Troubleshooting Views: 22

In 90% of cases the countersink angle is wrong! The most common mistakes: using a 120-degree drill to enlarge a 90-degree countersink, or using a 90-degree tool for 82-degree US screws. With mismatched angles the screw head contacts along only one line at its edge, clamping force drops sharply, and vibration loosens it further. Other causes: 1. Countersink too shallow, screw head protruding; 2. Oily hole wall reducing friction; 3. Poor screw quality with inaccurate head angle; 4. Insufficient torque; 5. Vibrating environment without locking measures. Solutions: first confirm the angle matches and use a countersink matching the screw; then check depth, clean the hole, use quality screws, tighten to specified torque; use locking screws or thread locker in vibrating environments.