Most PCB manufacturing houses have a procedure for routing and scoring on your PCBs. This information is usually placed on a separate layer (eagle usually uses layer 46). You simply draw rectangles on this layer to represent the milling pattern. You should reach out to your PCB manufacturer to determine how to specify the depth that you want the milling done at (most milling is completely through the PCB) and possibly the tool size for the milling (most offer very limited tool sizes).
Most PCB manufacturing houses have a procedure for routing and scoring on your PCBs. This information is usually placed on a separate layer (eagle usually uses layer 46). You simply draw rectangles on this layer to represent the milling pattern. You should reach out to your PCB manufacturer to determine how to specify the depth that you want the milling done at (most milling is completely through the PCB) and possibly the tool size for the milling (most offer very limited tool sizes).
