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Bolts specifically refer to screws with a relatively larger diameter; they can also be without a head, such as double-headed bolts. Generally, it is not called a \"double-headed bolt\" but rather a \"double-headed stud\". The most common form of a double-ended stud is one with threads at both ends and a smooth shaft in the middle. Most typical use: anchor bolts, or in situations similar to anchor bolts, for thicker connections where ordinary bolts cannot be used. 02 Specification standards: The complete designation for a double-ended bolt with a thread size of d=M12, a nominal length of L=80 mm, and a performance grade of 4.8 is GB 901 M12×80. 03 Main applications: 1. Used in large-scale equipment where it is necessary to install accessories such as sight glasses, mechanical seal seats, gearbox frames, etc. This is where double-headed bolts come in handy: one end is screwed into the main body, and after the accessories are installed, a nut is placed on the other end. Since the accessories are often removed, their threads can wear out or get damaged; using double-headed bolts makes it very convenient to replace them. 2. Double-ended bolts are used when the thickness of the connecting body is great and the bolt length is very long. 3. Used for connecting thick plates and in situations where hex bolt connections are not feasible, such as concrete roof trusses, roof beam suspension systems, and single-track beam hangers. 04 Purpose of anti-loosening: In practical applications, external loads such as vibration, changes in load conditions, and high-temperature creep of materials can lead to a reduction in friction force. At certain moments, the normal pressure between the threaded parts disappears, resulting in zero friction force; this causes the threaded connection to loosen. If this situation repeats itself, the threaded connection will eventually become loose and fail. Therefore, anti-loosening measures must be taken; otherwise, it will affect normal operation and lead to accidents. 05 Surface treatment: Double-headed bolts generally require surface treatment. There are many types of surface treatment for bolts; the most commonly used methods include electroplating, blackening, oxidation, phosphating, and non-electrolytic zinc coating. However, electroplated fasteners account for a large proportion in the actual use of fasteners. It is particularly widely used in industries and fields such as automobiles, tractors, home appliances, instruments, aerospace, and communications. However, for threaded fasteners, it is required not only to have a certain degree of corrosion resistance during use, but also to ensure the interchangeability of the threads, which can also be referred to as thread fit. To simultaneously meet the dual performance requirements of \"corrosion resistance\" and \"interchangeability\" for threaded fasteners in use, it is highly necessary to establish specific standards for electroplated coatings. The GB/T5267.1-2002 standard is one of the standards in the **\"Surface Treatment of Fasteners\" series; this standard includes: GB/T5267.1-2002 ； GB/T5267.2-2002, two standards. This standard is equivalently adopted from the international standard ISO4042 ； 1999. This standard replaces the GB/T5267-1985 standard. 06 Basic Knowledge and Maintenance: Producing double-headed bolts requires specific equipment and machine processing. The actual processing procedure is relatively simple, and it mainly involves the following steps: First, it is necessary to straighten the material using a straightening machine; only after this step can the next one be carried out. The next step is to use a cutting machine to cut the straightened, long pieces into the lengths required by the customer, thus completing the second step. The third step involves using a thread rolling machine to create threads on the cut short pieces. At this point, a standard double-headed bolt has been manufactured. Of course, if other requirements exist, additional processing steps will be needed. Generally, a bolt refers to a screw with a relatively larger diameter; according to this definition, a screw has a much smaller diameter compared to a bolt. Double-headed bolts lack heads; they are also sometimes referred to as double-headed studs. A double-headed bolt has threads on both ends, with no threads in the middle; the middle part is a solid shaft. Double-headed bolts are used in large equipment such as reducer frames. In practical use, external loads combined with temperature effects can cause friction to decrease; over time, this leads to the loosening and failure of the threaded connection. Therefore, it is necessary to carry out proper maintenance of the double-headed bolts on a regular basis. Double-headed bolts or foot bolts can develop problems due to prolonged mechanical friction. When such problems occur, it is necessary to remove the engine oil pan and carefully inspect the condition of the engine bearing shells, as well as check whether the gap between them is too large; if it is, they should be replaced promptly. When replacing the double-ended bolts, the connecting rod bolts must also be replaced. For some large-scale equipment such as nail-making machines, if it is noticed during normal operation that the engine is not running stably or if unusual noises are heard, it is necessary to stop the machine immediately for inspection, in order to prevent more serious problems from arising. During each maintenance session, the newly replaced double-headed bolts and other components that have been replaced must be inspected. The inspection should focus on the heads and guiding parts of the double-headed bolts; it is also necessary to carefully check each part of the threads for any cracks or dents, as well as to verify whether there are any changes in the shape of the bolt teeth. Check whether there are any abnormalities in the pitch; if such abnormalities exist, it must not be used anymore. A torque wrench should be used when installing the rod cover. It must be tightened in accordance with the specified standards; the torque should neither be too high nor too low. Additionally, care should be taken to choose double-headed bolts and studs from compatible manufacturers.