Would the white plastic be Delrin? I have a couple of sheets of that (2' x 2' x 1/2") and rods. EBay, McMaster Carr sell it in blocks and tubes.
It may have been. ACC glue doesn't stick that well to it. I always thought of delrin as being blackish, maybe just my "old school" memory. It has the same characteristics as a roller (for sheet Al) that I'm pretty sure is delrin. At 6" diameter and 8" long though, I'm "saving" it for something where the size is necessary. Normally, I don't keep track of what type of plastic something is. Styrene is soft and flexible and doesn't make good screws, acrylic and lexan are clear and more rigid and not so easy to cut, ABS and PVC make pretty good pipe.
I have a "gizmo" made out of Sched 20 PVC that I can climb on, at 230 lbs. (6' 3")
http://www.hudsontelcom.com/uploads/DomeAdv.pdf
I wrote the instructions with help from an associate in the "survival" business. Some of the left handed perspectives were his, with me doing the technical details. (I'm hiding out) Y2K got a lot of questions about the gizmo.
In any case, the machine I have listed has a metal frame and supposedly cuts Al and Cu. Brass is mostly copper, with some zinc added. Hardware store aluminium is softer than copper, the alloying materials can make it almost as hard as steel. I'm not too impressed with the theoretical accuracy, it certainly ain't a South Bend or Bridgeport. But for work with wood or plastic, should give results within most model builder's tolerances of a few thou. But again, no threading capability.
Mostly, I'm trying to make a point. You are not getting into machining as a machinist, you need to make parts for your models. Accuracy is more to the point of "TLAR", that looks about right. The part I mentioned before is to fit a 2-56 machine screw. When I make the screws, I usually cut the threads with a die. Sometimes by hand, some times on the lathe. As long as the die fits, it'll work. Most times a chunk of coat hanger, occasionally a brass rod. If it's a few thou undersized or over sized, the die does well enough, so long as there is a semblance of threads. 00-90 threads are a little touchier, but the same standards apply. Mainly, I'm trying to convey that you may not need a full blown machine shop.
.