Experiences in winding small toroidal cores.

 

When you build something every now and then, you sometimes have to wind a bobbin.

A bandpass filter has several e.g.

Commonly used cores are T37 or T50 models.

Inner diameter is 5.21 mm or 7.7 mm. Very small. It is not easy to hold the core and the wire. You actually lack a third hand.

Several ways have been devised to solve this.

You can clamp the core with a wire in a vice.

 

The wire can be easily threaded and pulled through.

Since the advent of 3D printers, clamps have also been printed.

 

 

There is also a solution via a kind of needle. Just look on youtube .

 

Jack K3JAS made a 3D version of this.

I couldn't open his file in my software.

I have traced it. The base is square (3 cm). This clamps better in a vice.

The cone is 5mm in diameter at the top and 15mm at the bottom.

Willy, ON5KN , printed the file. (1x at 100% and 1x at 50% of the size)

When testing I noticed that the diameter at the top (5mm) could be a bit smaller.

For t50 cores, winding is fairly quick. After 2 to 3 turns, the wire stays in place and does not need to be held any more.

For t37 cores the shape is too big. For this I used the 50% version.

 

 

 

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I got more reactions. I add this stl in the zip file.

Have fun building circuits and winding coils.

 

73 Jean-Marie ON7EN