Most polyesters thread very poorly.
I avoid them. If you are going to try it, use lots of lubrication/coolant, and very very light cuts. You will need to single-point them, I wouldn't try a tap.
But even then, I don't like trying. The threads might function, but they will most likely chip and not look attractive, at best.
There are so many standard acrylics to choose from, that I find no reason to use PR's, if they need to be threaded.