How to measure wire gauge?

[belwar]

Can anyone recommend a good method to accurately measure the diameter of magnet wire? Digital calipers just dont seem like the right tool. What do you all use? Micrometers? I can't imagine anyone here having a laser diffraction setup.

Belwar

[Alex/Tubewonder]

Take a length of wire and strip the enamel, wind 20 or so turns tightly on a nail or pencil. Measure the length covered by wire, divide by number of turns.

[chevalij]

I use a micrometer. Much easier and usualy pretty cheap. I got mine for about $20 at a local discount store. Even if you wind it around a nail, you still have to measure it and 20 turns is still only going to be about 0.060 for 42 with insulation.

[Joe Gwinn]

Can anyone recommend a good method to accurately measure the diameter of magnet wire? Digital calipers just dont seem like the right tool. What do you all use? Micrometers? I can't imagine anyone here having a laser diffraction setup.

Calipers are not accurate enough for measuring #42 wire and finer. A micrometer that can do ten thousandths of an inch (or the metric equivalent) is required. Be very careful not to crush the soft wire, yielding false readings. One trick is to bend the wire into a little zigzag, so there are multiple strands between the micrometer anvils.

The wire houses instead use optical comparitors, which do not squeeze or distort the wire.

[David Schwab]

One trick is to bend the wire into a little zigzag, so there are multiple strands between the micrometer anvils.

Great tip!

[essemfraise]

It's hard to get a reliable 1/1000 mm with a palmer, so I use it as comparator. Insert 2 parallel wires between the jaws, a known one, and the measured one. Bring the anvils til contact, then the locked wire is the heavier, the free one thinner. With multiple known samples you can achieve a good classification.

[Mal88]

Cleaning the Insulation off Copper

It is important not to measure the insulation - just the wire, and one good way that we used decades ago (in the '60s) was to heat the wire with a cigarette lighter, then dip the hot wire into a cap of Methylated Spirits. This would strip the residue leaving bare copper. And yes - go gently with the micrometer...

Cheers

Malcolm

[essemfraise]

In my opinion, it is important to know exactly how heavy is the insulation. For measuring the copper, I simply wrap the wire around a great distance, e.g around a table, measure dc resistance, and compare to standard gauge value.

[Mal88]

While you may well be measuring resistance this can translate mathematically to give you the wire diameter - if the distance is accurately known and the temperature is well controlled.

The problem is the 'Filling Factor' and you really need two sets of measurements here - the diameter of the wire with its insulation, and the diameter of the wire without its insulation.

The reasoning is that with hair-thin wire, the insulation is a substantial part of the overall diameter and consequently you will get misleading results if you incorrectly assume that the insulation is zero thickness.

The misleading results are encapsulated in that you cannot directly tranlsate insulated wire diameter and turns and resistance in the one simple equation, and you have to know the insulation thickness so that you can make the correction in the equation to get consistent results for a standard percentage filling of the bobbin!

[salvarsan]

Wire Specs

Wire manufacturors agree to produce wire according to
NEMA's MW 1000-2003 document. It has tables that
explain nearly everything you should expect when
buying wire -- all wire gauges, all insulations.

It is available for free download at:
http://www.nema.org/stds/mw1000.cfm/

-drh

[David Schwab]

All the rolls of wire I have here have the dimension of the wire written on it in pencil, so they much have checked each batch?

But If you need to find the gauge of an unknown wire, one good idea is what pickup maker Clint Searcy does. He takes known samples of various wire gauges, and mounts them on a microscope slide, and then compares them with unknown samples using a USB microscope.

He posted some photos at MIMF once, and it wasn't hard to tell them apart.

[RedHouse]

All the rolls of wire I have here have the dimension of the wire written on it in pencil, so they much have checked each batch?

But If you need to find the gauge of an unknown wire, one good idea is what pickup maker Clint Searcy does. He takes known samples of various wire gauges, and mounts them on a microscope slide, and then compares them with unknown samples using a USB microscope.

He posted some photos at MIMF once, and it wasn't hard to tell them apart.

I went over there for a search, no hits, do you have a link David?

[David Schwab]

I went over there for a search, no hits, do you have a link David?

I don't have a link.

It might be in the library by now... you have to register to see the library, and then do a search. It sometimes takes a while for threads to get archived.

[soundmasterg]

Since not all wire/insulations are equal, and you end up with thinner or thicker insulations of each type that could be 42 for example, I would think you would still have to measure thickness with a micrometer instead of just measuring DC resistance from wrapping some wire around something.

Greg

[Clint Searcy]

I think the trick your looking for is here.

http://www.searcystringworks.com/mlere.html

I got that idea from an old friend that help me solve pickup mysteries sometimes. He uses a normal microscope.