Grade 5 Hex Cap Screws are manufactured from medium carbon steel. Our Grade 5 material meets or exceeds SAE J429 Grade 5 specifications. All products are manufactured with rolled threads. Zinc plated material meets or exceeds ASTM F1941. Typical hardness on diameters 1/4 to 1 inch is HRC 25-34. On diameters over 1 inch to 1 1/2 hardness will range from HRC 19-30. Tensile strength for diameters 1/4 to 1 inch is a minimum of 120,000 psi and for diameters over 1 inch to 1 1/2, 105,000 psi.Stelfast, Inc.