Button head socket cap screw, also known as a domed cap screw or allen screw, is a screw type that features a raised, dome-shaped head that is smaller than traditional socket screws. This makes it ideal for applications in which the heads of other fasteners could potentially snag or catch on moving parts or panels.

The domed shape of the head gives it a larger bearing surface than standard socket cap screws and helps to distribute force more evenly across the head. It’s also more visually aesthetic than flat head socket caps. These fasteners are driven with an allen wrench (hex key) and have an internal hex drive that allows for greater torque capacity than traditional phillips or slotted drives.

Socket cap screws are used in a variety of fastening and clamping applications, including assembling machine components and die castings. They’re often paired with hex bolts to fasten shaft collars, gears and knobs on rotating shafts or stationary guides or pivots. The hex shape of the head enables the user to apply more force to the threaded body of the screw than is possible with a round head screw, but they can be harder to remove due to their depth. For these reasons, they’re often used for high-stress, permanent applications. Socket caps screws have a deeper hex recess than traditional socket screws, which increases their preload strength and allows them to withstand higher levels of tightening force. They’re also available in a wider range of sizes to accommodate many different applications. button head cap screw