Stud bolts, also known as double-end screws or double-end studs, are threaded fasteners with threads machined at both ends. The middle shank can be either fully threaded or unthreaded smooth bar. They are used to fasten and connect mechanical components, and widely applied in mining machinery, bridges, automobiles, motorcycles, boiler steel structures, tower cranes, long-span steel frames and large-scale construction projects.
1. General Introduction to Stud Bolts
According to industrial standards, fasteners with heads are defined as bolts, while headless fasteners threaded at both ends are formally named studs. The most common type of stud bolt features threads on both ends and a smooth unthreaded shank in the middle. Typical application scenarios include equipment anchor points, joints of extra-thick plates, and positions where standard headed bolts cannot be installed due to insufficient length.
2. Specification Marking Standard for Stud Bolts
Example based on DIN standard equal-length stud bolts: For an equal-length stud bolt with thread size d=M12, nominal length L=80mm and property class 4.8, the complete standard marking is: DIN 939 M12×80.
3. Main Application Scenarios of Stud Bolts
Installation of auxiliary accessories on large main equipment, such as sight glasses, mechanical seal seats and reducer brackets. One end of the stud is screwed into the main equipment body. After the accessory is mounted, a nut is fastened onto the other end. As these accessories require frequent disassembly and assembly, their threads are prone to wear and damage. Stud bolts facilitate convenient replacement and maintenance.
When the combined thickness of two connected workpieces is large and a fastener of extra long length is required, standard headed bolts cannot meet the length and space requirements, so stud bolts are adopted for long-distance connection.
4. Necessity of Anti-loosening Treatment for Stud Bolt Connections
During equipment operation, alternating vibration loads, variable external loads and high-temperature material creep will continuously reduce the friction force between thread pairs. Under extreme working conditions, the normal pressure between threads may disappear momentarily, resulting in zero friction and loosening of the threaded connection. After repeated cyclic loading, the threaded joint will gradually relax and lose its fastening function. Therefore, anti-loosening measures must be equipped for stud bolt connections to avoid equipment breakdowns and safety accidents caused by connection failure.
