NPSF American Pipe Thread
ANSI B 1.20.1

The parallel, internal thread National Pipe Straight Fuel is coupled with tapered, external National Pipe Taper without use of a sealant.
The flank angle is 60°.

Nominal Diameter Major Diameter
mm
Tapping
Drill Size
mm
TPI Pitch
mm
1/16" - 27 NPSF 7.582 6.304 27 0.940
1/8" - 27 NPSF 9.929 8.651 27 0.940
1/4" - 18 NPSF 13.236 11.232 18 1.411
3/8" - 18 NPSF 16.673 14.671 18 1.411
1/2" - 14 NPSF 20.819 18.118 14 1.814
3/4" - 14 NPSF 26.166 23.465 14 1.814
1" - 11 1/2 NPSF 32.718 29.464 11.5 2.209