Pipe Threads

American Standard Taper Pipe Threads (NPT)

Nominal Size (ID)	Actual OD	Close Fraction	Threads per inch	Length of engagement (hand tight)	Hand tight turns	Wrench make up turns	Length of effective thread
1/16	0.3125	5/16	27	0.16			0.2611
1/8	0.405	13/32	27	0.18	4 1/2	2 1/2	0.26
1/4	0.54	17/32	18	0.2	4	3	0.401
3/8	0.675	11/16	18	0.24	4 1/2	3	0.408
1/2	0.84	13/16	14	0.32	4 1/2	3	0.534
3/4	1.05	1 1/16	14	0.34	4 1/2	3	0.546
1	1.315	1 3/16	1 1.5	0.4	4 1/2	3 1/4	0.682
1 1/4	1.66	1 5/8	11.5	0.42	4 1/2	3 1/4	0.707
11/2	1.9	1 7/8	11.5	0.42	4 1/2	3 1/4	0.724
2	2.375	2 3/8	11.5	0.436	5	3	0.756
2 1/2	2.875	2 7/8	8	0.682	5 1/2	3	1.136
3	3.5	3 1/2	8	0.766	6	3	1.2
3 1/2	4	4	8	0.821	6 1/2	3 1/2	1.25
4	4.5	4 1/2	8	0.844	6 3/4	3 1/2	1.3
5	5.563	5 1/2	8	0.937	7 1/2	3 3/4	1.4063

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