"Size","UNC (TPI)","UNF (TPI)","Across flats F","Head height H"
"1/4″ (6.35)","20","28","7/16″ (11.11)","5/32″ (3.97)"
"5/16″ (7.94)","18","24","1/2″ (12.70)","13/64″ (5.16)"
"3/8″ (9.52)","16","24","9/16″ (14.29)","15/64″ (5.95)"
"7/16″ (11.11)","14","20","5/8″ (15.88)","9/32″ (7.14)"
"1/2″ (12.70)","13","20","3/4″ (19.05)","5/16″ (7.94)"
"9/16″ (14.29)","12","18","13/16″ (20.64)","23/64″ (9.13)"
"5/8″ (15.88)","11","18","15/16″ (23.81)","25/64″ (9.92)"
"3/4″ (19.05)","10","16","1-1/8″ (28.57)","15/32″ (11.91)"
"7/8″ (22.22)","9","14","1-5/16″ (33.34)","35/64″ (13.89)"
"1″ (25.40)","8","12","1-1/2″ (38.10)","39/64″ (15.48)"
"Reference only — confirm against drawing. ASME B18.2.1. REL India"