A Cap screw is a six-sided fastener threaded all the way down its length to hold components together. When tightened, this type of screw can generate a significant amount of clamping force that prevents the mechanical connection from loosening over time. Cap screws are available in a wide variety of sizes and styles, as well as different finishes and materials to suit varying environmental conditions and requirements.
Hex cap screws (also known as socket head cap screws) feature a hex-shaped socket with a flat bearing surface that fits over a hexagonal drive on a wrench. The flat socket head provides a low-profile appearance that makes these fasteners ideal for use in confined spaces where bolts and nuts cannot be used.
In general, hex cap screws come in both fully-threaded and partially-threaded options. Fully-threaded hex cap screws are designed to be installed all the way into a threaded hole, while those in lengths longer than 2″ will have a shoulder (also referred to as the body or unthreaded portion of the screw) that must be accounted for in determining the proper head diameter for the particular size.
Grade-2 hex cap screws are made from low-carbon steel and are designed for use in applications that require lower clamp loads or do not involve high stresses. Grade-5 hex cap screws are made from medium carbon steel and are heat-treated, quenched and tempered to provide greater tensile strength for use in more demanding applications. Grade 8 hex cap screws are high-strength fasteners that meet SAE J429 Grade-8 specifications, and are typically employed in flange bolting applications or other heavy-duty industrial applications where controlled clamp forces and strong load capacity are required. Cap screw