Mainspring steels

[Phil Russell]

Having been educated by Jim in the science of mainsprings and spring rates etc I am still puzzling over what difference the various steels used to make springs can have.
I also have a vague memory of it being possible to calculate spring rate from the spring dimensions, albeit maybe only an approximation ... but maybe memory is fading.
But... to the original question: What steels are used to make springs and what are the differences between them? Which is best ? Is one steel inherently 'softer' than another? Is one likely to last longer?
I am also pretty sure I have heard the term 'Swedish steel' but always thought that is marketing hype similar to 'Jersey Potatoes' or 'Lincolnshire Potatoes' which just mean 'grown in wherever'.

Just Lockdown musings.
Cheers, Phil

[TonyL]

I asked the very same thing years ago, Phil, and I'm sure this will be a regularly recurring subject amongst springer fans.
Can't remember the / any definitive outcome, but my quest had me looking up much information on-line surrounding music wire and valve spring wire. Interesting way of spending a few hours researching.

[Phil Russell]

I asked the very same thing years ago, Phil, and I'm sure this will be a regularly recurring subject amongst springer fans.
Can't remember the / any definitive outcome, but my quest had me looking up much information on-line surrounding music wire and valve spring wire. Interesting way of spending a few hours researching.

Is this a case of 'great minds think alike' or 'fools seldom differ'? Sorry Tony, couldn't resist. I like to think the former.. But it is a question I have often thought about. I could, like you, spend time googling but thought there may be some expert on here who would say 'Ah, yes, good question. The answer is '.

And I admit it was brought back to mind by reflecting on an experience a couple of years ago with an LGU (.177) which was making about 11.2 on receipt but over maybe 3 months of intermittent use lost maybe 2 ft lb. A new spring sorted it. But I have heard of others who found the same with LGU springs ... weakening over time.

Cheers, Phil

[TonyL]

Seem to remember Umarex / Walther citing music wire, Phil.

And I could be wrong, but were the weakening springs put down to not being scragged?

[averageplinker]

Seem to remember Umarex / Walther citing music wire, Phil.

And I could be wrong, but were the weakening springs put down to not being scragged?

With the LGU I seem to recall the springs weakening was put down to a smaller than optimum transfer port for 12ftlbs by some and it was claimed to have cured it by opening out the TP at touch.
Rich

[Phil Russell]

With the LGU I seem to recall the springs weakening was put down to a smaller than optimum transfer port for 12ftlbs by some and it was claimed to have cured it by opening out the TP at touch.
Rich

Not in my case. I had opened the tp out to 3.2mm (I think that was the recommended size) on receipt. My notes are below:

Started at c. 10.4 with AA Field, some stock resonance / twang. Transfer port at 2.6 (?) so drilled out to 3.2mm. Added a delrin slip washer to spring guide. Then at c. 11.8/11.9, twang still present. Stripped again, found 2 steel washers in piston under top hat. Removed. Tried a 0.5mm PTFE piston liner but just too thick so used a steel one. Replaced only one of the steel washers. Left the delrin slip washer. Lubed with moly grease on spring. Now 11.8 consistent (c. 795fps) with twang gone.
Feb 2016 tested: power dropped to c. 10.5, approx. 750 fps. Fitted new spring and removed slip washer. Now c 11.2.

Cheers, Phil

[lightning22]

Having been educated by Jim in the science of mainsprings and spring rates etc I am still puzzling over what difference the various steels used to make springs can have.
I also have a vague memory of it being possible to calculate spring rate from the spring dimensions, albeit maybe only an approximation ... but maybe memory is fading.
But... to the original question: What steels are used to make springs and what are the differences between them? Which is best ? Is one steel inherently 'softer' than another? Is one likely to last longer?
I am also pretty sure I have heard the term 'Swedish steel' but always thought that is marketing hype similar to 'Jersey Potatoes' or 'Lincolnshire Potatoes' which just mean 'grown in wherever'.

Just Lockdown musings.
Cheers, Phil

Swedish steel was in the advertising for the Airforce springs IIRC.

[Phil Russell]

Well ... this has been interesting. A quick google and Wiki shows me that there are lots of different steels, as Blackbeard says. I guess I expected this, indeed if you google a bit further you can find descriptions of the various grades of spring steel complete with all sorts of data regarding their properties.
But ... there is always a but.... I wonder if we will ever be told which particular steel a particular spring is made from? I did come across a site where you could indeed design your own spring from a particular steel spec/code.
Cheers, Phil

[Black Beard]

The only way to identify the steel would be to stick it into a test device that measures the % of alloying element content and then look up the nearest specification. This is standard metallurgy test gear but a bit too expensive for the home airgunsmith.

[Kuyajonathan]

Not in same vane but connected, does tempering make any difference when manufacturing air gun springs?
If so can they be revived by re tempering ?
Seems BSA Mod / LJ springs seem to survive usage after 100 yrs, or were they just exceptionally well made at the time compare to later springs ?

[FPoole]

I think it is down to the heat treatment and how close the temps were kept to optimum. There is an optimum temp for hardening and an optimum temp for the tempering back to spring hardness. This is assuming a quality steel was used. The tempering process can be anything from brittle and stiff to near mush and I've had springs that were soft and went flat as well as springs that broke in a few 1,000 shots. I've also had springs that stay at the intended performance level for 10,000 shots, but that's about the limit. I always wanted a spring made from Vasco-wear valve spring wire. I've heard of knives made from it that were almost un-sharpenable, but they held their like nothing else. In the end I just buy a few springs at a time and they are almost always just fine.

[Black Beard]

It is the hardening process that extends the yield point up so that when the spring is compressed the material doesn't yield. If it is too hard the yield point will be very high but the spring will be brittle. If it is too low the spring will yield and not spring back properly. The alloying elements let you push the yield point up further while avoiding brittleness. You need to get the heat treatment right though.