5/16-18 UNC Die Round Adjustable Split Threading Die 1” OD Inch Thread HSS Tool,1” OD Inch Thread HSS Tool 5/16-18 UNC Die Round Adjustable Split Threading Die, Type: Adjustable round die,UN round dies are the most commonly used general purpose dies for external threading, Split round dies are adjustable for threading different thread limit, Thread Type: UNC, Die 1” OD Inch Thread HSS Tool 5/16-18 UNC Die Round Adjustable Split Threading.