Socket Head Screw are a common type of fastener found across many industries and manufacturing processes. They are also commonly known as Allen screws, Hex head screws or socket bolts, they are fasteners with a hexagonal drive hole built into the heads and require a wrench to install and remove. This drive feature is a key differentiator between them and other screw head styles such as Phillips or flathead screws.
A socket screw can be found in applications where there isn’t enough clearance to install a traditional nut and bolt or where the installer needs access to the load-bearing area under the head of the screw to preload it with torque. The head of a socket screw is also generally lower in profile, which can be beneficial for aesthetics or in environments where the screws are exposed to extreme weather conditions.
There are a number of options for socket screw materials, including steel, stainless steel and brass. Stainless steel socket screws typically offer greater corrosion resistance than other types of fasteners, although they are often more expensive. Brass socket screws can be a more cost-effective option for those looking to reduce their costs but may be less durable than steel or stainless steel alternatives. Combined zinc-nickel plating is an alternative to standard galvanised steel and can offer up to twice the hardness of standard zinc finishes, but it’s important to note that it may be less resistant to corrosion than solid brass.
The diameter of the shank is the most significant variable when choosing a socket screw type, as this will determine how much torque can be applied to the fastener and whether it can withstand shear applications. Socket screws are available with a variety of thread lengths and can be inserted into either countersunk holes or threaded to the full diameter of the shank.
Some of the most popular varieties of socket screws include cup, hex and button head. All are able to be used in tight spaces and have high tensile strength, but each offers a unique set of features. Cup head socket screws are the most popular for industrial production and assembly lines, as they have a wide head for easy handling. Hex socket cap screws have a flat head that sits flush with the surface it is installed into, which can help prevent loosening due to vibration and lateral movement. And button head socket screws have a rounded, dome-shaped head that can be used in locations where there’s limited overhead or clearance.
Other variations of socket head screws include low head and flat head designs that are suitable for use in countersunk holes or in specific mounting positions. These variants are often shorter than the average socket cap screw, and they’re used in applications such as furniture manufacturing, machine tooling, metal stamping dies and power tools. They’re also well suited to security applications. In addition to the differences in head style, some of these options also have extra locking strengths. These variations have a nylon pellet inserted into the internal hex drive that acts to resist loosening through vibration or from excessive torsional strain.