spring material question for the folder gurus

[jdm61]

Okay, folder guys, here is a question for you. Disregard for a moment things like cool factor, ease of machining, grinding, etc., corrosion resistance and what have you. If you had to rate the commonly used spring materials used in folding knives strictly on how well they function as a spring, how would you rank them? I am talking about titanium, carbon steels like W1, 5160 etc. stainless steels like the 400 series, aluminum (in some frame locks like the cheaper version of the Lion Steel mono bloc knife) and whatever else you than think of. I am particularly interested in materials for frame or liner lock knives as those springs are under compression for maybe 98% of the time, so the first thing that I would be concerned about is how well something maintains it "springiness." My second concern would be which material is least susceptible to metal fatigue over time? Also which one is the most wear resistant at the lock up point? Are there some other materials that you think might work really well like maybe 15N20 or some of the higher carbon simple stainless blade steels like AEB-L/13C26 or 12C27 that are not used typically?

 

[Frank Niro]

I'm sure the end answer is that titanium works just super for liner locks !!! For that purposer and function it is simple to manage. Frank

 

[Bill DeShivs]

1095 is the perfect spring steel.

 

[Stacy E. Apelt - Bladesmith]

I agree - 1095 is the champ if you aren't trying to get a certain look of durability.
For stainless springs 440-C and CPM154 are both good.

The best answer to your question is :
The best spring material for a folder is usually the material you made the blade from. Properly heat treated, any steel that makes a good blade will make a good folder spring. That way the spring and blade will match in look, wearability, and workability. Obviously, when the blade material is something out of the norm, the spring may need to be a different material.

 

[jdm61]

Stacy, if you were trying to make a liner/spring for a liner lock out of say CPM 154, would you need to bend the lock bar to its unsprung position before you harden and temper it?

I agree - 1095 is the champ if you aren't trying to get a certain look of durability.
For stainless springs 440-C and CPM154 are both good.

The best answer to your question is :
The best spring material for a folder is usually the material you made the blade from. Properly heat treated, any steel that makes a good blade will make a good folder spring. That way the spring and blade will match in look, wearability, and workability. Obviously, when the blade material is something out of the norm, the spring may need to be a different material.

 

[Daniel Fairly Knives]

A few days ago I tried to cut some Titanium wire by bending it repeatedly to fatigue... I couldn't. I could do that easily with steel wire.

I'm not sure how this would compare to fatiguing heat treated spring steel. It seemed obvious to me that Ti is as tough as can be when repeatedly flexed.

How do you heat treat steel that is bent anyways? I feel there are reasons why Ti is used, despite old marketing hype Ti really is a great material.


By the way I have some steel framed liner locks and they are great, just giving some reasons why Ti is used too.

 

[jdm61]

Good question re heat treat. LOL. Fatigue is a big question obviously. We know that you can bend steel back and forth until it fails, but we also have examples of steel and titanium both surviving through MUCH worse torture than we would ever inflict in uses like automotive valve springs. Obviously, the big advantage that titanium has in the application for both springs and valves is one of a reduction of weight/inertia for avoiding valve "float" at very high RPM's and not necessarily one of absolute strength for a given diameter. I am breaking one of my previously stated rules of this thread, but the one downside of titanium is cost.

A few days ago I tried to cut some Titanium wire by bending it repeatedly to fatigue... I couldn't. I could do that easily with steel wire.

I'm not sure how this would compare to fatiguing heat treated spring steel. It seemed obvious to me that Ti is as tough as can be when repeatedly flexed.

How do you heat treat steel that is bent anyways?

 

[Bill DeShivs]

Steel springs are shaped (bent) before heat treating. They are treated the same as any steel.