Hello John, you've asked some good questions. Let's take them in
... Does twisted wire typically have a harder end result than heat
hardening or am I not heating it at a high enough temperature?
You are correct, any significant amount of work hardening will
produce harder metal than precipitation hardening. Precip hardening
isn't really a replacement for work hardening, it's a different
technique to get good hardness, though not maximum hardness, where
work hardening is not practical.
... I have read that you can twist the wire until one end breaks
but I am worried that over twisting will make the metal brittle.
Again, I'd say your instinct is correct. I've done the "twist 'til
it breaks" trick before too and noticed micro-cracks appearing
elsewhere along the length of the wire. Also, you have little
control over where the break occurs (see next paragraph). Unless
these micro-cracks are something you actually want -- needless to
say that's rather unlikely -- you might want to use a different
Part of the reason this isn't an entirely successful technique is
that it can be quite tricky to anneal a coil of wire perfectly
evenly throughout. In other words you're going to end up with wire
that has varying hardness before you start your twisting process
and that means that the twisting is very likely to cause hardening
faster at some points than others. It's at those "harder, faster"
points that you're going to get micro-cracks and quite possibly
total failure (it snaps).
Also, is there any advantage/disadvantage to twisting in one
direction and then reversing the drill in the other direction
(toggling between the two)?
Hmmm, my memory is letting me down a bit on this one but I remember
I did the reversing trick only once because the results were
terrible. As I recall it the hardening was very inconsistent along
the length of the wire and that was quite useless to me, not to
mention that the reversing was MUCH more likely to cause breaks
somewhere along the length of the wire.
FWIW I suggest you might want to alter your twisting process to
twist longer lengths of wire at a go. For instance you mention that
you "clamp the wire into the chuck and hold the other end with a
pair of pliers". I've found that this isn't an ideal technique
because it leads to too much variability in the final results.
A better approach, IMHO, is to anchor one end of the wire to a hook
in wall or shelf, pull the wire taunt, and then twist. This allows
you to do longer lengths of wire (I've gone as long as 2 or 3
meters) which, again, I've found helps get better, more consistent,
and more controllable twist-hardening results.
While twisting I have noticed under magnification that the surface
of the wire is not as smooth with tiny breaks on the surface.
I see two possibilities heRe: (a) they're not actually breaks,
they're linear imperfections that are not very noticeable before the
wire is twisted but become quite noticeable because of the twisting.
I've often seen this on my wire, largely because I draw it myself as
opposed to buying it at pre-determined gauges.
And (b) they are actually cracks which means that you've
over-hardened the metal and stress cracks are starting to appear.
When this happens it is usually caused by inadequate or uneven
annealing prior to the working, in our case it's the twisting,
When making jump rings I am coiling around a mandrel, hardening
the coil in my oven (as described above), polishing the coil and
then cutting into rings.
I would do it slightly different: pre-polish, coil, cut, then
(anneal for best results) and harden. Tumble polish with stainless
steel as a final step if necessary.
If you do the twist-harden then coil method you will, in my
experience, have a lot of problems getting tight and well-formed
rings. Besides, who needs the hassle?
in The City of Light
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