NPT Fitting Sizes are based on the "PIPE" that would typically thread into these couplings. Use the Chart below to find the proper size match.
Its important to understand that both the Male and Female NPT fitting has a 1.8 DEG taper applied to the thread. This taper is intended to create what is called an interference fit once threaded together. It is expected that the male mating fitting will not thread all the way down. Sufficient tightness is created approx 1 turn or less past hand tight, any further and you risk damaging the fitting. To get a liquid tight seal you will need to use thread sealant that is appropriate for your application.
NPT Half Couplings are tapered threaded fittings and can only be threaded from one end. Typically one end of the fitting has a large chamfer on the outside that designates "UP". You should always verify yourself before welding.
All Fittings are quality checked with an L1 NPT Thread Gauge before we add them to inventory. We will not replace improperly welded fittings.