Carmex Thread Mills Solid Carbide - With Through Coolant - UN (UNC UNF UNEF UNS) - 1/4 x 28 - MT7Meet the Carmex MTB Solid Carbide Thread Mill with Through Coolant. Built for machinists and engineers who demand precise internal threads in metal components, it delivers superior chip control and extended tool life. Thread forms supported: UNC, UNF, UNEF, UNS and UN threads (1 4 28) for versatile compatibility with common fastener standards. Diameter and pitch: 1 4" diameter with 28 threads per inch, optimized for clean, accurate internal threads.