ASTM F835 Flat Socket head cap screws have a countersunk head with a flat top surface and hexagonal recess. The ASTM F835 specification covers the requirements for quenched and tempered alloy steel hexagon flat countersunk head cap screws, having material properties for high-strength requirements. Dimensional specifications are governed by ASME B18.3. Flat socket head cap screws are commonly used in applications in which it is necessary to recess the head of the fastener flush with the surface.