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Creating variable thickness in wire


#1

Hello All, Does anyone know of a fast or simple method to create
controlled variations in gauge, thickness, diameter in a single piece
of wire? For example, lets say you have a 2 inch piece of 12 ga and
you want to create a SMOOTH taper to 18 ga in the center (both ends
are 12 ga). Hammering creates dimples, the rolling mill creates a
flat section, grinding may be a possibility. Any suggestions are
welcome.
Thanks, Will E.


#2

Hi Will, anneal only half of wire (hold the other part into water).
Put wire into a drawing bench and pull. The soft, annealed part will
become thinner, the hard part stays the same. If you do not have a
drawing bench try the vice and a pair of drawing pliers (watch your
back though)! Cheers, Klaus


#3

I would hammer the wire before I cut it off. A planishing hammer
used with overlapping strokes should produce a pretty even surface
after using a cross pein of some sort to get the shape. After the
planishing, light filing and sanding will remove any last traces of
the work process. By the way, a planishing hammer has a very very
slight dome and a perfect finish. Marilyn Smith


#4

Will, the only way I can think of to do what you want would be by
chemical milling, which amounts to etching or electrostripping.

In principal what you’d do would be to bend your material into a U
shape, and gradually lower it into the etch bath, a little bit at a
time. So, the part that enters first gets etched for the whole
time, and the part that is submerged last gets only a short etch.
When it’s done you’d straighten the wire.

In practice there are all the usual "ifs and buts and maybes"
associated with etching. The wire would have to be uniform throughout
its length, not just in composition but also in terms of hardness.
You’d need to stir or agitate the liquid, probably. You’d need to
experiment with different rates of lowering and various total etching
times. It’s possible to envision variations that would keep the wire
straight throughout the process, but they would be more applicable to
production situations.

For silver you could use dilute nitric acid or ferric nitrate
solution. For other metals you’d need an appropriate etchant.
Electrostripping is like electroplating in reverse, in fact that’s
just what it is. All chemicals have safety issues associated with
them, which I’m not going into here, just pointing out that there’s
more that you need to be aware of besides the basics of the method.

Incidentally, this technique is used to make extremely fine points
on various wires for scientific purposes.

Kevin (NW England, UK)


#5

How about the following, very simple handwork approach? Place the
wire on a hard, slightly convex surface. Take a hard steel rod ,
such as a smooth ring mandrel, held at a slight angle to the wire,
and smoothly roll out the wire with the rod. This should give you
the desire d results with a little practice. Works for me with
sterling.

Good luck!
Richard Bynum
Oakland