Tools, Sharpening and Power Machinery - tool to cut plastic

I'm doing a project where I want to cut opening in the side of plastic pails. (It's for hamster pets to hide, & I'd rather recycle a pail than buy new products at pet store $$!). My hot knife works well for foam, but this is more heavy. I want to get a smooth edge that scissors dont give you. Anybody have a tool for this? Thanks.

You would want to drill a 3/8" hole first, then use a jigsaw to cut your larger hole. The 3/8" hole gives the jigsaw blade a place to start cutting. Once you are done, the edges of the hole could be eased with some 80 grit sandpaper if the cut is too rough or the edges seem to sharp.

If you don't have a jigsaw, but you have a drill and drill bits, you could also make a square or rectangular hole by drilling a 3/8" hole at the 4 corners of your square, then score the perimeter of the square with your utility knife (and a new sharp blade). Scoring the outline of the square hole four or five times then giving it a good whack with a hammer ought to do the trick.

If you want a round hole, look into buying a hole saw and arbor. That way you could drill a round hole in the bucket. Hole saws come in a variety of sizes.

Thanks for that feedback. I do have a drill and xacto knife. The opening does not have to be round. I mainly want to make sure that the cut edges are smooth. The hot knife is a good tool for that on light materials. I'll try it out tomorrow!