Lightening a Mainspring

[Flintandsteel]

You tell ‘me Wick!

 

[Versanaut]

Some GREAT information here! Thank you all for your help.

Can I do any harm by re-tempering it? Thinking, I might try that, then narrow them a bit if there is no improvement.

450-500 degF.. Oven Temps with Wife's permission.. maybe even run the oven on a cleaning cycle with the spring in there. Not sure that temp. is enough based on some of the input above. Hmmm

Could also immerse in the lead pot. It's PID controlled to 715.. I might be able to get to 725.. but be afraid to screw up the pot.

Also have a coal forge I tinker around with. I don't really make anything of note there. Not very temp controlled by me either.

Regarding removing metal and narrowing it, I am guessing I should leave the bend alone? Especially regarding the protrusions noted in the pictures?

Thanks!

versanaut

 

[rich pierce]

Looks like a poorly designed spring. Spring work is expensive. Not recommended for the inexperienced.

 

[mooman76]

W

Worst piece of trash Kit ever published.

If it's that bad, do you have another suggestion?

 

[Zonie]

Versanaut: Don't use the oven on it's cleaning cycle. The temperatures needed to burn away carbon from burned on food is much too high and you'll end up annealing the spring.

Yes, you can retemper steel. If the temperature your using is below the temperature that was used initially, it won't do anything. If it is a higher temperture, the steel will end up just like it would have ended up if the higher temperature was initially used.

Your lead pot method is a good one if you keep the temperature close to the temperature that pure lead first melts at. That would be around 620° F. You could go up to 700°F but I don't think it would be a good idea to go higher than that so adjust your pot so it doesn't overheat the lead.

 

[LRB]

What Zonie said. 700°F might be better than nothing, and there's nothing lost if it was never tempered right to start with, but 750°F is the ideal temp for common spring steels, even most alloy spring steels, if the hardening was done right, and the spring is of a common spring steel. If you could get the lead somewhere between 725° and 750°, that would do it better.

 

[LRB]

If it's that bad, do you have another suggestion?

I can give you temps to heat treat one, but I can't give you much as to dimensions and such. Seeing the lower leaf up against the upper at half cock in that one photo would worry me. As Rich said, it looks like a poor design to start with. I believe there is way too much spread in the V, which will cause excessive stress, going by the other photos. Even properly heat treated, a spring will only give so much in a bend.

 

[LawrenceA]

Made and modified a few springs but not heaps.
I was taught that to make the spring thinner is the best as it means the spring is under less stress when worked.
Things to watch are that the thickness can be tapered but there should be no hills or valleys. Think of a longbow. Nice gentle taper.
Polish the length of the spring. This reduces stress points.
A molten lead bath works for tempering springs with the shift between martensite and pearlite happening at as low as 250 C. but it is not an instant thing at low temps. It happens slowly. Just need to soak it longer to get more temper.

Also percussions do not need the spring strength of a flintlock.

Good luck

 

[LRB]

Made and modified a few springs but not heaps.
I was taught that to make the spring thinner is the best as it means the spring is under less stress when worked.
Things to watch are that the thickness can be tapered but there should be no hills or valleys. Think of a longbow. Nice gentle taper.
Polish the length of the spring. This reduces stress points.
A molten lead bath works for tempering springs with the shift between martensite and pearlite happening at as low as 250 C. but it is not an instant thing at low temps. It happens slowly. Just need to soak it longer to get more temper.

Also percussions do not need the spring strength of a flintlock.

Good luck

 

[LRB]

Pearlite is not in the picture. If all went right in the quench, you are working with untempered martensite. You would only get pearlite if your quench oil was too slow, or in an annealing process. when you pass 1333°F/1350°F, coming up to quench heat/critical heat, pearlite is converting to an austenite solution, until you reach full conversion at whatever the recommended critical heat is, and for any soak time recommended. Then you quench in an oil that is at a useful efficient speed of cooling. When the quench cools the steel below 900°F, pearlite is no longer a worry if you used the correct oil. Somewhere around the 400°F range, the austenite will begin conversion to martensite, at the speed of sound, and then slow down. Once martensite begins, the speed to finish is normally of little importance. Some steels only take seconds, others can take 10/12 minutes or more to finish. Now you have untempered martensite, so full of stress it can crack without any assistance. The stress is in the atomic structure of the crystals steel is made of. The atoms in their tetragonal homes that form grains are being forced/drawn toward the centers of these tetragonal homes. When you apply temper heat, these atoms relax, and drift back away from the centers with some drifting back out completely. The temper is all an atomic action and not a structure change. No pearlite involved. You would pretty much have to reheat the steel to somewhere above 1350°F, and slow cool it. Anneal it.

 

[LawrenceA]

Pearlite is not in the picture

Please accept my apology for using the wrong structure names.

 

[Scota@4570]

As previously stated springs should be drawn at about 750*F. I use my bullet casting pot and thermometer. Wrap some wire around the spring to hold it submerged in the lead. Let it soak for 15 minutes.

This would be the first thing I 'd do with a new spring. IF you don't have a thermometer for your lead pot you have an excuse to buy one now. IF you know a bullet caster ask to borrow his pot and thermometer? Drawing at a lower temperature will accomplish nothing.

I thin springs on a belt sander. I polish with polish-o-ray on a cloth wheel. Be very careful not to blue the spring. Be very very careful to avoid catching it on the wheel and flinging it across the room. IF possible hold the spring with vice grips. Otherwise, spring get hot, burns you finger, drop the spring, off it goes. You can not file a hardened spring.

 

[M. De Land]

I used to anneal all spring stock worked into V or Flat springs with my heat treating furnace but once read of a black smith method of tempering that evolved a mixing a 50/50 solution of 30 wt. clean motor oil and Kerosene. The spring (V or Flat) was place in a flat bottom container on it's side and the part covered with the solution and lit on fire and let burn out by it self out of the wind. It takes a good 20-30 minutes usually. It seemed pretty unscientific to me but ever curious I tried it a few times and it worked perfectly. I've never had a spring weaken or break from this temper draw method and I"ve made quite a few over the last 40 plus years of gun work. I have no idea as to the actual heat involved but have come to trust it and use the method exclusively.
Odd how these old fellows came up with methods that worked so well discovered by simple trial and error.

 

[springfield art]

There seems to be some interchanging of terms spring thickness and width and potential confusion, at least in my opinion. On flat V type springs I would always narrow or thin the width, with the width being 90° to the V, or the direction of the red arrows in the photograph. View attachment 40860

Good illustration! That's what I'm looking for!

 

[Sam squanch]

If you are going to temper in burning oil, wear a leather apron, leather work boots, and do it outside on a windless day. After a rain. I’ve had good luck, and bad luck with this method. The 50/50 mix of kerosene and oil is a new one , I want to try it. I just use a lead pot now.

 

[GREENSWLDE]

I used to anneal all spring stock worked into V or Flat springs with my heat treating furnace but once read of a black smith method of tempering that evolved a mixing a 50/50 solution of 30 wt. clean motor oil and Kerosene. The spring (V or Flat) was place in a flat bottom container on it's side and the part covered with the solution and lit on fire and let burn out by it self out of the wind. It takes a good 20-30 minutes usually. It seemed pretty unscientific to me but ever curious I tried it a few times and it worked perfectly. I've never had a spring weaken or break from this temper draw method and I"ve made quite a few over the last 40 plus years of gun work. I have no idea as to the actual heat involved but have come to trust it and use the method exclusively.
Odd how these old fellows came up with methods that worked so well discovered by simple trial and error.

Mr.M. Burning off was and is still a common method of tempering old spring steel. I use it frequently if I dont know the origin of the steel ,but my prefered method is colour by eye,but here cleanliness is next to Godliness. Slightest hint of contamination -even a finger print will Kill the Colour and you need an eye for colour.. This Blue is indescribable and is best learn by sitting next to Nelly.( Old BRUMMY expression for watching a Master who used a cuffed ear as sign of dissaproval at the Wrong colour ) .. My ears only rung Twice. Old Bony,the itinerate Black Smith ( who appeared as if by magic at the farm after a nod in the Bar ).. had hands as hard as the Horse shoes he made. O.D.