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
SPTM Thread Mills - Internal Stub Acme
SPTM Thread Mills - Internal Acme
TM - Metric Thread Mills -30 degree Helical Flutes - Solid Carbide - Full Profile
TM - Metric Thread Mills -15 degree Helical Flutes - Solid Carbide - Full Profile
TM - Metric Thread Mills -Straight Flute - Solid Carbide - Full Profile