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Grip stability vs ergonomics + misc.

Cliff Stamp

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Joe Talmadge :

I'm not sure what you mean by stable grip -- do you mean a secure grip?

Yes.

a highly-secure handle that is not comfortable for hard use means blisters and pain that I'd rather not have in my hands.

Nor would I. But hard use to me is not extended use. It is more low volume high stress work. If the force you are using is rather low then grip security becomes less of an issue as well of course so does the lock's strength and security.

Although in the case of the Strider, for me, the grip wasn't even that secure.

That would be a problem then as if it neither secure nor ergonomic then it is not of much use for any type of work.

Mike :

Cliff's claim above about the Busse folder is preposterous.

Jerry is making a folder, based on what I know of him as a knifemaker (his commitment to quality etc.), the abiities of his knives which I have seen from direct use and the discussions I have had with him about the folder to make sure I understood the intended goal - I am confident in the abilities it will have. I would have (and in fact did) make similar statements about the Basic before using them and before they were even out. Could I be wrong, of course. It is obviously possible that the Busse Combat folder will be both weak and insecure, I just don't think it is a very likely one.

John, concerning the stabs, unless the stab is directly inline with the center line of the thrust the lock will take a very sudden hard thrust trying to fail it. This force can be in any possible direction, one of which is straight down across the back of the blade. How much force obviously depends on how hard you can stab something.

You also talked about whittling and how that can cause bent liners or bent axis/rolling locks.

I said that it is possible during cutting for a force to act against the blade so as to close it and described several ways that this could happen. The question of is this enough force to fail a lock depends on if you are strong enough to do it. This is very easy to test. I would simply do full force one handed thrusts on the handle with the blade viced. If it held I would be confident that I am not strong enough to break the lock.

-Cliff
 
Cliff:
The force from a stab is distributed throughout many components of a folding knife; the stop pin, the pivot, and the lock. The chances of you putting enough pressure on the lock itself that it will break (not just fail) are basically zero. If you don't believe me get a nice reliable folder and go out and try it yourself, if you can do it we will all be more careful to make sure that our stabs are straight and true.

I said that it is possible during cutting for a force to act against the blade so as to close it and described several ways that this could happen.

Yet you still have not described this so called force that can do this. Please go on with this sentence and explain in more detail. And please don't use such absurd examples such as cutting rope or whittling wood.

This is very easy to test. I would simply do full force one handed thrusts on the handle with the blade viced. If it held I would be confident that I am not strong enough to break the lock.

You give me a test, yet you give no reason what good this test would do. How are you using you're knives that such use puts the force of "full one handed thrusts while the blade is immobilized"?

I remember one poster some time ago that viced his folders and hammered the handles, bending the liners. In real life, blades will not be immobilized, when you are holding onto a knife and such a sudden force is exerted, the knife will either fly out of your hand or your hand will be pushed away taking mostly all the shock. This is unless you are He-Man of course. His "test" was ridiculous, as is yours.

How many bent liners or sheared axis/rolling lock pins have you seen that were due to NORMAL USE, Cliff? This can even include abuse, as is it seems to be your inclination. Abuse is sometimes unavoidable in emergencies, and how a knife stands up to abuse can be important. Prying for example is abuse but how a knife handles prying can be important to some. So how are you using your knives that it causes locks to break Cliff? How many locks have you even HEARD of that have broken due to normal use?

While ultimate lock strength is a factor. And we all have a desirability towards stronger locks. To put this factor above mostly everything else is ludicrous.

-Johnny
 
John :

How are you using you're knives that such use puts the force of "full one handed thrusts while the blade is immobilized"?

That would be the upper limit of force I could exert while doing a cut.


when you are holding onto a knife and such a sudden force is exerted, the knife will either fly out of your hand or your hand will be pushed away taking mostly all the shock.

I think it was Sing who noted some time ago that after doing any heavy impacts or stresses on a folder that you should check to see if you can actually retain your grip on the folder as this sets the actual highest level of force the blade will ever see. This is fairly easy to test. And should be done by the individual as this could easily make high stresses on the lock not possible - for them of course, it doesn't mean that it would not be a problem for someone else.

How many bent liners or sheared axis/rolling lock pins have you seen

I have never used an axis nor a rolling lock nor do I ever plan to buy one for reasons stated in the other thread. I have a couple of rolling lock folders coming but they are not mine and thus I will just be doing a light work if any with them. The liner locks I have rejected as unusable were because of unreliability and not low fail strength.

But then again I don't need to have failed a dozen locks to avoid using them in the first place. I started off using slip joint folders and after having twists such as described above close the knife I pretty much switched to fixed blades for serious dynamic work as when the twisting happens with them it is not a problem.

With the much stronger locks out there now there are quite probably a number of them that are strong enough to be able to take any accidental stresses during a cut. The strider folder for example was failed at 600-800 lbs at 2" from the pivot. Even if I cut that in half and am applying the force at 4" that is still well beyond my current ability to exert a force on the lock with one hand.

As another example, I tried in many ways to fail the lock on the Uluchet and it held up fine. I would be confident that would not break nor disengage during work including accidental twisting or high impacts.

Prying for example is abuse

Most folder blades will break fairly readily. They are usually like 1/8" with flat / hollow grinds. On a sideways pry the blade will snap under low strain. I have done this on a few low end blades, a couple of SAK's and a Sypderco Endura. It never came to me to do a straight pull on the lock but I don't pry like that anyway. Higher end folders will of course use better steels, but at that profile and simiar ones prying is more likely to damage the blade than the lock.

While ultimate lock strength is a factor. And we all have a desirability towards stronger locks. To put this factor above mostly everything else is ludicrous.

Yeah, which Joe Talmadge has been saying for quite some time. As he has noted, a lot of failures are from the locks simply disengaging not actually breaking. Reliability is probably more important than the failure limit as if the lock is not reliable then it will fail in normal use long before you ever get to see the benefits of the high failure point.

-Cliff
 
Disengauging is my greatest worry, and I have a couple of liner locks that I do not trust much more than a slip lock. A few are better and OK.

I've had a couple of old backlocks where the spring bar (? termanology) has have broken.

Its the the blades snapping, or buckling that most often finishes off my folders. The thin bladed ones anyway, but then I like them for cutting, and I've gone and overdone the prying when I've known better - laziness on my part by not bothering to get a better tool for the job.
 
The curious thing about liner locks (and most others) is that in terms of reliability they can be much worse than a simple slip joint. Most of the old slip joint folders I have (some 30+ years) are very stiff. Once they are open it takes a significant amount of force to close them. On the other hand, once most locks disengage there is little force necessary to close the blade.

About 2 years of so ago Joe Talmadge mentioned to me that he had heard reports of liner locks failing during use because of torquing disengaging the lock (low straing, cutting cardboard and the like). I tried this kind of thing and other like the spine whack test on some slip joints and they performed really well.

In terms of light blades, yes, that is another reason I would opt for something like the Strider (3/16") or the Busse Combat folder as I would be very surprised if it came out in less than 3/16" and 1/4" would not surprise me. The uluchet is 1/4" but is a folding hatchet/ulu not a knife.

You need to match the lock strength to the blade strength, on a fully flat ground folder with 1/8-1/16" stock with a full distal taper, how strong do you need the lock to be anyway as the blade will break readily. However when you go to 3/16"+ (or 1/8" with thick sabre grinds) you have a blade which is able to take considerable stress. See the recent post by Barry Jones on tests performed on one of his folders.

-Cliff


[This message has been edited by Cliff Stamp (edited 09-03-2000).]
 
I said:
The chances of you putting enough pressure on the lock itself that it will break (not just fail) are basically zero.

Since you did not comment on this I will assume that you agree.

I also said:
Yet you still have not described this so called force that can do this. Please go on with this sentence and explain in more detail. And please don't use such absurd examples such as cutting rope or whittling wood.

You also have not commented on this, I'll assume that you have no examples in which ultimate lock strength would be a concern.

I said:
How are you using you're knives that such use puts the force of "full one handed thrusts while the blade is immobilized"?

You replied:
How are you using you're knives that such use puts the force of "full one handed thrusts while the blade is immobilized"?

As I said, that is not the upper limit. The upper limit is a lot lower due to reasons I have already specified.

I asked how many bent liners or axis/rolling lock pins you have seen or broken yourself.

You replied:
I have never used an axis nor a rolling lock nor do I ever plan to buy one for reasons stated in the other thread. I have a couple of rolling lock folders coming but they are not mine and thus I will just be doing a light work if any with them. The liner locks I have rejected as unusable were because of unreliability and not low fail strength.

But then again I don't need to have failed a dozen locks to avoid using them in the first place. I started off using slip joint folders and after having twists such as described above close the knife I pretty much switched to fixed blades for serious dynamic work as when the twisting happens with them it is not a problem.

With the much stronger locks out there now there are quite probably a number of them that are strong enough to be able to take any accidental stresses during a cut. The strider folder for example was failed at 600-800 lbs at 2" from the pivot. Even if I cut that in half and am applying the force at 4" that is still well beyond my current ability to exert a force on the lock with one hand.

So basically you have seen and heard of ZERO.

I said:
While ultimate lock strength is a factor. And we all have a desirability towards stronger locks. To put this factor above mostly everything else is ludicrous.

you replied:
Yeah, which Joe Talmadge has been saying for quite some time. As he has noted, a lot of failures are from the locks simply disengaging not actually breaking. Reliability is probably more important than the failure limit as if the lock is not reliable then it will fail in normal use long before you ever get to see the benefits of the high failure point.

I guess this is your way of agreeing with me.

-Johnny

 
Ok I'm not real sure on all the details of this debate and what its about but there are a few things I can add.
John wanted an example of normal cutting use that would put pressure on the lock in a way that it would fail. I recently used a delica 98 to cut a a 3/4" peice of PVC pipe out of a ring of silicone sealer. The pipe was running from the inside of a barn outside to a faucet, and was going through a 2" hole in the sheet metal wall. The ring of sealer around the pipe was very thick and pliable, so in order to cut it i had to push the knife clear though and rock the handle up and down as I slowly turned the knife to follow the hole. That puts lots of closing strain on the blade because after it cut through, the silicone pushed back together closing around the back of the blade. So there was no room for it to move up, the handle moved down, and that levered the blade farther along the cut. I could really feel the knife flexing as I did this and think that it was getting close to the limit of the locks strength. Basically any type of cutting where you use a levering action to cut will put strain on the lock. Its most common when your cuting something that the back edge of the blade can get hung up on, like the silicone, or thick plastic, or a number of things.
Had the knife closed up on me, I don't know if it would have been because of a broken backspring, or a broken pin. But does that really matter? All the components of the knife are part of its overall strength. The locking mechanism requires force to be exerted and absorbed in different areas and directions in order to work. Downwards pressure is put on the spine of the blade and has to be transferred to something different. In the case of a lock back, the tooth on the backspring engages with the blade and is pulled out towards the point of the blade as pressure is exerted. The pin holding the backspring has to be able to withstand that force or the knife will close. As the blade is pushed down and the backspring is pulled forward, the tang of the blade works like a lever with the backspring and pushes against the pivot pin. If the pivot pin can't withstand that force, the knife will close. All components of the knife are parts of the lock.So if the pivot pin fails, the lock has failed.
Now, given the fact that I still carry lockbacks, it should be obvious that I do appreciate ergonomics over brute strength to a certain degree. The knife has to be able to hold up under daily use, without wearing out in a short period of time due to frequent strain on the lock that is close to its maximum tolerance. So the stronger the lock the less likely it is for my daily usage to test or strain the lock enough to cause excess wear and make it eventually fail. But I also want it to be convenient. If you ask me there are enough options out there that are strong enough, that you shouldn't carry a brick around that you can't stand holding on to,just because its strong. Instead you need to look at ergonomics and strength as a package and find the knife that you think delivers both adequate strength and good ergonimcs.

------------------
It'll feel better when it stops hurting.
 
PVC piping, those silican tubes, and other plastic stuff are tricky to cut. They do put excessive stresses all over the place and push ones confidence with any lock knife. I now prefer to use the SAK wood saw which gives me back the control.

Slip locks one treats with respect. Other locks give you confidence directly to how you preceive the overall build quality of the knife. Asking the question: do I have confidence that this knife/lock will take it?
Disengagement really throws one; it puts your heart into your mouth. The danger is that there is no warning. When it goes, it happens fast.

Liner locks when executed well are good. However, now that I own and have seen quite a few, the security varies wildly from excelent to a real liability.

I don't have first hand experience of the newer locks such as the rolling and axis, but have the impression that they have come about in answer to the short comings of the liner locks.

Liner locks merrits have been promoted so heavily that if anyone says a bad word about them they are likely to be flamed. I know there are some really good ones, such as the CR's, and a huge amount of people have invested heavily in them. But, in my book they are not the be all to end all. They may be more convenient for opening and closing, but for me they are no better than a well executed backlock.

Locks on folders have yet to challenge the fixed blade. The answer has not been found yet. I only wish that each new lock was not promoted as if it had, and that more adventurouse efforts were made in attempt to reach the fixed blade goal.

I think that the liner lock has had its day and its time to move on. The best executed of all the types of lock are very, very, good and a real asset. But, in use, people will do the oddest things with them and so if there is a fault with the system someone will find it.

It is rare to find a folder who's lock strength to blade strength to overall design is badly matched. But they are not a fixed blade.
 
Matt, I have experienced similar, but for me that is less of a problem that the accidental high unexpected stresses. When I am cutting material that is resisting strongly and the blade is binding I will go slow and carefully. I have used folders in the past that have "opened" up during this type of use, the Endura to be specific. But of course when you see the lock area growing a visible gap you realize that hey, you might want to stop what you are doing. Of course a stronger lock would solve the problem.

As Greenjacket noted there are other tools that work well on hard materials. I recently had to cut some frozen rubber tubing off of some copper pipe. I was using a SAK (Rusksack) and putting a lot of pressure on the lock as I was stabbing the point in, leaning on it to drive it through and using it like a can opener to cut through the tubing. After getting halfway through I switched to the wood saw and finished in seconds.

Locks on folders have yet to challenge the fixed blade.

Have you used a Uluchet yet? It has a very strong and secure lock (I have walked on it, done full powered chopping / prying) - but the tradeoff is that it does not open and close nearly as easily as common lock types. For me though I would much rather have strength and security rather than ease of opening and closeing on a heavy duty tool.

John :

The upper limit is a lot lower due to reasons I have already specified.

I would hope so, otherwise it would not be a sensible upper limit to use as the safety margin would be far to small. Usually I will go for 25% at a minimum and 50% or more if possible, depends on many things.

After thinking about this for awhile I think I would extend the handle with a bar so as to get about 25% more torque on the thrust. This would cover such effects as the extra force that can happen in high stress situations as well as to account for other things such as simple increases in strength over time. It is your hand though, you can test as low as you like.

-Cliff

[This message has been edited by Cliff Stamp (edited 09-05-2000).]
 
Some very good points.

Matt:
John wanted an example of normal cutting use that would put pressure on the lock in a way that it would fail.

I wanted an example that would make a liner lock or an axis/rolling lock fail. I did not include lock backs because many of those are not strong enough IMO. However, I did not just want an example that would merely make the lock fail, because there are many things people do that can cause that. I wanted an example that would cause a lock to break (bent liner, sheared/bent axis/rolling lock pin).

Cliff in an earlier thread was questioning all folders because they were not strong enough for heavy use. And said busse's upcoming folder would be suitable for what he considers heavy use. I'm not questioning this. I was merely asking what he would ever use a knife for that would cause the liner of a liner lock to bend or axis/rolling lock pins to shear.

-Johnny
 
Strength for the folder's type. The Uluchet is beefed up for its job, but it is not exactly a knife to have in your front pocket. The decision of what anyone is prepared to carry more often than not comes down to comfort and precieved job description. There are other tools for tougher specific tasks.

Here are two extreme cases that would put pressure on the best lockers:

Using the knife to chisel cut with a hammer. Some prying done at the same time!

Digging out arrow heads from the trunk of a tree. Stabbing, gouging and twisting to penetrate the wood.

Watching, I was waiting for the blades, or tip at least, to snap.

As I've said before, people will do remarkable things, and after wounder why their tools have broken. Obviously it was the tools fault.

Scientific testing by defenision is ruled by controls. People never stick to the rules. Subjective testing done well are just as valid. Most that one ask from tests is to show up any obviouse faults or shortcomings.

[This message has been edited by GREENJACKET (edited 09-07-2000).]
 
John :

Cliff in an earlier thread was questioning all folders because they were not strong enough for heavy use.

For me yes, with a few exceptions, like the MPF, Buck/Strider, Uluchet etc . .

I was merely asking what he would ever use a knife for that would cause the liner of a liner lock to bend or axis/rolling lock pins to shear.

Many of the folders have low tolerances, I remember Sal Glesser saying that they intended to use 600 in.lbs as a heavy use baseline but too many folders failed long before that, so they lowered it down to 450 in.lbs .

Considering the position of the piviot and the lengths of the handles on some of the larger folders you are looking at a lock that will break in the 100-150 lbs range. That is easily possible for a heavy exertion.

There have been a number of comments about what is physically possible and what is not in relation to the force to be exerted during cutting. I have to admit that in this regard I am somewhat skewed as a lot of the people I know that use knives on a regular basis for heavy work are fisherman, farmers, carpenters, and have grown up doing hard physical work for 8-12 hours (min) a day to make sure they could put food on the table. And on top of that they had to cut, and carry, enough wood to burn during the winter.

As an example, my father grew up farming and fishing, and at 12-13 he was doing a full share of work which would include hand lining 25+ lbs cod for hours at a time and carrying 100+ lbs sack of potatos collected in the drills. That was when he was a *kid*, and they all did that.

If you have not done hard physical work on a regular basis then maybe a couple of hundred pounds sounds like a lot, but in reality it is not even close to the limit of what is possible. I know lots of people that could easily do that without it approaching the max they could do.

As for not being able to hold on to a knife, in general your isometric strength is far in excess of your ability to actually lift. The last time I talked to copfish he said he wanted to move up from the #1 CoC which is rated at 140 lbs. Assuming that he is stronger that that, which is logical since he wants a harder gripper, and that his isometric strength is about 20% over that (which is the general increase); it is possible and likely that he can retain his grip at the 200 lbs level.

Greenjacket :

The Uluchet is beefed up for its job, but it is not exactly a knife to have in your front pocket.

There is on reason that you could not stick a 4-6" blade instead of the hatchet/ulu head. You would then have a folder that had tremendous strength and security but a much lower ease and speed of opening/closing. It would certainly fit my defination of a heavy use folder.

-Cliff
 
Um, your grip strength numbers are way off. I'm on the small side, and I have no significant trouble holding on to 300 lbs. I can't lift that much, but if it's already up, I can hold it. However, unless you use your folders as climbing pitons, you will be seeing impact forces, not pure loads. Especially in cases where comething goes wrong and the spine of the knife is making contact. Think you can catch 300 lbs dropped from, let's say, one foot? That's more along the lines of what is happening here.

--JB

------------------
e_utopia@hotmail.com
 
No I don't think I could stop 300 lbs even if I extended the contact range significantly because I can't hold onto 300 lbs in the first place. My grip would fail and my hand would simply open up.

I would estimate that about 275 lbs is the max at which I can retain a closed grip. Assuming I am at 100% which I currently am not since my right index finger knuckle is currently seriously strained.

Could I stop 275 lbs dropped from 1'? I don't know. I know however that in any case that my grip would not be the limiting factor however I do not think that there wouldn't be one. I would probably simply dislocate my shoulder if I attempted a sudden jerk.

That is what happened to my brother last summer when he was rock climbing without any gear. I think he was about 175 at the time and caught himself with one hand after a slip. His grip held, his shoulder didn't.


-Cliff
 
Cliff, you are right on the uluchet, but it wouldn't make the most aesthetically pleasing folder that people want today.

Its sometime since I was really fit. I think I'm typical of most and know it takes me two weeks of hurt to get fit again. It would take three months to get really fit under hard work - my wife would love it if I lost those lbs. Those who do physical work day in day out and have done for a lifetime are remarkably strong. The wirey type of bloke. Its embarrassing how bad most people are today in the richer nations.
Manual work does not pay well and a Battle Mistress would be way out of their league. Industrial tools and farm implements have to surfice. A fit person with stout tools have been doing the job for generations. When the Battle Mistress retails for less than $100, then we might see them in the fields.

So there is a place for tough folders. There are people with the strength to push the construction to the limit and give them a run on endurance. I count myself as someone just playing with knives, as I just do not work them long enough. I can afford to go up market and have found a few knives up to the job. The lower priced knives have improved no end, but their price is creeping up. Quality also varies widely.

If a folder markets itself as being tough, then it really needs to be. The locks on slim tapered bladed folders need only be tough enough. But those that want to compete with the butch fixed blades will be worked hard by fitter people than I. Unless of course they are priced beyond the range of those who could stretch their physical strength.

I say test them as hard as you like. There are those who can put stresses and strains on a knife that I couldn't think of how they counld do it.

Hope your hand gets better.
 
Cliff,

You talk about people lifting heavy things or how strong people are, but I do not see how this has any revelance. You still have not given me an example of how you would use a knife that would put anything close to the amount of pressure that would bend a liner from a liner lock. How are you using your knives that you break the locks? That is the basis of this discussion is it not?

Eutopia:
However, unless you use your folders as climbing pitons, you will be seeing impact forces, not pure loads.

I would have to agree completely.
 
Cutting hard toffee;
Cracking the pelvic bone of a young roe deer;
Chisel cutting soft metal: manganese, soft steel and lead.
Some plastics.
Plasterboard/jiprock.

Materials that have plastic properties that require pressure to part them rather than keeness, as they too readily bind up a knife. Two handed with full body weight.
 
Cutting those materials puts pressure on the stop pin not the lock. Having the blade bind and pulling it out will never ever generate enough force to break a lock.

-Johnny
 
Once the blade is deep into this type of material, it becomes stuck. Its the getting the "dam" knife out that puts the pressure on the lock. Its when the blade jams and the user becomes frustrated that the oddest things start to happen.

I can make my BM Cub liner flex under duress, but then I'm being stupid.
Other things are much more likely to go wrong. Disengagement is bad enough for me.

If we only used a knife for making straight cuts; why have any thickness to a blade?


[This message has been edited by GREENJACKET (edited 09-11-2000).]
 
Just happened the other day. Topping a hedge, we were taking three meters off the top. The vertical branches were less than an inch thick but there was plenty of weight above. The branches were too flexy for the chainsaw so we went in with a gerber folding saw and other knives.
My friend cut through one of the branches which sprang with tension like a trap. The gerber went flying and he bust his hand.

Its the unexpected that does the damage. anything. csgheblacroh
 
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