Ed

The reason I was asking this question is because I was involved in a
discussion about building a coffee roasting drum to be used in a gas BBQ
grill and it was suggested that a music wire cotter pin might be used in
it's design.

When I built my roasting drum I considered using a spring for the door latch
but opted not to as I was worried about the reliability in an environment
that you are shooting for a 500 F temp.

Seems to me you have confirmed this.

Thanks.

--
Roger Shoaf
If you are not part of the solution, you are not dissolved in the solvent.

"Ed Huntress" wrote in message
news
"Roger Shoaf" wrote in message
...
At what temperature does a music wire spring lose it's temper?

Not to be difficult about it, but a music wire spring has no temper,
unless
it's been heat treated. Music wire is not heat treated, and it's not
normal
practice to heat treat it.

It gains its hardness and strength from being drawn through wire dies --
through work hardening, in other words. Home made music wire springs are
usually wound in that condition, with no heat treating involved.

However, maybe what you want know is how much you can heat it before it
begins to lose its hardness. In an important sense, it never loses the
stiffness of its spring resistance, by the way. The steel has the same
stiffness whether it's hard or soft. But softening it lowers its yield
strength, so it *does* lose its ability to take a load. You can easily
exceed the yield strength of a soft-steel spring, and it won't recover its
original length when you take the load off after that.

Music wire is plain, high-carbon steel, and so it begins to lose hardness
at
a low temperatu around 280 deg. F. It progressively loses more hardness
as you heat it up to the range of 700 deg. F or so.

Ed Huntress