On Thursday, April 19, 2018 at 10:47:28 AM UTC-4, JBI wrote:
I am a student and need to be able to custom cut a thin piece of PVC
pipe of the kind found in bathroom drains, which is a lot thinner than
sch 40.

First ask if you have to use the thin stuff. The Sch 40 is a little more forgiving.

But you won't cut that with a knife either. Can't be done.

You either saw it (the finer tooth the better) or use a tubing cutter. I use a tubing cutter and get very clean cuts but I don't cut anything bigger than an inch.

Holes. Drill bit or hole saw depending on size. Make sure you have the pipe held securely.