How to choose suitable hardware fasteners?

In different scenarios, the "tensile force, compressive force, shear force, and vibration" that fasteners need to withstand vary significantly, making this the foundational premise for selection.

  Determine the Load Type  

    Tensile Scenarios: Such as steel column connections in steel structure bridges or mechanical spindle fixation, require high-strength bolts (e.g., Grade 8.8, 10.9) to avoid tensile fracture.  

    Shear Scenarios**: Such as furniture connectors or curtain wall frame fixation, require attention to the fastener's "shear strength," prioritizing models with washers or larger heads (e.g., countersunk screws) to disperse shear forces.  

    Vibration Scenarios**: Such as automotive engines or high-speed rail bogies, require anti-loosening fasteners (e.g., nuts with nylon rings, self-tapping locking screws) or paired with spring washers and lock washers to prevent vibration-induced loosening.

  Estimate the Load Magnitude 

Based on design drawings or actual requirements, refer to the fastener's "mechanical performance grade" (e.g., bolt strength grade):  

- Ordinary civilian scenarios (e.g., furniture, decoration): Low-strength fasteners like Grade 4.8 or 5.6 are sufficient.  

- Industrial equipment (e.g., machine tools, engineering machinery): Medium-to-high-strength fasteners like Grade 8.8 or 10.9 are required.  

- Special scenarios (e.g., aerospace, bridges): Ultra-high-strength Grade 12.9 or custom alloy fasteners (e.g., titanium alloy, stainless steel) are necessary.

The specifications (size, precision, connection method) of fasteners must fully match the "aperture, material, and assembly space" of the connected parts to avoid issues like "cannot install" or "cannot tighten."

  Determine Core Specification Parameters

    Coarse Thread (e.g., M8×1.25): Universal applicability, suitable for most scenarios.  

    Fine Thread (e.g., M8×1.0): Good self-locking and fatigue resistance, suitable for vibrating or thin-walled connections.  

    Self-Tapping Thread (e.g., ST4.2): No pre-drilled hole required, directly tapped into wood or plastic, suitable for furniture and decoration.  

    Size: Select the "nominal diameter" based on the aperture of the connected part (e.g., M4, M8 bolts correspond to 4mm, 8mm apertures), and select the "length" based on the connection thickness (bolt length should extend 2-3 pitches beyond the nut to avoid being too short for fixation or too long and wasteful).  

   Precision: For ordinary scenarios, select "standard precision" (e.g., Grade A or B per GB/T 90.1). For precision equipment (e.g., electronics, medical devices), "high precision" (e.g., Grade A or custom tolerance) is required to avoid assembly gaps due to dimensional deviations.

  Select Compatible "Head and Tail Types" 

The head determines the "installation tool" and "aesthetics," while the tail determines the "fixation method":  

    Pointed Tail (Self-Tapping Screws): Directly tapped into wood or plastic, no pre-drilling required.  

    Flat Tail (Machine Screws): Used with nuts, suitable for metal parts connections.  

    Expansion Tail (Expansion Bolts): Suitable for concrete or brick walls, fixed via expansion sleeves, with strong load-bearing capacity.  

    Hex Head (Hex Bolts): Installed with a wrench, high torque, suitable for industrial equipment.  

    Cross-Slot/Flat-Slot (Pan Head Screws)**: Installed with a screwdriver, suitable for furniture and appliances, with good aesthetics.  

    Countersunk Screws: The head can be embedded into the connected part, suitable for scenarios requiring a flat surface (e.g., instrument panels).