Big Gator Tools STI-UNC100SNP - V-TapGuide® - for Screw Coarse Thread
STI-UNC V-TapGuide® handles10 Unified Coarse Thread sizes (9 holes): 9/16-12, 1/2-13, 7/16-14, 3/8-16, 5/6-18, 1/4-20, 12/24, 10-24, 8-32, 6-32". Can be used on flat surfaces, round parts and corners.