I've had a fair amount of bacardi and coke but will try to help. First thing is never to disconnect and earth conductor with the main supply still live. This is a very easy way to kill yourself and wont really tell you much. Do you have a 40 amp mcb and seperate rcd or is it a combined rcd and mcb? It doesnt take alot to trip a 30mA rcd, apart from 30mA a dodgy computer power supply or filter unit could do it. Does the protection trip with only the router,vfd and the computer/ cnc running? Can you run the vfd and router on its own without the cnc controller? If it still trips this way and doesnt trip when you use your lathe then it could be the spindle motor. You will need an insulation tester to check the windings. A multimeter wont find any high resistance faults.
Ran out of bacardi now:cry: