Carmex Thread Mills Solid Carbide - Fast Type - For Hard Materials - UN (UNC UNF UNEF UNS) - 5/16, 3/8 x 24 - MT3Engineered as an evolution of Carmexs MTSH line, the FSH solid carbide thread mills deliver precise internal threading in the toughest materials. Designed for machinists who demand stability, wear resistance, and fast cutting in hard alloys, this tool excels where others struggle. Threading capacity: Compatible with UNC UNF UNEF UNS threads in 5 16" and 3 8" sizes with 24 TPI for accurate, repeatable internal threads. Material & shank: Solid carbide