Winding a closed coil extension spring?

[JoeCB]

hello all.. I've posted this question elsewhere and had no luck. I'm hoping someone here has had some experence with a closed coil spring.
I'm in need of some guidance on winding an extension spring. I have wound many compression springs on the lathe, no problem. But I have been asked to make an extension spring with closed coils. The material is .037 music wire. I set up a mandrel and a copper tube to guide, clamp and hold tension on the wire. All apparently goes well but no way the coils remain closed once the spring is cut loose from the mandrel. I beginning to wonder if it's even possible to cold wind a closed coil spring??? Any thoughts or guidance will be much appreciated.
Joe B

[Steve_in_Mich]

I think if you twisted the wire as you wrap the mandrel it might wrap tighter or loose depending on the direction of rotation relative to the coil wrap direction. Could give it a try on a bolt clamped in a vice and vice-grips pliers to give the twist as you wrap. 1:1 2:1 ?? experiment some. Then again maybe you won't be able to counter the internal stresses in the wire you are using that causes the coils to separate.

[Harold_V]

I'm of the opinion that you can't accomplish that task by winding on a mandrel. Springs aren't made that way on spring winding machines, likely for the same reason you're struggling. I'll be quite interested in hearing of your success should you solve this riddle.

Harold

[spro]

It would seem that there is evidence in the measurement of expansion over the previous mandrel. Another attempt could be made with a smaller. It's not for me to Guess at this but the fellow has put considerable work into the setup. There is also the consideration that there was heat applied, not in the way we would do it.

[Bob_W]

JoeCB:

I may not understand exactly what you are trying to do, but if you are winding 'standard' extension springs it is not difficult. When you wound the compression springs you would have been guiding the wire onto the mandrel ahead of the previous coil. Depending on how close you wanted the spacings the amount you would lead the previous coil would be changed. For an extension spring you guide the wire so that it lags the previous coil and actually has to 'slip' over the previous coil. If you guide with too much lag the wire will jump back over the previous coil. The amount of lag and tension on the wire will determine the preload on the spring with the coils closed. Hard to explain but easy to do.

Bob

[Flybynight]

Might try this.
I have seen a "Spring Winder" that was home made.
He made a "Screw" that was the ID of the spring, With the Pitch of the screw the dia of the wire.
He then took a block of steel and drilled a hole that was the OD of the spring.
He had a side hole that he put the wire into the Screw and then wound the spring by turning the screw.
Came out a perfect Screw.
If you can't see my discription and you are interested I would draw a Pic of it for you.
Jim

[Victor_R]

Maybe this will help. http://home.earthlink.net/~bazillion/extension.html

[Harold_V]

Hey, Victor. That's a great link. Tends to disprove that which I thought. Much appreciated!

Harold

[JoeCB]

Thanks to all you fellows for the responses, espically Bob-w ... yes the "lagging" idea is apparently the key to getting a closed coil. I played with it a bit last night and it helps, but I kept getting the wire jumping back on the previous turn. I have an idea for a guide that will force the lagging coil into it's proper place. I'll let you know...

Thanks again,

Joe B

[Conrad_R_Hoffman]

I've wound 'em successfully using the lag method, but I'm pretty sure that commercial springs start out with more tension closed than mine do. There are tricks one can do if the feed tube is a close fit on the wire, and you put a bit of angle on it. That can give a tighter fit on the mandrel and probably give tighter closed coils.

Also, be very careful winding springs- it can be dangerous under power. I built a spring and coil winder, nothing more than some bearings and a Jacobs chuck with a hand crank and turns counter. I make whatever mandrels/arbors I need on the lathe, then hand crank the final items. Fast and safe.

[dly31]

I don't know if it is true, but I once read that screen door springs, which have a high initial tension, were wound by twisting the wire and using a lot of tension in the wire feed.

[JoeCB]

hello guys, I'm back to report success. After several attempts, varying tension and lag angle I finaly got it! This spring was a bit unusual as it had 3 different diameters. The mandrel had to be stepped and of course each step size required several trials to develop the correct diameter to yield the required finished spring size. My jurry rigged a wire guide and follower had to be articulated and counter weighted to follow the ste sizes in the mandrel. Please excuse the "cobbled" set-up, but for a ont time job it worked... High tech made from 100% scrapundium.
Again, thanks for the help.
Joe B