This may or may not interest or help some of you but I imagine some would want to see how simple I look at it. I don't own a lathe so I have to use Southern ingenuity. I cant remember where I got the idea, but I'm sure I did not think of this all by myself.
I often use a coupling nut in my attachments in my handles. Imagine the nut is attached to the tang and now I need a threaded rod with a ball on it.
I take a piece of square stock, in this case 416 and cut almost through to form a cube, leaving it to remain attached to the main bar. I then drill a hole for the threaded rod, in this case a machine screw to eventually engage the coupling nut. I hard solder the screw into the hole.
The reason I cut the cube almost off is to be able to hold it by the bar but also the cut isolates the heat when soldering, the cut preventing the bar from sucking the heat away from the cube. After the solder, I can finish the cut.
I also cut of the machine screw head. Now we have a cube on the screw that needs to be turned into a ball. I then, by hand, just start grinding the square into round. I eyeball it.
Then I cut in some facets to begin the other dimension.
After that, I just eyeball it to get it close to round or whatever the shape I want. Sometimes it might be an acorn shape.
I then chuck it up in a cordless drill and go tot he grinder.
You can see (above) that it is still not perfect. I start the grinder and turn on the drill to spin opposite the belt direction. I keep it spinning pretty fast and just move it around accordingly to get the shape.
I grind on the hard platen and then switch to the slack belt to make it look more satin. I can just spin it in the drill and hold sand paper or scotchbrite on it till I like it.