Progress!
Today I was able to prep the column for filling with epoxy resin. I plugged the holes that I had made to attach the top bearing bracket and levelled the column on a trestle in preparation for the final epoxy granite fill.
Attachment 250902All was running smoothly when a friend dropped by to say hello and check on the progress of the build. We chatted for a while and when he left about an hour later I went back to check if the epoxy had started to go off. Horror! There were two puddles of leaking resin on the floor. One was coming from a hole which had penetrated the top dovetail vee. It had been there from the start and I had not noticed it (since I didn't drill it.) The other more serious leak was coming from the bottom of the column where it is bolted to the base. Evidently there is a void in the bottom of the casting around 1.5mm thick and that too had escaped my attention. It was too late to do much apart from mopping up the leaking resin since I couldn't lift the machine off the trestle and getting access to both leaks was just about impossible. As it turned out I would have lost about two or three tablespoons of liquid resin so I am guessing there are a few voids in the epoxy granite fill around both the leaks.
Attachment 250904 In this pic you can see the resin dripping out of the lower column flange joint.
By mid afternoon the resin had solidified and I was able to lift the machine vertical again and give it a good clean and refitting the head back on to the vertical slide. I had previously lapped the gib and found that just over half of the gib had never been bearing on the inside of the dovetail. I was able to get about 90% contact without losing all of the adjustment in the gib. Most of the non contact area now hangs out the bottom of the dovetail in the head anyway. With that heavy unit back in place I placed a sling around the machine to hoist it back on to the machine cabinet.
Attachment 250908
My problem is that I have a one tonne chain hoist to lift the machine but once on the machine base I had to move it around four metres to where it lives in my workshop. The only option was to "waltz" it across the concrete floor, rocking it from one foot to the other whilst negotiating a path around some other closely spaced machines, and a car. Not good if you have a crook back.

I have covered what was the open back of the column with a 1.5mm thick aluminium sheet. It is a bit scratched but I will powder coat it later, if I can get access to a bigger oven. Come to think of it, that is probably the next project. The cover is purely cosmetic. I will also have to find a way of attaching the variable frequency drive to the column. It was previously fitted to the black steel cover that housed the original switch panel and power supply for the DC motor. I discarded all those items when I converted the motor to a 3 phase induction unit but I kept the original cover in place to keep dust and swarf out of the stepper motor drive an ball screw. With the drive now on the outside of the column I will ditch the black steel cover all together. The machine now looks a bit naked and flimsy with just the cast iron column holding up the head but it certainly feels solid, and heavy, now!
Attachment 250906 Here you can see the aluminium back which covers the rather untidy looking epoxy granite fill. Two sets of holes towards the top will be used for a bracket to support the VFD.

My next step is to refit all the vertical drive components and then add the extra set of ball nuts to the X and Y axes. I have a new idea for getting preload springs in between the double ball nuts. If I can work out how to model the springs in my CAD programme I will post details shortly.