hello good sirs or possible misses!
as the title suggests, i am trying to determine the diameter of the spindle so that i can further consider a project. although the i.d. of the wheel assemble would likely be less accurate it will help me with additional research.
here are two images to help get everyone on the same page assuming i am describing something incorrectly.

here is what the king pin/spindle assembles will look like and i am interested in the diamter of the shaft the bearing rides on just below the threads; the clean polished section.


the inside diameter of the bearing in the hub assemble

thank you for your time!
live long and prosper!