Can a mainspring be made stronger?

[M. De Land]

Hi,
I used to use that method and half the springs were mushy. For me, there is nothing easier than popping the spring in my heat treating oven for an hour, and there is no smoke.

dave

I don't understand mushy Dave, either it's tempered too much and it will bend and take a set or if not enough it will break. None I have treated with this method have ever demonstrated either characteristic to this point. I have a programmable Even-heat furnace I use for all my tool making and case coloring. Excellent, accurate ovens they are in my opinion.

 

[M. De Land]

I've got a Fusil De Chasse made back in the 90s. It shoots alright and is mostly reliable as long as the flint is "just right" and everything is just how it needs to be. I believe that the mainspring is fairly weak, as it takes considerably less force to **** than other flintlock I have messed with. I don't have a way to measure it, so i apologize in advance for those who need numbers on these kinds of things.

The lock in question is an L&R Trade Lock. Very low round count, around 100-150 at most. I have disassembled it and made sure everything was smooth and lubed. I have been told by a few people who I consider wise on the subject, that these locks are fairly notorious for weak mainsprings. The lock is also suspiciously easy on flints. It always sparks, but nothing like my others and seems noticeably slower.

Is there anything I can do to the mainspring to give it a little more oomph? Maybe heating it and opening it up a little more? I was planning to contact L&R to order a replacement, so figured I had nothing to lose. I have an assortment of torches and metal working tools. Just looking for some tips. I appreciate your thoughts!

I have never trusted cast springs very much and as a consequence always shape file and forge mine from various thicknesses of spring stock I buy from Brownell's. Some folks have had good success with and swear by them though.
I have learned the hard way though over the years that with either, dressing the edges around the bend back and limbs is probably just as important as is the correct hardening and temper draw.

 

[M. De Land]

I have never trusted cast springs very much and as a consequence always shape file and forge mine from various thicknesses of spring stock I buy from Brownell's. Some folks have had good success with and swear by them though.
I have learned the hard way though over the years that with either, dressing the edges around the bend back and limbs is probably just as important as is the correct hardening and temper draw.

Another thing on spring making that is probably borderline heresy on this forum to mention is how handy it is to learn how to make coil springs on your lathe if you have one. You can make any size or length needed with very little trouble and there are a surprising amount of the more modern locks out there that use them.

 

[M. De Land]

How about a toaster oven and an oven thermometer, I read that in a knife making book.

One of the main characteristics of a good heat treating oven is it's ability to heat evenly and consistently with a temperature fluctuation of no more than 3-5 degrees. It take an accurate thermo-couple housed in a well insulated oven body to accomplish this repeatedly.
A good steel heat treat oven must be able to generate at least 1800 degress F. and most good ones will go to 2000 degrees F which is need for such steel alloy as A-2 for example.

 

[dave_person]

Hi,
They were tempered too far and took a set. However, I did not use a mix with kerosene just motor oil. That could make a difference I suppose depending on the temperature to maintain burning. With a programmable oven, I don't need to use any burning oil anymore.
dave

 

[LRB]

How about a toaster oven and an oven thermometer, I read that in a knife making book.

Not great, but better than guessing. If you know your steel is 1075/80/85/95, and you have heat control such as an oven, here are the proper temps for a spring. 1475° to harden. Best common oil is canola oil warmed to 130°. Motor oil is a poor quench oil no matter what you add to it, and is a health hazard. Especially poor for the 10xx steels. Temper 2+2, that is two tempers, two hours each, at 750°. Air cool to ambient between tempers. That heat will show no color in the steel. It will be gray neutral. If you have a lead pot that will hold the temp at 750°, it is a superior way to go, and you can cut the soak time in half. I would not be afraid to cut the soak times to 30 minutes each in a lead bath.

 

[45man]

I have made my own springs but I do not bend or fold steel. I cut to shape and polish. I find they last forever as long as there are no scratches. Heat to hardening temp, drop in oil. Then put the spring in your lead pot at 600 degrees for an hour, fish it out and set on the pot edge, turn the pot off and let all cool slow. DO NOT quench.
If you heat the bend to open the spring it MUST be hardened and tempered again. If not it will break at the first ****. I have home made mainsprings and frizzen springs I made still good after over 60 years.

 

[45man]

I have not heated my quench oil to harden. I use ATF.

 

[ThumperJones]

Thanks for all the great info guys. This has turned into quite the informative thread! I don't have anything of any intelligence to add myself unfortunately. Other than it seems to my peabrain that a cast spring would never work in the first place. But, I reckon they do! It will interesting to see the difference.

I hope the new one goes in fairly smooth. The inletting if needed will be new to me.

Going hunting with the gun and original spring in the morning, then maybe the mail man will show up with the new one.

 

[M. De Land]

Thanks for all the great info guys. This has turned into quite the informative thread! I don't have anything of any intelligence to add myself unfortunately. Other than it seems to my peabrain that a cast spring would never work in the first place. But, I reckon they do! It will interesting to see the difference.

I hope the new one goes in fairly smooth. The inletting if needed will be new to me.

Going hunting with the gun and original spring in the morning, then maybe the mail man will show up with the new one.

One needs to take into account how original Golden age springs were made.
After forming and dressing they were heated in a coke forge, brought to bright red heat and quenched usually in animal or vegetable based oil. Temper draw was accomplished as I have described in a Kerosene (coal oil) and oil mix or in melted lead. They did not use timed heat soak practices but relied on steel color after brightly polishing them, acquired from experience and their springs have lasted in some cases a century or two. A very good spring can be made in a torch flame and many have been.
Modern heat soak protocols are usually rated in per inch of thickness of the alloy used. Mass of the alloy used is an important consideration in the hardening, annealing and tempering times needed for quality finished springs, and as mentioned earlier a finished main spring is no where near the same mass of an inch thickness of the same material.
No harm is done in and oven especially if the spring is wrapped or coated to keep out air but soak times required are excessive in my opinion, especially for temper draw.

 

[LRB]

There is no measurable carbon loss at temper heats, even with very long times. If temperature degree is controlled to be stable, the atomic shift of carbon atoms will reach a position among the iron atoms that is related to the set and controlled degree of heat. Temper hardness is dependent on the set degree of heat desired, and the time required for the atomic shift to be completed. To be complete takes an amount of time relative to the alloy of the steel. Adding time will not change it's hardness once the shift is completed, but does assure a complete shift has happened. Adding a higher degree of temperature is the only way to change the temper hardness. A second temper is simply insurance that all that is supposed to convert, did convert. With simple 10xx steels, you could safely cut soak time down in half.

 

[Flintleather]

Thanks for the advice guys. I'm going to call L&R shortly and see if I can buy a spring. If so, I may try the whole annealing and reshaping deal. Nothing to lose, and I may learn something I can use later.

But I ain't gonna try it just yet, there are squirrels to hunt!

Thanks again fellas

Call L&R, i had the same problem with my Queen Anne and they had me send the lock back to them. They replaced the main spring free of charge, all it cost me was shipping. The lock is much better now, spring force increased and it no longer needs a perfect sharp flint to spark. I think the lock time increased a lil too. Flintleather

 

[LRB]

I have not heated my quench oil to harden. I use ATF.

Heating to around 130° lowers viscosity and cools the steel faster and more evenly. That would seem to be counter productive for a faster cooling speed, but it is not. Warm oil cools faster.

 

[springfield art]

I've got a Fusil De Chasse made back in the 90s. It shoots alright and is mostly reliable as long as the flint is "just right" and everything is just how it needs to be. I believe that the mainspring is fairly weak, as it takes considerably less force to **** than other flintlock I have messed with. I don't have a way to measure it, so i apologize in advance for those who need numbers on these kinds of things.

The lock in question is an L&R Trade Lock. Very low round count, around 100-150 at most. I have disassembled it and made sure everything was smooth and lubed. I have been told by a few people who I consider wise on the subject, that these locks are fairly notorious for weak mainsprings. The lock is also suspiciously easy on flints. It always sparks, but nothing like my others and seems noticeably slower.

Is there anything I can do to the mainspring to give it a little more oomph? Maybe heating it and opening it up a little more? I was planning to contact L&R to order a replacement, so figured I had nothing to lose. I have an assortment of torches and metal working tools. Just looking for some tips. I appreciate your thoughts!

Buy it a gym membership? (Just a dumb joke!)

 

[Billy Boy]

I used to follow the elaborate protocol for spring tempering as is found in various publications on the subject but most of them are based on per inch of thickness of the steel in question and a new main spring will have many times less mass. I read in one of my gunsmith books about an old black smith trick of mixing a 50/50 solution of 30 wt oil and Kerosene, covering the spring in the solution on it's side in a small flat dish and lighting it with a propane torch. Do this out side and let it burn it self out. It will take 15-20 minutes but the spring will be as well tempered as any of the sophisticated protocols produce. I have used it for many years and have never had it fail. Simple easy and effective!

After heating cherry red and quenching in oil, I put the spring on the bottom of mama’s oven and run the auto clean cycle. It is right around 700 degrees and lasts about 3 hrs. Has worked on about 5 or so springs I have done that way. Coupla of those springs have been in service for several years. It is a more satisfying experience ( and safer) if she is
at a quilting meeting when this happens..

 

[45man]

If you polish hardened steel to shiny and heat to blue it will work. That will be around 600 degrees. The problem is over shoot due to shape and thickness. A few degrees more in a spot will be brittle. Most quench when blue but letting it cool slow is better.
Even my mold cherries are taken to 300 degrees for tool steel for an hour and cooled slow as the oven cools. 700 is too hot for springs.
The funniest thing I ever seen on the net is to anneal brass or copper to form and then reharden it. I want the magic ferry to explain that and also want a brass magnet.

 

[45man]

Heating to around 130° lowers viscosity and cools the steel faster and more evenly. That would seem to be counter productive for a faster cooling speed, but it is not. Warm oil cools faster.

That is true but ATF is seed based and is thin as is. It can take high heat. I never had flame, just smoke.

 

[LRB]

I have made my own springs but I do not bend or fold steel. I cut to shape and polish. I find they last forever as long as there are no scratches. Heat to hardening temp, drop in oil. Then put the spring in your lead pot at 600 degrees for an hour, fish it out and set on the pot edge, turn the pot off and let all cool slow. DO NOT quench.
If you heat the bend to open the spring it MUST be hardened and tempered again. If not it will break at the first ****. I have home made mainsprings and frizzen springs I made still good after over 60 years.

Lead does not melt at 600°.

 

[M. De Land]

Lead does not melt at 600°.

That is true but the lead does not have to be melted to use as a temper draw if the pot brings it up to and holds at 600 degrees F. The spring will float on top not sinking much if any deeper into the lead even if it is melted. I also feel 700 F for and hour or two is higher and longer than needed for spring steel of this mass. One of course wants both hardness and toughness of the spring, both contributing to the ability to resist set.
600 degrees F. will produce a dark blue color on bright steel.
I like and use Brownell's tough Quench which is especially formulated to quench oil hardened steel, spring or tool. It is a mineral oil.
Good quality springs can successfully be drawn at either temp (600-700 F.) but here are the numbers on 1095 flat spring stock, for Rc and PSI. Rc is Rockwell C scale of hardness and PSI is pressure per square inch of yield strength
draw temp F. Rc PSI
400 62 320,000
600 55 270,000
700 49 238,000
800 45 212,000
I feel the 600* draw will yield the best balance of hard and tough for general main springs, flat or bend back, if properly dressed.
62-64 Rc is file hard.

 

[LRB]

Sorry, but you have no idea of what you are talking about. Common high carbon steels make the best springs at Rc hardness between 42 and 46. And a good file is 65 to 67 Rc. 62 Rc would not last long as a file. Mass has nothing to do with temper heat, only time in soak, and longer times make no change once the atomic shift has completed, it is locked unless a higher temperature is then applied. If a piece of steel was tempered to 55Rc, at 500° temp, then cooled and reheated to 500°, it could soak all day and never get softer or have any change in Rc.