Primary Coil Clamp Pin

I spent sometime yesterday trying to figure out a good way to make the required electrical connection to the innermost end of the primary coil.

As you can see in the picture the connection needs to clamp onto the end of the 1/4" copper tubing and then pass through the 12mm perspex disc underneath the primary coil. In this pic the disc is still covered with protective plastic coating.

This is a side on pic taken level with the primary coil. You can see the anti-strike perspex disc above the primary coil and the 12mm thick disc below. After long consideration I decided that I needed a fitting that would clamp on to the end of the primary and have a protrusion that would pass through a clearance hole in the 12mm disc below. This "protrusion" would need to be threaded to allow a copper lug to be fitted on the underside. I had bought a drawing app for my ipad called iDraw and thought I would throw a quick design together. I've used this app before for designing the toroid mounting pin, it's not the most technical drawing app but it matches my abilities.

I started with a small length of 16mm diameter round copper bar. I turned down 25mm of it to a diameter of 8mm and then the next 25mm to 14mm diameter.

I cut the turned section off with a hacksaw then cleaned up the cut end in the lathe finishing the 14mm diameter section to a length of 22.375mm.

Here's the finished blank. Next I drilled the hole for the 1/4" copper tube (6.75mm drill bit used) and the holes for the clamping M3 grub screws. Decided to deviate from the plan and have 2 clamping grub screws at 180 degree to each other.

Using an M8 X 1.25 die I cut threads on the end of the 8mm diameter section (about 15mm of threads) and then cut the M3 threads for the grub screws.

Here's the finished article fitted with an M8 stainless nut and copper electrical lug.

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