The barrel diameter of a P14 at that point is about .600" so 1/2" threads seems about right. However, the length of the threaded section is seemingly about the same as the diameter or 1/2". So, with seven threads showing, that makes either 1/2-13 NC or 1/2-14 NPT. A little more coarse than 20TPI. And yes, I have way too much spare time today. Tom