A socket head screw (also called Allen screws) has a head that is recessed in a counterbored hole. This allows the head to sit flush with the surface of the part being fastened, which gives a cleaner appearance. They can be used where there is limited space for wrenching and offer excellent clamping strength. They are available in both inch and metric sizes and are typically fully threaded.
Socket head capscrews are very versatile and often used in applications requiring both high strength and good looks. They are found in machine tools, steel fabrication, die-casting applications, furniture manufacture, and automotive production. They are also common in electrical applications and industrial equipment due to their ability to provide a strong connection with very little effort.
There are several types of socket head cap screws, including low head, flat head, and button head. They all use an internal hex drive and can be used in many different applications, although they are most commonly seen in areas where there is limited clearance to install a nut or bolt.
Hex head socket cap screws have a deeper hex recess and thick side walls which make them stronger than traditional socket capscrews and offer higher preload ratings. Flat head socket cap screws have a thinner head and are less likely to cam-out than hex heads. Button head socket cap screws are very similar to flat heads and have a more rounded head profile. They are ideal for use in safety applications where protrusions on bolts and screws may snag clothing or equipment on moving machinery.