I was building a off-dock crane to unload containers from a barge. I wanted to have a rotating crane supported on a tube structure on a circular platform with a lower man-platform also circular. I needed a circular base plate to attach the tubes base to the concrete pylon foundation; again circular.
To cut the perfect plastic circles in 1.5", 2" and 3" diameters without having any internal circular hole I used Carter's accuright circle cutter that attaches to my band saw table. See below:
http://www.carterproducts.com/...rightr-circle-cutter
This creates circles of any diameter(depending on the band saw blade size) up to about 4 feet in diameter.