9/16-12 A194 2H Heavy Hex Nut Plain . A194 2H Heavy Hex Nuts are manufactured from 1045 steel to meet or exceed ASTM A194 Grade 2H. Hot-Dip Galvanized material will meet or exceed ASTM A153 and/or ASTM F2329. Galvanized nuts are over tapped per ASTM A563. Typical hardness is HRC 24-35 for diameters up to 1 1/2 inches, HRB 95 - HRC 35 for diameters over 1 1 1/2 inches. Proof load strength is 175,000 psi.