Why will be the threads G 1/8 and 1/8 NPT offered for pressures and then a nominal pressure selection of 400 bar? Where does Fine from?
Basically, Successful is very simple: From a certain pressure limit, the thread flanks are no more ?strong? enough to resist the force of the applied pressure. If the pressure is too high, there is a risk of shearing for the thread. Incidentally, the pressure limits result from DIN EN 837-1.
Attention: The maximum pressure up to which a thread can be used depends not only on the thread diameter, but additionally on the selected sealing type and the material of the counter-thread.