Machining PVC

Compared to aluminum, CFC, or even Delrin, PVC is easy. (It is an odd smell as it cuts.)  It is soft enough that you want to cut at low speed to avoid melting.  I needed to put a not quite blind 1.31" hole that diameter all tge way through and it was startlingly easy.  Tapping a 1/4-20 hole for a thumbscrew to lock the draw tube in place was very quick.  The next step is cutting a 5.5" length of pipe on the chop saw then using the mill to get very square ends on it.  The focal length of the objective is 152mm.  This should bring the focal point right out the end of the tube, where the draw tube  starts.  A drawtube about 2" long will allow eyepieces with focal lengths of 6mm to 40mm to focus there.  I am putting a helical focuser at the end of the draw tube which adds about an inch so perhaps a 5" tube.

Next I need to bore the draw tube to 1.25" ID.  Fortunately, I have a 1.25" Forstner bit to put in the lathe.  Then tap a hole for another 1/4-20 thumbs crew to hold the eyepiece there.