"John B." wrote in message
...
On Fri, 19 Jun 2015 18:15:00 +0800, Techman
wrote:

I need to replace a broken light duty torsion spring and need some
advice.

It's broken right at the bend, I may be able to buy a new one but it
will have to come from the UK to Australia and I need it ASAP.

https://dl.dropboxusercontent.com/u/...ring%20(1).JPG

https://dl.dropboxusercontent.com/u/...ring%20(2).JPG


The spring returns an aluminum flap through and rotates through an
angle
of around 90°.
The wire diameter is 4.5mm and the overall length of the spring is
around 24".


I can get some 3/16" diameter "piano wire" (4.76mm) or 5/32" (4mm)
from
my local hobby shop. Will piano wire work OK as a spring in this
sort of
application?


Will I have trouble cold bending the ends?

I was thinking of drilling a 5mm hole through a heavy piece of metal
and
using pipe, then a hammer, applying the bend. I would try to leave a
more generous radius than the on the original.

Thoughts?


Thanks guys.

I've made a number of springs from music wire and they seem to work
pretty well. and yes, a bit more generous radius on the bends will
probably last longer.

I would think that you could bend 3/16" by hand, or perhaps a couple
of pairs of pliers, so a fancy jig shouldn't be necessary, and I
wouldn't hammer on the bends as it might work harden then even more
and could cause them to fail.
--
cheers,

John B.


3/16" steel welding rod can be bent by hand, but the work hardening at
the bend stiffens it there and causes the whole piece to curve rather
than allowing a tight localized radius. When I need a tight U bend
with straight legs I have to rubber-hammer the rod around a mandrel.

AFAIK music wire is hardened by cold drawing and doesn't respond to
heat treating as well as you might like.

-jsw