External Pipe Thread Design, Specifications and NPT Pipe Thread Tolerances

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NPT, ANPT and NPTF thread data Table. Note that NPT 5" to 24" OD sizes are not included in the table.

NPT, ANPT and NPTF Threads
NPT, ANPT and NPTF

NPTR pipe Threads
NPTR

NPTG and NPTC Pipe
NPTG and NPTC

External Pipe NPT Thread Dimensional Data Table

Pipe
Size
T.P.I
D
O.D.
O.D.
of Valve
NPT
ANPT
NPTR
NPTF
NPTG
NPTC
1/16
27
.313
-
-
1/8
27
.405
-
-
1/4
18
.540
-
-
3/8
18
.675
-
-
1/2
14
.840
.863
-
3/4
14
10.05
1.081
-
3/4-14NPTC-1
-
-
1.096
3/4-14NPTC-2
-
-
1.114
3/4-14NPTC-3
-
-
1.134
3/4-14NPTC-4
-
-
.159
1
11-1/2
1.315
1.346
-
1-1/2
11-1/2
1.660
-
-
1-1/2
11-1/2
1.900
-
-
2
11-1/2
2.375
-
-
2-1/2
8
2.875
-
-
3
8
3.500
-
-
* 3-1/2
8
4.000
-
-
* 4
8
4.500
-
-

* Does not include ANPT, NPTF, NPTG or NPTC.

Pipe
Size
T.P.I
Pitch Dia. Small End Pipe
Eo
Tolerance
E6
Tolerance
NPT
ANPT
NPTF
NPTG
NPTC
Turns
of
Gage
Inches
on
Dia.
NPTR
Turns
of
Gage
Inches
on
Dia.
1/16
27
.2712

One
Turn
Large

One
Turn
Small

± .0023
-

One
Turn
Large

One
Turn
Small

1/8
27
.3635
± .0023
-
1/4
18
.4774
± .0035
-
3/8
18
.6120
± .0035
-
1/2
14
.7584
± .0045
.7718
+ .0000
- .0045
3/4
14
.9677
± .0045
.9811
+ .0000
- .0045
3/4-14NPTC-1
.9677
± .0045
-
+ .0000
- .0045
3/4-14NPTC-2
.9856
± .0045
-
+ .0000
- .0045
3/4-14NPTC-3
1.0057
± .0045
-
+ .0000
- .0045
3/4-14NPTC-4
1.0302
± .0045
-
+ .0000
- .0045
1
11-1/2
1.2136
± .0054
1.2299
+ .0000
- .0054
1-1/2
11-1/2
1.5571
± .0054
1.5734
+ .0000
- .0054
1-1/2
11-1/2
1.7961
± .0054
1.8124
+ .0000
- .0054
2
11-1/2
2.2690
± .0054
2.2853
+ .0000
- .0054
2-1/2
8
2.7195
± .0078
2.7508
+ .0000
- .0078
3
8
3.3406
± .0078
3.3719
+ .0000
- .0078
* 3-1/2
8
3.8375
± .0078
3.8688
+ .0000
- .0078
* 4
8
4.3344
± .0078
4.3656
+ .0000
- .0078

* Does not include ANPT, NPTF, NPTG or NPTC.

Pipe
Size
T.P.I
Pitch Dia. Small End Pipe
Eo
Tolerance
NPT
ANPT
NPTR
NPTF
NPTG
at
L1 + S
Thrd

MNPTC
at

L1 + 8-1/2
Thrd

1/16
27
.2875
-
-
1/8
27
.3800
-
-
1/4
18
.5025
-
-
3/8
18
.6375
-
-
1/2
14
.7918
.8008
-
3/4
14
1.0018
1.0112
-
3/4-14NPTC-1
-
-
1.0268
3/4-14NPTC-2
-
-
1.0447
3/4-14NPTC-3
-
-
1.0648
3/4-14NPTC-4
-
-
1.0893
1
11-1/2
1.2563
1.2658
-
1-1/2
11-1/2
1.613
-
-
1-1/2
11-1/2
1.8413
-
-
2
11-1/2
2.3163
-
-
2-1/2
8
2.7906
-
-
3
8
3.4156
-
-
* 3-1/2
8
3.9156
-
-
* 4
8
4.4156
-
-


Length specification Table for NPT, ANPT, NPTF, NPTR, NPTG and NPTC pipe threads

Pipe
Size
Threads
Per.
inch
Pitch

Handtight
Engaged
Effective Thread Length
NPT
ANPT
NPTF
NPTR
NPTG
NPTC
1/16
27
.0370
.16
.2611
-
-
1/8
27
.0370
.180
.2639
-
-
1/4
18
.0556
.200
.4018
-
-
3/8
18
.0556
.240
.4078
-
-
1/2
14
.0714
.320
.5337
.320
.6771
3/4
14
.0714
.339
.5457
.332
.6964
3/4-14NPTC-1
.0714
.339
-
-
.9461
3/4-14NPTC-2
.0714
.339
-
-
.9461
3/4-14NPTC-3
.0714
.339
-
-
.9461
3/4-14NPTC-4
.0714
.339
-
-
.9461
1
11-1/2
0.870
.400
.6828
.422
.8348
1-1/2
11-1/2
0.870
.420
.7068
.446
-
1-1/2
11-1/2
0.870
.420
.7235
.463
-
2
11-1/2
0.870
.436
.7565
.496
-
2-1/2
8
.1250
.682
1.1375
.638
-
3
8
.1250
.766
1.2000
.700
-
* 3-1/2
8
.1250
.821
1.2500
.750
-
* 4
8
.1250
.844
1.3000
.800
-

 


Mechanical Tolerances for Taper Pipe Threads

Mechanical Tolerances for Taper Pipe Threads

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