Slipjoint spring heat-treat

[orca8589]

Last night, I was thinking about the fact that some of my slipjoints open easily, and others are "nailbreakers".

Does anyone know: are the springs in slipjoints heat-treated the same as the blades? I hear terms like "spring-temper", which can apply to blades, but I'm wondering do knifemakers & manufacturers use the same heat treating process on all the steel parts of a slip joint? Some of my old U.S. Schrades are "nail-breakers", but some are easier; and I have Rough Riders that are the same way: some harder to open, others are really easy.

Are stainless springs on a slipjoint easier to open, or carbon steel ones? Are certain patterns easier to open? I have two split-spring Whittlers that are the smoothest opening slipjoints I own. I have a small Peanut, brand new, that takes a ridiculous amount of effort to open.

Any thoughts? (By the way, I prefer stronger backsprings.)

thx - cpr

 

[jackknife]

I think that too many manufacturers get a little carried away with the strong spring thing. I don't want a weak spring, but it's the user that is the safty. I've found that one problem with a really strong spring is, when you get aged, you end up giving away knives that you can't open anymore.

However they heat treat the springs, Victorinox should be the industry standard. They always get it just right.

 

[sceva]

It is my understanding that the springs should be tempered to tha same hardness as the blades so that you get even wear between them. I would think that the spring tension would be controlled more by the shape and thickness of the springs and not the temper.

 

[John L]

Most blades are in the range of 60 on the Rockwell scale. Springs are in the 49-50 reange.....alot softer. Both blades and springs are hardened and then tempered differently. The ease of opening has something to do with the stiffness of spring...but the amount of pretension is a much larger factor.

 

[ken erickson]

Most blades are in the range of 60 on the Rockwell scale. Springs are in the 49-50 reange.....alot softer. Both blades and springs are hardened and then tempered differently. The ease of opening has something to do with the stiffness of spring...but the amount of pretension is a much larger factor.

Well said. If the spring was tempered any harder than 46 to 50 range or so it would have more chance of breaking. The opening and closing tension is a result of the spring pre-tension, tang geometry and placement of the nail pull. I might also add the spring design and the location of the center pin can and does make a difference also.

Ken

 

[orca8589]

Well said. If the spring was tempered any harder than 46 to 50 range or so it would have more chance of breaking. The opening and closing tension is a result of the spring pre-tension, tang geometry and placement of the nail pull. I might also add the spring design and the location of the center pin can and does make a difference also.

Ken

What is "pre-tension"? Would that be pre-bending the spring to a shape that allows more or less tension? (Like what we'd do with the hammer springs in our cap pistols as kids, to make the hammer hit the cap harder? )

thx - cpr

 

[ken erickson]

What I call pre-tension is the amount that the spring has to be moved from its relaxed position to the point were it rests on the tang when the knife is closed all the way or open all the way. If you did not have some pre-tension the blade would be loose in the open and closed. The knife manufacture or knife maker has the ability to put more or less pre-tension on the spring.

Hope this helps out a bit.

Ken

 

[KnifeHead]

...what Ken and johnl said. :thumbup:

I'll say this though, it will make all the sense in the world to you if you saw it demonstrated, but until then...it is probably just making you have more questions.

 

[ken erickson]

...what Ken and johnl said. :thumbup:

I'll say this though, it will make all the sense in the world to you if you saw it demonstrated, but until then...it is probably just making you have more questions.

This would be a perfect little video for youtube! I need to check into a camcorder. (are they still called this?)

 

[orca8589]

...it will make all the sense in the world to you if you saw it demonstrated...

Okay - I hadn't thought of that. So I went out in my garage and took apart a cheapy slipjoint (RR Barlow). I drilled out an aluminum plate & put the parts on it, worked the joint a little, and now I understand this whole thing a lot more. Now I'm working on getting it back together with ebony scales, so we'll see if I actually get the spring tension consistent between the two blades.

This would be a perfect little video for youtube! I need to check into a camcorder. (are they still called this?)

Or one of those "WIP" threads with pics, showing the relation of the parts. :thumbup:

thx - cpr

ps - "Camcorders" are only called that by old folks & dinosaurs. Don't feel bad; I asked where I could get a new VCR at Target last week. The girl laughed out loud at me. Really hurt my feewings.

 

[kc custom]

I've Rc-ed a fair amount of old blades and springs and usually the blade is harder than the spring, though I've also seen a fair amount of blades that tested at Rc-50 right along side the springs. No wonder some of them were easy to sharpen!
Ken