Material For Coil Springs

savarin

savarin

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I need to make a couple of compression coil springs 6mm od, length about 12mm, wire diameter 1 to 1.5 mm.
They need to be pretty strong springs.
I've just made a test one out of tig wire to see if the winding is easy (it is) but that doesnt have sufficient compression resistance.
And, I want a material that wont rust.
Any ideas?
 
Find a Ace Hardware store. They carry a assortment of music wire. The wires are in 3 foot lengths, depending on the spring you want to wind, maybe long enough an may not be. The wire is already harden and what I call "spring tempered" ready to wind a spring out of. You can also buy it off or eBone if you like, too.
 
I am far from an expert on this subject, I am curious about the application - this sounds like a really stiff spring for it's size.
302 and 316 stainless are commonly used for springs, you should be able to find wire for sale somewhere. It won't rust, but it will be a real bear to wind.

A 6mm OD with 1mm wire means a 4mm ID, so you need to wind it on something like a 3mm mandrel. I doubt you will be able to wind 12mm + waste between centers with a 3mm mandrel on the lathe the way most folks do. You will need to rig up some kind of follow steady between the mandrel and the tool post to keep the mandrel from bending/breaking/popping out the center. Going to bet that the mandrel will still wind up and twist/break though.
For sure you will have to anneal the wire before winding. Stainless anneals around 2000 F, but both 302 and 316 work harden, so it will probably come out of the mandrel hard (they can't be heat treated).

Is there no way to change the design? You might just have to purchase a commercial spring :(
Maybe you could "thread" a rod of 316 with 90 degree "threads," then drill/ream out the core leaving you with a flat coil spring. You would have to figure out a way to round of the edges a bit to prevent breakage. Just tossing out an idea for an alternative, dunno if it would work.
 
4gsr said:
Find a Ace Hardware store.
Click to expand...
No such animal in Oz:(
They carry a assortment of music wire. The wires are in 3 foot lengths, depending on the spring you want to wind, maybe long enough an may not be. The wire is already harden and what I call "spring tempered" ready to wind a spring out of. You can also buy it off or eBone if you like, too.
Click to expand...
I think thats what we call piano wire and it was my first thought but I dont know if it rusts or not.
 
I've bought spring steel rod(music wire) from radio control model shops, they generaly carry from rediculusly small to about 1/4 inch in meter lengthes. It's used for servo links and landing gear mostly(by radio control modlers).

Stuart
 
savarin said:
No such animal in Oz:(

I think thats what we call piano wire and it was my first thought but I dont know if it rusts or not.
Click to expand...

It does rust. It is a constant issue for the RC community.
As far as I know, the only spring that resists rust is a stainless spring.
 
Maybe some polyurethane rod or tubing would work. Won't rust and has a high spring rate. I use the stuff for die springs in some applications.
 
Hobby shops the sell model making supplies usually carry spring steel music wire in small diameters and around 3' lengths. The wire is just high carbon steel and will rust. McMaster Carr sell spring temper stainless steel but you would need to buy a 1/4 lb. of it. Another option may be spring temper brass or bronze.

Now I look at your profile and see that this isn't likely to help you much in your location.

As an aside, take a look at Lee Springs online catalog. They have a wealth of information there for just about any conceivable small spring. From that info, you should be able to design your spring. You will need to calculate things like free length, the force at working length , o.d., i.d., wire diameter, number of coils.

Here is a previous post on spring making. http://www.hobby-machinist.com/threads/spring-winding-calculations.37275/#post-318392

Bob
 
Find you an old whip antenna. IT's made of a grade of stainless steel. Sorry, I didn't catch the part that it needed to be rust resistant.
Next thing to try, is to find a spring manufacture in your neck of the woods that will sell you a length of wire. Doing that, you may have a selection of spring wire in grades of stainless all the way up to some of the Inconel grades to pick from.
 
Thanks, now I know 304 can be tempered to spring temper I will do some searching.
 
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