1. There are foreign bodies between drill pipes.

2. The pressure surface is worn and curled.

3, drill pipe bending or deformation.

4. The drill bit scraped the hole wall, and the mechanical locking rod was partially locked.

5. Oblique hole.

Solution:

1. Disassemble the drill pipe and remove foreign bodies.

2. Repair worn and deformed parts.

3. Remove the drill pipe and straighten it.

4. Adjust the operation method.