Steel, sae 1111 through 1114 or steel, qq-s-637 1211 through 1213, 0.594 in. Min, 0.656 in. Max lg, 0.313 in. Diameter head, 0.188 in. Head lg, 0.250 in. Min 0.254 in. Max shank dia, 0.438 in. Shank lg, 0.156 in. Hole drilled axially centered in shank end, 0.250 in. Deep