Carmex Thread Mills Solid Carbide - With Through Coolant - Whitworth BSW BSF - 3/8 x 20 - MT7Introducing the Carmex MTB solid carbide thread mill with through coolant a precision threading tool built for Whitworth BSW and BSF threads (3 8 in. diameter, 20 TPI). Designed for machinists who need reliable chip control, durable form, and consistent thread quality in challenging materials and hole depths. Through Coolant Bore: Coolant is fed through the bore to carry away chips and keep cutting temperatures in check, promoting cleaner threads and