1. First, remove the sludge and debris from the broken surface of the bolt. Use a center trowel to carefully break the center of the fractured section. Then, use an electric drill to create a pilot hole with a diameter of 6 to 8 mm at the center of the broken bolt. Ensure that the hole is drilled straight and deep enough. After drilling, remove the small drill bit and replace it with a larger one, preferably 16 mm in diameter, to enlarge the hole further. This step will help provide a better grip for the next process.
2. Take a welding rod with a diameter of 3.2 mm or smaller. Set the welding machine to medium or low current settings. Begin surfacing welding from the inside of the bolt hole, working your way outwards. Start the arc at the beginning of the weld to avoid damaging the outer wall of the broken bolt. Continue the welding until you reach the top of the bolt. Then, build up a cylindrical shape around the hole, ensuring the diameter is between 14 to 16 mm and the height is about 8 to 10 mm. This will form a solid base for the nut to be attached later.
3. Once the surfacing is complete, use a hand hammer to gently tap the end face of the welded area. This tapping will cause the broken bolt to vibrate along its axis. The heat generated during the welding process, combined with the subsequent cooling and mechanical vibration, will help loosen the bolt from the surrounding threads.
4. Carefully inspect the area after tapping. If you notice any signs of iron rust or metal particles coming out of the fracture, it’s a good indication that the bolt is loosening. At this point, place an M18 nut over the welded area and weld it securely in place. This will give you a strong grip to turn the bolt out later.
5. Allow the welded assembly to cool down completely. Once cooled, use a pipe wrench or plum wrench to grip the nut and twist it back and forth. While doing so, gently tap the nut face with a small hand hammer. This combination of twisting and tapping will help free the broken bolt from the threaded hole.
6. After successfully removing the broken bolt, use a suitable thread chaser or tap to clean and recondition the threads inside the hole. This step is essential to remove any remaining rust, dirt, or debris, ensuring the new bolt will fit properly and securely.
This method is effective when dealing with broken bolts that are difficult to extract using traditional tools. It combines welding, mechanical vibration, and careful threading to restore functionality without damaging the surrounding structure. Always ensure proper safety measures are taken, such as wearing protective gear and working in a well-ventilated area.
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