>Is it necessary to heat music wire to get a good 90 bend
>and if so what's the best way to do it?
Don't do it! Heating music wire sufficiently to soften it
will also anneal it and destroy its strength. Once annealed
there's no way to get the strength back other than cold working
(i.e. by destroying the part you just made). Heat treatment
won't work -- wrong kind of steel.
This is what I do to make clean bends in hefty music wire (between
3/32" and 5/32"):
1) First decide on which side of the bend you want to be as straight
as possible. On RDS this will be the part of the wire which sits
in the pocket.
2) Clamp that part in a vise, tightening just short of forming flat spots
on the wire. Vise-Grips or very hefty pliers may also work for the
smaller wire sizes.
3) Bend the protruding part over, using a large piece of metal. Apply
the bending force as close to the vise jaws as possible to keep the bend
localized. Wear eye protection in case things go SPROING! accidentally.
Hammering on the metal piece may be necessary for really heavy wire.
4) Bend about 5-10 deg PAST the intended angle. Then bend back
to the intended angle.
Note 1: The reason for going "too far" and then returning is to relieve
the huge residual stresses (about 1/2 of yield stress!) in the steel which
would otherwise remain. The bend will be much stronger then.
It's easy to observe that these stresses are there: It takes a lot of
force to get from 90 to 100 degrees bend the first time, but starting
the backward bend from 100 to 90 takes much less force. The residual
stresses at the surface are helping you when you go back.
Note 2: If the wire cracks at the vise edge, put a softer-material
block between the wire and one vise jaw face, and bend against
the edge of the softer block to get a larger radius. I've used copper,
soft aluminum, even maple.
- Mark
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