Thanks folks!
Strine, that was perhaps the most interesting reading I've done in awhile. Alot of geophysical concepts that I was aware of, but never seen together and from a survey accuracy standpoint.
My plan remains this: Next time the forge fire is hot, I'm going to punch a hole near the top through the side. Then, I plan to mark the center of the top and drill it on my press and in a vise. I plan to clean up the taper on my belt grinder, as close to center as possible. Then, I guess I'll hang the bob from a string and let it spin, and mark the sides with a felt marker where I need to remove steel to keep the point centered as it spins. In my mind, this should make it as centered as possible.
Although it most definately won't be precise enough for Strine to survey and align the sides of the Sears Tower ( :wink: ) it should be functional for a homebuilder.
I'm considering using this one as a prototype to keep around the shop and then welding up a billet of junk steel damascus and forging another out of it for a gift. If not for Christmas, then maybe for his birthday in January. That'd be pretty swanky! A damascus plumb-bob! It'll be the jewel of his tool belt and he the envy of the worksite. :lol: