I want to skim another 2 thou off it, but since I lost the accidental gouges I'm getting a bit wary of removing any more meat.

The best lube for cast iron seems to be humble paraffin.

It has two hard spots. I know exactly where they are and may create a tool path that avoids them until cut end.

The boring head was the wrong tool to use. Need more rigidity.

I did have success insetting a 10x10mm bar of gauge plate square along the back edge. The required accuracy was way beyond the ability of my calipers so I wound up skimming 5 microns at a pass until I got a fit. Eventually got to the point where I could tap it in.

Hopefully that means the bar was bent rather than me cutting a 'banana' :whistling:

The bar stands 8mm proud, gives me something square to line up on and will have a doo-dad on the top to hold a splash guard. I am fed up with losing coolant when the workpiece precludes dropping a sheet of plastic in a T slot. I've tried all sorts but everything leaks and is a right royal pain in the bum. Time to do the job proper I thought.