Making/Tempering Springs

[Across The Pond]

Hi - can anyone tell me a 'home gunsmithing' (ie simple home tools) method for making flat springs from music wire? I want to make a replacement wire bolt/trigger spring for my repro Colt cap and ball revolver.

I can get the annealing process done OK, making the shaping of the wire easy -the problem comes when I try to temper the formed steel back to a good spring temper.... (my process - learned from a model airplane website - is heat the wire to cherry red, quench in water, then put the spring into the oven, take it up to 200C, then allow it to cool slowly to ambient with the oven door shut) .... but it always snaps when it's first bent.

I'd just buy one but 1) I'm fairly sure that the wire spring is only commercially available for the Colt SAA/Navy/Army - not the '49 pocket that I want it for and 2) I'd like to be able to make it myself!

Regds, ATP.

 

[BobCat]

Your procedure sounds ok but you need to be sure you don't overheat in the first step (austenitizing) - there is cherry red, orange, and white. You want cherry red to light cherry red - not getting toward yellow, you can get grain coarsening, or incipient melting at the grain boundaries.

Quench promptly in oil or water. Water is a severe quench, and your music wire probably has enough carbon in it that oil will do fine, with no propensity for quench cracking.

Temper - well, 200 C is about 392 F, which ought to be fine... but I'd try about 315 C (about 600 F), and I'd limit tempering time to 30-60 minutes. No need to furnace cool, and there are types of embrittlement you can get from too long a dwell in certain temperature ranges. Just take it out and air cool it, or oil quench (nothing gained or lost by quenching from the tempering temperature, really).

The 200 C temper ought to be ok but may be too low/brittle. The 315 C temper might be a little soft, but should not be brittle.

And by all means, please post feedback on your experiment! Let us know what worked, ok? Thanks!

Regards,
Andrew

 

[jrhines]

Polish the quenched wire until it has a mirror finnish. Put a piece of scrap steel bar, say 2" wide x 12" long x 1/8" thick in the vise so you can lay the potential spring on top of it. That is clamp it across the 2" width with , say, about 8-10" of it hanging out in the air. Now heat the underside of the scrap with a torch until the spring just starts to turn a light straw color. Try to heat it evenly. As the spring starts to turn blue back off the torch. As the blue color increases remove the heat. When an even blue, slide the spring down the scrap toward the vice, to a cool place. DO NOT QUENCH. Let it cool in the air, it should retain its blue color. Now if the tempering was good, you should have a spring.

 

[BobCat]

Another thing, if you're interested

If you want to know more about practical heat treating, try:

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=A361141&Location=U2&doc=GetTRDoc.pdf

or just go to http://stinet.dtic.mil/ and search on "heat treatment" and see what you come up with.

Regards,
Andrew

 

[Across The Pond]

Thankyou to Bobcat and J Rhines

Thanks gents; good practical advice - much appreciated. As soon as I can make another spring or two (likely over the Christmas holiday period now), I'll try your suggestions and post back with the results. Practical skills like this are sooo useful in the UK, as there are very few 'real' gunsmiths left here these days.....

Regards, ATP

 

[wolf_from_wv]

Try these...

http://home.earthlink.net/~bazillion/intro.html

http://www.again.net/~steve/page7d.htm

 

[Jim Watson]

J.B. Wood did an article on making wire springs to replace leaf springs in obsolete guns and I think he just cold bent his music wire.

 

[Firehand]

If you have/can get the Brownell's catalog, in the section where they sell springs & stock they've got some tips on making springs, including hardening/tempering

 

[Riss]

If I recall from somewhere in the Brownells archive, some old timer gave the following recipe for making s spring. Heat till almost cherry red hot, put into a small shallow container with used motor oil. I believe that you were then to put the torch to the oil and after it started burning good to cover in ashes and leave it until cool to the touch. That should get your initial quench, and then a little reheat, and a long heat soak.

 

[Alpacca 45]

Hell, I'm in good company on this old thread! Hi Firehand!

Ok, for wire springs. they are cold formed from music wire, or if you need stainless, from hard drawn 18-8 wire, they need no heat treatment at any stage.

I've put a link to a thread with some good references for how to do it

http://www.thehighroad.org/showthread.php?p=5771419

Enjoy

 

[rcmodel]

If you want flat gun springs, you have to start out with better steel then music wire.

It is not good enough stuff due to low carbon content compared to high-carbon spring stock.

rc

 

[Alpacca 45]

Greetings RC,

For flat wire springs (my reading of it is - wire torsion springs) music wire is the stuff.

The carbon content does contribute to music wire's tensile strength, however the springy-ness at high stresses is due to the work hardening the wire got when it was drawn.

In the case of 316 stainless wire, the only way to get it hard is to cold draw the stuff, it can't be hardened by heat treatment.

a spring doesn't actually have to be hard, so long as you design it to stay within its elastic limit when it is working.

Safe working stresses in music wire springs are pretty amazing, typically over 100,000psi - far higher than anything else in a gun.

 

[rcmodel]

I understand that.

But he said he wanted to make a two-arm bolt spring for a SA revolver out of round music wire stock.

And I said music wire doesn't have enough carbon in it to pound it out flat, harden it, and temper it.

If he wants to make an original style two-arm flat bolt spring, like the one on the left:

He needs to start with high-carbon flat spring stock.
Not music wire.

If he wants to make a music wire spring like the one on the right, he needs to cold bend it and not try to anneal & re-temper it.
Because music wire doesn't have enough carbon in it to harden & re-temper it.


rc

 

[Jim K]

Maybe things are different in the UK, but I see no point in a lot of work for a $2 spring; I keep a dozen or so on hand all the time. I have made those springs out of spring wire (cold shaped) more for the fun of it than out of necessity. They worked OK, but a better idea is to properly feather the flat spring before installation so it won't break and won't gouge the cylinder.

Jim

 

[rcmodel]

+1

It also helps if you round and polish the end of the slot between the two leaves to get rid of the stress riser left from the square factory slot cut.

rc

 

[navyretired 1]

I've made many springs like this with nothing but music wire and smooth jaw pliers. Slowly and easly bend into shape without annealing wire. After shapeing it's ready to use. Music wire Is spring wire and you only have to get the right diameter for correct spring action.