I'm still yet to try your tuning test above, I now have bigger problem
When I run some g code as a quick test (with spindle motor stopped, the main RCCD in my workshop trips after a few mins. So I rewired the power supply going to my rotary phase converter to before the RCCD in my workshop,
Now when I run the mill, after about 30 secs it trips the RCCD in the house (which it's not connected though).
In my house I have coming out of my mains supply meter I have two pairs of 16mm2 cable. One set goes to my house consumer unit, and the other out to my workshop.
I don't see how something in my workshop could impact the RCCD in the house, any thoughts?