Spring winding advice

As a suggestion, try an arbor that's close to the desired diameter of the spring, and stretch the hell out of the wire as you wind it onto the arbor.

I have ABSOLUTELY NO CLUE if this will work for you, but I know that taking a bent-up, ugly, twisted piece of wire and stretching it straight does a dandy job, presumably because I've exceeded the elastic limit everywhere that it's bent. So I'm trying to think how you can get the same effect for a wire for which you want a controlled bend.

Alternately, make a split arbor, lubricate the hell out of it, hold both ends of the wire tight on the arbor, then expand the arbor until the wire stretches a bit. The more splits in the arbor the prettier the spring will be -- but what's the matter with a square spring if it works?

Again, the idea is to put the wire in the position you want, then stretch it past its elastic limit in position.

Tim Wescott fired this volley in news:tJidndpvFsNhHtXRnZ2dnUVZ snipped-for-privacy@web-ster.com:

Did. Didn't change a thing. It didn't even make the resultant "spaghetti" any smaller than if I had not.

I think the expanding arbor thing might be more trouble than buying or making a whole range of arbor sizes until I find one that works .

LLoyd

The old-fashioned spring-winding accessories for lathes, dating back to the '20s, put a *lot* of tension on the wire, as Tim says. I don't know how much, or whether it will work in your case, but you might try increasing tension until it breaks, and then back off.

The yield strength of fine, hard-drawn carbon-steel wire is pretty amazing. Small diameters of music wire approach 300,000 psi.

I suspect that with such a light bend your whole process would be very susceptible to variations in wire size and hardness, and possibly even the mood of the operator and the phase of the moon. If you're making more than a few springs it may be more accurate to say "obtaining a whole range of arbor sizes and constantly fiddling with which one to use on a particular day".

I _think_ that my expanding arbor idea would be much more repeatable, if tedious to make the first time.

Alternately, if you're starting with a straight or not too bent wire, you could make the spring with a series of small bends, i.e. octagonal, hexa-deca-agonal, etc. It'll be ugly, but it would work.

Come to think of it, if you have a mill and an index table, you could make a many-sided arbor and get a spring of many small bends that's nice and regular, instead of some hand-bent horror.

I have no rule of thumb, but you ought to be able to get the right arbor size using a binary search or whatever you want to call it. Same idea as bracketing when shooting. You know 5/8 dia is going to be too big. So try something like 3/8 dia. If that is too small then try 1/2 inch dia. Assuming that is too big, then estimate the correct size based on one being too big and the other too small.

I would think having the same tension on the wire would be important. I would wrap the turns too close together and then stretch the sping to the right length.

Dan

I've designed and prototyped quite a bit of coil winding tooling for odd lamp filaments that are made spring winding machines. (These are low volume, expensive, typically high-watt lamps for medical applications and studio lighting, etc.) If there's a tight spec on the coil diameter, it's almost always necessary to pick the final mandrel size by trial and error, and the company doing this has been at it for about 80 years. But it doesn't usually take more than 1 or 2 tweaks, and I don't imagine it will in your case either as long as the wire is consistent.

BTW, the machines (Sleeper & Hartley winders) have some provision for back tension on the wire, but can't apply an awful lot. More important is keeping the wire guide bushing close to the mandrel while winding.

" snipped-for-privacy@krl.org" fired this volley in news:3a3c1700- snipped-for-privacy@g35g2000yqa.googlegroups.com:

Yes and yes. I have an adjustable tensioner, and can break the wire with it, if I clamp down too tightly.

The wire I have is _almost_ straight -- 0.013" wire on a 5" diameter spool.

The long, hard way for me would be to wrap it on the correct arbor, then, on the arbor, anneal, heat treat to harden, then temper and strain- relieve. Then it would come out spot-on every time. This might even be the way large diameter light-force springs are made (??).

But I only have two springs to make now, and probably one or two every few years after that (at least for this machine). And I don't have a heat treating oven.

I think I will just try a binary search on the right size arbor. The tension, I can keep constant; even measure.

I'm betting the arbor size will be _really_ critical, because I'm going to be counting on a certain (large) amount of recovery of the coil to get it back to its nominal size.

LLoyd

If your wire is music wire or something similar (straight-carbon, at around

0.9% - 1.2%C), you will never recover the combination of strength and ductility it has now through heat treatment. No kind of heat treatment. Most of the wire's strength is the result of draw-hardening (work hardening) and that strengthening mechanism produces different results from phase-conversion through heat treatment.

Could you turn an arbitrary shallow taper, wind a spring, mark the spring before releasing it (maybe a paint strip to tell you where each turn ends up) and then find the mandrel size directly?

Spehro Pefhany fired this volley in news: snipped-for-privacy@4ax.com:

OOOO! Yer a smart guy! I have a whole junkbox full of "arbritrary tapers"!

I do like that one.

Thanks, LLoyd

"Ed Huntress" fired this volley in news:4c489066$0$4988$ snipped-for-privacy@cv.net:

Thanks for that. I might have wasted a small fistfull of money finding out.

LLoyd

Might find some info here. I believe he has a formula to determine the arbor size you need.

"Steve W." fired this volley in news:i2a70m$9d2$1 @speranza.aioe.org:

That was the first search I hit, too.

There's no formula, just "pick an arbor just a little smaller than the desired size of the spring."

It's also a very non-technical approach to the subject, with a lot of "this'n'that will vary, but there's no way to know how..." stuff.

I was kind of hoping someone had a table with different wire metals and rules, plus maybe a nomograph plotting diameter vs. wiresize vs. abor size.

(Hopin' too much, huh?)

LLoyd

I have an entire book (a little old MAP book, or similar) on spring-winding and other non-cutting jobs on small lathes. It's in a box, in my storage area, three miles away. Otherwise I'd pull it out for you.

But I'd be skeptical of any specific formula. You might get a ball-park number out of it. But there's nothing you won't learn by wrapping the wire, hard, around a few test "arbors," like pieces of pipe or bar stock.

Oh -- only 5/8". The way you were going on, I was picturing something like 5" to 10" diameter.

Why not try just a few turns on 1/2" and 3/8" and measure what you get. That will probably let you calculate something quite close to your needs. Maybe it will show you that you need a third try at 1/4", but I doubt it.

For the really large ones that I was picturing, I would have suggested three staggered rollers to put a pre-bend into the wire separate from the arbor.

Good Luck, DoN.

can you do this quick&dirty by having a roller (narrow guided with the wire or wide, length of the arbor) press the wire against the arbor right where the wire contacts the arbor? (arbor and roller make a pinch roller)

dave

Its not the diameter, its the music wire. This is hardened, which causes this exact problem. it makes great springs, but is HELL to make a permanent bend in. Ever re-string a guitar? Getting the wire to take a bend on the tuning pegs is a real challenge, and trying to not get the wire poked all the way through your finger.

I think you will have to experiment, but you can wind the wire around drill bit shanks to find the magic size that results in the desired relaxed coil diameter.

Jon

That number is scary if you get wrapped up in your wire. I made some .078 dia springs for a line at work. Tight wound, < 9/16" dia. I carefully cut each length of wire, made damn sure it couldn't grab me and ran the lathe on slowest rpm.

I'll never work off a spool. It is way too dangeous.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

When I make springs, either carbon or stainless, I set the springs in my oven. I was looking for the temperatures when I ran into this.

Not what I was looking for, sounds like it is geared to making sure a spring keeps its characteristics.

Is more what I was looking for.

Whenever I make springs, I ask uncle for the stress relieving temps since I never can remember them. Uncle ran coil winders for a number of years before trying selling Orchids.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller