Hand spun Aluminum Toroid for Teslacoils

I have started spinning my own toroid's, it's a lot of work but it's definitely worth it. The outer dimensions are 180x 50 mm, the maximum coil diameter is 80mm. Capacitance: ~7,9pF

The result with 1.0 mm Aluminum sanded finish:

 

The result with 1.0 mm Aluminum polished finish:

Projectvideo:

 

If you want to spin something you first need a mandrel to spin the metal sheet onto. The mandrel can be made of a variety of materials, but if you want it to last you're best off making them of steel. I started with two steel disks (190 x 45 mm).

 

To spin a toroid you need two different mandrels, one to spin the inner radius and one for the outer radius. The toroid consists of two spun halves, bolted together. Download the construction drawings

 

To get the outer radius without a CNC lathe is pretty difficult, I solved the problem with a lathe copy construction and scraped and sanded the grooves out later. A steel cylinder with the right diameter is stationary (and firmly) placed on the lathe frame, the cutting tool holder holds a rod with the same shape as the cutting tool. This rod will follow the radius of the cylinder and transfers it to the mandrel.

 

The other mandrel with the inner radius was a bit more easy, a large m16 bolt with a hole to clamp my cutting tool. This way the radius is easily adjusted.

 

you also need some tools for spinning, I made two spinning rods out of solid steel. One with a round end and one with a flat end. The round end is used for forming the inner and outer radius, the flat one is to smooth out the outer radius. I used the stove to heat up the rods and cooled them in oil to make them harder.

 

As lubricant I use a glycerin based soap, the advantage of this is that you can easily clean the disks (and yourself) after spinning. I found a useful spinning guide on the web, you can download it here.

 

The different steps of spinning a toroid:

 

The toroid in action:

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