PDP 8 panels. Feedback

Jon Elson elson at pico-systems.com
Tue Oct 27 11:33:38 CDT 2015

On 10/26/2015 11:38 PM, Chuck Guzis wrote:
> On 10/26/2015 08:54 PM, wulfman wrote:
>> To effectively drill in plastics you need to run the 
>> drill press on
>> the highest speed you can and use a freshly sharpened 
>> drill bit.
> If this is Perspex/Plexiglas, I've had great results with 
> a good sharp Forstner bit in my drill press at medium (say 
> 750 RPM) speed and a not-too aggressive feed..  No 
> melting, just lots of crumbly shavings. I've done this 
> with sizes down to about 1/4", but no smaller.  When 
> you're almost through the material, turn it over and 
> complete the hole from the back side.   Very clean edges, 
> with no chips at all
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.)

Even better than just plunging an end mill is to use a CNC 
mill and a cutter smaller than the required hole diameter.
You use a pocket boring routine, set up for "climb milling" 
and after working through the material in several depth 
steps just less then the desired diameter, does a finish 
pass at full depth to bring it to final hole size.  This 
takes longer to describe than it actually takes the machine 
to perform, and leaves beautiful holes.


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