Expansion bolts (also known as expansion screws or metal expansion anchors) are the most commonly used retrofit fasteners in building renovation, mechanical and electrical installation, and engineering anchoring. These products achieve secure fastening through the principle of physical expansion anchoring; they require no pre-embedding, are simple to install, offer stable load-bearing capacity and represent excellent value for money. They are widely used for fixing installations to substrates such as concrete and brick walls.
Product Principle and Structure
An expansion bolt consists of a threaded rod, an expansion sleeve, a flat washer, a spring washer and a hexagon nut. During installation, a hole is drilled in the wall or substrate and cleaned before inserting the bolt. As the nut is tightened, the shank is pulled, causing the conical tip at the rear to compress the expansion sleeve, causing it to expand outwards and grip the hole walls tightly. Permanent anchoring is achieved through strong frictional and locking forces, making this an economical anchoring solution that requires no pre-embedding and is highly efficient to install.
Materials and Manufacturing Quality
Standard expansion bolts are precision-manufactured from high-quality Q235 carbon steel. The material is substantial, with uniform tube walls and consistent shank strength, making them resistant to breakage and deformation. The entire production process—including cold heading, thread rolling and stamping—is fully automated, ensuring full, clear threads and smooth engagement. The expansion tube features uniform wall thickness and achieves full expansion, eliminating common quality issues such as thin-walled tubes, misaligned threads and susceptibility to cracking.
The surface is galvanised to provide effective protection against rust and oxidation, making them suitable for standard indoor and outdoor conditions; for specialised applications, processes such as hot-dip galvanising and blackening are available to enhance corrosion resistance and extend service life. All finished products undergo random tensile strength testing, dimensional verification and visual inspection prior to dispatch, ensuring they meet pull-out strength requirements and provide secure anchoring, in accordance with engineering acceptance standards.

Restrictions on suitable substrates: Primarily intended for solid concrete and solid brick walls; use is not recommended for hollow bricks, lightweight walls, aerated concrete walls or loose masonry, as there is a high risk of poor anchoring and detachment.
Do not use in high-frequency vibration or heavy-load applications: This product is suitable for static load-bearing applications and is not recommended for high-risk conditions such as ceiling fans, heavy-duty vibrating equipment, critical load-bearing structures at height, or high-voltage equipment, to prevent loosening or detachment caused by prolonged vibration.
Standardised drilling and installation: The diameter and depth of the drill hole must match the bolt specifications; ensure the hole is thoroughly cleared of dust; do not use excessive force during installation; Tighten evenly; avoid over-tightening, which may cause the shank to break or the sleeve to crack.
Select the appropriate anti-corrosion variant for the application: The standard galvanised version is suitable for dry indoor environments; for outdoor, open-air, damp or water-exposed locations, or ventilated outdoor units, it is recommended to use the thickened galvanised version with superior corrosion resistance to delay rusting and extend service life.
Proper storage and handling: Store in a dry, well-ventilated warehouse, avoiding exposure to rain, dampness and direct sunlight, which can cause oxidation. This prevents rusting of the threads and flaking of the coating, which could affect assembly and anchoring performance.