1. Visual Inspection
Rust and Corrosion: If the screw surface shows obvious rust, oxidation, or peeling coating (especially in humid environments), it should be replaced immediately.
Deformation and Wear: Check for dents in the head, missing threads, or stripped threads. Such damage can lead to tightening failure.
2. Tightening Performance Test
Torque Test: Use a torque wrench to check for looseness. If the torque value is below the standard or cannot maintain the tightening force, it needs to be replaced.
Tapping and Listening: Gently tap the screw. If it makes a dull sound (possibly due to internal cracks) or is loose, it indicates failure.
3. Thread Condition Assessment
Thread Integrity: Check the threads for missing teeth, wear, or stripped threads. Damaged threads cannot provide effective friction.
Mounting Hole Inspection: If the threaded hole has expanded due to repeated disassembly and installation (for example, a tire screw has been disassembled and installed more than 10 times), the screw must be replaced and the hole repaired. 4. Environment and Frequency of Use
Highly corrosive environments: Stainless steel screws (grade A4) should be replaced if rust appears in bathrooms and chemical plants.
High-frequency vibration environments: In mechanical connections or vehicle components, screws that have loosened due to fatigue should be replaced even if they appear intact.
5. Special Scenarios
Gypsum board installation: Screws that are rusted or insufficiently penetrate the surface paper should be re-secured and painted with anti-rust paint.
Metal plate connections: Tapping screws that cannot be driven vertically or are installed at an angle may require replacement due to uneven force.
Replacement Recommendations
Disposable: Tapping screws are prone to wear; it is recommended that they be disassembled and replaced with new ones.
Compatible Materials: Stainless steel is preferred for humid environments, while alloy steel is preferred for high-strength applications.
