I guess it is true that if you want something to be done, you must do it yourself
I finnaly solved the |==/ \==| problem.



I did it just like Peter said. The hardest part was to locate the exact center of the circle (you can see that I was a tinny little bit off the centre, but that wont affect anything). When I found the centre then I just made my cnc mill rotate the grinding tool in circles, each time with a tinny little bit greater diameter, till I got a smooth finish
I think that somewhere around next week I will be ready to assemble the whole thing. Then there will be only the coil winding left and the circuit part.