Using an Axis of Rotation to Measure Straightness

[littlestworkshop]

I have been playing with making my own spherical air bearings for fun, my first were cast in epoxy and more recently I made one from steel which I lapped and polished. But I am doing it on a much smaller scale (5mm ball). I was wondering if you had any rules of thumb for the load capacity of spherical air bearings. I have read that for a flat bearing 0.3 X P X A is a good estimate but I think I get less partially because of the radial components of the forces. Great vids by the way.