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How do you identify bsp and npt threads

July 6, 2017

How do you identify bsp and npt threads

Use the charts below to measure and identify your fittings.

BSPT & BSPP SIZE & PITCH	DASH SIZE	BSPT MALE THREAD OD		BSPP MALE THREAD OD		BSPT FEMALE THREAD ID		BSPP FEMALE THREAD ID
inch – TPI		mm	inch	mm	inch	mm	inch	mm	inch
1/8 – 28	-02	9,5	0.37	9,6	0.38	8,4	0.33	8,6	0.34
1/4 – 19	-04	12,8	0.50	13,0	0.51	11,2	0.44	11,9	0.47
3/8 – 19	-06	16,3	0.64	16,5	0.65	14,7	0.59	15,2	0.60
1/2 – 14	-08	20,4	0.80	20,8	0.82	18,3	0.72	19,1	0.75
5/8 – 14	-10	22,5	0.89	22,8	0.90	20,6	0.81	20,8	0.82
3/4 – 14	-12	25,9	1.02	26,3	1.04	23,9	0.94	24,6	0.97
1 – 11	-16	32,6	1.28	33,1	1.30	29,7	1.17	30,7	1.21

BSPT (British Standard Pipe Thread) is similar to NPT except there are important differences. The angle across the flanks of threads (if you sliced the fitting in half long-ways and measured the angle from root to crest to root) is 55 degrees instead of 60 degrees as it is for NPT.

British Standard Pipe Parallel thread

Parallel (straight) threads, British Standard Pipe Parallel thread (BSPP; originally also known as British Standard Pipe Fitting thread/BSPF and British Standard Pipe Mechanical thread/BSPM), which have a constant diameter; denoted by the letter G.

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

NPT stands for National Pipe Tapered threads, also known as ANSI/ASME B1. 20.1 pipe threads. It is a U.S. standard for measuring tapered threads on threaded pipes and fittings. Threaded pipes can give an effective seal for pipes using hydraulic fluids.

Thread Dimension of Compression Fitting

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