Talking about Torquing

Fatty_Boomsticks · May 21, 2005

When purchasing a folder the lock-type is the biggest single factor in my consideration. Liner locks seem somewhat less than secure to me. While searching the forums about liner lock failures there seemed to be a lot of talking about torquing stress. From what I gather forumites are talking about stress applied as noted B see attached sketch.

Am I on the right track?

Dammitt! Dammitt! whaddya mean i cant post attachments ?!

word pictures must do-
"B" is bending applied 'downwards' on the blade of folder held horizontally in 'sabre grip'. This would seem to be the typical 'failure mode' of liner locks. The word torque methinks correctly would be twisting applied horizontally along blade in 'sabre grip'.

I want know how locks typically fail but I just cant understand what you guys are saying... help!

DaveH · May 21, 2005

Twisting a knife like a screwdriver.

Does that help?

Fatty_Boomsticks · May 21, 2005

Thanks Dave, yes it helps.

severtecher · May 21, 2005

The best example of torque for the layman i believe is as follows: When you awake with a piss boner in the morning, go to the toilet and push down on the boner. When your feet fly out behind you, this is torque.

USAFSP · May 21, 2005

The biggest issue I see with the torque test is, that 90% of us will never torque a knife to the point where the lock will fail. The people doing the tests are trying to find the point where the lock will fail and release so they are doing it on purpose. Then they compare a few different knives, and show which ones held longer. The tests are not bad ones, but the amount of force used is not something that the rest of up will do on a normal basis. Maybe in an extreme situation, but then you have more to worry more then what kind of knife you are carrying. You should just buy a knife from a reputable company with a design you like and not worry so much. Someone is always gonna come out with a stroger lock, and a test will be performed to make it fail. I wouldn't worry so much.

arawn · May 21, 2005

severtecher said:
The best example of torque for the layman i believe is as follows: When you awake with a piss boner in the morning, go to the toilet and push down on the boner. When your feet fly out behind you, this is torque.

This was one of the funniest things I've read in a LONG while.
I just shared with my wife and best friend (as they were curious as to why I was cackling with glee).

B.

Cliff Stamp · May 21, 2005

USAFSP said:
The biggest issue I see with the torque test is, that 90% of us will never torque a knife to the point where the lock will fail.

Torque failures have been seen cutting cardboard and weeds in the garden. If you don't exceed that with your knives you really don't need anything "tactical". The heaviest torques I have personally induced just take moderate wrist strain, nothing that would bother the blade on even the light use folders I carry.

The problem comes when you see knives with very thick blades promoted for extreme use which you can disengage and even break the lock so easily thus the heavy blade isn't a functional adavantage and much slighter knives actually have a wider scope of work not to mention out cutting the thicker blades.

As well it only needs to happen once in your lifetime for it to matter. Most safety equipment is actually only called into use for a small percentage of the population. Everyone however tends to want to have it for obvious reasons, because no one wants to be part of the small statistic that fails to have it when needed.

Not all knives need to be able to handle torques, in fact I have several fixed blades that would be likely to snap under torques that I have used to disengage and break liners/integrals. Those fixed blades however are promoted for specific use, which is very light cutting. They are certainly not pressed for "tactical", heavy duty, emergency, survivial, etc. .

-Cliff

Fatty_Boomsticks · May 22, 2005

Thanks guys

Seeing more clearly now- torque failure tests maybe a valid evaluation however, I agree with USAFSP, for my purposes I would rarely, if ever, put high stress on a folder this way.

The bending stress applied in direction of blade closing is the failure mode I am really interested in. Doing what forumites call the spine whack test while perusing possible knife purchases lately has left me aghast at how many locks disengage easily

once bitten twice shy

yoda4561 · May 22, 2005

The thing with torquing (I've had it happen once or twice, no cuts thankfully) is that it usually happens when you're cutting something that's stiff(plastic sheet, heavy duty cardboard), and the blade binds in the cut for whatever reason. I usually apply a light twist and then pull the blade out, which usually gets the job done. Sometimes I'm a bit careless as I'm used to my locks working properly, and if you pull "up" instead of "back" (It's too early in the morning/late at night to try to describe it better) sometimes the twist+ stiff material+ pulling motion can unlock a liner or framelock and close it on your fingers.

Cliff Stamp · May 22, 2005

Fatty_Boomsticks said:
The bending stress applied in direction of blade closing is the failure mode I am really interested in.

This is inconsequential in all practical uses because it takes very high loads to break locks if you apply them perfectly perpendicular, of course as a human, it is also near impossible to do that.

-Cliff

Fatty_Boomsticks · May 22, 2005

Cliff Stamp said:
This is inconsequential in all practical uses because it takes very high loads to break locks if you apply them perfectly perpendicular, of course as a human, it is also near impossible to do that.

-Cliff

Cliff

I thought this was [in an improvised sense] exacly what the "spine whack" test was doing. Seems I've misunderstood again.

Cliff Stamp · May 22, 2005

The spine whack tests sudden shocks, the loads are usually light, but the speeds fast. The sudden impact jars the lock and can cause it to release. The actual force applied is really low usually.

Torquing is a much slower application of force, but usually goes heavier in terms of force, it still never approaches the break point of the locks, which is hundreds of pounds of force for ~1000 in.lbs of torque for the stronger locks.

Depends on the knife if it is relevant, on something heavy like the Manix I want it to be torque stable under full wrist strain as otherwise the heavy blade is a waste of time.

Some spine whacks can be taken to very high levels of course, I have done them at times to full speed impacts with a baton and some locks can take this readily, some can not.

Just pick what you want in a knife and realize that you do have many options available.

-Cliff

Fatty_Boomsticks · May 23, 2005

Thanks Cliff

Can now grasp differnce between high impact/impulse spine whack & much slower & much heavier loading where you just couldnt hold the handle.

Also can dig Yoda's torque situations & your note on hefty blade, torquing & wrist strength interdependence in knife use.

Thanks again.