should. You'll get more life and reliability out of the folder that way. Lastly. Know the difference between marketing hype/ BS vs real data. No lock is full proof. They all can defeat and if you look at the facts they do just that on occasion.

STR
 
If you are cutting and the blade binds in the material you will apply force opposite the force you applied when cutting in order to extract the blade from the material.
 
I always perform the test hard too. Don't care what other people think. I had a high end prod. folder close up on my wife's fingers a few yrs. back when she was cutting insulation from an old refrigerator door. When she was using the knife she hit the spine of the knife on the bottom of the door when when she was using it, and the friggin thing failed and sliced open her fingers. Not wicked bad but bad enough as to where I do all the cutting when it comes to using my folders now. Well at least I open and close them for her put it that way. I don't want any of the liner moving at all when I am using them either. So if the spine whack test is not for folks don't do it. I for one will do it and if a knife fails it I send it back. I also hit the blade out near the point and not back by the handle. It puts more stress on the knife so if it is going to fail I want to know about it. I have had plenty of times when the blade will get bound up a bit and don't want any surprises when trying to free it, as in wiggling back and forth or up and down like it is wedged in. Anyways I perform and live by it. keepem sharp
 
I am against whacking the spine at all, it puts unnecessary stress on the locking mechanism, which may lead to failures down the line. On liner locks, I usually push the top of the spine of the blade to test for movement, that is usually good enough for me. Also, I pretty much do not buy production liner locks because I don't trust them, I had a couple benchmades that shut on my hand during hard use, however I have a few that are exceptions, MOD ATFK, Strider AR, are two that I have found to be very solid liner locks IMHO, especially the AR. I have a problem right now with a Marzitelli custom I traded for, if I push the tip of the spine, the blade moves on the lock, I am trying to come up with a remedy without sending it to the maker, maybe it needs to break in, it seems the lock slips on the tang, but I don't trust it right now, sux.
 
Hard H2O said:
If you are cutting and the blade binds in the material you will apply force opposite the force you applied when cutting in order to extract the blade from the material.
Click to expand...

this person speaks the truth.




if I get a knife that is new to me, and I notice any kind of give or play in the locking mechanism... of course I'm going to check it... wtf not?
if a knife can't handle a spine WHACK test, it is a POS lol
 
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