I need to cut kind of thick plastic
But the hole in my car is too small to mount the speaker on top, and the hole in the plastic is just slightly too small to fit the surround of the speaker if I mount it from the bottom. I figure it will be a lot easier to widen the hole in the plastic rather than in the car's sheet metal, but it's still not easy. Any tips? I've tried a box cutter knife, pocket knife, soldering iron, torch with soldering iron attachment, chisel, etc. Probably gave myself cancer from the fumes from trying to melt it. It's not terribly tough plastic, but it's kind of thick, so it's not easy. Plus it's difficult to cut a circle from the inside. I need to increase it from 13 cm diameter to 13.5 cm.