1. First, remove the sludge on the surface of the broken screw and head, use the center punch to kill the center punch of the cross section, then use the electric drill to install the drill with a diameter of 6-8mm, drill the hole at the center punch hole of the cross section, and pay attention to that the hole must be drilled through. After the hole is drilled through, remove the small drill bit and replace it with a drill bit with a diameter of 16mm. Continue to expand and drill through the hole where the bolt is broken.

2. Take the electrode with diameter less than 3.2mm, use medium and small current to build up welding from inside to outside in the hole of broken bolt, and take half of the whole length of broken bolt at the beginning of welding. At the beginning of overlay welding, the arc striking shall not be too long to avoid burning through the outer wall of the broken bolt. After overlaying to the upper end face of the broken bolt, one cylinder with diameter of 14-16mm and height of 8-10mm shall be continuously overlaid.

3. After surfacing, hammer the end face with a hammer to make the bolt vibrate along its axis. Due to the heat generated by the previous arc and the subsequent cooling, plus the vibration at this time, the thread between the broken bolt and the body will be loose.

4. After careful observation, when it is found that there is a small amount of rust leaking out from the fracture after knocking, the M18 nut sleeve can be taken and welded on the post head of overlay welding.

5. After welding, use a ring spanner cover when it's cool and hot, and twist it left and right on the nut, or hit the end face of the nut with a small hammer while twisting it back and forth, so as to take out the broken bolt.

6. After taking out the broken bolt, use a suitable wire hammer to process the screw thread in the frame once to remove the rust and other sundries in the hole.

Whether it's the tiny screws of electronic equipment, the general screws of furniture and electric appliances, or even the large screws used in engineering, construction, bridges, transportation equipment, airplanes, trams, automobiles, etc., the screws occupy a very important position in these fields.