A dremel and a steady hand.
Go slowly and let the cutting wheel do the work.
Looking to add a few more usb port onto the side of my carpc case. it's a metal and seems quite tough. Would the Dremmel be the right tool? Looking to make decently clean cuts.
The little metal wheel is what i'm looking for right?
If you mean the metal-cutting wheel that is impregnated with fiberglass strands (I believe that's what they are!), then yes.
You can use the regular cutting wheels, too, but they will wear out faster.
Regular cutting wheels can also shatter so its probably better to go with a metal cutting wheel. The metal cut off wheels are either diamond (the good ones) or fiberglass and should be alot more durable.
Even with a dremel with cutting wheel, you will want to have a nice file set on hand. Cut the rectangle just a tad small and then file it to perfection.
My 2007 Yukon XL setup. http://www.mp3car.com/vbulletin/show...64-5000-a.html
Personally I would use a drill bit the diameter of the width to drill out most of the slot and then use the files.
Maybe use the cutting tool mentioned above if you have left a lot of metal between the holes made by the drill.
I bought one of these yesterday from Harbor Freight Tools. It says use a 3/8 inch pilot hole which is a little too big for USB so I used 1/4 inch and squared it off with some needle files and then used the tool.
I cut some perfect rectangles in light sheet metal. Should work great for plastic too if it isn't too thick.