From: "Henry Kolesnik" on Thurs,Apr 7 2005 10:15 pm

Get a nice piece of smooth round rod and tightly wind a little over a
lineal
inch of wire closely spaced as possible. Count the turns in one inch
and
divide the number of turns into one inch and you'll have a very good
measurement without any cost.

73
Hank WD5JFR

Albert wrote in message
...
Does anyone know how to measure or determine the wire size. I have
tons of motors, solenoids, and similar items. I need some #24 wire
and
some #30 for a coil, but have to be sure regarding the wire diameter
as it's a critical ap and the author of the article says 'don't
substitute'.

I know I can weigh it, provided it's not on a spool or motor winding
already.

My local electrical shop has a wire gauge, but it stops at 18 gauge.

A microscope might work, but ones that have calibrated distance
measuring on the eyepiece are expensive.

Perhaps a milliohm meter might be able to measure the difference in
resistance of a foot of it or so, but that's hardly a standard item
either.

Any suggestions?

A non-destructive measurement is best. Along about
1946 my middle school (we called it "junior high" back
then) electric shop instructor demonstrated how to use
a mechanical caliper and how NOT to squeeze too hard in
doing so. Soft-drawn copper common to wire is fairly
easy to squash when using a caliper. Using one requires
a VERY light touch on the wire, just enough to be able
to pull it slightly through the caliper jaws. Even so,
pulling on soft-drawn copper wire is going to distort it
slightly so the measurement is going to be on the small
side. Snipping off ten or twenty short lengths, then
measuring the total width and dividing by the number of
lengths will be a bit better in accuracy.

A pocket optical comparator is handy for this and other
uses, especially when trying to get a measurement on
something already mounted with epoxy, varnish, etc. as
in windings of electric motors. While the "100-foot
resistance test" is a practical idea with a roll of
wire, it is hard to do when the wire comes from a
motor or transformer giving its all to the project.

As a practical matter, the wire size in small (such as
HF range) coils won't matter much on either the
inductance or Q tolerance. For example, Dropping from
30 AWG to 32 AWG isn't going to be a disaster in
cylindrical ("solenoidal") or toroidal forms. The
change in inductance will be aligned-out on trimming
in the circuit itself. Q is going to change much more
depending on the material of the coil former and the
presence of nearby conductive objects such as shields.

If a Twenty is too much for a pound or so of new wire
stock, then nobody can afford a Q Meter or inductance
meter to do an accurate measurement. Get with some
friends/acquaintences and share the cost of new stock.

Just some practical thoughts after doing a bit of
winding in my time...