"Mike" m.j.willis @rl.ac.uk wrote in message
...
In order to avoid the problems you have noted,
find a thicker piece of scrap
material. Make a sandwich with your aluminum
panel as the filler. Clamp
together solidly as near to the hole position as
possible. Drill through the
whole sandwich. It is the only way I know to
drill neat holes in really thin
panels.

If your panel is not that thin, say 1mm, drill a
very small hole, say 1 mm
using a PCB drill and open it out to the
required size using a sequence of
slightly larger drills and a reamer.

The best way is to use a hole punch. You don't
find these very often. A QMAX
type cutter is a good substitute but you have to
drill a hole for the screw.
Fortunately, the damage caused in drilling the
screw hole is usually
confined to the scrap "int' middl' t'ole".

A Punch is a good way if you are within about 2
inches of the edge...
Try a Whitney #5 punch. You can find the punch
kit and accessories here

http://www.newmantools.com/roper/5jr.htm

I've been using one of these for over 25 years.
They also last if you don't abuse them.