Homebrew PCBs

Most of us are probably using CAD software to design our PCBs but if 
you're still scribing patterns for drilling and cutouts directly
to metal during case construction then you should consider creating 
CAD templates, printing and pasting them to the metal instead. Even 
if you don't intend using a CNC setup, these templates make things
more accurate for component placement and allow for efficient 
repeatability in case of screw ups. Also, the same template can be 
used as the basis for a dimensionally accurate "decorative"
finish.

Freeware PCB CAD software abounds and while they may be intentionally 
limited when it comes to actual PCB design, generally, there is no 
limitation when used for something like case design if you choose the 
right one. In other words, provided devices such as pads and "known" 
components are not being used, your design can be any size.

The link below is a set of pictures demonstrating the use of CAD 
software and printed templates to CNC drill and center drill 
(equivalent to center punching but under CNC) a 12" X 6"
sheet of aluminum that becomes the front, back and base of the case. 
Holes over 1/8" were drilled manually after center drilling.
Cutouts were nibbled using templates as bounds. Finally, a decorative 
finish printed on self adhesive film was then used for the front and 
back.

http://www.pbase.com/eldata/caseconc