NPT thread mills come in straight, helical and staggered tooth design. They will cut both internal and external threads. NPTF are for dryseal applications.
NPT / NPTF
NPT/ NPTF 30 degree Helical Flute Thread Mills
NPT/ NPTF 15 degree Helical Flute Thread Mills
NPT/ NPTF Staggered Tooth Thread Mills