A hex head screw is a screw with a hexagonal head that can be tightened with a wrench (wrench) or a socket, which engages the outer surface of the hex head. These types of fasteners have an external hex head and should not be confused with an internal hex head or hex socket -- the latter have an internal hex socket that can be driven with a hex bit or wrench.
A screw is a mechanical fastener with a threaded shaft that fits directly into a part. The term hex head screw generally refers to machine screws with pre-fabricated machine threads. Machine screws are similar to bolts, but they are usually threaded throughout the shaft.
Wood screws and self-tapping screws may also sometimes have hex heads when high torque is required. However, wood screws and self-tapping screws have tapered shafts with sharp threads designed to cut mating threads in the parts they are fastening.
Some hex head screws have slotted or Phillips heads and standard hex heads so that a screwdriver can be used when a wrench or socket is not available or is not convenient. This can be called a combination screw.
Hex head screws may have full bearing heads, washer heads, or flanged heads with bonded washers. They are available in galvanized steel, galvanized steel, organically coated steel, stainless steel, bronze, nylon or bi-metal.
A hex head screw designed to mate with a machine thread, also known as a hex head screw, set screw, or machine screw, is used to secure one object within or to another object.
American National and Unified Standard Heavy Hex and Hex Cap Screws, ANSI/ASME B18.2.1-1996, specifies that the ideal size range for screws is 0.25–3 inches (6.35–76.20 mm) in diameter.
Some types of these screws are designed to tap their own holes (also known as lag screws or trainer screws) and are commonly used for:
attaching heavy wood or objects to wood
Secure heavy objects to masonry
Secure light objects to wood or steel.
These types of hex head screws have a tapered point that can be easily inserted into a pilot hole or a nylon plug, a pointed point designed to pierce wood or light gauge steel, or a drill bit designed to move wood.
Self-drilling hex head or Tek screws for joining metal to metal. These types of hex head fasteners have a grooved tip that self-drills when installed, eliminating the need for a pilot hole.
Self-drilling hex head screws have drill points of varying lengths, depending on the thickness of the metal securing the fastener.