Thank you all for your support, especially the kind remarks of aniki he does like me!!
The Brass insert I refer to is the central piece into which fits the spindle and forms the lateral support.
It is not possible to get oil to stay on the surface of a plain bearing such as this when operating in the vertical mode.
The oil just drains away down the spindle and out the other end, resulting in the spindle running "dry" after a few days
which is why I guess the whole bearing becomes loose after a while due to wear.