Are Folders Locking Mechanisms Safe?

I have 4 spydercos right now, A delica, Endura, Tasman salt, and a rescue. All have the same Boyd dent lock back. Never heard of how strong these are?? They seem rock solid! Love the lock back!
 
Bonescraper said:
I have 4 spydercos right now, A delica, Endura, Tasman salt, and a rescue. All have the same Boyd dent lock back. Never heard of how strong these are?? They seem rock solid! Love the lock back!
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If they are done correctly they are very strong. :thumbup:
 
Josh K said:
I believe that means an additional 100lbs per inch. The blade is 4". ;)
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Actually the longer the blade, the more pressure on the lock face. So 100lbs of force on the tip of a 2" blade produces 200lbs-inch of torque on the pivot.

100lbs on a 4" blade produces 400lbs-inch of torque on the pivot.

Either way buy a knife suited to the task, if you are cutting into objects that can cause the blade to jam and put pressure on the spine, get a beefier lock, Strider, CRK, Spyderco, Benchmade, Kershaw with a solid lock. For simple things a slipjoint is fine.

The right tool for the job. No knife is meant to be intentionally closed when locked. That produces cuts on 1st knuckles to the bone and such...

RAO or someone has a tank of a folder, Noss4 likes it, you can't hurt it.
 
In general you should always be prepared for the lock to fail. Not that I've never done something that relies on the lock, it's just something to be aware of.
No matter the mechanism, you will find a faulty one eventually (you just might be unfortunate enough to buy the first ever defective Sebenza:eek:).

As far as measuring lock reliability by strength ratings, that's a little silly. Relatively small forces applied in the right way can get a lock to fail. Even one rated to resist hundreds of pounds of force.
When testing locks I primarily use static load, and a few very very light spine whacks on a soft-ish surface.
I must stress that a hard spine whack will only wear out your lock. I pretty much destroyed a Spyderco Chinook III that way, and that's one of the toughest locks you'll ever come across.
 
Josh K said:
It really depends on the model. Spyderco's Military knife has a liner lock engineered to hold over 100lbs per inch of blade.
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This makes no sense to me. You're saying per inch of blade, so as per your reply further below, 4 inches on the Military, means it holds 400 pounds. By that assumption, you would say a 10 inch blade holds 1000 pounds. This makes no sense because if you consider basic physics, the blade acts as a lever arm. The longer the lever arm, the easier it is to push. Think of a seesaw. If you sit close to the fulcrum on a seesaw, you can't move the person on the opposite end if he sits further away from the fulcrum.

Are you sure it's not 100 pounds "per square inch" ? PSI rating makes more sense. IF it's a PSI rating of 100 pounds, than if you add 100 pounds of pressure in an area on the blade that's 1 inch long (regardless of where on the Military blade that one inch is (front, back, middle, whatever), the lock will fail.
 
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harkamus said:
This makes no sense to me. You're saying per inch of blade, so as per your reply further below, 4 inches on the Military, means it holds 400 pounds. By that assumption, you would say a 10 inch blade holds 1000 pounds. This makes no sense because if you consider basic physics, the blade acts as a lever arm. The longer the lever arm, the easier it is to push. Think of a seesaw. If you sit close to the fulcrum on a seesaw, you can't move the person on the opposite end if he sits further away from the fulcrum.

Are you sure it's not 100 pounds "per square inch" ? PSI rating makes more sense. IF it's a PSI rating of 100 pounds, than if you add 100 pounds of pressure in an area on the blade that's 1 inch long (regardless of where on the Military blade that one inch is (front, back, middle, whatever), the lock will fail.
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I had problems getting this issue down as to the Spyderco thing. Sal has a machine and I assume they lock the blade so the various knives pivot at the same spot.

It is lbs in. per inch of blade; 100 lbs in. per inch of blade length. So, a 4 inch blade is 400 lbs inch of torque = about 33 foot pounds.

I think that is right - it is confusing, but the numbers are in inches and we are used to feet.

As to spine wacking, the energy needs to take into account the kinetic energy (for simplicity) or you can have fun with "jerk" calculations. It is easy to put 100 pounds of force on a lock by overdoing a simple spine wack test.

If we move to pressure, i.e. PSI, it can get pretty high due to the small areas involved.

Spine wack tests should be for reliability, not strength, if you want a knife to last a good time.
 
I personally keep moving towards frame-locks for added safety. They aren't foolproof either, but I find a good titanium frame-lock is solid enough for me to feel comfortable stabbing stuff(not that there's a need to often).
 
100eyes said:
I personally keep moving towards frame-locks for added safety. They aren't foolproof either, but I find a good titanium frame-lock is solid enough for me to feel comfortable stabbing stuff(not that there's a need to often).
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Is a frame lock different than a liner lock or a lock back? Sorry for the questions but I'm learning here.

Bill
 
harkamus said:
This makes no sense to me. You're saying per inch of blade, so as per your reply further below, 4 inches on the Military, means it holds 400 pounds. By that assumption, you would say a 10 inch blade holds 1000 pounds. This makes no sense because if you consider basic physics, the blade acts as a lever arm. The longer the lever arm, the easier it is to push. Think of a seesaw. If you sit close to the fulcrum on a seesaw, you can't move the person on the opposite end if he sits further away from the fulcrum.

Are you sure it's not 100 pounds "per square inch" ? PSI rating makes more sense. IF it's a PSI rating of 100 pounds, than if you add 100 pounds of pressure in an area on the blade that's 1 inch long (regardless of where on the Military blade that one inch is (front, back, middle, whatever), the lock will fail.
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So yes, if Spyderco made a liner lock with a 10" blade, and rated it "hard use" it would hold 100lbs on the end of that, which is 1000lbs.

I understand physics, I'm just quoting Sal as I recall.

Point was that well made locks from reputable companies aren't prone to failing.
 
In theory, yes, they are safe.

In practice, there are many things that can cause a lock to fail, such as dirt, debris, and wear, as well as faults in the manufacturing process or design.

You should never assume that a lock is 100% safe. If you need a 100% guarantee, get a fixed blade.

The folders I carry are Spyderco and CRK. IMO they have the best locking mechanisms in the business, engineered to perfection.
 
I think a decent answer to your question is that, yes, folder locks are safe but, no, they aren't foolproof. Any can do the job and any can fail under extreme circumstances.
 
Knife Outlet said:
I think a decent answer to your question is that, yes, folder locks are safe but, no, they aren't foolproof. Any can do the job and any can fail under extreme circumstances.
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The thing about it is I just didn't think I was appling that much pressure, especially enough to cause the lock to fail. It may have been a accumulative reaction to the kife being used in a manner it was not designed for. Once or twice no problem, but over and over... failure. I now wish I wouldn't have thrown the knife out, but I did.

Thank You everyone for your responses. Hearing what people think and how they feel about their locks on their knifes is interesting.

Bill
 
harkamus said:
This makes no sense to me. You're saying per inch of blade, so as per your reply further below, 4 inches on the Military, means it holds 400 pounds.
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There is a lot of confusion over this. The "100 lbs per inch of blade length" is intended to mean that a knife that is held at the fulcrum (pivot) and has a 1" blade can support 100 pounds being applied at the tip of the blade before the lock fails. The same knife with a 4" blade would not support 400 lbs, but rather 25 lbs. at its tip. Here is some information about lock strength posted by Sal a while back:

There is no governing body that sets rating. Spyderco employs our own in-house rating system in the construction of our designs. We set the desired standard when we design the model and build to that standard. We test (break) the models in development and continue to test (break) the models to ensure that our standards have not changed.

In-house Lock strength standards
Light Duty = over 25 inch/lbs of lock strength per inch of blade length
Medium Duty = over 50 inch/lbs per inch of blade length
Heavy Duty = over 100 inch/lbs per inch of blade length.
Very Heavy Duty (MBC) = over 200 inch/lbs of lock strength per inch of blade length.
We also have our standards for G-10 (ours is custom made), blade strength, and other general safety issues.

Basically, the FRN pieces will be Medium and heavy. SS pieces are ususally in the heavy duty range. The Very heavy duty will be pieces ike the Gunting, Yojimbo, Chinook, Manix, Lil Temperance, etc.

Light duty pieces will be the smaller pieces, Kiwi, Ladybug,etc.

Also note during testing, the locks aren't simply "releasing", but instead something actually breaks:

On the break, defeat is not acceptable.

If a part bends or breaks which causes the defeat, we will generally improve the failed part (re-engineer or different material).

We like to apply force until something actually breaks.

And just something I found interesting:

For your own info, we have tested many "fighting" knives made by competitors with lock strengths that fall into our medium and light duty useage. Some of the "so called" hard use, tougher than tough, etc. knives don't even make our heavy duty rating. IMO, don't believe all of the advertising you read.
 
Hitthespot said:
Is a frame lock different than a liner lock or a lock back? Sorry for the questions but I'm learning here.

Bill
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Yup, they're all different. Here are some examples; frame lock, liner lock, lock back.

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Frame locks and liner locks are similar, but I've found frame locks are typically much safer due to the fact that your hand grip is holding the lock in place.
 
100eyes said:
Yup, they're all different. Here are some examples; frame lock, liner lock, lock back.

Frame locks and liner locks are similar, but I've found frame locks are typically much safer due to the fact that your hand grip is holding the lock in place.
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OK, I see the difference. That was easy. A picture is worth a thousand words!

Thank you very much 100eyes.

Bill
 
Any lock can fail. The probability of a lock failing is minimized by how the lock is manufactured. A lock needs to be manufactured well! That is the most important. If you do not trust locks. Buy a small fixed blade.
 
This is one of the many reasons that I prefer fixed blade knives. However, I carry folders more often for "sociological" reasons. I agree with those who have opined that the type of lock is less important than the quality of the materials and workmanship. I also agree that proper maintenance (including cleaning) is essential to keep any tool in reliable condition. That said, any mechanical system will fail if you push it hard enough. Have to carry a folder? Don't make the mistake of buying "bargain" tools. Get the best knife you can, and respect its limitations.
 
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To me the lock on a knife is sort of like a safety belt in a car. I use my knives carefully.
I could probably get by with a slip joint. I often do :D
 
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