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National Pipe Straight thread (NPS)

Both NPT and NPS have the same thread angle 60° included angle and have flat peaks and valleys, and pitch (TPI, thread per inch). However, NPT threads are tapered and NPS threads are straight (parallel). Be noticed that NPS need a gasket or O-ring to create a seal.

 

  Thread size     TPI     Major diameter (mm)  
NPS 1/8"

27

10.287
  NPS 1/4"  

18

13.716
NPT 3/8"

18

17.145
NPS 1/2"

14

21.336
NPS 3/4"

14

26.670
NPS 1"

11.5

33.401
NPS 1 1/4"

11.5

42.164
NPS 1 1/2"

11.5

48.260
NPS 2"

11.5

60.325

 

 

National Pipe Taper thread (NPT)

American National Standard Taper Pipe Thread (*Ref), often called NPT for short. The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other. In other words, threaded pipes are able to provide an effective seal for pipes transporting liquids, gases, steam, and hydraulic fluid.

 

  Thread size     TPI     Major diameter (mm)  
NPT 1/16"

27

7.950
NPT 1/8"

27

10.287
  NPT 1/4"  

18

13.716
NPT 3/8"

18

17.145
NPT 1/2"

14

21.336
NPT 3/4"

14

26.670
NPT 1"

11.5

33.401
NPT 1 1/4"

11.5

42.164
NPT 1 1/2"

11.5

48.260
NPT 2"

11.5

60.325

 

 

*Ref: Learn more about American National Standard Taper Pipe thread