The main categories include ordinary screws, machine screws, self-tapping screws and expansion screws.
Cap screw Cap screws used to be limited to full teeth.
Hex cap screw and Hex bolt Hex bolt As the name implies, the head is a hexagonal external thread fastener designed to be rotated with a wrench. According to the ASME B18.2.1 standard, the Hex cap screw has a smaller head height and rod length tolerance than the conventional Hex bolt. Therefore, the ASME B18.2.1 hex screw is suitable for mounting on all hex bolts. The place also contains large hex bolts that are too large to be used.
Socket cap screw, also known as a socket head screw or a screw with a hexagonal inner hole in the head, can be tightened or loosened by inserting a hexagonal (hexen, Allen wrench or Allen key) into the inner hole. Hexagon socket head screws are most commonly used with cylindrical head screws. The head diameter is about 1.5 times the main diameter of the thread (1960 series). Other head types include a Bottom head cap screw and a tapered screw hole. Countersunk head cap screw. The counterbore design allows the screw head to be rotated without the need to be exposed on the surface of the object being fixed, so it is often used where the surface is small and the conventional wrench is inconvenient to use.