[fciron]

That is a poor candidate for spinning,

I would either make male and female dies and try to form the taper onto some existing tubing (1/2 or 5/8", stretching is easier than shrinking) or I would work up a pattern and roll up the cones.

They're smaller than any slip roll I'm aware of, but .032" could easily be bent with round nosed pliers or over a 1/2" bar. Then weld the seam grind off the excess and true up over the s same 1/2" bar. You could make a precisely sized mandrel, but it might not save enough time to be worth it.