Cliff, try my slip joint test its clearly more relevant than your Potato, or can in the bag theory. Now if you somehow clamp your grip directly on the frame lock and have all your pressure pushing on the lock bar holding it closed you may have a point, in theory. But holding a knife for using it you just will not prevent the lock from moving the little it moves to fail. All the pressure of your grip is not on the lockbar its self. Therefore the hand reinforceing the frame lock is just a false idea. Like Ive said in this thread before try and prevent a slipjoint from closing by reinforceing the spring with your big strong hands, it isnt going to work.
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Framelock strength question
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Cliff Stamp
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db said:
This changes the compressability dynamic and brings torque into the equation. You are also placing your hand in a completely different position, when using a Integral your tips of your fingers are braced against the bar, this allows for maximal applciation of force, against the bar on a slipjoint it is th fleshy part of your hand which is *much* more compressable as it is just solid flesh.
But even if you invert your grip and stick your fingers or use your thumg, you are still dealing with a different senario because as the bar raises the pressure changes dramatically under the *same* force as the surface area changes, this allows continued compression, which doesn't happen for integrals because the sufrace area is constant. Nor does it happen with liners - which is why you can white knuckle them open.
Pff, Dynometers used to measure grip strength are calibrated in Kg. It is common to use masses to put forces into perspective with the knowledge that the force is just the gravitional weight, similar to how you can refer to long distances in terms of time.
-Cliff
Nice try Cliff. Are you now saying skin does compress? what happened to the potato idea? Is there no tork involved when a frame lock fails. I've backed up my point and you are doing nothing but nit picking and now making up foolish arguemints. I'm done trying to reason with you. believe what you want, but your hand reinforceing theory is wrong and if it wasn't a slip joint would be a fixed blade.
Edit..
Also if I modify my grip I can press on a liner lock holding it locked. So big deal.
Edit..
Also if I modify my grip I can press on a liner lock holding it locked. So big deal.
I can see what both Cliff and db are saying.
But the real problem with a frame-lock or liner-lock failing is NOT whether the hand reinforces the lock enough to prevent the failure, it's the fact that the blade-tang and lock geometry is not correct in the first place for the lock to fail.
Liner-locks and frame-locks that work reliably over many years of useage are not easy to create.
So why not buy a knife with a better lock like the Axis-lock, Arc-lock, or Balisong latch-lock? Or even the old lock-back?
Allen.
But the real problem with a frame-lock or liner-lock failing is NOT whether the hand reinforces the lock enough to prevent the failure, it's the fact that the blade-tang and lock geometry is not correct in the first place for the lock to fail.
Liner-locks and frame-locks that work reliably over many years of useage are not easy to create.
So why not buy a knife with a better lock like the Axis-lock, Arc-lock, or Balisong latch-lock? Or even the old lock-back?
Allen.
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Here's what Sal had to say about various locks. Obviously he may know a thing or two so people would do well to take heed of his opinions relative lock integrities and strengths and weaknesses.
"Linerlocks are very difficult to make reliable and long lasting. Spyderco has had the advantage of having a number of bright people (Michael Walker, Bob Terzuola, Vince Ford & Spyderco R&D) help to refine our linerlocks over a 15 year period. We also test each one more than once in the mfg & QC process.
The advantages of a linerlock are convenient unlocking and that it will fit into almost any pattern. As a Chris Reeve style Integral Linerlock, it also permits a very thin knife with very few parts.
The disadvantages are; they are very difficult to make consistently reliable, they have limited lock strength, material selection for blade and lock interface as well as interface angles are all critical to function and wear.
The Axis lock is reliable and strong. It's been around for 15 years so it has time to be refined. Like just about all locks, they are subject to debris obstruction and spring failure. It requires dual liners which is not always desirable. It has quite a few parts.
So, there you have an opinion from one who should know just a tad more than the rest of us on the subject. I added this even though he doesn't mention framelocks as the design parameters of the mating surfaces are similiar and therefor subject to the same issues within cetain boundaries.
Brownie
"Linerlocks are very difficult to make reliable and long lasting. Spyderco has had the advantage of having a number of bright people (Michael Walker, Bob Terzuola, Vince Ford & Spyderco R&D) help to refine our linerlocks over a 15 year period. We also test each one more than once in the mfg & QC process.
The advantages of a linerlock are convenient unlocking and that it will fit into almost any pattern. As a Chris Reeve style Integral Linerlock, it also permits a very thin knife with very few parts.
The disadvantages are; they are very difficult to make consistently reliable, they have limited lock strength, material selection for blade and lock interface as well as interface angles are all critical to function and wear.
The Axis lock is reliable and strong. It's been around for 15 years so it has time to be refined. Like just about all locks, they are subject to debris obstruction and spring failure. It requires dual liners which is not always desirable. It has quite a few parts.
So, there you have an opinion from one who should know just a tad more than the rest of us on the subject. I added this even though he doesn't mention framelocks as the design parameters of the mating surfaces are similiar and therefor subject to the same issues within cetain boundaries.
Brownie
Cliff Stamp
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db said:
Yes, read the above posts. Your skin readily compresses until light loads, and then stops compressing allowing the application of heavier forces. If this wasn't the case you could not actually depress a back lock.
When you apply force to a frame lock you are directly opposing the force on the lock, thus there is little torque, the main issue is simply a force balance.
If however you try to stop a slip joint from closing by apply a force to the blade and one to the back spring, the torque would mean that the force on the backspring could be at a leverage advantage of about a factor of ten. This is a rather large effect obviously.
Anyway, concerning your idea about slip joints and lock backs, I took a Gerber Gator and using my index finger and thumb pinched the tip of the lock release behind the blade tightly. I then had several friends try to depress the lock, they either could not or found it massively more difficult.
This would be trivial to show using weights on the lock release to show that the release force was greater when I applied force to the top of the lock bar. The same would hold for a slip joint if you applied heavy resistance to the backspring.
If you really can't see the physics involved is no different than actually depressing the lock bar, I could video this and put it on line. I have a few other vids I should be putting up in a month or so, depending on when various knives get here and when I get around to doing certain things with them.
Can you change your grip to reinforce a liner lock, sure, however naturally when your grip tightens on a liner in normal using grips, it acts to unlock it, thus the "white knuckle test", on a integral it acts to inforce it. If it could not do one, it could not do the other as both are the exact same dynamic and it is *much* easier to reinforce an integral as you can apply force directly to the bar, whereas with a liner it is indirect across the top, and thus you are just getting a side effect of a shear.
-Cliff
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allenC said:
Usually because you can't get the blade / steel / handle, etc. that you want. I would greatly prefer back locks over liners and integrals, some people don't like back locks however as they find them problematic in white knuckle grips, it takes a really artificial grip for me to see failure though with that type of lock, so much so I don't see it as a practical limitation.
-Cliff
AllenC.. Very true, I totally agree with your post.
Brownie Its just my opinion on the hand reinforcing locks is wrong. Id say sure a hand can if you modify your grip in some way but this can be done with any style lock, no matter what one it is. I surely dont know as much as Sal about locks and dont even want to pretend that I do.
Cliff That lock back test of yours seems meaningless to me, your finger vs. your friends finger, big deal. The little bit a frame lock needs to move to start to fail and the little bit of give in the flesh of your hand =bad news. My point if you would have cared enough to read through out this thread is your hand does not reinforce a frame lock. Sure you can try to reinforce the lock by using some sort of abnormal grip but this can be done with any style lock, and I personally dont think it is very effective. Sure it may help some little bit but holding the knife safely and cutting more carefully would be a better choice. Depending on flesh to hold a lock in place witch may work, or most. likely not work is just a very bad idea, and I personally would not premote or suggest its a benifit.
Brownie Its just my opinion on the hand reinforcing locks is wrong. Id say sure a hand can if you modify your grip in some way but this can be done with any style lock, no matter what one it is. I surely dont know as much as Sal about locks and dont even want to pretend that I do.
Cliff That lock back test of yours seems meaningless to me, your finger vs. your friends finger, big deal. The little bit a frame lock needs to move to start to fail and the little bit of give in the flesh of your hand =bad news. My point if you would have cared enough to read through out this thread is your hand does not reinforce a frame lock. Sure you can try to reinforce the lock by using some sort of abnormal grip but this can be done with any style lock, and I personally dont think it is very effective. Sure it may help some little bit but holding the knife safely and cutting more carefully would be a better choice. Depending on flesh to hold a lock in place witch may work, or most. likely not work is just a very bad idea, and I personally would not premote or suggest its a benifit.
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db, I wasn't disputing your position at all sir. In fact, I think you are on the right path.
My view relative the subject here is that with a framelock, I may "feel" the lock starting to move [ disengage ] in use [ and stop whatever I'm doing to cause that ] if the action/cutting is not too fast, where there will be no feel when a linerlock starts to release unintentionally.
The framelock may give you a little time to stop what you are doing before it releases completely. I trust the framelocks to a certain extent, but no matter who makes a alinerlock, I will not trust them for SD, and thats just my own views and I realize others will and do disagree.
I don't see the hand stopping a framelock from disengaging myself but I would also not rule out that possibility as feasable, just unlikely and again not something I'll trust to keep my fingers from suffering damage.
Brownie
My view relative the subject here is that with a framelock, I may "feel" the lock starting to move [ disengage ] in use [ and stop whatever I'm doing to cause that ] if the action/cutting is not too fast, where there will be no feel when a linerlock starts to release unintentionally.
The framelock may give you a little time to stop what you are doing before it releases completely. I trust the framelocks to a certain extent, but no matter who makes a alinerlock, I will not trust them for SD, and thats just my own views and I realize others will and do disagree.
I don't see the hand stopping a framelock from disengaging myself but I would also not rule out that possibility as feasable, just unlikely and again not something I'll trust to keep my fingers from suffering damage.
Brownie
Cliff Stamp
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Db, you are the one who suggested the lock back test. Yes in a normal grip you apply little force to a lock back spring and thus can't enforce the lock - which is why no one has ever argued for grip enforcement for that style of lock. However with an Integral the forces applied in normal grips do act to directly support the lock, and in such cases the lock is made more stable, because once a decent amount of force is applied the flesh isn't compressible further, as noted with the lock back pinch.
I finally got a slip joint this weekend and was readily able to prevent the blade from releasing by applying force to the backspring with my thumb. I used a swing-joint like on a straight razor to eliminate the torque consideration and it was trivial to show that the blade could be held rigid in a normal cutting grip (fingers curled around the handle, thumb along top).
When gripping an integral, your fingers naturally curl against the lock bar in a normal grip, and this is in your hands position for application of maximal force, in excess of the pinch grip strength I used on the lock bar or swing-lock many times to one. Thus the potential for enforcement is actually far greater for the integral. The natural grip on a liner goes the opposite which is why they are much more prone to white knuckle failure than Integrals.
-Cliff
db said:
I finally got a slip joint this weekend and was readily able to prevent the blade from releasing by applying force to the backspring with my thumb. I used a swing-joint like on a straight razor to eliminate the torque consideration and it was trivial to show that the blade could be held rigid in a normal cutting grip (fingers curled around the handle, thumb along top).
When gripping an integral, your fingers naturally curl against the lock bar in a normal grip, and this is in your hands position for application of maximal force, in excess of the pinch grip strength I used on the lock bar or swing-lock many times to one. Thus the potential for enforcement is actually far greater for the integral. The natural grip on a liner goes the opposite which is why they are much more prone to white knuckle failure than Integrals.
-Cliff
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I'll tell you my pet theory. It's just a theory because I haven't even thought out the mechanics to see if it makes any real sense -- it's just the best theory that fits my lock-testing experience.
The most important observation is about spine whack failures. I see far more failures with a light to medium whippy snap than with a hard hammer blow. The whippy snap is my secret to getting locks to fail that the owner claims he'd already tested and don't fail.
What that tells me is that it's not the spine force that's critical (although on some very bad locks, spine force is all it takes), but how fast that force is dumped into the blade & lock. If the force dumps fast enough, it somehow gets ahead of the coefficient of friction and the lock starts moving, after which the lockup is doomed.
Now, once the lock is moving, I don't need to now stop the lock by taking 100% of the force on my hand -- which is why I think hand strength isn't the critical issue here. All I have to do is absorb enough force, for the tiniest fraction of a second, that the lock sees a slower-moving force, the lock takes care of the rest. Or, in other words, I don't feel it takes a ton of hand reinforcement on a frame lock to defeat a spine whack test.
Like I said, I don't know if that makes sense, but it fits my results better than anything else. Note it's not easy to find framelocks that fail the spine whack in the first place, and sometimes it just fails once and then never again, so I haven't had the luxury of testing over and over with and without finger pressure on the lock.
A frame lock is theoretically susceptible to whatever a liner lock is. It pretty much removes the white knuckling problem, and greatly reduces the spine whack problem, but introduces a counterclockwise torquing problem due to the finger engagement with the lock itself.
The most important observation is about spine whack failures. I see far more failures with a light to medium whippy snap than with a hard hammer blow. The whippy snap is my secret to getting locks to fail that the owner claims he'd already tested and don't fail.
What that tells me is that it's not the spine force that's critical (although on some very bad locks, spine force is all it takes), but how fast that force is dumped into the blade & lock. If the force dumps fast enough, it somehow gets ahead of the coefficient of friction and the lock starts moving, after which the lockup is doomed.
Now, once the lock is moving, I don't need to now stop the lock by taking 100% of the force on my hand -- which is why I think hand strength isn't the critical issue here. All I have to do is absorb enough force, for the tiniest fraction of a second, that the lock sees a slower-moving force, the lock takes care of the rest. Or, in other words, I don't feel it takes a ton of hand reinforcement on a frame lock to defeat a spine whack test.
Like I said, I don't know if that makes sense, but it fits my results better than anything else. Note it's not easy to find framelocks that fail the spine whack in the first place, and sometimes it just fails once and then never again, so I haven't had the luxury of testing over and over with and without finger pressure on the lock.
A frame lock is theoretically susceptible to whatever a liner lock is. It pretty much removes the white knuckling problem, and greatly reduces the spine whack problem, but introduces a counterclockwise torquing problem due to the finger engagement with the lock itself.
