I have a step bit that I got from Lowes. It wasn't very expensive, and it worked for my plastic guitar amp foots-witch. It looked like the ones in the above amazon link, but not as expensive.

Yeah well... I wouldn't use it for more than just that... xD

well they're pretty damn handy anyway.

for more than just modding gameboys

Thank you all for your answers!

I think I'll go for the "take it easy" thing. I'll start with the thinnest bit I have and then keep changing it to a bigger one until it fits perfectly.

I know a dremel is the best thing for mods, but I'm not planning to do this "massively", so it's not worth for me to get one right now.

yeah a dremel comes in real handy when you're doing stuff like modding gameboys, models, etc, etc.

Get a dremel son.

I used an exacto knife and a lighter, the result is ugly, but the jack's little ring covers up the hole anyway so unless you have one of those premade prosound boards where the jack's just like the standard dmg jack, it doesn't have to be perfect, just don't crack the plastic and it'll look like this:

A screwdriver and a lighter.

Best bit for this:
http://www.amazon.com/Insty-Bit-1-4-For … B001ENU79Q

Only heavy duty drills for metal are made of cobalt afaik. You don't really need that.

edit: and Timbob is correct, 5.5mm or 6mm is fine for 3.5mm jack (you need to drill the outer diameter, not the inner 3.5mm)

@Timbob It's supposed to be for a female minijack. What you meant is a jack like the one on guitars right?

@kineticturtle Dear god, how expensive xD

http://www.amazon.com/Irwin-Industrial- … s=step+bit

I just use a drill. Start with 2 mm or so, then 4 and then 6 mm to fit in the female jack thing.
not really rocket science i guess.

I don't have any idea from that, sorry
If you use standard drill bit to do a hole, it might be good idea to do first a small hole with smaller bit. I've heard otherwise plastic would crack...

Yeah that was exactly what I was meaning. Sorry but I sometimes forget important English technical vocabulary xD

I forgot to say that the man in my local shop offered me a 3.5mm bit made of cobalt, which he said was perfect for plastic.. Any tip on that?