1/2-20 x 1 1/4 A563 Hex Coupling Nut Zinc . A double chamfered hex nut used to join to externally threaded parts of equal diameter and pitch, often two pieces of threaded rod. Manufactured from 1010 - 1018 equivalent steel. Hardness = Rockwell B68 - C32 Tensile strength = 60,000 psi. minimum. Note - there is no single standard for coupling nut dimensions. These values are offered as a guide; deviations from these specifications may occur.