Does heating a spring to bend it lose its temper?

[Bottlecapdigger]

I want to make a custom spring out of a garage door spring for a project. If I heat it with my torch shape it to what I need and let it cool slowly. Will it still retain its spring tension? BCD. Thanks

 

[larry_g]

It may. It depends on what you heat, how you control it, and how much of the coil you heat and then expect to act like a spring. If you heat a small area to make a hook end say then most likely you will succeed.

lg
no neat sig line

 

[lis2323]

I thrive at cooler temperatures.

It doesn’t take much heat in the spring for me to lose my temper.

 

[rsanter]

Odds are yes, if,you heat to the point of being pliable so you can bend it. Then odds are you will loose its temper

 

[Bottlecapdigger]

How do I keep the spring tension? Should I be quenching it after it's formed and still red hot? I should be paying more attention when I watch " forged in fire". BCD.

 

[slowtwitch73]

Yes it will lose its temper.

 

[Sevenhills1952]

Many years ago I had to drill some car leaf springs, center where they clamp together at differential housing. I wasn't having luck, grandad next door saw me working and showed me how to take temper out with torch, letting them cool slowly. When cool they were easy to drill. To put temper back we heated them back...then lowered them in a pan of motor oil. He said oil for a spring.

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[joe_padavano]

Springs use heat treated steel, typically. Heating the steel hot enough to bend it then letting it air cool will anneal the steel, which means you lose the heat treat. Note that this does NOT change the stiffness, or "springiness", it lowers the STRENGTH of the steel. What that mean in a practical sense is that the annealed part of the spring will yield at a lower load than the rest of the spring, causing it to bend or stretch under load. It will also break at a lower load.

 

[matt_i]

Agree with the suggestion to heat it, bend it to what you need and then oil-quench. The oil may flame locally but usually there's enough mass for it not to catch fire. I would not use a hydraulic oil or ATF as those seem more flammable to me. Motor oil would be perfect.

Now that is part 1.

The 2nd part is to polish some of the blackened area that you just quenched back to shiny/silvery bare metal with sandpaper.

Now to spring-temper it which means you want a blue-purple color, a kitchen oven is a good thing to roll with provided you can get the oil out of it (solvent clean, etc). A good alternative could be a propane grill. Around 500-600F is what you want.

The natural color of the polished steel would go from golden/straw color to blue/purple color, and the latter is what you want for a spring. The former is good for edge tools or those parts which aren't really designed to flex.

Its a homebrew method so the exact parameters are a little loose but that's the general direction I would proceed.