If any of you have machined Plexiglas, you will understand the challenges here. The cutting tools must cut as freely as possible to keep heat from building up. Just a small excess of heat will lead to microscopic cracks forming and the possible failure of the part.
This is why I took the extra time to make the boring tool shown below. It is a tooth of a broken HSS reamer welded to a couple of CRS scraps. The cutting edge was put on with a small grinding wheel in a hand held die grinder. The scooped out shape allows the cutting edge to peel off material like a knife.
Not the least bit pretty - but quite effective!