Wow! This is so far beyond me I wont even ask how you did it.
Hell, I'll ask... how did you machine your toy?
Beautifully done, Jim.
I think I know how he did it because I made a double headed bolt with a captive nut in the middle, like this one.
But, I ain't telling.
Tom
It should be fairly easy to make a doughnut with a ball turner. The radius of the ball turner is set to the cross sectional radius of the doughnut and the center of rotation of the ball turner is set to the diameter of the doughnut. Turn the bulk of the doughnut, leaving a central web and carefully finish by turning away the web. There would be some cleanup to remove the last remnants of the web.Just trying to think of a good way to turn a donut like that is making my head hurt, without even trying to do it with a dumbbell going through the middle.