On 10/27/2015 11:59 AM, Chuck Guzis wrote:
  On 10/27/2015 09:33 AM, Jon Elson wrote:
  The ultimate way to drill holes in Plexi is with
an end
 mill.  It can
  make a slight chipping when it punches through the back,
 so you
 either need a backstop material or lighten up the feed a
 bit just
 before it goes through.  (This of course requires a
 center-cutting
 end mill, I prefer 4-flute for this.) 
 Sure, but I'm assuming that the original poster doesn't
 have a Bridgeport mill at his disposal.  But a drill press
 is quite within the budget of most hobbyists.  I'd think
 that if you already owned a vertical mill, you'd know how
 to work with plastics.
 
You CAN use an end mill in a drill press if you are
careful.  You get no self-centering, so the work must be
**SECURELY** clamped, as the cutter may try to walk.  But,
you'll get perfectly round, smooth holes.
Twist drills tend to wander and make triangular and slightly
helical holes.
Obviously, you can only do this with small size end mills in
a drill press.
Jon