From: Alan Inness <intek@escape.ca>

Peter, I have a couple of Excello knee mills I am retrofitting right now and
they have a vertical box to the left of the quill that contains a vertical
ballscrew fitted with a thrust bearing top & bottom, a timing belt pulley is
mounted at the top end for drive.
The ball nut has a bracket attached that bolts to the quill.
Al I.