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Standard Taper Pipe Threads NPT Basic Dimensions, American National Standard

Standard ANSI Hardware

Basic Dimensions, American National Standard Taper Pipe Threads, NPT

Related:
National Standard Taper Pipe Threads Size NPT Chart - Includes both External and internal Pipe Thread Data
.

Notes:

Taper Pipe Threads

ANSI/ASME B1.20.1-1983 (R2006)
All Dimensions Given in inches

Nominal
Pipe
Size
Wrench Makeup Length
for Internal Thread
Vanish
Thread,
(3.47 thds.),
V
Overall Length
External Thread,
L4
Nominal Perfect
External Threadsa
Height
of
Thread,
h
Basic Minor
Dia. at Small
End of Pipe,b
K
0
Length,c
L3
Dia., E3
Length, L5
Dia., E5
1⁄16
0.1111
0.26424
0.1285
0.3896
0.1870
0.28287
0.02963
0.2416
1⁄8
0.1111
0.35656
0.1285
0.3924
0.1898
0.37537
0.02963
0.3339
1⁄4
0.1667
0.46697
0.1928
0.5946
0.2907
0.49556
0.04444
0.4329
3⁄8
0.1667
0.60160
0.1928
0.6006
0.2967
0.63056
0.04444
0.5676
1⁄2
0.2143
0.74504
0.2478
0.7815
0.3909
0.78286
0.05714
0.7013
3⁄4
0.2143
0.95429
0.2478
0.7935
0.4029
0.99286
0.05714
0.9105
1
0.2609
1.19733
0.3017
0.9845
0.5089
1.24543
0.06957
1.1441
11⁄4
0.2609
1.54083
0.3017
1.0085
0.5329
1.59043
0.06957
1.4876
11⁄2
0.2609
1.77978
0.3017
1.0252
0.5496
1.83043
0.06957
1.7265
2
0.2609
2.25272
0.3017
1.0582
0.5826
2.30543
0.06957
2.1995
2-1⁄2
0.2500d
2.70391
0.4337
1.5712
0.8875
2.77500
0.100000
2.6195
3
0.2500d
3.32500
0.4337
1.6337
0.9500
3.40000
0.100000
3.2406
3-1⁄2
0.2500
3.82188
0.4337
1.6837
1.0000
3.90000
0.100000
3.7375
4
0.2500
4.31875
0.4337
1.7337
1.0500
4.40000
0.100000
4.2344
5
0.2500
5.37511
0.4337
1.8400
1.1563
5.46300
0.100000
5.2907
6
0.2500
6.43047
0.4337
1.9462
1.2625
6.52500
0.100000
6.3461
8
0.2500
8.41797
0.4337
2.1462
1.4625
8.52500
0.100000
8.3336
10
0.2500
10.52969
0.4337
2.3587
1.6750
10.65000
0.100000
10.4453
12
0.2500
12.51719
0.4337
2.5587
1.8750
12.65000
0.100000
12.4328
14 OD
0.2500
13.75938
0.4337
2.6837
2.0000
13.90000
0.100000
13.6750
16 OD
0.2500
15.74688
0.4337
2.8837
2.2000
15.90000
0.100000
15.6625
18 OD
0.2500
17.73438
0.4337
3.0837
2.4000
17.90000
0.100000
17.6500
20 OD
0.2500
19.72188
0.4337
3.2837
2.6000
19.90000
0.100000
19.6375
24 OD
0.2500
23.69688
0.4337
3.6837
3.0000
23.90000
0.100000
23.6125

aThe length L5 from the end of the pipe determines the plane beyond which the thread form is imperfect at the crest. The next two threads are perfect at the root. At this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface of the pipe. L5 = L2 − 2p.
b Given as information for use in selecting tap drills.
cThree threads for 2-inch size and smaller; two threads for larger sizes.
d Military Specification MIL-P-7105 gives the wrench makeup as three threads for 3 in. and smaller. The E3 dimensions are then as follows: Size 21⁄2 in., 2.69609 and size 3 in., 3.31719.

The basic dimensions of the ANSI Standard Taper Pipe Thread are given in inches to four or five decimal places. While this implies a greater degree of precision than is ordinarily attained, these dimensions are the basis of gage dimensions and are so expressed for the purpose of eliminating errors in computations.

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