Spring winding advice

I need to wind a couple of large-diameter, fine wire springs. (light force, balancing device. And I cannot find any "stock" springs that fit
the bill)
I have good luck with wire that is larger, and whose elastic limit is mightily overcome by the radius of the arbor. Then they relax only a little, and come off the arbor a few percent larger than they were wound. I have OK luck with very small diameter springs of fine wire.
But with 0.013" music wire, I'm having trouble getting the right arbor size for a large-diameter spring. At anything near the desired size, the wire is only slightly bent by the process; so I know I'll need a MUCH smaller arbor -- but how small?
I need a spring es-aKly 5/8" o.d., 1-7/8" long, of twelve turns of 0.013" phosphated steel music wire.
Anyone have a rule-of-thumb for sizing the arbor for fine wire sizes?
Or, am I stuck trying 15-20 different diameters until something just works?
LLoyd
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On 07/22/2010 09:57 AM, Lloyd E. Sponenburgh wrote:

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
Wescott Design Services
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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 <G>.
LLoyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

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.
--
Ed Huntress



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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
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On 07/22/2010 10:52 AM, Lloyd E. Sponenburgh wrote:

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.
--

Tim Wescott
Wescott Design Services
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On Thu, 22 Jul 2010 12:52:03 -0500, "Lloyd E. Sponenburgh"

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.
--
Ned Simmons

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On Thu, 22 Jul 2010 12:52:03 -0500, Lloyd E. Sponenburgh wrote:

What kind of diameters are we talking about? Could you do some test bends around, say, drill bits?
Good Luck! Rich
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you know, don't you, that the 'real' spring winding machines extrude the wire against an angled anvil that is tilted in X,Y (presuming the wire is fed in Z) so that it causes the wire to bend to the desired spiral - if you build that, then it's simple enough to adjust to get the diameter and spacing you want, no adjustable mandrils required
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The first time uncle explained a spring winder it took me a while to realize he was describing what you wrote above.
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
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Yep; well, _fed_, not extruded, in most cases. I get to see one in animation every time an episode of "How it's Made" comes on.
But Bill, I need two springs. I have a spring winder.
And FWIW, I've already made them successfully.
LLoyd
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I wonder if an equivalent could be made from a scissors knurl with grooved rollers. Tilt the near end down to grab the wire between the lower roller and the shaft in the spindle, and adjust the upper roller or the crossfeed screw to change the wire loop diameter.
There is an adjustable fine wire feeder in your MIG welder.
jsw
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I'd have to re-build it to accommodate 13-thousanths wire. Its low end is 0.025", right now. At 0.020, the wire just hides in the wheel groove, and slips. I tried it with my roll of 0.020" music wire. Wheel turned, wire didn't feed.
LLoyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> fired this volley in

I wasn't doing this for spring winding. I was trying to weld with it. No soap.
LLoyd
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On Jul 25, 9:28am, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:

How about dressing a Dremel cutoff wheel to a V shape and grinding a new groove near the edge of the roller, then spacing it out to align with the wire tube? I don't know how long a shop-made unhardened roller would last, probably enough to wind a spring but not enough for much welding.
jsw
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On Fri, 23 Jul 2010 20:32:59 -0700, "Bill Noble"

That's true for inexpensive springs with loose tolerances. Precision springs are still wound on mandrels. Look in McMaster to see the difference in tolerance and price between standard and precision springs.
--
Ned Simmons

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On Jul 22, 12:57pm, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:>>

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
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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
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

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.
--
Ed Huntress



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