A Cap screw is a fastener with a flat head that is usually threaded on both sides. These types of screws are used in situations where the screw needs to be flush with the surface it is being installed in. This could include applications like putting together aircraft where too many protrusions would hinder the aerodynamics of the plane.
These types of screws are available in a variety of materials which can enhance their resistance to certain environmental conditions or stresses. They also come in a range of diameters and lengths, and can have either fully or partially threaded shafts. This allows them to be used in a variety of application and environments, and can allow them to fit into a correspondingly sized hole.
Hex cap screws can be manufactured in a variety of grades, which dictate the material that is used and how the screw is heat treated. Grades are usually specified based on how important it is to meet specific chemical and mechanical properties. Grade A screws are generally made from low carbon steel and are not heat treated. Grade 8 is a higher standard, and requires the use of medium carbon steel and is heat treated to a much greater degree.
Grade B7 is a high strength fastener that is typically used in flange bolting applications with very high pressure requirements. These fasteners are typically produced from alloy steel that is quenched and tempered. They can be used in applications requiring high strength and corrosion resistance. Cap screw