Straight flute thread mills come in a large variety of sizes and are crest cutting for internal threads only.
Straight Flute - Metric
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- BSPP / BSPT Thread Mills - Straight Flute