It would usually be done by a router, or better yet a router table so you can control the speed of the cut a little better by holding the drum and not the router. Having worked with Plexiglass and seen how the pros finish off edges on acrylics when making various projects such as display cabinetry and whatnot, the secret weapon for a super smooth finish is to burnish the edges with a propane torch. That's right!...fire. But you must move very quickly you want the shell to melt but not burn. Not a job for a novice, but if you are

a skilled tradesman this will take a few seconds and oila!...smooth as glass, no chatter

from the router bit and no sanding. The other trick I learned about drilling holes in plexiglass is to use a dull drill bit and start a hole smaller than required and finish it off to required size with a step drill. If you use a brand new drill bit the actual size you stand a pretty good chance of catching an edge and creating a run or crack in the material. If you do try this yourself, for goodness sake do it outside and be safe. But you can do it, there is no such word as can't....can't just takes longer!

Glen

thank you so much!! that is very helpful, what kind of bit in the router table!! what about possibly using a dremel and bit of some sort!! About the drilling part I like that Idea, I was thinking of doing it slow because I cracked a piece of plexiglass years ago going behind my stove because I was in a hurry!!

Forget the dremel, they are wonderfully versitile tools, but not for this, you need a 45 degree router bit from Lowes or Home Depot that has a roller bearing on it. Get a 1/4 inch shaft, not a bigger one or you will need a heavy duty router with a large collet. You can rent a router if you don't have one. You need to protect the edge right up close to where you will be cutting with blue painters tape so the bearing does not burn the acrylic material. Cut from inside the shell first all the way through the shell, then tape the outside and cut a tiny eighth inch chanfer countercut with the same 45 degree bit to give a bearing edge. Depth adjustments are critical here, so know what you are doing before procedeing. Pictures of what you will be making are available elsewhere on this site. Research first, then cut. If you are not confident that you can do this yourself, ask a friend with carpentry skills to do it for you. Stay away from sanding at all if you can, otherwise use 320 grit wet dry emory cloth, you are not sanding wood, don't even try it with 100 grit regular old wood sandpaper.

Glen

And, if you are not using a router table, you need to make sure the shell is held firmly in place so it doesn't flip up from the weight of the router on one side or it doesn't move around and the router must be held exactly vertical at all times. Disaster could await if the process is not thought out and caution is not exercised. If you haven't done so already, do a Google search on "cutting bearing edges". There's some real good info out there, and of course, on this site. (Without the appropriate equipment I think I'd have them professionally cut.)