I am moving an old wooden spiral staircase from one location to another.
It was assembled by slipping the treads (6″ thick, solid wood) loosely over a 3″ galvanized steel pipe (4″ hole in each tread). Then the excess 1/4″ space was filled with some type of natural fiber and cut nails were driven in to wedge each step in place. It worked this way the first time, but I’m afraid the treads might rotate after a while.

Looking for a better method to put this thing back together that will keep each step where it belongs.

Any antique spiral staircase experts out there?