I did it this way. Used a carbon bit after I placed masking tape where the hole was to go (it helps keep the bit from slipping). Go slow.You can use a drill but you have to go slow. Also, you can try using packing tape, then drilling (still need to go slow though).
Tape isn't supposed to stop chipping and cracking. It's there to keep the bit from slipping all over the plastic while you try to drill through it.Id say the slow drill gives the best, cleanest hole.
Those cubes are cheap, get one(or similar plastic) and use it for practice.
Once you get it, its easy.
Gotta kinda start out fast, then drill slow thru it.
I used to melt the holes, but you get a big unsightly ring of melted plastic around each hole that sometimes cannot be removed.
IME, tape aint gonna stop chipping and cracking- thats caused by not having a solid surface to drill into.
There is a special plastic drill bit that you could buy, but it wont completely solve the issue.
That styrene plastic is brittle . . .
Some people melt them in with a soldering gun.
That is what I did as well. I have to say I really like codykrr's idea. That looks nice and gives ample amounts of ventilation.The only problem I have had drilling that type of plastic is using a drill bit that is too large. I use about an 1/8" drill bit, and I don't have any problems. I can go as fast as I can without any cracking.
I use a dremel at top speed.