I. Mild Stripping: Restoring Engagement, No Special Tools Required
When the screw groove is only slightly worn and not yet fully smooth, try the following methods first:
Rubber Pad Friction Enhancement Method: Cut a piece of bicycle inner tube or elastic rubber and cover the stripped screw head. Then, use an original-sized Allen wrench to turn it counterclockwise. The elasticity of the rubber can fill the wear gap and enhance friction to transmit torque.
Tape/Cloth Wrapping Method: If rubber is unavailable, use electrical tape or multiple layers of paper towels to wrap around the screw head, increasing the roughness of the contact surface and aiding engagement.
Tap Insertion Method: Align the Allen wrench with the groove and gently tap the handle with a hammer to make the tool embed deeper. Then, slowly rotate it. This method is suitable when the tool is not fully engaged.
II. Moderate Slippage: Removal with Specialized Tools
If the above methods are ineffective, specialized tools must be used for intervention:
1. Screw Extractor (Broken Thread Extractor)
Applicable Scenarios: Screw head is still intact but the groove is severely worn.
Operating Steps:
① Use a center punch to mark a positioning point in the center of the screw to prevent drilling deviation;
② Pre-drill a hole using a drill bit 1-2mm smaller than the screw diameter (e.g., a 4mm drill bit for an M6 screw);
③ Insert the reverse thread extractor and rotate it in the opposite direction at low speed to unscrew it.
Recommended Tools: High-cobalt carbide drill bit + single-ended reverse thread extractor, high efficiency and low risk.
2. Saw Out a Slot for Modification
Use an angle grinder or saw blade to cut a slot on the top of the screw head, then use a flathead screwdriver and a hammer to gently tap and unscrew it.
Precautions: Wear safety goggles during operation to prevent metal shavings from flying.
3. Larger Hex Wrench Impact Insertion Method
Select a larger hex wrench and forcefully hammer it into the stripped thread hole. Utilize the interference fit to increase the engagement force, then attempt to unscrew it.
III. Severe Stripping or Breakage: Advanced Solutions
1. Welded Nut Assisted Removal
Place a hex nut over the stripped screw remnant and weld it securely using electric welding or TIG welding. After cooling, use a wrench to rotate the nut and remove the screw. Suitable for larger screws, but care must be taken to avoid high-temperature damage to surrounding parts.
2. Precise Drilling + Thread Remover
Drill a hole in the center of the screw using a high-cobalt carbide drill bit, then insert a thread remover to unscrew it in reverse. This method requires a high level of skill and is recommended to be performed by a professional.
3. Chemical-Assisted Loosening
If the screw is stuck due to rust, spray WD-40 or a special rust remover first, wait 10–15 minutes for penetration, and then attempt to disassemble.
IV. Prevention Recommendations: Reducing Stripping at its Root Cause
Use High-Quality Tools and Screws: Use S2 alloy steel Allen wrenches to avoid uneven force caused by deformation of soft tools.
Control Tightening Torque: Refer to the recommended torque for the screw specification (e.g., 10–12 N·m for M6 8.8 grade screws). Use a torque wrench to avoid overtightening.
Regular Inspection and Replacement: Regularly inspect screws that are frequently disassembled or exposed to high vibration environments. Replace screws immediately if slight wear is found.
