How to use a vernier caliper to measure 30 AWG wire size?

Hello, I have a vernier caliper like:

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and tried to measure small AWG wire size. I do not have in hand any small wire that I know the size to compare. I do need to measure the precise size of the wire I have. Now, the problem is that when I put some pressure with the vernier, the reading can change from 30 AWG to 34AWG, which make a huge diffence in my calculations... And I also have to take into account the insulation and taking out! I do not have a wire gauge.

Should I put the pressure or not?

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Hi, I have a DeALL digital caliper and I get #14 wire at .079" suppose to be .080" I can't make the reading change with any amount of pressure, short of what would damage the caliper. I was taught in machine shop to run the caliper up against the measured item with moderate pressure and take the pressure off but still "trap" the piece. Here's a site for wire and standard gauge sizes. I always knew they were different but still the mind boggles!!

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but this is even more confusing comparing solid 20AWG to different stranded configurations:
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Perhaps you could tell us why? Coil winding?

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Why do you have to "take into account" the insulation? Just strip it off to measure the wire.

You shouldn't need to apply pressure; if that changes the reading then the extra pressure is squashing the thing you are measuring.

You might want to measure across two diameters, at 90 degrees to each other, in case the wire is out-of-round.

Not sure what diameter 30 or 34 AWG gauge is, but it may be too small to measure accurately with vernier calipers.

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A few points:

  1. First, the obvious: was the caliper "zeroed" properly?
  2. 0.001" doesn't seem like much to be concerned with; the next size up or down is .008" or .012" smaller or larger.
  3. I would apply **hardly any** pressure when measuring small wire, especially copper. It will deform (gets smaller) under pressure, unlike larger stuff that is typically measured in a machine shop.


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Jean is barking up the wrong tree anyway.

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