The knobs on my reels have just been simple cylinders. They might look better with some shaping, perhaps a “waist”.
Here is a material blank mounted on a mandrel, ready for turning.
I want to make a concave arc cut on the cylinder, and the setup is to use the mill as a lathe.
The mill headstock is horizontal and a tall toolpost is fastened to the rotary table. I have used a similar setup to cut convex spherical surfaces on counterweights and center screws.
This plan view sketch may help to explain.