The structural characteristics of bolts are mainly reflected in their basic components, head shape, thread type, and special designs to meet the connection requirements under different working conditions.
A bolt is a fastener consisting of a head and a threaded shank (a cylinder with external threads). It needs to be used with a nut to achieve a detachable connection between two parts with through holes. Its core function is to generate axial locking force through rotation to firmly fix the components.
Main structural characteristics include:
Diverse Head Shapes: Common head shapes include hexagonal, round, square, and countersunk heads. Hexagonal head bolts are the most widely used, as they are easy to tighten with a wrench or socket. Countersunk head bolts are used in situations requiring a flat surface after connection and can be fully embedded inside the part.
Threaded Shank: The shank is machined with standard threads, divided into coarse and fine threads. Fine threads have better anti-loosening performance and higher connection strength, suitable for vibration environments; coarse threads are the conventional choice and have strong versatility.
Defined Performance Grades: Bolts are classified into several grades based on strength (e.g., 3.6, 4.8, 8.8, 10.9, 12.9). Grades 8.8 and above are high-strength bolts, primarily used in critical connections in steel structures. They are typically made of low-carbon alloy steel and undergo heat treatment.
Special Anti-Loosening Structures:To prevent loosening, some bolts are designed with holes in the head or shank, allowing for mechanical locking via wire or cotter pins. These are commonly used in aerospace or high-vibration equipment.
Modular and Integrated Designs: For example, hexagonal bolts integrate the bolt, flat washer, and spring washer. This pre-assembled structure improves assembly efficiency and enhances anti-loosening performance.
