======================= I don't mean to belabor the obvious, but as this is alt.machines.cnc, do you have a cnc lathe?
If so, an old technique may help. If you lathe has enough swing, rig a faceplate. It will be an interrupted cut so HSS may better than carbide, but G2/G3 and lots of patience may be a solution.
If a strictly manual lathe you can use the method described in one of Lautard's "Machinists Bedside Readers" to generate a radius using a series of plunge cuts. see
and several of the catalog tool supply houses also carry these books. This is not a actual radius but series of tiny steps that approximates a radius, most likely good enough as machined, or file/polish to suit.
What equipment do you have available and what are the sizes of the dies?
Unka George (George McDuffee)
...and at the end of the fight is a tombstone white with the name of the late deceased, and the epitaph drear: ?A Fool lies here, who tried to hustle the East.?
Rudyard Kipling The Naulahka, ch. 5, heading (1892).