Thursday, October 29, 2009

Toroid Wire Stripping

I have always had a problem stripping very short lead-ends from toroid coil wires, this is especially a problem for surface mounting a coil.

I have asked the question on several forums of; "how others do it?", but until now, nothing was an acceptable method for my fingers.
  • I have tried burning the end with a torch - wire will not take solder afterwards.
  • Folded Sand Paper - works good for long leads, but not for short SMD board mounting.
  • Scraping with a blade between finger or thumb - Fingers are too fat, blade too sharp, wire is too small and wiggly.
  • And, many other forum suggestions.

There are two problems with toroids winding that must be resolved;
  1. How to keep the wires tight and secure while working with it.
  2. And then, how to remove the insulation on very short leads.
  • Use Hot Glue, filling the centre will prevent the wire movement.
  • The technique that I use is; Fill the centre with Glue, and squeeze it between fingers, using a strip of Teflon Mat Sheet as a release medium (otherwise the Glue will stick to skin and it will HURT!). 
  • The pressure between your finger and thumb pvides a nice looking indent on the surface of the the glue.
  • Glue that overflows, can be pulled off around the edge of the toroid.
  • Note: I don't think the Hot Glue will degrade the performance of the toroid even at High Frequencies.

Fill the Centre with Hot Glue
Fold the Teflon
Mat Sheet
Squeeze Between Fingers
Caution - It can be HOT!

  • Scrape the leads "at the edge of a block of wood!"
  • Rotate the toroid as necessary, it only requires scraping on the four sides of each wire, doing two wires (or more) at a time.

Turn 180 Deg, Scrape the other side

Turn 90 Deg, Scrape the two other sides of each lead

It seems simple and silly now, but why didn't I think of that, I have been doing it "the hard way" for a very long time.

The results - a Good looking, stable Toroid, filled with Hot Glue, and ready for though-hole or surface mount.

Toroid - Ready to Mount

Building toroids, with short leads, are now fun again!


One of my Hot Glued Cores was used in a QRP transmitter final stage, RF current was enough to heat the core, and melted the glue which ran onto the surface mount parts below. I now do not recommend using Hot Glue for high current or heated cores.


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