Tap Chart - Pipe Threads

NPT = National Pipe Thread

NPT stands for National Pipe Thread and is an American standard thread. It may also be referred to as MPT , MNPT or NPT (M) for male external threads and FPT, FNPT or NPT(F) for female internal threads. A thread sealant must always be used to achieve a leak free seal (except for NPTF). NPT is the US standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid tight seal.

NPTF = National Pipe Taper Fuel

NPTF is a dry seal tapered pipe thread. Visually, NPT and NPTF pipe threads look identical. Both thread types rely on thread interference for tight, robust connections.

The primary difference between NPT & NPTF pipe threads is that NPT threads require a sealant to prevent leakage, while NPTF threads do not. NPT sealants can dissolve under high pressure and high temperatures, contaminating fluids and gases.

NPS = National Pipe Straight Taps

High Speed Steel Straight Thread Pipe Taps (NPS) are designed for tapping holes or couplings for low pressure work that will adjust at assembly to the taper of external threads. A sealant must be used to secure a pressure tight joint.

NPSF = American National Standard Fuel - Straight Pipe Taps

Produce a straight internal thread intended for assembly with NPTF external taper pipe. NPSF straight threads cover a range from 1/16" to 1". The tolerance of these taps and the truncation at the crest and root of the thread will provide for crest and root interference when assembled with NPTF external NPTF taper pipe.