Life cycle of a Torsion spring

coop1957

coop1957

Joined
Oct 22, 2002
Messages
2,624
I've had a Scallion for five years now. Great little knife. Finally the torsion spring broke. The spring never got weak. Kershaw set me a new one gratius. I was wondering do they have a life cycle?
I figure that I open it up 20 x a day.
20 x 365= 7,300 a year x 5 years = 36,500 openings.
 
Hi 1957,

Interesting question and I have no answer.

Not to hi -jack your thread but if you have a Kershaw that you will not be using for awhile should you store it open position (to take pressure off the torsion bar)
or just leave it closed?

ken
 
I would think pull the knife apart and removing the torsion bar might be the best way :-P

or just use the knife! That's what they're made for :)
 
ken k said:
Hi 1957,

Interesting question and I have no answer.

Not to hi -jack your thread but if you have a Kershaw that you will not be using for awhile should you store it open position (to take pressure off the torsion bar)
or just leave it closed?

ken
Click to expand...

I am not 100% certain, but I don't believe that it matters one way or the other.
 
I've been told KO stores all his open. I do the same with mine. That way there is no stress on the torsion bar.
 
Just to get things back on track (you thread jackers!! :rolleyes: :D), the torsion
bars are tested to 10,000 openings.
 
The torsion bars in the knives I've had haven't seemed to worn down at all in the hundreds of opening I've put on each. I don't think you have much to worry about, except on the VERY long term.
 
Good spring steel wont care whether or not it is stored compressed or not.

It isnt storing a spring while compressed that causes it to wear, but how many times that it is flexed.

As long as the spring is within its elastic limits, it will not care either way.
 
My original estimate of 36.5k openings may be a little low. My wife thinks I need to seek help. Knifestrabation is not a mental disorder.
 
i guess it really depends on the user seeing as i just broke the one in my new speed bump after a week.
 
Torsion bars are made from music wire. They hold their shape very well and do eventually wear out.
Getting replacements is pretty simple as state above.
If you open and close it maybe 100 times in a few minutes, that might break it too.
The steel heating up from all the flexing will make it softer, then when you finally give
it a break it will stiffen back up. I think at that point is when most breakages occur.

mike
 
1.) Boa - EDU'd for 4 or 5 years continuously. Finally had spring fail.Didn't play with knife - but used daily and a lot - probably at least 7-9 thousand opening/closing cycles. Spring broke - returned to Kershaw -K'shaw replaced the knife.
2.) Mini-cyclone.Spring failed after a few weeks.This had the original notched spring. Replaced with non-notched spring provided by Kershaw - no further problems - but probably only a few weeks use total on this knife since.
Most of us probably fiddle with a new knife a bit excessively when we first get it ( yah- my girlfriend's commented on this once or twice). If you "play" with your new speed-safe knife obsessively - you probably can fatigue the spring prematurely. Fortunately - it's no big deal to replace.In my limited experience ( with the possible exception of the notched original springs on the cyclones)- in regular tool use - these last a very long time.
 
I must say that the torsion spring was very easy to replace. I think that the springs will last longer if you occasionally take the knife apart and clean out all the pocket lint crap.
 
Do the larger springs in the bigger knives have an inherently longer life expectancy? I mostly carry my Bump, and Tyrade, with the Leek getting less carry, and a Chive getting almost no carry.

DD
 
Daniel Dorn said:
Do the larger springs in the bigger knives have an inherently longer life expectancy? I mostly carry my Bump, and Tyrade, with the Leek getting less carry, and a Chive getting almost no carry.

DD
Click to expand...

I was thinking the same thing, and my conclusion was....no.
Bigger springs yes, but also bigger blades
Smaller springs, smaller blades.

If that makes sense.

mike
 
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