Socket Screw are tall-headed, internally driven, high-strength screws that feature a threaded shank the length of their entire body. Typically, they are used in equipment or machines that need to move or be adjusted and stand up to vibration. They generate a compressive load, which differs from the fastener tensile load generated by bolts and most other screws, to hold parts beneath their cup – the concave, hollowed end. They are available in many head and shaft sizes and with various coatings such as zinc, black nickel, brass or combined zinc-nickel.
They are commonly known as Hex or Allen head screws as they have a hexagonal recess built into their heads that is used with an Allen wrench (also referred to as hex key). This feature, along with the fact they have an internal drive and are much smaller than other screw head types like Phillips head, slotted and flat head screws, makes them ideal for use where there isn’t enough clearance to install or manoeuvre a standard screwdriver.
Socket screws are available in a wide variety of materials and can be produced to meet different standards such as ASME B18.18, ISO 403, DIN 5580, ISO 4145, NF F16-90, and ASTM A193. Steel socket screws are the most popular choice as they are strong and cost effective but they can also be manufactured in materials such as DFARS sourced aluminium and bronze for applications where weight is a primary consideration.