Accurately measuring diameter of very fine copper wire ?

[Jim Yanik]

..


But that realm of low forces is where grime/gummy lubricant etc
affects the feel.

you should not be making the mesaurement if the tool or workpiece is dirty.

 

[Adrian Tuddenham]

Tightly, of course.



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.

Poor graduate.

 

[Smitty Two]

But that realm of low forces is where grime/gummy lubricant etc affects the
feel. I would say that , on my Moore & Wright one anyway, someone has
determined that 2Kg clutch release force is about right for consistency.
Obviously fine copper wire is going to compress but it will compress
consistently, gauge for gauge, on a consistent 2 Kg force over the diameter
of the plattens. So I'd disagree with your expert.

Well, he's dead now, so he can't argue the point with you ... but I'd
say if your mic is grimy and gummy, it's not a precision instrument now,
even if it once was.

 

[spamme0]

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?

Sometimes, when a measurement is difficult, it's time to reformulate the
problem.

If your objective is to rewind a coil, take your best shot at wire size
and rewind the darn coil. If the resistance and inductance come out right,
Isn't that what you really want? If not, try different wire.
Self-resonant frequency will give you some idea whether your
winding technique matches the original for capacitance between
layers.

 

[[email protected]]

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?

 

[[email protected]]

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?

 

[N_Cook]

I do so agree, like minds and all that

 

[Adrian Tuddenham]

Make the bundle by winding the wire 32 times around two spaced pegs so
as to be certain that all the 64 wires this produces between the pegs
are parallel and not intertwined. Slip the wire off the pegs and do not
twist it, but squeeze the parallel section so that it takes up a
cylindrical shape.

Wrap another length of the same wire tightly around the outside of the
cylindrical section for a known number of turns (20 at least). Unwind
the wire and measure its length and divide by 20 to calculate the mean
circumference of one turn.

Do exactly the same thing with a length of wire whose diameter you do
know (probably something much larger, so that you can measure it
easily). You may not be able to wrap as many as 20 turns, so adjust
the divisor accordingly.

The ratio of the lengths of the one-turn circumferences will be the
square of the ratio of the wire diameters.

 

[N_Cook]

Make the bundle by winding the wire 32 times around two spaced pegs so
as to be certain that all the 64 wires this produces between the pegs
are parallel and not intertwined. Slip the wire off the pegs and do not
twist it, but squeeze the parallel section so that it takes up a
cylindrical shape.

Wrap another length of the same wire tightly around the outside of the
cylindrical section for a known number of turns (20 at least). Unwind
the wire and measure its length and divide by 20 to calculate the mean
circumference of one turn.

Do exactly the same thing with a length of wire whose diameter you do
know (probably something much larger, so that you can measure it
easily). You may not be able to wrap as many as 20 turns, so adjust
the divisor accordingly.

The ratio of the lengths of the one-turn circumferences will be the
square of the ratio of the wire diameters.

Friday afternoon after a long tiring day yesterday, I cannot
thought-experiment my way into this. I'll have to have a go with some
thicker wire to start with, to work out the method you've outlined

 

[N_Cook]

]
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,..

Make the bundle by winding the wire 32 times around two spaced pegs so
as to be certain that all the 64 wires this produces between the pegs
are parallel and not intertwined. Slip the wire off the pegs and do not
twist it, but squeeze the parallel section so that it takes up a
cylindrical shape.

Wrap another length of the same wire tightly around the outside of the
cylindrical section for a known number of turns (20 at least). Unwind
the wire and measure its length and divide by 20 to calculate the mean
circumference of one turn.

Do exactly the same thing with a length of wire whose diameter you do
know (probably something much larger, so that you can measure it
easily). You may not be able to wrap as many as 20 turns, so adjust
the divisor accordingly.

The ratio of the lengths of the one-turn circumferences will be the
square of the ratio of the wire diameters.

Friday afternoon after a long tiring day yesterday, I cannot
thought-experiment my way into this. I'll have to have a go with some
thicker wire to start with, to work out the method you've outlined

Why not measure the resistance and calculate the diameter from that?
(Assumes the wire is just copper and is round).

For this very fine wire it is only ever enamelled/lacquered wire I ever
deal with, being used as magnet wire, pick-up coils and the like

 

[Adrian Tuddenham]

On Tuesday, August 4, 2009 10:38:19 AM UTC-4, N_Cook wrote: [...]
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,..

Make the bundle by winding the wire 32 times around two spaced pegs so
as to be certain that all the 64 wires this produces between the pegs
are parallel and not intertwined. Slip the wire off the pegs and do not
twist it, but squeeze the parallel section so that it takes up a
cylindrical shape.

Wrap another length of the same wire tightly around the outside of the
cylindrical section for a known number of turns (20 at least). Unwind
the wire and measure its length and divide by 20 to calculate the mean
circumference of one turn.

Do exactly the same thing with a length of wire whose diameter you do
know (probably something much larger, so that you can measure it
easily). You may not be able to wrap as many as 20 turns, so adjust
the divisor accordingly.

The ratio of the lengths of the one-turn circumferences will be the
square of the ratio of the wire diameters.

Friday afternoon after a long tiring day yesterday, I cannot
thought-experiment my way into this. I'll have to have a go with some
thicker wire to start with, to work out the method you've outlined

I believe some variation of this method was the standard way of
determining the gauge of wires many years ago. It had the advantage
that the reading was averaged over a number of wires (some of which may
not have been exactly circular in cross-section) and, once established,
could be used by anyone with a ruler to give a fairly good degree of
accuracy.

 

[mike]

On 27/09/2013 15:53, Adrian Tuddenham wrote:

]
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,..

Make the bundle by winding the wire 32 times around two spaced pegs so
as to be certain that all the 64 wires this produces between the pegs
are parallel and not intertwined. Slip the wire off the pegs and do
not
twist it, but squeeze the parallel section so that it takes up a
cylindrical shape.

Wrap another length of the same wire tightly around the outside of the
cylindrical section for a known number of turns (20 at least). Unwind
the wire and measure its length and divide by 20 to calculate the mean
circumference of one turn.

Do exactly the same thing with a length of wire whose diameter you do
know (probably something much larger, so that you can measure it
easily). You may not be able to wrap as many as 20 turns, so adjust
the divisor accordingly.

The ratio of the lengths of the one-turn circumferences will be the
square of the ratio of the wire diameters.




Friday afternoon after a long tiring day yesterday, I cannot
thought-experiment my way into this. I'll have to have a go with some
thicker wire to start with, to work out the method you've outlined

Why not measure the resistance and calculate the diameter from that?
(Assumes the wire is just copper and is round).

For this very fine wire it is only ever enamelled/lacquered wire I ever
deal with, being used as magnet wire, pick-up coils and the like

I'll skip the lecture on going to insane lengths for no benefit and ask
one question...

Why do you care?

What is it about your application that requires such precision in the
diameter of the insulation?

The obvious solution, and one that is actually related to winding coils,
is to wind 20, 500, how many you feel are needed, turns on a solenoid.
Measure the length of the solenoid and divide by N. You can get
arbitrary precision for THIS spool of wire.

For manually wound coils, the number of turns you can get in a unit volume
is related more to the skill of the winder than the dimensions of the wire.

 

[kilowatt]

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?

How about winding the wire onto a piece of 1/16th inch piano wire, do ie; 100 turns and then measure the overall length. Presumed that the wire has no enamel.


My best way.
KW

 

[tuinkabouter]

Take 10 meter. Measure the resistance.
resistance is 0.0175 ohm per meter per square millimeter.
From this you can find the area.
Area is 1/4 pi d*d This will give the real copper diameter.

Two prerequisites. Pure copper and the wire is round.

 

[N_Cook]

Take 10 meter. Measure the resistance.
resistance is 0.0175 ohm per meter per square millimeter.
From this you can find the area.
Area is 1/4 pi d*d This will give the real copper diameter.

Two prerequisites. Pure copper and the wire is round.

That applies to most copper wire but not these finest dimensions where
that formula breaks down