I have cut several holes in the top of my case for a project im working on, but hte problem is that no matter how much i file the edges they still look too jagged and ugly to me. then i thought of putting a moulding around them, sort of like the way that locking strip looks on case windows. i thought of maybe taking some really small tubing and cutting a slit in one side and sticking it along one edge, but i cant find any black tubing thats small enough (like 1/4 to 1/8 inch diameter) i thought maybe someone here has done something like this or knows what would work well besides tubing with a slit in it. thanks for the suggestions!
You need blow hole trim. A standard modding item sold cheaply by most modding shops. To apply, always cut off more than you think you'll need. 3.5 times the diameter of the hole is a safe bet. When working it around the hole edge, try and compress it as much as possible so that the two ends, when they meet, firmly push against each other, holding the trim wedged in place around the edge of the hole. See my project (early on) for an application.
Check auto-parts supply stores too. I picked up some door edge molding at a local Pep Boys (USA), black, worked great. Nice thing is, the door molding has glue or something on the inside, so it stays attached quite well. The store I got it from also had chrome finish available. It was a 25' long peice, for I don't recall how much, but it wasn't a lot (probably less than $15)