Typically used on pipe 3" and smaller, threaded connections are referred to as screwed pipe. With tapered grooves cut into the ends of a run of pipe, screwed pipe and screwed fittings can easily be assembled without welding or other permanent means of attachment. In the United States, the standard pipe thread is National Pipe Thread (NPT).
The reason for this is that as NPT connections are assembled, they become increasingly more difficult for the process to leak. The standard taper for NPT pipe is 3/4" for every foot. Threaded End is abbreviated on drawings as TE.
Threaded fittings have threads that are either male or female. Male threads are cut into the outside of a pipe or fitting, while female threads are cut into the inside of the fitting. As screwed pipe and fittings are assembled, two pieces are pulled together. The distance that is pulled together is called the thread engagement.
