Socket Head Screw, also known as Hex head cap screws, Allen button socket bolts and hex Allen caps are tall headed, internally driven high-strength fasteners that have a hexagonal drive hole and are driven with hex wrenches or Allen keys. These screws have a wide flange under the head to prevent crushing thin or soft materials and provide a cleaner appearance without any protrusions that could catch on tools, hands or clothing.

Socket head screws can be used in a variety of applications that require strength and cosmetics including die fixturing, metal stamping, machine parts and clamping. They are primarily tensile (stretching) fasteners, but can have some shear capability as well. They are used in applications that need good grip, where there is limited space for wrenching, and in many security applications because of their impressive clamping strength and security.

These screws come in various materials, finishes and sizes. For instance, you can choose from a zinc plating that is standard or a combined zinc and nickel plating that provides up to twice the hardness of the normal variety. Brass and stainless steel versions are available as well for those that want a stronger or more durable finish.

When deciding on the type of socket head screw to use for your application, it’s important to keep in mind that stated length measurements for all cap screw types refer to the bolt’s total length from the shaft to the end including the head. Socket head screws, low head, and flat head caps screws are all rated for maximum tensile strength, while ones with nylon pellets have extra locking strength and are typically used when there is minimal clearance to wrench.