doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Little OT - Spring Making Question

I'm developing a prototype for a shotgun accessory which utilizes small torsion springs which I make myself. I wind .020" music wire around a 1/8" rod (5 wraps) and then "stress relieve" the springs by cooking them in a kitchen oven for about an hour at 500 degrees F. I've noticed that with springs which I haven't stress relieved the prototype seems to work better. What exactly does cooking the springs do? Does it make them stiffer, softer, should I bother to cook them at all? Whats the downside if I don't cook them? Thanks for any input you can give. John C.

I imagine you are annealing the steel, making it softer although I thought a higher temp would be required. I think making it softer would decrease its "spring strength". It would also make it easier to bend into a new shape if it is softer.
On the other hand it would be less likely to break under stress.

Do not heat the springs. Music wire as received is already heat treated properly. Forming a coil or other shapes does cause slight additional work hardening, but not enough to cause problems. Small commercial wire springs are formed directly from heat treated wire and are ready to use right off the forming machine. Larger springs are formed from annealed wire( in some cases, red hot wire) because the forming forces and machine wear are much less. They are heat treated after forming. One more point, a kitchen oven is a lousy heat treating device because the temp controller is usually very crude.

OB

What you are doing would be called tempering the springs. The temperature you cite, 500 F, would be marginal, but might trade some hardness for some toughness. The amount of time is not important, but the maximum temperature is very important. Agree that this is not necessary or desirable. Use 'em as you wind 'em. Wire diameter, spring diameter, coil spacing, and wire modulus combine into a spring constant - the amount of force required to stretch or compress the spring some set amount. If the spring is designed such that the coils completely collapse before the plastic deformation of the steel is reached, the spring will not break and will take very little set. The further you are from the plastic deformation limit, the more cycles it will last before breaking from fatigue.

"Wire diameter, spring diameter, coil spacing, and wire modulus combine into a spring constant - the amount of force required to stretch or compress the spring some set amount. If the spring is designed such that the coils completely collapse before the plastic deformation of the steel is reached, the spring will not break and will take very little set. The further you are from the plastic deformation limit, the more cycles it will last before breaking from fatigue."

Huh?!

John C - these are the things you need to consider when designing springs. They are not greatly complex, although they may seem so if you are unfamiliar with them. "Cut and try" is one approach to machine design - sometimes it works very efficiently. However, if you arrive at a point where you are not making progress with your machine, you may need to consider some paper design work. Just trying to point you in the right direction if you don't find what you need from "cut and try."