National Standard Taper Pipe (Npt) Threads Size Chart
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1National Standard Taper Pipe (NPT) Threads Size Chart
Length of
Hand
Wrench
Length of
Nominal size
Threads
Actual OD
engagement
tight
makeup
effective
(inside diameter)
per inch
(tightened by hand)
turns
turns
thread
1/16
0.3125
27
0.16
0.2611
0.405
27
0.18
4½
2½
0.26
1/8
1/4
0.54
18
0.2
4
3
0.401
3/8
0.675
18
0.24
4½
3
0.408
1/2
0.84
14
0.32
4½
3
0.534
3/4
1.05
14
0.34
4½
3
0.546
1
1.315
11.5
0.4
4½
3¼
0.682
1¼
1.66
11.5
0.42
4½
3¼
0.707
1½
1.9
11.5
0.42
4½
3¼
0.724
2
2.375
11.5
0.436
5
3
0.756
2½
2.875
8
0.682
5½
3
1.136
3
3.5
8
0.766
6
3
1.2
3½
4
8
0.821
6½
3½
1.25
4
4.5
8
0.844
6¾
3½
1.3
5
5.563
8
0.937
7½
3¾
1.4063
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