Thanks for that Jazz. Gives me some hope for experimentation with the existing spindle. The machine is still under final construction so when I am set up properly I'll include higher DOC in the runs. I've only done a bit of quick machining to help build the last bits of the bed so used the 0.5mm DOC from the previous much weaker machine.

I'll also dig out the VFD manual and set up the display for amps. Seem to remember this being an 8A VFD but it was a while back so I'll confirm so I can see how it is coping.