1-8 ASTM A563 GRB HVY NUT HDG .024” ASTM A563 GRADE B HEAVY HEX NUT HDG ASME/ANSI B18.2.2 1987 IFI-7 AF 1.575-1.625” TH 0.956-1.012” Tapped Over Size per ASTM A 153 class C