1. First, clean the mud from the broken screw head. Use a center punch to center-punch the broken section. Then, use an electric drill with a 6-8 mm diameter drill bit to drill a hole at the center punch location, ensuring the hole penetrates completely. After drilling through, remove the small drill bit and replace it with a 16 mm diameter drill bit to enlarge and drill through the hole.
2. Using a welding rod with a diameter of 3.2 mm or less, apply a medium to low current to the drilled hole of the broken screw, working from the inside out. Begin welding at half the length of the broken screw. Do not extend the arc too far at the start to avoid burning through the outer wall of the broken screw. After welding to the top face of the broken screw, continue welding to create a cylinder with a diameter of 14-16 mm and a height of 8-10 mm.
3. After welding, use a hand hammer to tap the end face to vibrate the broken screw along its axial direction. The heat generated by the arc and subsequent cooling, combined with the vibration, will loosen the threads between the broken screw and the machine body.
4. Carefully observe the surface. When a small amount of rust is observed leaking from the fracture after tapping, place an M18 nut on the welded column head and weld them together.
5. After welding, let it cool slightly. While still warm, use a wrench to twist the nut back and forth, or tap the end face of the nut with a small hammer while twisting. This will remove the broken bolt.
6. After removing the broken bolt, use a suitable tap to machine the threads inside the frame to remove rust and other debris from the hole.
