Specifications of International Thread Standards

The parallel pipe thread National Pipe Straight Coupling is combined with the tapered fitting threa National Pipe Taper using a sealant. The flank angle is 60°, the profile was originated by William Sellers.

Nominal DiameterMajor Diameter
mm
Major Diameter
Inch
Tapping
Drill Size
mm
TPIPitch
mm
1/8" - 27 NPSC10.0340.3958.636270.941
1/4" - 18 NPSC13.3290.52511.227181.411
3/8" - 18 NPSC16.7680.66014.656181.411
1/2" - 14 NPSC20.8880.82218.161141.814
3/4" - 14 NPSC26.2351.03323.495141.814
1" - 11 1/2 NPSC32.8481.29329.48911.52.209
1 1/4" - 11 1/2 NPSC41.6031.63838.25211.52.209
1 1/2" - 11 1/2 NPSC47.6741.87744.32311.52.209
2" - 11 1/2 NPSC59.7112.35156.36311.52.209
2 1/2" - 8 NPSC72.2142.84367.31083.175
3" - 8 NPSC88.1253.46983.23683.175
3 1/2" - 8 NPSC100.8324.97095.93683.175
4" - 8 NPSC113.4894.468108.58583.175
NPSC