Real NOS PAF era plain enamel wire....

[Possum]

Its rather pointless though, because we are stuck with the wire that is being made NOW, the fact is that the most common diameter I found in 99% of PAF's I unwound isn't being made currently. They will make it custom for you if you want to buy 100 pounds of wire, but really it wouldn't be a huge difference anyway. So that choice isn't available, though yeah I do have some old stock thats in the that diameter I don't use it because there's not enough of it to consistently make the same recipe for the next five years, and I tend to save it for important rewinds. Besides the PAF tone simply isn't in one single part of the pickup, the coils are important but they are only one piece of the whole. I'm very happy with the wire we're getting, its consistent and I can rely on it not to make some dramatic change like REA's stuff did. I've really got everything nailed down in every part of the pickup and making it all do exactly what I want it to. There is one odd thing about Elektrisola's wire is that their measurements are very conservative and I sometimes wonder if their laser is a bit off the mark, because historically all the other wire that was being made wasn't what they tend to make as far as common diameter goes. It'll be interesting to see finally what this old 50's wire sounds like, I'll post when I get to it in probably a month or so....

[Joe Gwinn]

There is no reason one cannot measure ohms per foot accurately (1% or 0.1%) at home, using only a digital multimeter (that has a 50 ohm range), a ruler, and a thermometer.

[big_teee]

There is no reason one cannot measure ohms per foot accurately (1% or 0.1%) at home, using only a digital multimeter (that has a 50 ohm range), a ruler, and a thermometer.

I never did understand the argument against measuring.
It makes logical sense to me if the wire is a given OD and a Given ohms per 10 ft at a given Temp?
WTF? You have to be in the Ball Park?
I measure everything that comes through here, and every roll is a bit different, some a lot different.
T

[Fuzzy Logic]

I just scored a 5lb. roll of PE from 1971 for $16, its 40 gauge. Very modern stuff. You have to be careful about this ohms per foot stuff. The data I got from Elektrisola was done in a lab, I'm not real sure you can get accurate measurements at home, I'm sure they have some kind of temperature controlled device and a high tech meter of some sort. The REA stuff always had ohms per foot written on each roll usually. I would think you'd need to measure a good long section, more than a foot then average it out since just a one foot piece is unlikely to match same from other parts of the roll. The actual insulation measurement can make your ohms measurement meaningless if its different from your other stock, so your wire could sound real bright or dark but have close ohm specs. Then there's bare wire spec which also varies, you have to acid strip the insulation or your measurement will be wrong. Elektrisola uses lasers to measure their specs and a simple micrometer is just not very accurate overall. I always mic new rolls of wire but in the end only winding coils and listening to a new batch is the final word.

Actually, one does not really have to acid strip the insulation in order to figure out the diameter of the bare copper wire. If one knows the ohms/foot the calculation of the diameter of the bare copper wire is relatively easy.

Ohms/foot = (ohm-circular mil/foot) / (cross section of wire in circular mils)

The standard value for the resistivity (ohm-circular mil/foot) at 20 degrees celsius is: 10.371 ohm-circular mil/foot.

The NBS copper wire tables of 1956 and 1966 indicate that the value of 10.371 would appear to be a correct value to use (unless very high quality wire, in terms of resistivity or conductivity, was used in those days for winding pickups, which I doubt) when assessing "vintage wire" as used in the fifties and sixties. According to the specifications as found on their website, this is also the correct value to use for assessing modern MWS wire.

The cross section of a bare copper wire in circular mils is the square of (diameter wire / 0.001).

From the above follows:

diameter bare copper wire = 0.001 x square root (10.371 / (ohm/foot))

And if one is able to measure the outer diameter of the insulated copper wire with sufficient precision, the insulation thickness is the difference between this measured value and the diameter of the bare wire as calculated above divided by two.

Since you have done a lot of lab testing, I guess it would be quite easy for you to verify the claims as made above.

BTW: for the most accurate results the standard value of 10.371 should be adjusted to 10.328 for modern Elektrisola wire (0.0024 size wire) and to 10.325 for their AWG 42 size wire.

[SonnyW]

Actually, one does not really have to acid strip the insulation in order to figure out the diameter of the bare copper wire. If one knows the ohms/foot the calculation of the diameter of the bare copper wire is relatively easy.

Ohms/foot = (ohm-circular mil/foot) / (cross section of wire in circular mils)

The standard value for the resistivity (ohm-circular mil/foot) at 20 degrees celsius is: 10.371 ohm-circular mil/foot.

The NBS copper wire tables of 1956 and 1966 indicate that the value of 10.371 would appear to be a correct value to use (unless very high quality wire, in terms of resistivity or conductivity, was used in those days for winding pickups, which I doubt) when assessing "vintage wire" as used in the fifties and sixties. According to the specifications as found on their website, this is also the correct value to use for assessing modern MWS wire.

The cross section of a bare copper wire in circular mils is the square of (diameter wire / 0.001).

From the above follows:

diameter bare copper wire = 0.001 x square root (10.371 / (ohm/foot))

And if one is able to measure the outer diameter of the insulated copper wire with sufficient precision, the insulation thickness is the difference between this measured value and the diameter of the bare wire as calculated above divided by two.

Since you have done a lot of lab testing, I guess it would be quite easy for you to verify the claims as made above.

BTW: for the most accurate results the standard value of 10.371 should be adjusted to 10.328 for modern Elektrisola wire (0.0024 size wire) and to 10.325 for their AWG 42 size wire.

This publication from Phelps-Dodge verifies that the 10.371 was the standard in 1961 - see paragraph C page 2.
http://bnordgren.org/seismo/wire.pdf

I believe that 10.371 is also the current International Annealed Copper Standard (IACS) value for 100% conductivity.
Table 1 Equivalent Resistivity Values For Copper
Conductivity at 20°C (68°F), percent IACS...................100.00
VOLUME RESISTIVITY
Ohm-Circular mil/f ..................................................10.371 000
0hm-mm2/meter................................................... ....0.017241

Elektriksola specifies a volume resistivity of 0.0171 ohm-mm2/meter which is lower than the IACS value, so I understand why the value should be corrected for Elektriksola wire, but why the difference between the two gauges?
Copper

Also
Here's a handy chart to correct the resistance


This is another useful publication I have used for years:
Technical Data

I measure the temperature at my workstation with an inexpensive but accurate Cole-Parmer digital thermometer, and correct all my published resistances to 20C using the chart from REA, or the equivalent formula which is built into my data worksheet.

[Possum]

Thats all well if you think that published charts are accurate at all ;-) There are standards for bare wire and O.D. for every gauge, but then there are wide range tolerances for those standards. You really can't accurately measure wire diameter with a micrometer anyway, it gets you in the ball park but only a laser is going to give you real accuracy. Bare wire diameter depends on who made it and what stage of wear the drawing dies are in. Then you're not considering if the wire was stretched when it was wound onto the roll, if it was then your charts don't mean anything. From my experience every roll of wire I've bought was stretched at the beginning of the roll due to higher toque from the smaller core diameter pulling on the wire. Some rolls radically change diameter when you get down to the core. Elektrisola's wire is no different and the wire is always fattest on the outside of a new roll of wire. That too, makes it kind of pointless to go around measuring how many ohms a foot of wire measures. Do you measure a piece from the start, middle or end?
If you use turn counts in your recipe, that never changes from pickup to pickup, so you have a very long length of wire thats relatively the same on every pickup and you note how many ohms the whole length is. With current wire, I get very close results every time and if there's a noticeable difference it means a short happened so I wind it over. Thats why I don't bother with ohms per foot, its just not practical for my work. For research, yes I wanted to know exactly what their lab said, because I had PE from about a 50 year spread and many of them were the same total O.D. But among those, insulation thickness varied more with the vintage stuff before '65. They also told me the earlier wire copper was less pure due to technology of the time, so ohms per foot back then was higher than currrent wire, but there's more to that than just copper purity......Unfortunately too, we can't really know what dielectric effects the old recipe for PE was vs. what they use now. We've had that argument before ;-) Currently EPA regulations change how the insulation enamel is made and what its made of, back then didn't matter. Some PAF's I got the wire really smelled good ;-) I even had a PAF where the insulation was never properly cured and it was still sticky all through the entire coil. Elektrisola told me they think the insulation never changed, but then they also told me the guys who make that stuff refuse to talk about the processes at all, uh huh.....

[JGundry]

Possum, everything has a tolerance. A reasonable tolerance for ohms per foot readings, charts etc.. is to be expected. But as far as the tolerance for speculation and assumption that is extremely wide and is not real useful in terms of making pickups.

[Possum]

Ohms per foot has no use for me in making pickups, is my bottom line. Total turns recipe = known resistance in known wire for known product. Thats all I need in a practical day to day situation, why make it more complex? I already know what all the specs for the wire I use, direct from Elektrisola's own lab done on their own wire, plus any other PE you care to mention, new or old, been there done that; it was research, but that work is done. Why spend time measuring lengths of wire when its not going to be the same at the beginning of a new roll as the end of the roll, its going to change as the roll gets used up, so literally you would have to measure every time you wound a new set of pickups ;-) and to what purpose? A turns recipe gives you a DCR thats going to only vary maybe .2K if that, and its the only thing you need to check in final QT. If you suddenly get a jump in the reading, plus or minus, your coil went sour and should be cut off and done over. Those are my methods and what I use day to day, simple, effective and quick. If ohms per foot has some value for you in making pickups then use it, but for me it has no actual production value; I know what my wire is and use what I know. I actually repurpose rolls when they get near the end and when wire gets thinner, and use it for a different purposes. You just have to "roll" with the roll ;-)

[David Schwab]

Ohms per foot has no use for me in making pickups, is my bottom line.

I think the point was to measure the resistance of the wire to determine it's diameter as compared to another sample.

[Fuzzy Logic]

.......
Elektriksola specifies a volume resistivity of 0.0171 ohm-mm2/meter which is lower than the IACS value, so I understand why the value should be corrected for Elektriksola wire, but why the difference between the two gauges?
Copper
.....

In the overview below, the ohms/1000 feet are listed for three manufacturers of magnet wire and for two AWG sizes in the order "Max d", "Nom d" and "Min d" where "d" is the diameter of the wire.

MWS

AWG 42: 1534, 1659, 1801
AWG 42.5: 1659, 1801, 1960

Values are based on a resistivity of 10.371 ohms per circular mil/ft (100% IACS conductivity).
Ref: http://www.mwswire.com/pdf_files/mws...Book082011.pdf

Essex

AWG 42: 1510, 1659, 1801
AWG 42.5: 1633, 1801, 1960

Minimum resistance values are based on maximum bare diameter ("Max d") and 101.6% IACS conductivity.
Nominal and maximum resistance values ("Nom d" and "Min d") are based on nominal bare diameter and 100.0% IACS conductivity.
Ref: http://www.spsx.com/uploadedFiles/Ma...ook_linked.pdf

Elektrisola

AWG 42: 1504, 1652, 1801
AWG 42.5: 1626, 1793, 1960

For "Min d": Resistance based upon copper conductivity of 100% IACS. Actual values for "Min d" may be up to 102% IACS.
Ref: http://www.elektrisola.com/fileadmin...asheet_eng.pdf
Note: Elektrisola specifies they use copper base material with a resistivity of 10.286 ohms per circular mil/ft (volume resistivity of 0.0171 ohm-mm2/meter).

Now what do we have here.

MWS specifies their ohms/1000 feet based on 10.371 ohms per circular mil/ft (100% IACS conductivity) and they do this for the whole range of "Max d" to "Min d" of a given AWG wire size.

Essex notes that they base their ohms/1000 feet value for "Max d" on 101.6% IACS conductivity and that "Nom d" and "Min d" values are based on a IACS value of 100%. So the resistivity is not really a constant value.

Elektrisola notes that they base their ohms/1000 feet value of "Min d" on 100% IACS conductivity but that actual values may be up to 102% IACS. Furthermore, when using the 10.286 ohms per circular mil/ft which they specify for their copper and the ohms/1000 feet listed on their website for AWG 42/42.5, the resulting diameter of the wire is less accurate than expected. From all this it appears that the resistivity of Elektrisola wire is even less constant than in the case of Essex wire. That is why I listed a value for two different wire sizes. The resistivity values I mentioned are based on the AWG size and corresponding ohms/1000 feet which they list on their website.

The only reason (imho) why the resistivity values are not that constant for Elektrisola wire may be that their wire is probably not as fully annealed as compared to the wire which MWS sells. Essex is probably somewhere in between these two.

This appears to be confirmed by the maximum recommended winding tensions for these three manufacturers: 34 gr. for Elektrisola, 27 gr. for Essex and 22 gr. for MWS. The higher the maximum recommended winding tension, the higher the tensile strength of the wire is and this indicates that the tensile strength which has been obtained during the hard drawing of the wire is not as much reduced by the annealing process for Elektrisola wire as in the case of MWS/Essex wire.

Technically the Elektrisola wire is the better wire because it has a high tensile strength combined with an overall better resistivity value. It will probably handle better and also break less. However, at the same time is also a wider spread in the ohms/1000 feet across the range of "Max d" and "Min d" for a given AWG size as compared to MWS/Essex wire. And if one is set to wind to a specific or fixed DCR one will need put a bit more wire on the bobbin when using Elektrisola wire.

All this is based on published specifications of the various manufacturers, in real life your mileage may vary.....

And since we are all sharing links here:

United States (National Bureau of Standards), 1914. Copper Wire Tables, NBS Circular 31
Copper wire tables : United States. National Bureau of Standards : Free Download & Streaming : Internet Archive

United States (National Bureau of Standards), 1966. Copper Wire Tables, NBS Handbook 100
http://library.bldrdoc.gov/docs/nbshb100.pdf

The NBS copper wire tables of 1956 used to be viewable/downloadable in Google books, but that link has disappeared....

[Possum]

Its the "real life" part that only concerns me. You just have to buy from different sources and wind the stuff to really know what it is and what you can use it for.
REA spools used to all have ohms per foot specs written on them for each spool.

I just opened a new roll last night. The outer windings are a whole .0001" thicker than the last roll's inner windings. Doesn't sound like much but makes a big difference in size of coils when you got thousands of turns on the pickup, that small difference adds up fast. I try to burn off the thicker part of the rolls on pickups like Tele bridges etc. to get down to the diameters I need. Everyone's wire is a little different, Wirenetics for example sells Elektrisola product but its like they buy the cast off over-spec spools or something because the diameters on everything they sell it seems are overboard sizes, FAT. But for certain pickups you WANT fat wire, so I go to them.

Fralin used to say that they would wind a test pickup on every new roll of wire they got in, but its not really a great method because of the stretched wire in the core of the roll. But the only way to know any wire isn't by reading specs, you have to work with it and it'll let you know real fast whats its good for and what its not good for.

[SonnyW]

The only reason (imho) why the resistivity values are not that constant for Elektrisola wire may be that their wire is probably not as fully annealed as compared to the wire which MWS sells. Essex is probably somewhere in between these two.

This appears to be confirmed by the maximum recommended winding tensions for these three manufacturers: 34 gr. for Elektrisola, 27 gr. for Essex and 22 gr. for MWS. The higher the maximum recommended winding tension, the higher the tensile strength of the wire is and this indicates that the tensile strength which has been obtained during the hard drawing of the wire is not as much reduced by the annealing process for Elektrisola wire as in the case of MWS/Essex wire.

Technically the Elektrisola wire is the better wire because it has a high tensile strength combined with an overall better resistivity value. It will probably handle better and also break less. However, at the same time is also a wider spread in the ohms/1000 feet across the range of "Max d" and "Min d" for a given AWG size as compared to MWS/Essex wire. And if one is set to wind to a specific or fixed DCR one will need put a bit more wire on the bobbin when using Elektrisola wire.
....

Thanks. I'm not sure, but I think I am a bit less confused now....maybe.

[Possum]

Just remember that stretched wire has higher ohms per foot, so by the time you get to the end of a 6lb. roll, ohms per foot has changed, and so has diameter, and so has work hardening....

[RedHouse]

I never did understand the argument against measuring...

Easy, consider the source! (LOL)

[RedHouse]

Just remember that stretched wire has higher ohms per foot, so by the time you get to the end of a 6lb. roll, ohms per foot has changed, and so has diameter, and so has work hardening....

So what makes you think the "end" of the spool had a differrent stretching/stretched factor than the rest of the spool?.

And BTW when you say "by the time you get to the end of a 6lb. roll" don't you really mean "by the time you get to the start of a 6lb. roll"?
(just wondering)