Hi Mr Monkey
Sorry I did not reply, As u can see from my other posts I milled the cheap Chinese table I bought with a 1 inch hinge cutter after I had covered it with wood. Making 4 PCBs at a time cutter depth must be the same at extremities.
Yoy will see from my other posts I have made a Gingery horizontal mill impersonation. Its a lot of heavy ironwork bolted together. There was a guy on here asking about distortion in a welded frame. Well I dont weld everything first off. Bolts can be sufficient but if something starts to move clagg a weld on it. Good reason for using steel bits.

Wishing u success with ur build Keith