How do I make a simple, flat torsion spring? (in stainless?)

I need 8 simple springs, they are not coil springs which push or pull along their axis. They are torsion springs which act tangential to their coil, but I need zero coils as the spring travel is less that 0.5mm and each leg is around 40mm long. so basically just a 40mm vee shaped piece of wire with around 5mm of the ends bent up at 90 degrees to locate in some holes. The wire diameter will be around 1mm or so

Would anyone be kind enough to educate me on what sort of wire I should be buying, and how I could heat treat it. I would love them to be stainless or somehow protected against corrosion but this isn't essential.

The springs are for my cars brake pads, they just apply a small amount of separation force to the pads to stop them rubbing on the disk - I don't have any at the minute and its fine, many cars just dont! They've rust and snapped and not having them makes my brakes whistle and whine when I roll up to a stop or turn on full lock.

I can buy replacement springs but a set will cost me £24 which seems like daylight robbery. I feel like I could bend all 8 with a pair of small pliers within about 60 seconds and harden them in even less time - I gather I would then draw out the temper a little and jobs a good un - but I've never made a spring, so I'm guessing here, and I don't know what material to use. Even if it ended up costing me the £24, it would be educational.

Music wire.

Search 'eBay' for 'Spring/Music/Piano Wire', I've bought different sizes off of there, quite reasonable prices including P&P

Not a direct answer - it may be worth trying an automotive brake specialist, likely to be cheaper than car dealership for such obscure items.

Cheaper than thought it would be £4 comes hardened and tempered.
**LINK**

Jon link looks like instrument wire (piano, harpsichord) not solid piano wire as in spring steel. May be wrong and it's a trick of the camera pixels but worth a check.

Hi Russ,

Solid piano wire is probably better option but try MIG welding wire as a cheap alternative.

Paul

My local model aeroplane shop sells piano wire in a range of sizes. Probably too thin for you, but I've bought stainless wire for making springs from dental technicians in the past

Edited By duncan webster on 08/12/2016 01:54:00

Ok thanks, plenty to look in to there.

As for mig wire, I wouldn't expect to get much of a spring of out that! Am I missing something here?

Music wire I've bought before in 4mm for a miniature T bar. Do I need to heat treat it to give it its spring or is already treated (and so, should I heat it up where I intend on bending it so it doesn't snap?)

Sorry for the novice questions here, I've not really any knowledge worth retaining in the field of heat treating and especially springs (I could make a centre punch and harden its tip, and I can heat treat silver steel but that's about the limit of my basic knowledge (and the 2 are basically the same thing)

Piano wire is hardened by the drawing process, if you heat it you will destroy the temper and you will never get it back, many have tried and failed. It can and usually is bent cold. Do not hit the bend in order to complete it as that is a sure way to induce a crack. I would ask myself what have I got most of 'time or money' I feel sure your 60 seconds is very optimistic and it will take you far longer.

Dusty thanks for the info, that's great.

As for time and money, the answer is, I take great pleasure in learning and achieving things like this, tinkering is my hobby I guess.

It may be possible to unwind a suitable coil spring for the material. Colin

Russ B, 18swg piano wire from your local model shop, next size up is 16swg which is 1.6mm thick.

Emgee

I have used Tig stainless 316l for various applications it seems springy as I found when making those fishing lures.

I don't know how critical the diameter is but 19 swg is just 1.016 mm if you can get it. 18 swg might be too thick.

Russell.

As far as I am aware music wire is solid, comes ready hardened and tempered. Can be cold bent meaning it loses its memory and therefore not the greatest steel used but poor quality.
If heat it up guarantee problems ranging from collapsing to breakages and would be either hit and miss through trial and error.

It will easily take a 90 degree cold bend as a tag either end.
Make the coil first leave ends long, cut to length then bend the tags about 2 mins each on conservative side after a practice and setup.

How it behaves is how it was designed to behave, if a steel had been used which was incapable of being bent past it's yield point then it would not be fit for purpose. Coil and torsion springs from music/piano wire give excellent performance and life, it's obviously good quality steel which does exactly what it's designed to do.

- Nick

Nick if you were making it correct you would harden and temper after!

How it behaves is material quality as in grade, hardening and tempering. Of which theres spring steel grades and theres spring steel grades of variable quality.
Just so happens this low grade spring steel used is not very hard or that springy compared to better quality and can only be hardened and tempered up to a limit hence it collapses past its yield. Fine for products that don't require much use or easy to make products without the necessity for harden and tempering which most will get wrong and come out anything from too soft to brittle.

Wondered why a brand new proper spring softens after a break in or first use?

Russ,

What make and model of car?

They normally last as long as the pads and new pads need new springs.

Hmm, that comes as news to me, as technical director in a company that designs and makes many hundreds of thousands of springs every year for demanding automotive applications. Incidentally, you don't need to harden and temper materials to make springs from them. As long as you keep within their elastic limit they will work fine - and they don't even need to be made of "spring" steel.