I. Mild Stripping: Repairable, Does Not Affect Overall Connection
Characteristics: Slight "slippage" during screwing, but can eventually be tightened;
The screw still provides some clamping force, with no obvious loosening;
No abnormal noise or displacement, function is basically normal.
Common Scenarios: Slight wear on threads after initial disassembly and assembly of plastic parts;
Torque slightly exceeded but does not damage the base material structure.
Remedies: Replace with a new screw of the same specification;
Add a small amount of thread-locking agent to enhance the engagement.
II. Moderate Stripping: Reduced Connection Reliability, Requires Intervention
Characteristics: Noticeable "free-spinning" during tightening, resistance suddenly disappears;
The screw cannot reach the predetermined torque, with a small gap at the contact surface; Slight abnormal noise or increased vibration occurs during equipment operation.
Detection Method: Use a torque wrench to test: The set target torque (e.g., 1.5Nm) cannot be achieved; Manually turning the screw, there is a noticeable loosening, but it does not completely fall off.
Risk Warning: Long-term use may lead to complete failure, especially in vibrating environments.
Remedies: Prioritize using a thread repair tool or wire thread insert to restore the threaded hole;
Alternatively, replace with a larger screw and re-tap.
III. Severe Stripping: Loss of tightening function, requires repair.
Characteristics: Screws cannot be tightened at all, continuously spinning freely;
Connectors are loose, misaligned, or even detach automatically;
Structural hazards exist, such as component displacement, noticeable abnormal noise, or functional interruption (e.g., a loose motor bracket causing equipment shutdown).
Typical Cases: Car sun visor hooks sag due to stripped nuts;
Antenna grounding screw stripping damages sheet metal holes, requiring replacement with patented self-tapping screws.
Judgment Criteria:
The breaking torque is more than 50% lower than the design value (e.g., originally designed to withstand 1.5 Nm, but measured only 0.6 Nm);
The inner thread of the screw hole is completely destroyed, with a visible "smooth hole".
Recommended Treatment: Immediately disable the connection point; Thoroughly repair using thread helicoil or metal repair adhesive + retapping; For critical components, consider replacing the entire part to ensure safety.
IV. How to Quickly Assess the Severity of Stripped Threads on-site? (Practical Three-Step Method)
1. Observe: Observe whether the thread is intact and whether there is debris or deformation on the hole wall;
2. Tighten: Try tightening by hand or with a tool, feeling for any sudden drop in resistance;
3. Measure: Use a torque tool to verify whether the set value can be reached. If the difference is >30%, it is considered moderate to severe stripping.
⚠️ Special Reminder: In critical structures such as automobiles, machinery, and electronic equipment, once signs of stripping are found, it is recommended to deal with it promptly to avoid greater losses. If load-bearing or safety components are involved, a professional should assess the repair plan.
