Methods to prevent nuts (or bolts) from automatically loosening during mechanical design and manufacturing include using semi-circular nuts:

1. Spring washer with backing; (simple to make)

2. Use hex socket nuts + cotter pins; (increased the processing procedures)

3. Added shimming lock washers; (Increased processing procedures)

4. Hexagonal head of semi-circular nuts with holes inserted with steel wire. (This has increased the processing procedures.)

Semi-circular nut lock torque test: This test is only required for screws with rolled threads. During the lock torque test, observe the small lock torque of the test plate. If the torque exceeds the specified standard value (which is determined based on the size/surface treatment of the screw), the product is不合格. An不合格 indicates insufficient lubricity on the screw surface or improper threading, requiring greater torque.