Bolt Shapes

Counterhead bolts are generally used where a smooth, non-protruding surface is required after connection, as they can be screwed into the part. Round heads can also be screwed into parts. Square heads can be tightened with greater force, but are larger in size. Additionally, to meet the need for locking after installation, some bolts have holes in the head and shank; these holes prevent the bolt from loosening under vibration. Some bolts have a thin shank without threads, called narrow-waisted bolts. These bolts are beneficial for connections subjected to variable forces. Special high-strength bolts are used in steel structures; their heads are larger, and their dimensions vary. Other special-purpose bolts include: T-slot bolts, most commonly used in machine tool fixtures, with a special shape where the sides of the head are cut off; anchor bolts, used for connecting and fixing machines to the ground, and come in many shapes; U-bolts, as mentioned above; and so on. There are also special welding studs, with threads on one end and no threads on the other, which can be welded to parts, and the other end can be directly screwed with a nut.