Saturday, August 10, 2013

Toroid winding can be fun.....well almost.

The dreaded toroid...
When I first started kit building some years ago it was the dreaded toroid winding that I never looked forward too. After winding and rewinding over time it has not become a dark task, it has taken some time to get the hang of it but I can say that I  no longer get uptight about the process. I have learned some tricks and some never ever skip steps when it comes to toroids. 
I am in the process of building my second K2 rig from Elecraft and there are lots of toroids to be wound. Now having said that if you want you can order per-wound toroids from the toroid guy. If you do order toroids that are per-wound I would encourage you to try to wind your own as well. What I have found is it's only practice that is needed to get the hang of the winding thing. In the past I have built many Elecraft kits were toroids have been involved, I have learned as I said some tricks, some must do stuff and things to stay away from when it comes to this art. 

My advice when winding single conductor toroid....
1. Most if not all the time you have more wire than you need so when told to cut a conductor to lets say 12 inches I give myself around 13-14 inches. A wise person told me "it's better to have and not need than to need and not have" 

2. If you are winding a toroid that has lets say 20 turns when you hit 19  I stop and count the turns just to make sure I am not at 20 or that I lost count and am only at 18!  I have had both happen.... it's better to check rather than cutting the excess wire and finding out you need to somehow add 2 more turns. 

3.Once the toroid is wound check the turns to see if they are more or less equally spaced. Take your time and move the windings around the core. Use a plastic tool or wooden tool for this a metal tool (screw driver) may remove the paint on the wire and cause a potential short.

4. Take the new toroid and see how it fits on the board. Sometimes you may have to squeeze the turns or open them up a bit for the toroid to fit properly. 

5. Once the turns are good and the fit is good you can trim off the extra wire. When I do this I always make on leg shorter than the other. I find you can place the toroid on the board with less effort by having the lead staggered in lenght. This is very evedent when you have a toroid with more than one winding..

6. Now that the toroid has the right amount of turns, it is spaced correctly, fits nicely and the leads are cut one longer than the other....its time to remove the enamel coating off the wire. There are some various
 ways to to this........ 
Getting ready for solder blob
A. Use a lighter to burn off the coating
B. Use sand paper.
C. The solder blob method.
D. Use a razor knife to scape the coating off.
E. I have heard some dipping the wire in var-sol....would not recommend it.  

I use the solder blob method and I have tried the sandpaper (find it just to rough for the delicate work that is needed) I have tried the lighter method but found on the smaller toroids I am not able to control the heat and end up burning off to much insulation. The razor blade scraping I have not tried and really don't want a razor knife that close to my fingers.'s the solder blob for me!! I find if I put the toroid in an alligator clip to hold it I can in a very controlled fashion remove the right amount of enamel from the toroid.
I change the tip on my Weller soldering iron to a larger tip and use a .030 diameter solder. Most of my board work is done with a .020 diameter solder.

7. Once the toroid wire has been stripped I use my DMM to check to make sure the coating has been removed and there is good continuity. Oh and for toroids that have more that one winding I check to make sure there is not shorts between the windings as well.

8. It's now time to solder the toroid in place and I find once the toroid is soldered in place before the leads are trimmed you can heat each solder blob up again and give each lead a LIGHT pull with a pair of pliers. This will allow the toroid to sit firmly on the board.

Some tips
1. Practice practice's like CW it's an art and over time you will get the idea and look forward to it.
2. Some toroids have nice rounded edges but be aware of those with sharp 90 degrees edges. These toroids can if your not careful remove the insulating coating from your wire and potentiality cause a short.

Using a paper and pencil to count
3. When  you have a toroid with 20 turns or more you can go buggy trying to check the turn count. What I do is lay the toroid on a sheet of paper and pencil make on the paper each turn. I then count the pencil marks and sometimes ticking them off as being counted.

4. Use two sizes of soldering tip's one (I use the Weller ETC 1/8 tip) for the solder blob used to melt the insulation off the wire. Then a thinner tip (I use the Weller ETR 1/16 tip) for soldering the toroid to the board.
ETR and ETC tips

Coming soon how to wind the bi-filar toroid and transformer toroid.


  1. I made a mini solder pot out of an old soldering iron to tin the leads of my toroids. Have a look at for more info. It really works great.

    73, Dan KB6NU

    1. Good morning Dan and very nice to hear from you. That is a very good unit and seems it does the job very fast, clean and easy to use. I have gotten some other ideas of how some other builders clean off the magnet wire and in an upcoming post will share these.....including your mini solder pot.

  2. I have used a variety of methods to remove the coating on magnet wires. Many are heat stripable and using the method you describe as the blob method works OK as does using a solder pot and dipping the ends. However, not all magnetic wire is heat stripable.

    The best tool I have found for removing the insulation on magnet wire is a simple tool made by Knipex and referred to as a strippig tweezers for coated wire. See:

    I have set and would like a second but the trouble is that it was not easy to find a distributor. Chads Tool Box in the US was one of the few and had a fairly stiff postage rate to Canada (but is much more reasonable to the US). I bit the bullet and ordered a set plus a set of the smaller blades plus a couple of other tools (had to try and make best use of spending so much on postage).

    They really are good to deal with, just their international postal rate was a bit much.

    Don't think that the blades are good for only one size of wire. I have the 0.5 mm size on mine and use it on wire from 18g through 30g. However, if I had a second pair I would put the 0.5 mm size on one and use 0.8 mm on the other - the 0.6mm size is standard. Using these on larger or smaller wire just requires a bit of extra care.

    Give them a try. Have a friend in the US send you pair. Better yet, get two and put a set of smaller blades on one and leave the standard on the other. You won't be dissapointed and will wonder how you managed without.

    And if you frequent the Elecraft forums, pass the word around, maybe Elecraft will catch on and start selling these.

    cheers, Graham ve3gtc

    1. Good morning Graham thanks for stopping by and taking the time to comment, these strippers look great and as you have given testimony to they work very well too. I have never seen such an animal before.

  3. Some good ideas thanks

    I've been scraping the enamel off magnet wire on toroid inductors for over 20 years. A cheap adjustable blade knife cutter works fine. I have a wood bench or sometimes use a small wood block and set the wire lead on it. Scrape and turn the toroid so you get 360 degrees removal of the enamel coating.

    My best cutter cost me $2.79 at the local hardware store and came with 10 blades. New blades are equally cheap.

    Examples (not exactly like mine but the same idea)

    Also if your going all this trouble, consider getting a L meter like the AADE. You are targeting an inductance and # of turns varies according to multiple factors.

    Changing the spacing, changes the inductance. Even kit builders need to raise their game.

    Thanks and best homebrewing


    1. Hello again Sal, just realized I impedance varies with freq not inductance...just have to get the inductance values from Elecraft. By the way the AADE meters look great and seem also like a nice kit to build. I think I am going to order one for sure.

  4. Good morning Sal, I too have tried now and then to strip the wire with a razor knife but had no luck. Maybe it was do to the fact that I just did not stick with it long enough. If I did not stick with winding toroids then today it would not be some easy.....In the past I have considered getting an L meter but I was of the understanding that the inductor value varied with frequency? If I was not sure what the frequency the inductor was going to be used at I would be hard to setup the turns. Also with the Elecraft kits that I have been building they don't give a value for the inductors. You are just given the number of turns and to cover about 80% of the core.
    Thanks for stopping by Sal and taking the time to comment.

  5. UR welcome OM. Elecraft lists inductor values in some manuals (K2 for example) Inductance is a fixed value and toroid Q varies within a frequency range, but nearly everything can be wound on a 6 material for HF, so I just have number 6 for HF and number 12 for my 2 meter homebrew rigs. I built part of the K2 from the manual with Manhattan construction as a 2-band transceiver and it works FB.

    I think your from Canada? Well a VE7 from Canada helps some people understand Some of the nuances. I love the AADE meter and got it after QRP.pops wrote about it

    73 es good DX

    1. Thanks very much Sal for the reply and yes I am from Canada....the VE3 is Ontario. I am about an hour outside of Toronto (where I drive to work each day) I will have to take a look at the K2 manual over a coffee tomorrow to find the inductor values. Thanks very much for all the great info!

  6. Hello Mike, thanks for the interesting post on winding of toroids.
    I use the 90 degrees edge of a tweezer to scrape of the coating of the wire. I use a thick piece of cardboard under the wire for scraping and for soldering.
    Since I build my Rigs stage by stage, I never wind all toroids at once. 73, Bert

    1. Good morning Bert, nice to hear from you! There are sure lots of ways to remove the coating on the wire. I seem to find the solder blob works well for me. On my Elecraft K2 build site I made a short YouTube video on the solder blob method.
      Have a nice weekend

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