Knife locks: Strength, Reliability and Spine Whack tests

[Alberto Salas]

Hi guys!

A few months ago we had a "war" about the "Spine Whack" test, we had quite a few threads about it, some of them went very bad!
Reading some of them, I started to wonder some things about lock strength and lock reliability. I didn't post them then afraid of increase the hostilities.

Well, is a new year now, and I still have some thoughts and doubts about locks, let's see if I can make myself clear with my poor English:

First, please don't turn this thread a war about how stupid the Spine Whack test is, or how good it is, this thread is not about that.

O.K. let's start:
Is not the same strength and reliability, pretty obvious, but very easy to forget. If the knife is strong, it will not close unless a huge amount of force makes it fail; if the knife is reliable, it will not close until the user removes the lock (aside of an accident).

The lock in a knife can BE unreliable if it was badly made: soft materials, loose parts, bad finish, etc. In most cases, it cannot be fixed.
Or it can BECAME unreliable by normal use: dirt, loose screws, wear, etc. In most cases, it can be easily fixed.

On the other hand, a knife can BE strong if it was made strong: good materials, thick parts, etc. You can't make a knife stronger once you buy it, and definitely, a thick strong knife is not a sign of a reliable knife (if anybody can post the pics of that infamous Dark Ops folder will be great! )

I think that a reliable lock should not fail: if the lock slips and let's the blade close, the knife is not weak, is unreliable. A truly reliable lock should break before let the blade close, a light knife, will break with relative easy, a big knife will need brute force to fail, but the reliable lock will die before give up!

Finally, if all that's true, the "Spine Whack" can be seen in two ways:

1. A light Spine Whack can help to CHECK the reliability of the lock under SOME circumstances, but NOT to prove it.
2. A strong Spine Whack can PROVE the strength of the knife. But, like the other case, will NOT prove its reliability.

What do you think?


BETO
====================
Sorry for my english

 

[billstevens]

I don't personally like spine whack tests. But if you feel you need to test it like that then I suppose it is a valid test. Although regular cutting shouldn't test the lock in the manner a spine whack does.

 

[markksr]

I think that lock failure in quality knives is not nearly as common as internet forums would have you believe...

 

[SIFU1A]

i think spine whacks should be called spine taps, ya dont have to hit it hard to see if the lock is locking properly, a lite tap will show ya all ya need to know imho.

heavy whacking is just too hard on the knife imho and is needless anyway.

i dont think failure, even in a cheap gerber folder is as common as a few yrs ago.

 

[MORIMOTOM]

after all those threads, i gave all my folders a few spine taps.

i didnt have any failures. emersons, crk, and a few customs. fwiw.

 

[yoda4561]

Yeah you know, I had my doubts until I tested my mini-socom after numerous reports of failure at microtech's old forums. For whatever reason their leaf/linerlocks would fail under a very light spine whack, like almost as light as the weight of the knife itself dropping 6 inches onto a hard surface. After about half a dozen of those it never failed again, IIRC most others had the same experience.

 

[biogon]

I think that lock failure in quality knives is not nearly as common as internet forums would have you believe...

In my experience it is more common than the internet forums would have me believe.

I've had at 3 custom folders that fail 100% of the time on just a spine push of an index finger. Two had 0.080" liners. One had a 0.060" liner.

I've had 1 custom framelock fail 100% on a light whippy spine tap.

I've had any number of production linerlocks fail.

The problem is that the vast majority of people never have a chance to use a linerlock in a situation that causes the failure mode. Most people cut using the edge and don't accidentally hit the spine on something.

-j

 

[Guinness70]

what real live situation does a spine wack reproduce?

i test by locking the blade and then try to close it without dissengaging the lock.
the only one to fail (so far) was a homeij linerlock with a flimsy locking liner about 0,5mm thick.
i could see it bend
..clear fingers...
FOUUUUUUR
failure...

even this test is not really gonna happen in real live.
since you will be applying pressure in the exact opposite direction while cutting.

 

[biogon]

what real live situation does a spine wack reproduce?
since you will be applying pressure in the exact opposite direction while cutting.

I have 3 situations where locks failed on me in real use.

1) I was cutting 4-ply cardboard and the blade gets wedged in there, stuck good. I wiggle the handle up and down to get loose. Lock fails.

2) I was cutting in the kitchen and when I put the knife down, I accidentally hit it on the open microwave door. Lock fails.

3) I was cutting out drywall in a crawl space and when I'm backing out, hunched over, I tap the blade on the wall. Lock fails.

-j

 

[udtjim]

In 45 years or more of using folders, I have never had a lock fail on any folder Not cheap ones , Not high dollar ones. Also the type of lock has made no difference that I could ever see. Do I do Whack tests? Hell no.

 

[bearcut]

I have 3 situations where locks failed on me in real use.

1) I was cutting 4-ply cardboard and the blade gets wedged in there, stuck good. I wiggle the handle up and down to get loose. Lock fails.

2) I was cutting in the kitchen and when I put the knife down, I accidentally hit it on the open microwave door. Lock fails.

3) I was cutting out drywall in a crawl space and when I'm backing out, hunched over, I tap the blade on the wall. Lock fails.

-j

Take this mans knife away from him before he hurts himself.

 

[biogon]

Ahh, I love spine whack test threads because it brings out all the folks I have to put on my ignore list.

-j

 

[bearcut]

Good one!

But seriously, have you considered a fixed blade?

 

[Halfneck]

After 100 full strength whacks I got my Spyderco Wenger Jr. to fail. Lock does not engage real well now, guess I'll send it in due to this design flaw.

 

[bearcut]

Of course you realise you just got put on the 'ignore list'.....

 

[Architect]

A "spine whack" test is one way to induce lock failer. Unlike the fellow above, I can't remember a single time when I "whacked" the blade and induced lock failure in a real life situation.

Another way, and one that is more realistic for me is a "wiggle" test. This is just a simple, low force approach where I use my left hand to wiggle the blade while holding the frame in the right hand. This test works really well on liner locks. This test is particularly good for testing when a knife will fail when cutting thick cardboard or other fibrous materials that can "grab" the blade. When you try to free the blade, usually by pulling "up and out" you get a "wiggle" on the blade that has a tendency to loosen a liner-lock.

When it comes to liner locks, there are a number of problematic issue such as gunk collecting in between the scale/frame and the lock and detent "drag-out" and "catch-in" that are a much bigger deal to me from an overall performance perspective than lock failure.

I think lock failure on most higher-quality knives is going to be much less of an issue than day-to-day performance on ease of opening and closing, cleaning and clip issues.

 

[cutter17]

I'm with SIFU...............spine tap should be the name and the method.:thumbup:

 

[orca8589]

Interesting tests. I don't see the need for a 'spine whack test' on my knives, but if others like having that kind of information, that's fine.

I personally stay away from the flame wars. There are so many variables in knife use, that it's impossible to apply every result learned, to everyone else's situation. That's why I always thought the Cold Steel "Our lock holds 130 lbs.!" advertising was so silly . I've never had a Buck 110, or any of it's clones, fail, and I've done some full-on gonzo crazy stuff with knives in my younger days. Now, I look at the need, and that's how I decide what to buy.

Like I said, no offense to you folks who like having the 'spine-whack' info, I just don't feel the need for it. If the knife holds an edge well, and locks up tight, it'll do what I need to get done.

thx - cpr

edited to add: please don't start posting about the pros/cons of CS products and/or tests. I don't want to turn this into another CS bashing thread.

 

[Unbreakable]

Lock failure is why I went to fixed blades instead of folders. Doesn't matter how tough a folder is... a two piece knife is still a two piece knife. I've never had a lock fail on me... but I know they can.

 

[cutlerylover]

In 45 years or more of using folders, I have never had a lock fail on any folder Not cheap ones , Not high dollar ones. Also the type of lock has made no difference that I could ever see. Do I do Whack tests? Hell no.

Same here...From $10 knives to $400 knives...Maybe we are just lcuky, lol...but never had one fail on me ever, while usign it or playign with one...