Threading PVC pipe is used for mechanically joining two sections of the plastic tubing. This process is used for containing higher pressures, greater than 100 pounds per square inch (PSI). Typically, threading PVC pipe is also employed for deep submersible well applications, where unusual stress due to long lengths is placed on the piping. Only schedule 80 and schedule 120 PVC pipe can be threaded. The wall thickness on schedule 40 PVC pipe is too thin. By following a basic procedure you can thread schedule 80 and schedule 120 PVC pipe.
Place the pipe in the vise with the end to be threaded 6 to 8 inches from the clamping mechanism.
Wrap the rag around the pipe where it will mate to the clamp mechanism. The rag will protect the surface of the plastic. Secure the pipe in the vise and do not over-tighten the clamp as this will crack the pipe.
Place the tapered arbor inside the plastic pipe. The tapered arbor will aid in keeping the manual threader centered and the sidewall of the pipe from prematurely cracking.
Slide the threader onto the pipe, smooth side first. The threads should be facing outward away from the end of the pipe.
Start the thread die with your hand. Turn the cutter in a clockwise direction. Push on the end of the die as you engage the pipe. This hand pressure will begin the threads evenly.
Continue to thread the pipe using the long handle to rotate the die. Run the threaded portion of the die onto the pipe. Stop threading when the backside of the die is in line with the end of the pipe.
Remove the die by turning it in a counter clockwise direction. Clean the new threads by wiping them with the rag after removing from the vise.