As I set the plastic shower pan into its mortar bed, I saw the problem. The drainpipe was 3/4 in. too long, the pipe was glued in place, and the plumber was long gone. Because the clearance around the drainpipe amounted to no more than about 1/8 in. on either side, no saw of mine would be able to trim the drain below the surface of the shower pan.
To solve the problem of cutting the pipe, I made a tubing cutter that works from the inside of the pipe. For a cutter, I used a drywall screw. Anyone who ever has stuck a hand into a pouch of drywall screws knows how sharp they are. As shown in the drawing, I ran a 2-in. drywall screw through a small block of wood. To this piece of wood, I affixed a small handle, which also functioned as a depth stop. In use, the handle rests atop the end of the pipe. Then I turned the device with the point of the drywall screw bearing against the inside surface of the pipe. After a few turns, I pulled out the cutter, and set the screw a little deeper. In no time I’d cut through the pipe.
Walter Gorr, Pittsburgh, PA