What is the max amount of torque that could be applied to 1 in male threaded NPT pipe when it is threaded into a 1 in female threaded body that is made from ASTM 126 cast iron. The dimensions of the threaded female body are shown below.
Torque installation of pipe fittings is not a recommended practice. Thread taper and quality, different port and fitting materials, plating thickness and types, varying thread sealants, orientation, and other factors reduce the reliability of a torqued connection.
I have never seen any plumber use a torque value on the npt fitting and piping joints. To be honest, they always use thread sealant and generally tighten joints until "it feels right" based upon their prior experience.