I am going to put about 400# on the end of a support that I want to swivel.
I figure I am going to use a #8 grade bold in a vertical position. This
will rest on one ball bearing.

I have seen these ball bearings used in weld on hinges for large wrought
iron gates. The weight rests entirely on these bearings, and there is a
zirk fitting.

What hardness are the ball bearings? Do you think the combination of the
two would be a lifetime application? I think this would be a very workable
thing, even if I just use a hinge intended for wrought iron use, and mount
the vertical shaft one or two inches offset, just to get it to ride on the
bearing.

It's for the bottom pivot point for a davit hoisting mechanism.

Thanks.

Steve