What is the toughest insulation to accidentally knock off?

[Builder7]

I consistently have shorts in my windings. Which insulation is most difficult to knock off? What brand and where to order in from? Yes I know it is probably something I am doing wrong. But I want to try with good wire to know that it is my technique, not just bad wire.

[jvin248]

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Haven't tested the wires myself ... see if you can find a material hardness chart.

I'd video tape a segment of your winding and then watch that to see if there is a technique issue (like scraping on a travel stop).

Dismantle a shorted coil and check where the short is happening. You may find it's at the outer coils, skips all the way through, or only at the first couple of layers against the rods (if Fender style). That should help identify when and how the wire is getting damaged.

Check all the contact points for the wire traveling up from the bobbin, through tensioners, over pulleys, through eyelets, and so on for any sharp burr or drag point. Then file and super-polish.

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[salvarsan]

The tough wire is APT, Armored PolyThermaleze or the heavy build HAPT.

An inductance meter (LCR) can suggest how far down the cut-through is, but you'll have to do some disassembly to find out.

[Joe Gwinn]

I consistently have shorts in my windings. Which insulation is most difficult to knock off? What brand and where to order in from? Yes I know it is probably something I am doing wrong. But I want to try with good wire to know that it is my technique, not just bad wire.

Are you smoothing the bobbins or taping the magnets?

The cumulative pressure of 5,000 or 10,000 turns of fine wire wound on a coil is very high, and will force the inner turns against one another and against the core former or magent. If this isn't perfectly smooth, the edges will cut into the insulation, et al. Coating the magnet cores with varnish isn't good enough. Paper of mylar or kapton Tape seems to be necessary on bare metal. And so on.

As for how hard the insulating varnish should be, it can be too soft or too hard. The ideal is that the cured varnish is roughly as hard as the copper wire, so it neither squeezes off nor flakes off.

Diagnosis: The best way to tell what's happening is to manually unwind one of the shorted coils under a bright light, and look.

[David King]

I have a big roll of HAPT 42awg and it sounds great though it's a bit challenging to solder.
There is also Teflon coated magnet wire which should be damn tough. The place that sells it is in VT and it's available up to 45AWG.
PTFE Copper Magnet Wire

Meanwhile get a tension gauge and set your wire tension somewhere between 5 and 10 grams.

[eschertron]

I'm not a winder, but I have a sort-of tangentially related question to the topic.

Are there winders that start out with a tension on the high side, then gradually decrease tension? So as to minimize the compaction/abrasion of the inner windings? Seems like that technique would help reduce the problems Joe mentions. At least an awareness of the issue might be enough.

And does a hand-scatter make the problem worse?

[bbsailor]

[QUOTE=David King;445464]I have a big roll of HAPT 42awg and it sounds great though it's a bit challenging to solder.
There is also Teflon coated magnet wire which should be damn tough. The place that sells it is in VT and it's available up to 45AWG.
PTFE Copper Magnet Wire

Meanwhile get a tension gauge and set your wire tension somewhere between 5 and 10 grams.[/QUOTE

For all who enjoy tinkering with new stuff here are some of my observations from using Teflon insulated wire to make coils. Teflon has a low dielectric constant, about 2, and this means that the coil will have about half the turn to turn capacitance thus raising the pickup self resonance but only noticeable if you buffer the pickup with a high Z buffer circuit to keep the coax capacitance from swamping this reduction. Lower turn to turn capacitance is caused by two things. 1. The thickness of the insulation and 2. The dielectric constant of the insulation material. The most effective buffering loss reduction or input impedance should be about 10 times higher than the coil reactance at resonance to clearly hear the effect of using this type of wire.

Joseph J. Rogowski