How Much Pull is Actually Needed?

Leverage! Doesn't the length of the blade, depending on the placement of the opening nick have something to do with the perception of "pull"? I'm just wondering?
 
AShearer said:
Leverage! Doesn't the length of the blade, depending on the placement of the opening nick have something to do with the perception of "pull"? I'm just wondering?
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Absolutely. If you took a blade and put multiple nicks on it from tip to tang, the required force to open would increase as you approach the tang.
 
Sabercat said:
Absolutely. If you took a blade and put multiple nicks on it from tip to tang, the required force to open would increase as you approach the tang.
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Yes. To my point. Leverage! You know, Atlas and all that:) So, all things considered, the longer the blade and the further the nick or pinch point the softer the pull?
 
AShearer said:
Yes. To my point. Leverage! You know, Atlas and all that:) So, all things considered, the longer the blade and the further the nick or pinch point the softer the pull?
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I believe this can be a big factor, and may be why I often have more trouble opening the smaller secondary blade than the main blade on a jack knife, despite it having a thinner spring.
 
r8shell said:
I believe this can be a big factor, and may be why I often have more trouble opening the smaller secondary blade than the main blade on a jack knife, despite it having a thinner spring.
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I guess it's obvious, but I agree Rachel. I've found that the smaller secondary blades give me more trouble opening. I mentioned earlier in this thread, I have a Washington Jack that I can hardly open without cutting myself! ;)
 
I think the spring is still the main factor when it comes to pull strength. My S&M English Jack has both blades at a little over 3.5", and they are both tough to open.

That being said, the sheepsfoot is probably an 8 while I'd give the clip a 9.

The spring makes them both tough to open, but the nick placement probably does add a level on the clip.

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Sabercat said:
I think the spring is still the main factor when it comes to pull strength. My S&M English Jack has both blades at a little over 3.5", and they are both tough to open.

That being said, the sheepsfoot is probably an 8 while I'd give the clip a 9.

The spring makes them both tough to open, but the nick placement probably does add a level on the clip.

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Totally agree. Like I said, all things being equal. If we had a spring of X strength and two blade lengths of X and X+, leverage should make the longer blade have a lower (by our standard) pull? Right??
 
Wouldn't makers take spring strength, blade length, nail nick placement, etc into account when designing a knife?
 
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I like the pull to be somewhere in the middle - around what might be called a 4 to a 6, I guess. I imagine if the pull is really heavy to me, that it can take it's toll on the knife where the wear points are. How much longer will a pivot pin or center pin last if it has less stress put upon it? The spring(s)? Tang(s)?

I tend to think this way about all mechanical things though. Makes me go easy on all my stuff. If something takes a bunch of force to operate, I start to think of where its going to break. Probably never happen with a folding pocket knife, I know. Oil them joints!
 
GE Jr said:
I like the pull to be somewhere in the middle - around what might be called a 4 to a 6, I guess. I imagine if the pull is really heavy to me, that it can take it's toll on the knife where the wear points are. How much longer will a pivot pin or center pin last if it has less stress put upon it? The spring(s)? Tang(s)?

I tend to think this way about all mechanical things though. Makes me go easy on all my stuff. If something takes a bunch of force to operate, I start to think of where its going to break. Probably never happen with a folding pocket knife, I know. Oil them joints!
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It shouldn't be a concern if the materials had been properly treated. You see knives with hundered years on their backs where minimal wearing has occurred, and poorly treated steel that almost disappeared from wearing in a few decades of use. Of course lubrication is mandatory, oil them joints!!
 
I enjoy softer pulls, myself. My lockback GEC 83 and Buck 55 are both very nice. Anything over a 6 or 7 more than likely won't get carried for long, especially if it has only a nail knick. If is pinchable, it's a bit of a different story. My spearpoint GEC 25 hurts to open with a finger nail, but I can pinch the blade easily enough that the knife still gets carried.
 
I like the nick as close to the tip as possible. That way you get a nice strong spring but without any opening difficulties. Victorinox are very good at this.
 
hughd said:
Is it possible to have soft pull with good snap?
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I don't see why not, as long as it isn't too soft a pull, and you aren't expecting a huge snap.
Disclaimer: I am not an engineer, and I've never made a knife.

If you think of the parts of the blade tang that are in contact with the backspring, there are two corners (at least on a knife with half stops) one corner moves the backspring from the closed position to the half way point. Then the other corner moves it again to snap the blade fully open. I imagine the tang could be shaped in a way to give less resistance during the first part, and more during the second part. Almost like a half-cam tang?

Someone please feel free to correct me if I'm totally off the mark. :oops:
 
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