First, thank you for the amazingly fast and detailed response.
I will install Solid Inspector2 and try it out.
In my first attempt at this, I did try to draw a cross section profile centered on a circle and use Follow Me to sweep the profile around. I seem to have a lot of problems keeping my drawing of the profile in plane, and when I did I was still having “open” problems. I was advised that the small diameters I was working with cause problems in Sketchup and that I should try extruding cylinders instead. I will go back and try drawing the cross section profile again and see if my drawing ability has improved any.
I will pay more attention in future to dragging out the radius on an axis. It didn’t occur to me before.
In this drawing, I was able to specify 96 segments for the large (25mm) disk but for the smaller disks I was limited to 48s( or 24s, I can’t remember). Should I be consistent in specifying the number of segments for circles in a drawing or does each circle stand on its own?