NTP & NPS Threads

NPT & NPS THREADS

NPT is NATIONAL PIPE TAPER (AMERICAN)
NPS is NATIONAL PIPE STRAIGHT (PARALLEL)
NPTF is NATIONAL PIPE TAPER FOR FUEL
NPSM is NATIONAL PIPE STRAIGHT MECHANICAL

Thread form per ANSI/ASME B1.20.1
Thread form per ANSI/ASME B1.20.1
Thread form per SAE J476
Thread form per ANSI/ASME B1.20.1

National Pipe threads are similar in function to BSP threads, but are not generally interchangeable.
NPTF threads (also known as Dryseal) are an improvement to NPT.
Controlled truncation of threads mean the metal-to-metal thread seal is at root and crest of threads, in addition to flanks of threads.
Use of thread sealant is recommended for NPT male and NPT female connection.

Measure NPT male thread OD and NPT female thread ID at first full thread near end of fitting.

NPT Threads Dimensions

NPSM Threads Dimensions

NPT THREAD SIZE & PITCH	DASH SIZE	MALE THREAD MINOR OD		FEMALE THREAD ID
NPT THREAD SIZE & PITCH	DASH SIZE	MALE THREAD MINOR OD		FEMALE THREAD ID
inch - TPI		mm	inch	mm	inch
1/8 - 27	-02	9,9	0.39	8,4	0.33
1/4 -18	-04	13,2	0.52	11,2	0.44
3/8 -18	-06	16,6	0.65	14,7	0.58
1/2 -14	-08	20,6	0.81	17,8	0.70
3/4 -14	-12	26,0	1.02	23,4	0.92
1 - 11.1/2	-16	32,5	1.28	29,5	1.16
1.1/4 - 11.1/2	-20	41,2	1.62	38,1	1.50
1.1/2 - 11.1/2	-24	47,3	1.86	43,9	1.73
2 - 11.1/2	-32	59,3	2.33	56,4	2.22
2.1/2 - 8	-40	71,5	2.82	69,1	2.72
3 - 8	-48	87,3	3.44	84,8	3.34

NPSM THREAD SIZE	DASH SIZE	FEMALE THREAD ID
NPSM THREAD SIZE	DASH SIZE	FEMALE THREAD ID
inch - TPI		mm	inch
1/8 - 27	-02	8,6	0.34
1/4 - 18	-04	11,9	0.47
3/8 - 18	-06	15,0	0.59
1/2 - 14	-08	19,1	0.75
3/4 - 14	-12	24,6	0.97
1 - 11.1/2	-16	30,5	1.20
1.1/4 - 11.1/2	-20	39,4	1.55
1.1/2 - 11.1/2	-24	45,5	1.79
2 - 11.1/2	-32	57,4	2.26
2.1/2 - 8	-40	68,8	2.71
3 - 8	-48	84,6	3.33

Thread size refers to the nominal bore of the pipe.
Subtract approximately 1/4”(6 mm) from thread meas ure ment for nominal pipe size.
Pitch is Threads Per Inch (TPI).