Replies

1. 
   davidmeiland | Feb 04, 2006 08:36pm | #1

   A sharp hole saw, and go very slow and/or cut intermittently to avoid overheating it.

2. 
   Stilletto | Feb 04, 2006 09:20pm | #2

   Be sure to put something under the are to be drilled,  scrap piece of 2x6 or something, the stuff likes to shatter otherwise.

3. 
   TTF | Feb 04, 2006 09:30pm | #3

   Also, pre-drill the center hole for the hole saw. The pilot hole makes the position much more accurate.

   Hold onto the drill tight and go slow - it will get ripped out of your hands.

   Finally, I suggest you hole-saw half way through and them flip it over, to avoid break-out.

    

1. 
   DonCanDo | Feb 05, 2006 12:04am | #6

   Also, pre-drill the center hole for the hole saw. The pilot hole makes the position much more accurate

   Experiment a little bit, but the last time I drilled holes in plexiglass, I ran the drill in reverse and more or less "burned" my way through.

   This may work for the 4" hole as well, but the heat might leave the perimeter of the hole looking cloudy.

   -Don

4. 
   WorkshopJon | Feb 04, 2006 09:50pm | #4

   Holesaw AND water as a coolant.

   WSJ

   
   

   ---

   Edited 2/4/2006 1:50 pm ET by WorkshopJon

1. 
   asmith | Feb 04, 2006 11:40pm | #5

   ...and, as I understand it, you can "de-haze" the edges of the cut by heating it with a torch. It'll give you a finished look.a.

5. 
   MAsprayfoam | Feb 05, 2006 03:00am | #7

   Echo Stiletto's comment.
   Supporting the work as you go through is the most important thing! Otherside you will be sure to get cracks.
   Clamp that down very tight onto a bench or the like.

1. 
   pgproject | Feb 05, 2006 03:56am | #8

   They make special bits for plastic; the difference being a very sharply pointed tip. Maybe use one of those for your pilot hole.

6. 
   Fonzie | Feb 05, 2006 04:10am | #9

   JoeyB,

   Sometimes it is a good idea to run the bit backwards for a while to help warm up the area being drilled.

7. 
   piko | Feb 05, 2006 05:16am | #10

   You may be able to 'practise' by clamping the material to some waste lumber and drilling a couple of smaller dia. holes inside the finished hole first. This may relieve some of the stresses building up. As asmith suggests, heating the edge with a torch will clean it...I did this semi-professionally for a while, and it's quite easy to overdo it and leave a hazy halo around the edge. Use a small-pointed flame, moving it quickly around - it's better to go twice gently...

   All the best...

   To those who know - this may be obvious. To those who don't - I hope I've helped.

    

8. 
   gordsco | Feb 05, 2006 05:18am | #11

   Depends on how thick the plexi. 4" holesaw could bind and snap a sheet ¼" or less. 4" holesaw in a sheet ½" thick might melt enough plastic to bind the holesaw to the sheet before the cut was finished.

   I like to use a jigsaw to cut holes or arcs in lexan or plexi. The sheet normally has a protective film on it so a smooth baseplate on a jigsaw should not scratch the surface. If your jigsaw has a less than perfect base take other precautions.

   I have cut odd shapes into ½" plexi with a jigsaw only to find the plastic had fused itself back together behind the cut.

   I drill a hole in the plexi and insert the jigsaw blade through the hole. Hold a full coffee cup of water under the sheet and let the blade run into the water as you cut. This keeps the blade cool and more importantly stops the plexi cut from becoming a molten plastic mess. The cut is very smooth using this method. As someone mentioned before you can melt the edge clear with a torch but be careful, too much and you can discolor or warp. Practice on some scrap first. Using the edge of a sharp utility knife as a scraper will also make a plexi edge look clear. A small file will dull any sharp edges without scratching the surrounding surface like sandpaper.

   I suppose you could achieve the same result and run a hose over the surface of the plexi while using a 4" holesaw. I've never tried it, I always seem to be over a finished floor.

    

   Gord

1. 
   brownbagg | Feb 05, 2006 05:24am | #12

   4 inch hole saw and run the drill in reverse. 2+3=7

1. 
   highfigh | Feb 05, 2006 07:45am | #13

   Actually, this is supposed to be for JoeyB There is a hole cutter available that has a drill bit at the center, an arm that lets you determine the diameter of the hole and a cutter that moves on the arm. It cuts a vertical edge at the outside and a bevel on the inside. Another way is by using s Dremel or Roto Zip with a hole cutting jig. An even cleaner way to cut without burning is by cutting the hole a bit undersized in whatever way you want, cut the correct size hole in a piece of MFD or ? and use that as a pattern for a router with a carbide straight bit at the slowest speed that gives you a good edge without melting the plastic. Ease the edges and use a small diameter torch to melt the raw edge but don't keep the flame on it for too long, or it will bubble and/or darken.If the part needs to be more durable and can tolerate scratches, polycarbonate is softer, but less brittle.
   "I cut this piece four times and it's still too short."

   Edited 2/4/2006 11:46 pm by highfigh

1. 
   DanH | Feb 05, 2006 08:15am | #14

   > There is a hole cutter available that has a drill bit at the center,
   > an arm that lets you determine the diameter of the hole and a cutter
   > that moves on the arm.Known as a "fly cutter". Would probably work on plex fairly well. Be sure to pre-drill the pilot hole, and have smooth shaft, not the cutting part of the pilot, in the hole while using the fly cutter.
   If ignorance is bliss why aren't more people

   happy?