National Pipe Threads (NPT)

National Pipe Thread Profile

Thread form angle : 60°
The taper rate of national pipe thread : 1 in 16
P : Pitch
n : TPI
H : Height of fundamental triangle
h : Height of thread
f : depth of truncation at crest or root

D : Major diameter of internal thread
D1 : Minor diameter of internal thread
D2 : Pitch diameter of internal thread
d : Major diameter of external thread
d1 : Minor diameter of external thread
d2 : Pitch diameter of external thread
L1 : Handtight engagement length
L2 : Effective thread length (external)
L3 : Wrench makeup length for internal thread

Number of threads per inch (TPI) :

n =

Pitch :

P =

Height of fundamental triangle :

H =

Height of thread :

h =

Crest and root truncation :

Minimum f =	0	mm
Maximum f =	0	mm

Handtight engagement length :

L1 =

Effective thread length (external) :

L2 =

Wrench makeup length for internal thread :

L3 =

Major diameter (mm)

0.000

invalid size

Minor diameter (mm)

0.000

invalid size

Pitch diameter (mm)

0.000

not specified

invalid size

For not specified tolerance, it means zero.

Size	TPI
1/16	27
1/8	27
1/4	18
3/8	18
1/2	14
3/4	14
1	11.5
1 1/4	11.5
1 1/2	11.5
2	11.5
2 1/2	8
3	8
3 1/2	8
4	8
5	8
6	8
8	8
10	8
12	8
14 O.D.	8
16 O.D.	8
18 O.D.	8
20 O.D.	8
24 O.D.	8

Size

TPI

1/16

1/8

1/4

3/8

1/2

3/4

11.5

1 1/4

11.5

1 1/2

11.5

2 1/2

3 1/2

14 O.D.

16 O.D.

18 O.D.

20 O.D.

24 O.D.

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Standard National Pipe Thread