National Pipe Tapered Fuel (NPTF)
This is a dryseal thread, the National pipe tapered thread for fuels. This is used for both male and female ends. This connection is still widely used in fluid power systems, even through itiIs not recommended by the National Fluid Power Association (N.F.P.A.) for use in hydraulic applications.
The NPTF male will mate with the NPTF, NPSF or NPSM female.
The NPTF male has tapered threads and a 30° inverted seat. The NPTF female has tapered threads and no seat. The seal takes piace by deformation of the threads. The NPSM female has straight threads and a 30° inverted seat. The seal takes piace on the 30° seat.
The NPTF connector is similar to, but not interchangeable with, the BSPT connector. The thread pitch is different in most sizes. Also, the thread angle is 60° instead of the 55° angle found on BSPT threads.