NPTF American Taper Pipe Thread
ANSI B 1.20.3

American Taper Pipe Thread for Dryseal joint without sealant compound. National Pipe Taper Fuel
The flank angle is 60°, the profile was originated by William Sellers.

Nominal Diameter Major Diameter
mm
Tapping
Drill Size
mm
TPI Pitch
mm
1/16" - 27 NPTF 7.870 6.00 27 0.940
1/8" - 27 NPTF 10.217 8.25 27 0.940
1/4" - 18 NPTF 13.577 10.70 18 1.411
3/8" - 18 NPTF 17.016 14.10 18 1.411
1/2" - 14 NPTF 21.211 17.40 14 1.814
3/4" - 14 NPTF 26.566 22.60 14 1.814
1" - 11 1/2 NPTF 33.195 28.50 11.5 2.209
1 1/4" - 11 1/2 NPTF 41.952 37.00 11.5 2.209
1 1/2" - 11 1/2 NPTF 48.021 43.50 11.5 2.209
2" - 11 1/2 NPTF 60.060 55.00 11.5 2.209
2 1/2" - 8 NPTF 72.642 65.50 8 3.175
4" - 8 NPTF 113.913 107.00 8 3.175