Paul Clay wrote in :

What's the best way/tool to cut or drill holes 1/8 inch to 5/16 inch in
diameter in thin gauge aluminum (for inserting potentiometers and
phono, power jacks, etc.)? I've tried using just a power drill and
genernal purpose drill bits and the results have been sort of ragged
(the edges of the hole are ragged and the process of drilling creates a
depression surrounding the drilled hole).


Get yourself a step bit. You just drill the starter hole, and then drill
with the step bit until you have the size hole you want. Much cheaper than
punches.