When a bolt break off flush with the surface of a workpiece, a person may encounter a broken bolt that is difficult to remove. A broken bolt can break because a person apply too much torque to a fastener, or a broken bolt can break because rust has caused the threads to becomes unyielding. Removing a broken bolt require a tool called a screw extractor.
Using a random drill bit to remove a broken bolt is ineffectively, and using the wrong tool can cause permanent damage to the workpiece. Success when using a screw extractor depend on precision and the matching of diameter. A person must match the diameter of the broken bolt to the diameter of a pilot hole and the diameter of the screw extractor.
How to Remove a Broken Bolt with a Screw Extractor
If a pilot hole is too large, the screw extractor will not have enough surface area to grip the metal, so the screw extractor will spin inside the hole without remove the broken bolt. If a pilot hole is too small, the screw extractor may snap, and a snapped screw extractor is difficult to remove because screw extractor are made of hardened steel. Different type of screw extractors are designed for different mechanical tasks.
Spiral flute extractors use a left hand thread to bite deeper into the metal as a person turns the extractor counterclockwise. Spiral flute extractors are self-tightening tools, and people commonly use spiral flute extractors for stripped screw head. Straight flute extractors provide a square taper, and straight flute extractors are useful for delicate tasks where a person must avoid lateral movements.
Socket-style extractors is designed for large bolts, and impact wrench provide the high torque that socket-style extractors are built to withstand. A person should attempt easier methods before using a screw extractor to remove a broken bolt. A person can apply penetrating oil to a broken bolt, and a person should allow the penetrating oil to sit overnight to loosen the threads.
A person may also use a left-hand drill bit to remove a broken bolt, because a left-hand drill bit can catch the threads and back the screw out during the drilling processes. If a screw head is stripped but not broken, a person can place a rubber band between the driver and the screw head to increase frictionally. Preparation is a necessary step before a person use a screw extractor.
A person must use a center punch to create a small dimple in the center of the broken bolt. The center punch create a starting point so that the drill bit does not wander. If the drill bit wanders, the drill bit may score the surrounding material and ruin the hole.
After a person drills the pilot hole, a person can tap the screw extractor into the hole and begin to turning the screw extractor counter-clockwise. A person should avoid using a high-speed power drill when using a screw extractor. High speeds generate heat and vibration, and heat and vibration can cause a screw extractor to slip or snap.
A person should use a tap wrench or a drill press to apply steady pressure, because steady pressure allows a person to feel the screw extractor bite into the metal. If a person feels the screw extractor slipping, a person should stop using force and instead apply more heat or more penetrating oil. Extracting a broken bolt require a person to match the tool to the specific size of the hardware.
Small screws require light pressure and high speeds, but large bolts require significant torque and a slow approach. If a person follows the correct diameter matching and uses steady pressure, a person can remove the broken bolt without destroying the workpiece.
