[Source] Very fine wire for optical cross hairs

Jewelry Discussion
1

I have a friend looking for a source of wire in the size range of
0.015 to 0.03 mm or 0.0005 to 0.001 inches. He is rebuilding an
optical instrument.

The material does not matter so much as the it has the tensile
strength and flexibility that it can be wrapped to secure the ends so
that a short length can be taught and perfectly straight. 10 inches
or 20 cm would be all that is required.

Stephen Walker

2

How about the stuff that is wrapped around bundles of jewellers saw
blades?

Hans Durstling
Moncton, Canada

3 
The material does not matter so much as the it has the tensile
strength and flexibility that it can be wrapped to secure the ends
so that a shortlength can be taught and perfectly straight.

I don’t know if it’s still true or not - there was a time when those
were made from spider web.

4

He might try glass fibers. That was one of the original uses for
glass filaments discovered by accident when a researcher at Owens
Corning blew compressed air at a mass of molten silica in an attempt
to cool it. Some of the first fibers were used to create the cross
hairs for the top secret Norden Bombsight installed in US bombers.
The story goes that the guy that developed it made a ton of strands,
and after selling the US military all they needed for gun sights,
was left with something like 99% of the fibers he made. He and his
fellow researchers who were messing around with different plastic
resins mixed up some experimental epoxy resin and used it to patch up
a broken wicker chair. So, like so many other ingenious inventions,
what they created accidentally would come to be a very important,
life-as-we-know-it changing new material, known to the world as
"Fiberglas".

This story was told to me by the son of one of the researchers at a
seminar on creating molds for making fiberglass aircraft parts, so I
can’t really stand behind it if someone wants to pick at some nits.
But glass fibers would most definitely work as cross hairs in
optical equipment and are available in sizes that would be pretty
hard to find in metal. Cheap too.

A buck and a half would probably buy enough to make a thousand cross
hairs. Wrapping it and putting it under tension might be problematic,
but doing the same with 0.0005 steel wire is going to be a bit of a
challenge too, I would guess.

Dave Phelps

5

My first thought would be to look for Flexinol (brand name) / nitinol
(generic) wire. This is a shape memory alloy wire whose special
properties would be of no use in this case, but it’s strong and
easily available in sizes as small as 37 micrometer (~.0015 inches).
It’s also cheap at ~US$6 for a meter and available from many
suppliers listed on Google. It’s often called “musclewire.”

SMA wire was developed for kinetic applications - applying a current,
thus heating the wire, will cause it to revert to a previous physical
shape (shorter, coiled, etc) and cooling will relax the wire. This
can be used as a “solid state” motor, actuator, etc. It’s likely to
lose these properties if torch-soldered, but I expect that would not
be undesirable in this case. Crimp connectors are commonly used, and
it should be able to be tied easily enough.(With magnification, tiny
tweezers, and a steady hand!)

~w
William Aarons

6

I seem to remember reading once where the crosshairs for WWII
aircraft bombsights were actually individual strands of web from a
black widow spider’s web. Very strong and very thin.

Best regards,
Chuck

7

I seem to remember reading once where the cross hairs for WWII
aircraft bomb sights were actually individual strands of black widow
spider web.

Regards,
Chuck

8

Years ago, actual hair was used. Spiderweb was also used. Both are
thin and quite strong.

9

You can have a foot or two of our left over one thousands of an inch
diameter 99.999 % gold wire at no cost. Contact us, if you are
interested.

Peter Bauer and Sandra Kay
http://www.ganoksin.com/gnkurl/ep809p

10 
You can have a foot or two of our left over one thousands of an
inch diameter 99.999 % gold wire at no cost. Contact us, if you are
interested.

I was talking to the Perth Mint the other, so I asked them about
gold above .999, it was interesting.

The finer you make the gold the more expensive it is to make.

Theoretically it’s possible to make 100% pure gold, but would be
hideously expensive, something about playing with atoms :frowning:

Regards Charles A.

11

If I recall correctly, the Canadians refine their gold for Maple
Leafs to .9999. Higher than any other gold coin.

Have fun and make lots of jewelry.

Jo Haemer
timothywgreen.com