Type

Symbol

Specification

Angle of thread hill

Metric General Thread

M

JIS B 0251

60°

Metric Fine Thread

JIS B 0252

Parallel Thread for Pipe

G

JIS B 0202

55°

Parallel Thread for Pipe

PF

JIS B 0254

Parallel Thread for Pipe

PS

JIS B 0253

Taper Thread for Pipe

R

JIS B 0203

55°

Taper Thread for Pipe

PT

JIS B 0253

U.S. Taper Thread for Pipe

NPT

ANSI B2.1

60°

1/8”

1/4”

3/8”

1/2”

3/4”

1”

1¼”

1½”

2”

Outer Diameter
(mm)

NPT

9.489

12.487

15.926

19.772

25.117

31.461

40.218

46.287

58.325

PT

9.728

13.157

16.662

20.955

26.441

33.249

41.910

47.803

59.614

PF / PS

9.728

13.157

16.662

20.955

26.441

33.249

41.910

47.803

59.614

Number of thread
(length 1”)

NPT

27

18

18

14

14

11½

11½

11½

11½

PT

28

19

19

14

14

11

11

11

11

PF / PS

28

19

19

14

14

11

11

11

11