The name "wedge anchors" (車修壁虎 in Chinese) is not arbitrary. The term "車修" (chexiu, literally "auto repair") indicates its original important application in the auto repair field—initially, it was often used for connecting and fixing key components such as automobile bodies and chassis. The metaphor of "壁虎" (bihu, meaning "gecko") vividly reflects its working characteristic: just like a gecko’s claws, it can tightly adhere to the surface of various substrates, providing stable fastening force. Today, its applications have long exceeded the auto repair field, becoming an indispensable fastening component in construction, machinery, and other industries.
Structurally, a wedge anchor is an elaborate combined device, mainly composed of four parts: a bolt, a nut, a washer, and an outer sleeve. Among them, the outer sleeve is the core component for realizing the fastening function. It is usually a hollow metal tube with evenly distributed grooves or notches on the tube wall—these notches play a key role in the expansion process. The bolt runs through the inside of the outer sleeve: one end is connected to the nut and washer, while the other end is designed with a pointed or flat head to facilitate insertion into pre-drilled holes. Although this structural design seems simple, it contains an ingenious mechanical principle.
Its working principle is based on friction force generated by expansion and mechanical locking. During installation, first, a hole matching the specifications of the wedge anchor needs to be drilled in the substrate (such as concrete, brick walls, or stone). The depth and diameter of the hole must be precisely controlled according to the specific model. Then, the entire wedge anchor is inserted into the hole, and a wrench is used to tighten the nut. As the nut is continuously tightened, the bolt is pulled upward, forcing the outer sleeve to expand. The grooves or notches on the tube wall open due to extrusion, increasing the diameter of the outer sleeve and making it fit tightly with the inner wall of the hole. At this point, huge friction is generated between the outer sleeve and the hole, and at the same time, the bolt and outer sleeve form a mechanical lock, thereby firmly fixing the external component to the substrate. This fastening method realized through physical expansion does not rely on chemical bonding and has extremely high reliability.
The characteristics of wedge anchors make them stand out among numerous fixing devices.
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Easy Installation: This is one of its major advantages. It has low requirements for the depth and cleanliness of concrete holes—even if there is a small amount of dust or debris in the hole, it can still ensure a good fastening effect. Moreover, no special tools are needed for the installation process; a regular wrench is sufficient, which greatly improves construction efficiency.
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Strong Adaptability: This is another highlight. It is not only suitable for various construction substrates such as concrete, dense natural stone, and brick walls but also can be used for connecting metal structures and metal profiles, and can exert stable performance on substrates of different strengths and hardness.
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Excellent Fastening Force: Wedge anchors perform well in terms of fastening force—their tensile force increases with the increase of embedding depth, enabling them to provide large load-bearing capacity. However, it should be noted that to ensure safety, the maximum actual safe load used must not exceed 25% of the calibrated value, to avoid loosening or fracture caused by overloading.
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Adjustability: This is also a major feature. By tightening or loosening the nut, the tightness of the connection can be flexibly adjusted to meet installation requirements in different scenarios.
Wedge anchors come in a wide range of specifications and grades to adapt to different application scenarios.
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Specifications: The common diameter range is from M8 to M12, and the length ranges from 20mm to 100mm. The specific size must be selected according to the usage scenario and load-bearing requirements.
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Performance Grades: According to manufacturing standards, there are grades such as 4.8 and 8.8. In the automotive manufacturing and repair fields where higher strength is required, the bolt strength grades of wedge anchors are divided into three levels: 8.8, 10.9, and 12.9. The higher the grade, the greater the tensile strength and yield strength, making them suitable for occasions with more stringent load-bearing requirements.
The application of wedge anchors can be seen in almost all industries.
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Construction Field: It is widely used for installing brackets, guardrails, pipe supports, ceiling hooks, electrical equipment, steel structures, handrails, cantilever brackets, escalators, cable trays, etc. Whether it is the curtain wall fixing of high-rise buildings or the lamp installation in interior decoration, its application can be seen.
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Automotive Field: It is a key component in automobile manufacturing and repair, used for connecting the car body and chassis, fixing important parts such as engine accessories, and ensuring that various components of the car are stable and reliable during driving.
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Other Fields: In addition, wedge anchors also play an important role in mechanical manufacturing, rail transit, and other fields, providing a solid guarantee for the stable operation of equipment.
However, there are some precautions to follow when using wedge anchors:
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When selecting specifications, comprehensive consideration should be given to the substrate type, load-bearing weight, and installation environment to avoid fixing failure due to mismatched specifications.
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Before installation, ensure that the hole size matches the wedge anchor. During drilling, the hole should be kept vertical to avoid skewing, which may affect the expansion effect.
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During installation, apply force evenly when tightening the nut to avoid over-tightening, which may cause the outer sleeve to break or the substrate to crack.
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For humid and highly corrosive environments, wedge anchors made of corrosion-resistant materials such as 304 stainless steel should be selected to extend their service life.
Although wedge anchors are small, with their exquisite structure, reliable performance, and wide applicability, they have become an indispensable fastening tool in modern industry and construction fields. From auto repair to high-rise building construction, they silently play a key role, guarding the stability and safety of various structures with gecko-like grip, and are truly "invisible guardians" in engineering construction.
