How to Loosen Broken Bolts

Bolts as they ought to be

When a bolt suddenly snaps halfway through removal, finishing the job might seem to be an exercise in futility. Sometimes, when a bolt's head is so stripped that a socket or wrench won't wrap around it, hopelessness sets in. If you have a broken bolt that requires removal, you're not alone--it has happened before and it will happen again. With the help of a special tool called a screw extractor, you'll be able to remove a broken bolt and continue working on your project.

Things You'll Need

• Drill
• Drill bits for metal
• Spiraled screw extractor
• Tap or crescent wrench
• Calipers
• Pliers

Instructions

1. Select the proper screw extractor for your bolt. The size of the bolt's shank must exceed the size of the screw extractor. A screw extractor performs its task by sinking into a hole bored through the center of the bolt's shank. If the screw extractor is the same or nearly the same diameter as the bolt, the bolt (and the material surrounding the bolt) will become damaged. Use calipers to measure the bolt's diameter. Select a screw extractor smaller in diameter than the bolt. For example, in order to remove a 3/8-inch bolt, select a ¼-inch screw extractor.

2. Drill a pilot hole into the broken bolt's shank. The pilot hole serves as an entry point for the screw extractor. Appropriate pilot hole sizes are stamped on the shank of each screw extractor. Select the proper drill bit according to the size stamped on the side of your screw extractor. Attach the drill bit to your drill and drill a straight hole at least three-quarters through the bolt's length.

3. Insert the screw extractor into the pilot hole. Hold the screw extractor in place, attach a tap wrench or a crescent wrench to its shank and slowly turn counter-clockwise. Continue to turn the screw extractor into the pilot hole. The screw extractor will bite and catch the broken bolt's shank.

4. Continue to tighten the screw extractor into the pilot hole. When the screw extractor becomes caught in the bolt's shank, it will begin to turn and loosen the bolt. Continue turning the screw extractor until the broken bolt comes free.

5. To remove the screw extractor from the broken bolt, grip the broken bolt with pliers, grip the extractor's shank with a wrench and turn clockwise.

Tips & Warnings

• Using a drill press ensures that your pilot hole is straight.

• Screw extractors are made of brittle, hardened metal. Treat them carefully, or they'll snap inside of the broken bolt.

References

• Irwin Industrial Tools: Screw Extractor Selection Guide