Guerilla guide to CNC machining:
Part 1
http://lcamtuf.coredump.cx/guerrilla_cnc1.shtml
And part 2
http://lcamtuf.coredump.cx/guerrilla_cnc2.shtml
Good read... with ASCII art illustrations... (tear dropping old school memories... back in the days where you had to do text-graphic porn to print on dot matrix printers...)