Can a mainspring be made stronger?

LRB said:

Clock springs used to be 1095 steel, and yes, it was heat tempered blue. Any of you, go make yourself a 1095 mainspring for a gun lock, or just a V facsimile of a gun lock spring. Harden then temper at 570°F, test it, and see how long that will last. Clock springs work with very different stress directions than do V springs of the size for gun use. A good lock main spring will be gray neutral in color if HTed in an oven. Ask world class gun maker Jerry Huddleston. He tempers springs at 725°, which I find a tad low, but obviously it works. Ask Jim Kibler. He is a professional metallurgist as well as one of the finest rifle makers in the country. He tempers at 750°. If he has time, he will talk to you.

Everyone has the privilege of settling on their own level of ignorance. No one has the right to impose it on others

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No one was imposing anything on anyone Wick, simply relating a different experience backed point of view. If one is tempering flat and V springs in the 600-700 degree realm and having good success with it than it is going to take more than a few key board strokes to make them change what is working for them. Personal testing of these higher tempering heats and experience will be the decider in my case. I've heard a lot of B.S. over the years spoken by those who insist that what they do is the only way it should be accomplished. Now it may be what you insist is the only correct way to temper a V spring might in fact be a better mouse trap then again it may be more B.S. There is always more than one way to skin a cat , in this case, temper a V spring.

M. De Land said:

No one was imposing anything on anyone Wick, simply relating a different experience backed point of view. If one is tempering flat and V springs in the 600-700 degree realm and having good success with it than it is going to take more than a few key board strokes to make them change what is working for them. Personal testing of these higher tempering heats and experience will be the decider in my case. I've heard a lot of B.S. over the years spoken by those who insist that what they do is the only way it should be accomplished. Now it may be what you insist is the only correct way to temper a V spring might in fact be a better mouse trap then again it may be more B.S. There is always more than one way to skin a cat , in this case, temper a V spring.

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Here is a photo of one I made for a hand gun and forgot I had on file. You can see the break in the original in the back. This was right after forging and filing out,before dressing out and heat treating. I drew the temper with the 50-50 oil and kerosene burn and this pistol is still going strong some 5-6 years later.


Finished spring ready for installation.

M. De Land said:

Here is a photo of one I made for a hand gun and forgot I had on file. You can see the break in the original in the back. This was right after forging and filing out,before dressing out and heat treating. I drew the temper with the 50-50 oil and kerosene burn and this pistol is still going strong some 5-6 years later.


Finished spring ready for installation.

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Well, the captions are out of sequence with the pictures but you should be able to figure it out.

I have the same but opposite problem. My main spring and the others are all too stiff. I have an original 1777 Charleville. It was made in 1815 so didn’t see much service. It is very hard to cock and is eating away at the front plate where the cock comes to rest. I’ve been checking with a lot of people who know these guns and the consensus is the spring is too strong.

Since this is original, I hesitate to do too much to the spring. I’ve been wondering about trying to re temper it. I came across this video and am now considering making a new one. Maybe this video will interest others.

Tempering a steel spring will not change the amount of force the spring delivers unless you screw it up and soften the spring too much.

Tempering the spring softens it so it won't break when it's bent. It does not change the strength of the spring as long as the hardness is enough to keep the spring from becoming bent.

If you do soften the spring so that it stay's bent after it has been used, it often will loose so much of its force that it won't work any longer unless it is re-bent back to its original shape and then tempered properly so it will maintain that shape.

In other words, don't retemper your spring. It's the wrong way to adjust the force that a spring will deliver.

The topic of obtaining the right spring force is complicated. I can heat a piece of steel, form it into a chisel, harden it and then temper it and it will work. Springs seem to be at a different level. That is why I am thinking about making a new one, that if it doesn’t work I can make another. I don’t want to experiment with the original one.

If anyone has more information on making one please let me know.

The force a flat spring creates when it is deflected depends on its length, how much it is deflected from its free state condition, its thickness and its width.

If your making a mainspring, the length is governed by the size of the lock because it only has "so much" space to work in.

The width of the spring works as a direct ratio. A spring that is twice as wide as another spring with the same length and thickness will produce twice the amount of power for a given amount of deflection. For instance, a flat spring that produces a 10 pound force when deflected 1 inch will produce a force of 20 pounds if it is twice as wide.

The force made by a spring with a different thickness works as a function of the cube of the thickness . Simply put, this means a very small change in the thickness will have a very large effect on the amount of force a spring will produce.

If your interested in the formula for the amount of force a spring will produce it is:

(E b t³ F) divided by 4 (L³) = load in pounds.

E = Modulus of elasticity in tension (for any steel use 29 million or 29,000,000)

b = Width of spring in inches

t = Thickness in inches

F = Deflection distance in inches

L = length in inches

This is a lot of interesting information. Thanks.
I’m just wondering, if you take two springs out of two different guns and they measure the same dimensions, will they have the same force? Many say never leave your gun cocked, because your spring will loose tension. How does that fit into the picture, if at all?

If they measure exactly the same, they should produce the same amount of force. Keep in mind, very small changes in the thickness of a leaf spring will have very large effects on the power of the spring. You might have noticed in the formula I gave, the length of the spring also works as a function of the cube of its value so very small changes in the springs length will also have very large effects.

As for leaving a gun cocked weakens a spring, if the stresses in the spring are not close to the spring material's yield point it won't matter. The spring will not be weakened.
The problem with this is, often, there can be an area in the spring where the stresses are high enough to be right at or exceed the yield point and if this happens for a long period of time, yes, the spring might bend slightly and become weaker.
That's why I always suggest that it is not a good idea to leave your gun cocked for long periods of time.

Thanks a lot for all this information. It all makes sense to me. I’m going to take a few days to reflect on it. Maybe I can get a hold of some of the same model springs and measure them to see if they are similar. I think I will look into making a new spring I can experiment with. Thanks for the help and info. I’ll keep you up dated. Greg.

it would seem if you could get hold of a similar spring you could grind the width, which I seem to recall in some previous MB article, was a method of reducing spring "strength". i also wonder why anyone ever would leave a gun cocked?