Screws for Office Chairs
There are various types and specifications of screws commonly used in office chairs, including 12.9-grade black internal hexagon set screws (M3, M4), M6/M8 furniture screws with semi-round heads, internal hexagons, washers, and knurled patterns, as well as M8*20 black zinc-plated 8.8-grade internal and external hexagon screws with anti-slip teeth.
1. 12.9-Grade Black Internal Hexagon Set Screws (M3, M4)
These screws are high-strength fasteners. The 12.9 grade indicates extremely high tensile strength (approximately 1200MPa), making them suitable for structural connections that need to withstand significant tension or vibration, such as the attachment of armrests, star bases, and seat plates in office chairs. Black oxide treatment enhances rust resistance while maintaining a low-profile appearance. The internal hexagon design requires a dedicated Allen wrench for installation, preventing loosening issues caused by stripped screws common with regular Phillips screws. M3 and M4 are nominal diameters suitable for thinner or medium-thickness connection parts, such as the fixation of plastic and metal components.
2. M6/M8 Furniture Screws with Semi-Round Heads, Internal Hexagons, Washers, and Knurled Patterns
These screws combine the advantages of semi-round heads and internal hexagons: the semi-round head can be embedded into the surface of components, reducing the impact of protruding parts on usage; the internal hexagon structure facilitates tool operation and can withstand higher torque. The washer design (flat or spring washers) distributes pressure, preventing the screws from loosening or damaging the connection surface. The knurled pattern increases friction, further preventing rotation. M6 and M8 are suitable for thicker connection parts, such as the connection between the chair back and seat plate, and the fixation of the pneumatic rod and star base, with M8 having stronger load-bearing capacity.
3. M8*20 Black Zinc-Plated 8.8-Grade Internal and External Hexagon Screws with Anti-Slip Teeth
M8*20 indicates a nominal diameter of 8mm and a length of 20mm, suitable for scenarios requiring deep fixation. The 8.8-grade strength (approximately 800MPa) meets the load-bearing requirements of daily office chairs. The black zinc plating provides good corrosion resistance, making it suitable for humid environments. The internal and external hexagon structure (i.e., both the screw head and nut are hexagonal) allows for bidirectional tool operation, making installation more flexible. The anti-slip tooth design can be embedded into the connection surface, preventing the screws from rotating due to vibration or external force, and is commonly used in critical parts such as the fixation of the pneumatic rod and chair seat.
Selection Recommendations
- Choose screw diameters based on the thickness and material of the connection parts (e.g., M3/M4 for thin plates, M6/M8 for thick plates);
- For high-strength requirements (e.g., star base connections), prioritize 12.9-grade or 8.8-grade screws;
- In humid environments, choose black zinc-plated or oxide-treated screws to enhance rust resistance;
- For vibration scenarios, select screws with anti-slip teeth or knurled designs.
