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Author Topic: AWG specification tolerance  (Read 2875 times)
K1VCT
Member

Posts: 186




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« on: May 16, 2017, 05:44:24 AM »

This is not a radio related question.

In my day job, golf course construction, the company I work for sells perhaps a million or so feet of wire a year, most of it 14-AWG.  That wire is commonly used for electric valves, and "valve in head" sprinklers, and more recently as the preferred wire gauge for data communication for control equipment.

Here's a little issue I'm seeing.  By chance, I had the opportunity to measure some of the wire.  I'm seeing 14-AWG wire measure out at .0645 on the largest sample, to .0575 on the smallest.  Most of it measures at .059 to .060ish.

I see that 14-AWG is supposed to be .064 inches.  I also assume there is an acceptable tolerance for that size.

I've seen some different charts and such... but nothing on the tolerance.

Needless to say, with the price of copper being what it is, I don't think the undersize is random or accidental, but more a case of "the candy bars are now a little shorter, but the wrapper and price remain the same".

Anyone have a clue on wire gauge tolerance.
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N1UV
Member

Posts: 62




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« Reply #1 on: May 16, 2017, 06:50:50 AM »

I can't remember there being a set standard for this.  There are obviously manufacturing tolerances (for the general "masses") and tolerances to Mil-spec.  Most wire manufacturers publish their size vs tolerance in catalogs, but do offer tighter tolerances (for an extra fee of course!).  Some examples:

https://www.superioressex.com/uploadedFiles/Magnet_Wire_and_Distribution/North_America/Magnet_Wire_-_Winding_Wire/EngData_book_linked.pdf
http://www.deringerney.com/assets/1/7/Wire-Strip_Size___Tolerance_Table.pdf
http://www.alloywire.com/wire_tolerances.html


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AA4HA
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Posts: 2620




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« Reply #2 on: May 16, 2017, 07:12:48 AM »

You can see the attraction to a manufacturer to run the absolute minimum of that tolerance. Maybe not to change the die size when extruding wire but to increase the tension on the take up spools to give the wire a bit more stretch coming off of the die. If they can get an extra 10-20,000 feet of wire each day that is cash-in-pocket for them.

There is a point where it starts to cause problems; If you have precision requirements or automated wire stripping then it becomes an assembly issue. You also get in to problems with ampacity ratings on the conductors and voltage drop problems.

A neat trick that would help you in determining if a spool or wire is over or undersize on conductor diameter... Measure the resistance of a spool of wire. You will need to know the exact length of wire and a very accurate measurement of temperature. With that you should get a calculation where the length and temperature match up (its a very simple formula).

If you see a higher resistance it can mean two things; The wire is smaller in diameter than you think... or the conductor is not pure copper.

I have used these techniques to make high power load resistors for power supplies (water cooled load resistors for power supply testing... e.g.; testing a 12 volt 200 amp supply for 24 hours by immersing the wire in a five gallon bucket of water that has a garden hose running water through the bucket to draw away the heat. (if you do not use the garden hose to constantly take away the heat then the resistance will rise and the current will drop, just put the bucket in your yard so it waters something (or just immerse the entire coil in your swimming pool)).
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
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