What is an RP thread?
It is a thread commonly called a parallel thread for JIS (ISO) pipes, and it is a parallel internal thread for tight coupling. (JIS B 0203)
Rp is a thread symbol used only for internal threads.
・The thread that fits into the Rp is a tapered screw for R (ISO) pipes.
・Thread angle is 55 degrees
・The name is expressed in inches,