How to lighten the pull on a traditional folder?

MTHall720

MTHall720

Joined
Sep 21, 2010
Messages
2,957
I have a really large Case Coke Bottle design knife. Love the dimensions, weight, and appearance. It is new so I am wondering if leaving the blade open at a 45 degree angle, plus applying dry lube and opening and closing it a lot would help. I need a light pull like a 3-5, but this knife is very tight, with a heavy pull to open, and snaps shut like a steel trap.
Any thoughts?
 
If the knife is properly made, that won't help.
Thinning the backspring carefully can weaken it considerably.
 
Thanks for the thoughts on this. That is was I didn't want to hear but I needed to hear it though. I love this knife except for that one thing. I'm not like a lot of people who don't mind a heavy pull. Not sure if this is true of all Case Coke bottles. Starting to think that maybe the way it is.
 
I think we're in similar situations, except that I bave a trad I wish was stiffer. We're all looking for the Goldilocks tension. But as with yours, it's a well made knife and I think we're stuck. Of the two problems, I think yours is the preferable one.

Zieg
 
I like that insight Zieg. I have a GEC 97 that has a pull I love, but wish that my Case had the same light pull. I also have a really big Case Toothpick which has a delightfully light pull. I guess each model made by each brand has its own characteristic pull strength or stiffness.
 
I have a customer who has limited use of one hand. He can't have automatics, so he periodically sends me slip-joints to modify by thinning the backsprings.
 
leaving the blade open at a 45 degree angle, plus applying dry lube and opening and closing it a lot
Click to expand...

Bill DeShivs said:
If the knife is properly made, that won't help.
Click to expand...
This has been my experience and the physics of spring steel backs it up.

Mr. Deshivs :
I've never done it but I thought I read here where a person could get in there with a small thin pry tool and pry between the blade tang and the spring to permanently bend the spring a little.

Would take many minute trial and errors rather than over doing it.

Is this an option ? Too hard on the frame of the knife ?
In my work I bend springs all the time to adjust / balance machine settings.
Even though the springs have adjust screws on them I can do it faster by bending the spring than wasting time with the unpredictable screw mechanisms.

Like I said . . . I've never actually done this to a folder (other than my Cold Steels but they don't count). I have one Boker though that if it is a viable technique I might then use it on .
 
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Bending the spring is a viable option- but it's hard to get in there and, once it's bent-unless you grind it flush it will stick up.
 
Some have reported issues on Case folders having rough edges or burrs on the blade tangs near the pivot, which adds friction against the liners, further aggravating any opening or closing issues. I'd inspect that first with a magnifier, just to be sure it's not a factor. Easy to fix if it is, using something to burnish the edges of the tang, like a ceramic hone or some fine wet/dry sandpaper.

One thing I've always noticed about older-pattern folding knives in carbon steel, or with carbon steel backsprings is, over time and with use the carbon steel will wear between the spring and tang, and the opening pull or closing snap will eventually ease up as a result. Not so much about changing or weakening the temper of the spring itself, but about (literally) loosening up the fit tolerance between the mating surfaces due to abrasive wear. The black 'dust' coming out of the pivot during cleaning or oiling of the knife is evidence of that steel wear. I notice this much more with knives put together in carbon steel, and less so with stainless builds (both blade and backspring), as stainless is more resistant to abrasion. Just be sure to keep the pivot clean and periodically oiled, so the swarf in the pivot doesn't bind it up.
 
Bill DeShivs said:
Bending the spring is a viable option- but it's hard to get in there and, once it's bent-unless you grind it flush it will stick up.
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Thank you.
I might try that on my really tight springed Boker. Nice knife other wise, plain high carbon and etched blades with black and green feather like jigging; I love the thing.
 
Obsessed with Edges said:
as stainless is more resistant to abrasion.
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I'd be a little careful there.
I'm a mechanic and have had chronic galling problems with some batches of fasteners made from stainless steel. It can happen when the threads are dry (not lubed) on most fastener materials but I have had it occur more often on stainless fasteners and to a higher degree.

Here is a LINK > > > to an explanation
See "EXPLANATION" at the link
Galling most commonly occurs between mating fasteners of materials which self-generate a corrosion-resistant oxide surface layer, such as stainless steel, titanium, aluminum and some other alloys. During assembly, contact between the high points on the threads wears away the protective oxide layers exposing the base materials. When the cohesive force between the materials exceeds the strength of either metal, solid-phase welding (galling) occurs.

While galling can occur between a multitude of mating surfaces, this bulletin focuses on the causes and prevention associated with threaded fasteners.
 
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I have carefully removed some steel from the inside corner of the blade's tang, to lighten up the pull. This has no effect on the thickness/strength of the backspring. It just makes it easier to get the blade to open without changing the spring to tang geometry in the open position. I go slow, and put some oiled tissue in the well, to keep filings out of the joint.
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Wowbagger said:
I'd be a little careful there.
I'm a mechanic and have had chronic galling problems with some batches of fasteners made from stainless steel. It can happen when the threads are dry (not lubed) on most fastener materials but I have had it occur more often on stainless fasteners and to a higher degree.

Here is a LINK > > > to an explanation
See "EXPLANATION" at the link
Galling most commonly occurs between mating fasteners of materials which self-generate a corrosion-resistant oxide surface layer, such as stainless steel, titanium, aluminum and some other alloys. During assembly, contact between the high points on the threads wears away the protective oxide layers exposing the base materials. When the cohesive force between the materials exceeds the strength of either metal, solid-phase welding (galling) occurs.

While galling can occur between a multitude of mating surfaces, this bulletin focuses on the causes and prevention associated with threaded fasteners.
Click to expand...

The mating surfaces in a folding knife pivot don't ordinarily have galling issues anyway, unless something's seriously wrong. This observation coming from my own experience using dozens of stainless-bladed/springed folders and never encountering such a problem. As quoted, the force between the two surfaces has to get pretty high for galling to happen, as could understandably happen with threaded fasteners being tightened down. But if the forces between tang & spring are that high in a folding knife's pivot, there are other things going completely wrong with the design or build of the knife. The ordinary rubbing happening between a blade tang & spring should never be under that much pressure. And when left to simple, light abrasion going on, the stainless will be more resistant to wear than a blade & spring of simple carbon steel. You just won't see the same degree of abrasive wear in the stainless builds, as compared to others in all-carbon steel construction.
 
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Obsessed with Edges said:
The ordinary rubbing happening between a blade tang & spring should never be under that much pressure. And when left to simple, light abrasion going on, the stainless will be more resistant to wear than a blade & spring of simple carbon steel. You just won't see the same degree of abrasive wear in the stainless builds, as compared to others in all-carbon steel construction.
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I see :thumbsup:
 
I would think that if you opened and closed the blade a lot, the spring moving would weaken it somewhat making it easier to open. Also the repeated action would cause minute wear between the the surfaces also making opening and closing easier. An engineer once told me to put an abrasive dust or compound where the spring and spring mate then activate for a while. When you are satisfied with the change flush out the compound with aerosol wd40 or other solvent under pressure.
 
A spring moving within it's elastic design limit does not get weaker.
Apply in abrasive or lapping compound in a knife joint can cause the abrasive to imbed itself in the steel and cause difficulty opening and later, excessive wear.
 
You might try flushing with soap and warm water while working the blade open and closed. Then dry and WD-40 it. There may be some manufacturing gunk left in there. --KV
 
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