Accurately measuring diameter of very fine copper wire ?

[N_Cook]

Not the first time I've met this problem.
Say nominally about 0.05mm . With a micrometer, how much are you compressing
it? could easily be out by 20 percent out and squaring that if using weight
to length via density or resistance calculation via resistivity, is very
iffy.
If access to a microgram resolution of weighing scales then a few metres of
the wire and density of copper and allowance for enamelling , but no highly
accurate weighing machine. Optically comparing under a microscope needs
known diameter standards.
How about a longish length , folded 6 times until 64 wires. Maybe
longer/more bulk. Hand twist together until it will not sensibly tighten any
more. Take average diameter, use packing factor allowance, and infer for 1
wire diameter, how better accuracy might that be.?
If I start from known good coil of say 46swg enamelled wire and do this 64
wire trick , to work backwards, how accurate/reliable would the manufacture
sizing be ?
Any other ideas?

 

[alchazz]

On Tue, 04 Aug 2009 15:38:19 +0100, N_Cook wrote:

Not the first time I've met this problem. Say nominally about 0.05mm .
With a micrometer, how much are you compressing it? could easily be out
by 20 percent out and squaring that if using weight to length via
density or resistance calculation via resistivity, is very iffy.
If access to a microgram resolution of weighing scales then a few metres
of the wire and density of copper and allowance for enamelling , but no
highly accurate weighing machine. Optically comparing under a microscope
needs known diameter standards.
How about a longish length , folded 6 times until 64 wires. Maybe
longer/more bulk. Hand twist together until it will not sensibly tighten
any more. Take average diameter, use packing factor allowance, and infer
for 1 wire diameter, how better accuracy might that be.? If I start from
known good coil of say 46swg enamelled wire and do this 64 wire trick ,
to work backwards, how accurate/reliable would the manufacture sizing be
?
Any other ideas?

In my analytical work on failed electronics, I would take a wire like
that and mount it vertically in a mounting medium that is used for cross-
sections. I would mount several samples near to each other. Then I would
cross-section the mount and measure the diameters using a microscope with
a calibrated filer eyepiece. The diameters with/and without the coatings
would be provided to the customer along with an average value.

At the time I was doing it, my lab would charge about $100 for that.
Depends how important it is to you for spending that much. Since I am
retired, I'm sure it's more expensive now.

 

[William Sommerwerck]

Here's a thought...

If you could find a table of resistance-per-unit-length for various wire
gauges, and had an ohmeter that could accurately read low resistances...

 

[Meat Plow]

On Tue, 4 Aug 2009 15:38:19 +0100, "N_Cook" <diverse@tcp.co.uk>wrote:

Not the first time I've met this problem.
Say nominally about 0.05mm . With a micrometer, how much are you compressing
it? could easily be out by 20 percent out and squaring that if using weight
to length via density or resistance calculation via resistivity, is very
iffy.
If access to a microgram resolution of weighing scales then a few metres of
the wire and density of copper and allowance for enamelling , but no highly
accurate weighing machine. Optically comparing under a microscope needs
known diameter standards.
How about a longish length , folded 6 times until 64 wires. Maybe
longer/more bulk. Hand twist together until it will not sensibly tighten any
more. Take average diameter, use packing factor allowance, and infer for 1
wire diameter, how better accuracy might that be.?
If I start from known good coil of say 46swg enamelled wire and do this 64
wire trick , to work backwards, how accurate/reliable would the manufacture
sizing be ?
Any other ideas?

Fender used 42 AWG and 43 AWG. If this is about rewinding that Landola
pickup I wouldn't get too scientific. I would browse the Stew-Mac site
and look at what they have to offer. Maybe there is an equivalent
supplier on your side of the pond.

http://www.stewmac.com/

 

[Smitty Two]

In article <h59hif$h7f$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Not the first time I've met this problem.
Say nominally about 0.05mm . With a micrometer, how much are you compressing
it? could easily be out by 20 percent out and squaring that if using weight
to length via density or resistance calculation via resistivity, is very
iffy.
If access to a microgram resolution of weighing scales then a few metres of
the wire and density of copper and allowance for enamelling , but no highly
accurate weighing machine. Optically comparing under a microscope needs
known diameter standards.
How about a longish length , folded 6 times until 64 wires. Maybe
longer/more bulk. Hand twist together until it will not sensibly tighten any
more. Take average diameter, use packing factor allowance, and infer for 1
wire diameter, how better accuracy might that be.?
If I start from known good coil of say 46swg enamelled wire and do this 64
wire trick , to work backwards, how accurate/reliable would the manufacture
sizing be ?
Any other ideas?

You only need two things:

1. A toolroom micrometer (not to be confused with a homeowner mic, or a
machinist's shop mic.)

2. The skill to use it.

I can't think in fractions of a millimeter very well, but a good
toolroom mic will read directly to 0.0001", and inferentially to
0.00001" within +/- 0.00002" or so.

The trick to not "crushing" the wire is to use the wire like a feeler
gauge, between the jaws of the mic., closing the mic slowly while
feeling for friction.

We buy 42 AWG single poly for guitar pickups, and order it specifically
as "min to nom." (minimum to nominal diameter.) The supplier checks his
stock with a toolroom mic, and ships only those spools on the low end of
the tolerance range. We verify it before putting it to use.

 

[GregS]

In article <h59odg$646$1@news.eternal-september.org>, "William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

Here's a thought...

If you could find a table of resistance-per-unit-length for various wire
gauges, and had an ohmeter that could accurately read low resistances...

I thought getting good contact would be a problem. Soldering might work.

If you could not get an optical scale, perhaps a printer could be used to make a scale.
600 dpi would be less than .04 mm.


greg

 

[Robert Macy]

On Aug 4, 10:02 am, Smitty Two <prestwh...@earthlink.net> wrote:

In article <h59hif$h7...@news.eternal-september.org>,

We buy 42 AWG single poly for guitar pickups, and order it specifically
as "min to nom." (minimum to nominal diameter.) The supplier checks his
stock with a toolroom mic, and ships only those spools on the low end of
the tolerance range. We verify it before putting it to use.

I would like to email directly and discuss winding guitar pickups.
Please email:
robert DOT a DOT macy AT gmail DOT com

Where do you buy 42 Awg wire?

We buy small quantities of 30-36 Awg at exceptionally competitive
pricing from
Fay Electric Wire Corp. (800) 245-9473
752 North Larch Avenue
Elmhurst, IL 60126
[not associated with them, or gain by posting this.]

Robert

 

[Robert Macy]

On Aug 4, 11:54 am, zekfr...@zekfrivolous.com (GregS) wrote:

In article <h59odg$64...@news.eternal-september.org>, "William Sommerwerck" <grizzledgee...@comcast.net> wrote:

If you could not get an optical scale, perhaps a printer could be used to make a scale.
600 dpi would be less than .04 mm.

greg

Interesting idea! I need an inexpensive optical scale from time to
time.

I have some 8.5 by 11 inch thermally stable paper printed in
Switzerland that has 300 lines per inch printed diagonally on it.
Yes, that's 150 black, 150 white per inch. Got 10 sheets at the
bargain price of $300 per page and these were 1980 prices.

In a printer doesn't the single blop of ink/laser powder spread out
over more than 3 to 4 of those pixels? Does gray scale modify the
density? Or, do printers still use those pseudo patterns to generate
gray scale?

Is there anybody out there to try this, look at it under a microscope,
and let us know?

Robert

 

[whit3rd]

On Aug 4, 10:38 am, "N_Cook" <dive...@tcp.co.uk> wrote:
[about measuring a small copper wire]

Say nominally about 0.05mm . With a micrometer, how much are you compressing
it?

Measuring microscope. Either a standard microscope with a
micrometer-driven stage and a crosshair reticle, or a microscope
mounted on an X/Y translation mechanism (calibrated, of course).
It's a standard item in instrument shops, and you can measure
the width to whatever edge-detection limit your microscope
has.

If the length is long enough, resistance and length will do the
same trick, BUT resistance measures average resistance
(average of radius squared), not average of radius.

 

[nesesu]

On Aug 4, 9:34 am, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

Here's a thought...

If you could find a table of resistance-per-unit-length for various wire
gauges, and had an ohmeter that could accurately read low resistances...

One uses a "4 terminal" ohmmeter.
To do this easily, use one DVM on ohms and connect it to as second DVM
on current to measure the 'ohms current' ; it is usually an even
current like 1mA , 10mA etc. Note the value. Then connect the ohmmeter
to the ends of the wire under test. Take the second DVM on mV and
measrue the voltage across a precise length of the wire under test.
Since that is a voltage [high impedance] measurement, contact
resistance has relatively little effect on accuracy.
One should also take into account the temperature, then plug it into
the resistance formula and arrive at the area then reduce that to a
diameter.

Neil S.

 

[Jeff Liebermann]

On Tue, 4 Aug 2009 15:38:19 +0100, "N_Cook" <diverse@tcp.co.uk> wrote:

Any other ideas?

Get a magnifier with replacable reticles:
<http://www.measuringmagnifier.com>
<http://www.tedpella.com/magnifier.htm>
<http://www.emsdiasum.com/microscopy/products/magnifier/measuring.aspx?mm=18>

If your wire is microscopic and too small for a 8x or 10x magnifier,
get a reticule (or graticule) for a microscope:
<http://www.reticles.com/ordering.htm>
<http://www.microscope-depot.com/reticles.asp>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[N_Cook]

Smitty Two <prestwhich@earthlink.net> wrote in message
newsrestwhich-CD4597.10025204082009@newsfarm.iad.highwinds-media.com...

In article <h59hif$h7f$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

Not the first time I've met this problem.
Say nominally about 0.05mm . With a micrometer, how much are you
compressing
it? could easily be out by 20 percent out and squaring that if using
weight
to length via density or resistance calculation via resistivity, is
very
iffy.
If access to a microgram resolution of weighing scales then a few metres
of
the wire and density of copper and allowance for enamelling , but no
highly
accurate weighing machine. Optically comparing under a microscope needs
known diameter standards.
How about a longish length , folded 6 times until 64 wires. Maybe
longer/more bulk. Hand twist together until it will not sensibly tighten
any
more. Take average diameter, use packing factor allowance, and infer for
1
wire diameter, how better accuracy might that be.?
If I start from known good coil of say 46swg enamelled wire and do this
64
wire trick , to work backwards, how accurate/reliable would the
manufacture
sizing be ?
Any other ideas?

You only need two things:

1. A toolroom micrometer (not to be confused with a homeowner mic, or a
machinist's shop mic.)

2. The skill to use it.

I can't think in fractions of a millimeter very well, but a good
toolroom mic will read directly to 0.0001", and inferentially to
0.00001" within +/- 0.00002" or so.

The trick to not "crushing" the wire is to use the wire like a feeler
gauge, between the jaws of the mic., closing the mic slowly while
feeling for friction.

We buy 42 AWG single poly for guitar pickups, and order it specifically
as "min to nom." (minimum to nominal diameter.) The supplier checks his
stock with a toolroom mic, and ships only those spools on the low end of
the tolerance range. We verify it before putting it to use.

Yes for the Landola pickup, the number of turns from measuring wire diameter
then weight/weighted circumferences and also by the 7.7Kohm ,assuming both
pickups are the same then this gives the same number , but does not agree
with counting a sample 1000 turns and ratioing , they were in fact laquered
together to defeat counting-off

For 2 reels of enamelled wire labelled as 2.4 thou/mil and 2.8 thou/mil and
my micrometer that has a 2Kg closure force (just checked via spring and
kitchen scales) before the torque clutch disengages.
I have to DIVIDE the reading by 1.15 for the 2.4 thou wire and 1.25 for the
2.8 thou wire. I suppose this is to do with the enamel thickness and the
wire is specified as the metallic diameter. I assume my wire gauge v
wight/resistance tables are for bare copper, not actually specified.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[N_Cook]

Robert Macy <macy@california.com> wrote in message
news:60a84456-5016-4099-95be-4fa0d691e89b@f20g2000prn.googlegroups.com...
On Aug 4, 10:02 am, Smitty Two <prestwh...@earthlink.net> wrote:

In article <h59hif$h7...@news.eternal-september.org>,

We buy 42 AWG single poly for guitar pickups, and order it specifically
as "min to nom." (minimum to nominal diameter.) The supplier checks his
stock with a toolroom mic, and ships only those spools on the low end of
the tolerance range. We verify it before putting it to use.

I would like to email directly and discuss winding guitar pickups.
Please email:
robert DOT a DOT macy AT gmail DOT com

Where do you buy 42 Awg wire?

We buy small quantities of 30-36 Awg at exceptionally competitive
pricing from
Fay Electric Wire Corp. (800) 245-9473
752 North Larch Avenue
Elmhurst, IL 60126
[not associated with them, or gain by posting this.]

Robert


I have emailed to you

 

[Michael A. Terrell]

N_Cook wrote:

Not the first time I've met this problem.
Say nominally about 0.05mm . With a micrometer, how much are you compressing
it? could easily be out by 20 percent out and squaring that if using weight
to length via density or resistance calculation via resistivity, is very
iffy.
If access to a microgram resolution of weighing scales then a few metres of
the wire and density of copper and allowance for enamelling , but no highly
accurate weighing machine. Optically comparing under a microscope needs
known diameter standards.
How about a longish length , folded 6 times until 64 wires. Maybe
longer/more bulk. Hand twist together until it will not sensibly tighten any
more. Take average diameter, use packing factor allowance, and infer for 1
wire diameter, how better accuracy might that be.?
If I start from known good coil of say 46swg enamelled wire and do this 64
wire trick , to work backwards, how accurate/reliable would the manufacture
sizing be ?
Any other ideas?

I wind 100 turns of fine gauge wire on a smooth rod and measure the
length with good calipers, then divide by 100. If there isn't enough
for a good measurement, wind 200 turns.

Or spend $50,000+ US for a precision optical measuring machine made
to monitor the diameter of wire as it is made or spooled.


--
You can't have a sense of humor, if you have no sense!

 

[William Sommerwerck]

I wind 100 turns of fine gauge wire on a smooth rod ...

Tightly, of course.

... and measure the length with good calipers,
then divide by 100.

There's a story that Edison asked a young man (presumably an apprentice) to
measure the volume of several light bulbs. The apprentice stated with a
ruler, a pair of calibers, trying to get precise measurements so he could
calculate the volume. When Edison saw him fussing around, he grabbed one of
the bulbs, filled it with water, and dumped into a graduate. I suspect the
whole exercise was intended to make a point, rather than measure the bulbs.

Unfortunately, I can't think of an equivalent "clever" way to indirectly
measure the wire's diameter.

 

[Smitty Two]

In article <h5bd7n$c7l$1@news.eternal-september.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:

they were in fact laquered
together to defeat counting-off

They were in fact laquered together, hopefully in a vacuum chamber, to
keep them from buzzing.

 

[Jeff Liebermann]

On Wed, 5 Aug 2009 07:22:55 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

I wind 100 turns of fine gauge wire on a smooth rod ...

Tightly, of course.

... and measure the length with good calipers,
then divide by 100.


There's a story that Edison asked a young man (presumably an apprentice) to
measure the volume of several light bulbs. The apprentice stated with a
ruler, a pair of calibers, trying to get precise measurements so he could
calculate the volume. When Edison saw him fussing around, he grabbed one of
the bulbs, filled it with water, and dumped into a graduate. I suspect the
whole exercise was intended to make a point, rather than measure the bulbs.

Unfortunately, I can't think of an equivalent "clever" way to indirectly
measure the wire's diameter.

There's always a way. Measure out a long length of wire such as 100
meters. Carefully weigh the 100m of wire. The density of copper is
8.92 gm/cm^3. The rest is math, which I won't attempt without my
morning coffee blast.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Robert Macy]

On Aug 5, 7:38 am, Smitty Two <prestwh...@earthlink.net> wrote:

In article <h5bd7n$c7...@news.eternal-september.org>,

 "N_Cook" <dive...@tcp.co.uk> wrote:
they were in fact laquered
together to defeat counting-off

They were in fact laquered together, hopefully in a vacuum chamber, to
keep them from buzzing.

Jon,

Could not reply to your email, so replying here:

Thank you. MWS is our second choice and first choice for very small
gauge wires, like 54 Awg wire
They have a wealth of technical information.
Regards,
Robert

 

[Wild_Bill]

If the coil has been covered in lacquer, then repeated soakings in lacquer
thinner should remove the lacquer that was used to bind the coil.

Some careful, light brushing, and agitation could speed up the removal. It
should become apparent when the lacquer has been removed as all of the
windings will be loose, and a final rinse in clean thinner should be enough
to remove any traces.

It would probably be helpful to have a jig/form handy to place the coil
windings on, something like two spaced dowels about the same size as the
inside dimension of the coil, mounted to a piece of wood or other material.
Then with a center point located between the dowels, the coil would turn
fairly easily for counting turns.

--
Cheers,
WB
..............


"N_Cook" <diverse@tcp.co.uk> wrote in message
news:h5bd7n$c7l$1@news.eternal-september.org...

Yes for the Landola pickup, the number of turns from measuring wire
diameter
then weight/weighted circumferences and also by the 7.7Kohm ,assuming both
pickups are the same then this gives the same number , but does not agree
with counting a sample 1000 turns and ratioing , they were in fact
laquered
together to defeat counting-off

For 2 reels of enamelled wire labelled as 2.4 thou/mil and 2.8 thou/mil
and
my micrometer that has a 2Kg closure force (just checked via spring and
kitchen scales) before the torque clutch disengages.
I have to DIVIDE the reading by 1.15 for the 2.4 thou wire and 1.25 for
the
2.8 thou wire. I suppose this is to do with the enamel thickness and the
wire is specified as the metallic diameter. I assume my wire gauge v
wight/resistance tables are for bare copper, not actually specified.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Smitty Two]

In article <2vdj75hf3bqopaho32i6qvi83qpluegdcn@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

On Wed, 5 Aug 2009 07:22:55 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

I wind 100 turns of fine gauge wire on a smooth rod ...

Tightly, of course.

... and measure the length with good calipers,
then divide by 100.


There's a story that Edison asked a young man (presumably an apprentice) to
measure the volume of several light bulbs. The apprentice stated with a
ruler, a pair of calibers, trying to get precise measurements so he could
calculate the volume. When Edison saw him fussing around, he grabbed one of
the bulbs, filled it with water, and dumped into a graduate. I suspect the
whole exercise was intended to make a point, rather than measure the bulbs.

Unfortunately, I can't think of an equivalent "clever" way to indirectly
measure the wire's diameter.

There's always a way. Measure out a long length of wire such as 100
meters. Carefully weigh the 100m of wire. The density of copper is
8.92 gm/cm^3. The rest is math, which I won't attempt without my
morning coffee blast.

Unfortunately, if you don't know what the insulation is, you don't know
squat.