A buddy is making the Parrot field rifle from the 1982 HSM plans. He asked me to make him the part which has a capstan-type bolt head which has 4 1/8" rods radially arranged with 1/4" balls on the end. He had thought he could bead 1/8" welding rod with a gas flame and get a nice ball, but he failed. I just couldn't imagine turning a ball on a 1/8" shank without it bending, so I thought for awhile, then took a 1/4" ball bearing and some old copper-clad 1/8" welding rod (gas welding) and made one. This is how I did it.
I put the 3-jaw chuck on the lathe, and chucked a short piece of the 1/8" rod and spun it at high speed and applied some abrasive cloth to remove the copper and polish the rod. Then I rechucked it so only about 1/4" was sticking out, and took a small center drill in the tailstock chuck and made a light centered spot in the end of the rod, just enough to get some clearance. Then I took a 1/4" ball end mill and chucked it in the tailstock chuck and again at high speed fed it into the rod until I had a nice spherical female end. I took a small smooth file and cleaned the edges. Then I re-chucked the rod so it stuck out about 1", and chucked a piece of 1/8" pipe in the tailstock chuck. I used the pipe to center the ball bearing and press it against the rod. I fluxed it with white flux and using silver bearing solder (low silver content) soldered the ball to the rod. Then I backed off the 1/8" pipe and spun the part and polished it. The ball isn't quite dead centered but it's way close enough, and it was quick and easy. The low silver content solder matches the color perfectly and you have to look very closely to see any fillet after polishing.