Screws for Office Chairs

There are various types of screws commonly used in office chairs, mainly including the following:

1. 12.9-grade Black Internal Hexagon Grub Screws
   These screws are renowned for their high strength. The 12.9 grade indicates that their tensile strength exceeds 1200 MPa, making them suitable for structural connections requiring high load-bearing capacity. Available in specifications such as M3 and M4, with relatively small diameters, they are often used for securing precision components in office chairs, such as armrest adjustment mechanisms or gas lift rod connections. Their 'grub' design (headless) reduces space occupation, the internal hexagon drive facilitates tool operation, and the black coating provides rust resistance and aesthetic appeal.

2. M8*20 Black Zinc-Plated 8.8-grade Internal and External Hexagon Screws with Anti-Slip Teeth
   These screws combine internal and external hexagon structures. The external hexagon allows for quick positioning, while the internal hexagon provides higher torque transmission capability, making them suitable for scenarios requiring frequent disassembly or withstanding significant shear forces. The 8.8-grade strength (tensile strength of 800 MPa) meets general furniture requirements. The M8*20 specification indicates a diameter of 8 mm and a length of 20 mm, suitable for connecting the chair seat to the legs. The black zinc coating enhances corrosion resistance, and the anti-slip teeth design prevents loosening, improving structural stability.

3. Furniture Screws with Semi-Round Head, Internal Hexagon, Washer, and Embossed Design
   These screws feature a semi-round head and are driven by an internal hexagon. Used in conjunction with washers, they can distribute pressure and protect the connection surface. Available in specifications such as M6 and M8, they are commonly used for fixing the chair back to the seat or in decorative areas where the screw head needs to be hidden. The embossed design (surface texture) increases friction to prevent rotational loosening, making them suitable for connecting wooden or plastic components.

4. 12.9-grade Set Screws 913 Internal Hexagon High-Strength Fasteners
   Set screws (headless screws) secure components through end pressure. The 12.9-grade strength ensures they remain tight during long-term use. The 913 model may refer to a specific design (such as flat-end or cone-end). Flat-end set screws are suitable for flat surface contact fixation, such as adjustment knobs or locking mechanisms. Their black headless design can be concealed within components, maintaining a clean appearance, and they are often used in the lifting or tilting adjustment functions of office chairs.

Selection Recommendations:

• Choose the strength grade (such as 8.8-grade or 12.9-grade) based on the stress conditions of the connection area.
• Consider the installation space when selecting the screw type (e.g., grub screws are suitable for narrow spaces).
• Prioritize zinc-plated or coated screws when rust resistance is a concern.
• For frequently adjusted areas, use screws with anti-slip or set screw designs.