UNC and UNF are symbols of Unified Screw Thread Series.
The Unified Thread Series was agreed on by the United States,Great Britain and Canada in1949 to obtain interchangeability. Recently, modifications have been made to the original 1949 specifications for ease of use.
The Unified Thread Series is a straight and parallel thread with a 60 degree angle and is classified into coarse threads, fine threads and extra fine threads:
UNC: ls the symbol for Unified coarse pitch threads.
UNF: Is the symbol for Unified fine pitch threads.
UNEF: ls the symbol for United extra fine pitch threads.
UNS: Is the symbol for Unified special threads.
UNC threads according ANSI B1.1:
UNF threads ANSI B1.1:
