Cutting styrene sheets (big ones) - Model Railroader Magazine

Matt:

What we bought was for cutting plastics.  More like this:

 (I copied the link, as Firefox wouldn't let me cut + paste.  If I typed it incorrectly, look under drill reamer)

I found it under "drill reamer".

The good thing about the finish, is, it leaves you with a machined milled surface.

I would use it in a regular router, as you have better control, power and a clat alignment.

Like I said earlier, that was using 1/4" polycarbonate which you absolutely can't score and break.  It's almost as tough as aluminum. 

But first, it appears that others have had excellent luck with scoring, which is far easier, less messy and inexpensive.

Best of luck.