National pipe thread

These threads are now used in materials other than steel and brass, including PTFE, PVC, nylon, bronze, and cast iron.

The use of tape also helps to limit corrosion on the threads, which otherwise can make future disassembly nearly impossible.

On the other hand, for sealing capability, tapered (pressure-tight) threads have crest and root shapes that differ from Sellers.

[4] National Pipe Taper Fuel (NPTF, also called Dryseal American National Standard Taper Pipe Thread, defined by ASME B1.20.3) is designed to provide a more leak-free seal without the use of PTFE tape (often referred to by the popular brand name "Teflon") or another sealant compound.

NPTF threads have the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.

In 1864, William Sellers, then president of Franklin Institute, presented a standard for nuts, bolts, and screws.