Homebrew PCBs

I am not sure ..if I make a board and put in a hole with a 
diameter of 8.15 mm as a drill size...I'm not sure if this 
will be milled when I send it to a board house..
.. just think that the mashines automaticaly will mill if its not 
a drill size that exsist.
I also think that the outline of board will be what is milled 
in eagle ...think eagle is pefect.. why is so many against it ?
in eagle the outline is layer 20 dimension
so can any help me 
will a hole be milled when it is in the project as a tool of 8.15 mm
and will the board be milled along the dimension line in layer 20 of eagle.. 
I  will be glad for response as it will make it easier to discuss with the board house ,when I have som background from you.
alex