How To Remove A Broken Bolt

Dealing with a broken bolt can be one of the most frustrating experiences in any repair job. Whether you’re working on a vehicle, household appliance, or machinery, a snapped bolt can halt your progress and potentially cause additional damage if not removed properly. The good news is that with the right techniques and tools, you can successfully extract that stubborn broken bolt and continue with your project. This guide will walk you through several proven methods to tackle this common problem, saving you time, money, and a lot of frustration.

What You’ll Need

Depending on which method you choose, you may need some or all of these tools:

– Penetrating oil (PB Blaster, WD-40, or oil of wintergreen)
– Center punch and hammer
– Left-handed drill bits
– Regular drill bits (various sizes)
– Screw extractor set
– Vice grips or locking pliers
– Drill
– Hammer and chisel
– Heat source (propane torch)
– Safety glasses
– Gloves

Method 1: Using Vice Grips or Locking Pliers

If enough of the bolt is protruding from the surface, this is often the simplest solution.

1. Apply penetrating oil to the broken bolt and surrounding area.
2. Allow the oil to soak in for at least 15-30 minutes (overnight is even better).
3. Grip the exposed portion of the bolt firmly with vice grips or locking pliers.
4. Slowly turn counterclockwise with steady pressure.
5. If the bolt doesn’t budge, apply more penetrating oil and try again after waiting.

Method 2: Drilling and Using a Screw Extractor

Step 1: Prepare the Bolt

1. Clean the surface of the broken bolt.
2. Use a center punch to make a small indentation in the center of the broken bolt.
3. This indentation prevents your drill bit from wandering.

Step 2: Drill a Pilot Hole

1. Select a drill bit significantly smaller than the diameter of the bolt.
2. Drill slowly into the center of the broken bolt.
3. Drill to a depth of about 1/4 to 1/2 inch, depending on the bolt size.

Step 3: Use the Screw Extractor

1. Select an appropriate-sized screw extractor (also called an “easy out”).
2. Insert the extractor into the drilled hole.
3. Turn the extractor counterclockwise with a wrench.
4. The extractor should bite into the bolt and begin to back it out.

Method 3: Using Left-Handed Drill Bits

Left-handed drill bits are designed to turn counterclockwise, which can sometimes remove the bolt during the drilling process.

1. Apply penetrating oil to the broken bolt.
2. Center punch the middle of the bolt.
3. Start with a small left-handed drill bit.
4. Drill slowly, applying moderate pressure.
5. As you drill, the counterclockwise rotation may catch the bolt and begin to back it out.
6. If the bolt doesn’t come out, gradually increase the drill bit size and try again.

Method 4: The Hammer Method

For bolts that aren’t too tight, sometimes shock can break the rust or corrosion bond.

1. Place a chisel on the edge of the broken bolt.
2. Position the chisel so that a strike would rotate the bolt counterclockwise.
3. Strike the chisel firmly with a hammer.
4. Repeat around the circumference of the bolt if necessary.
5. Once loosened, remove with pliers or vice grips.

Removing a Broken Bolt in a Recessed Hole

Recessed holes present a special challenge, but there are solutions:

1. Use a small drill bit to create a pilot hole as deep as possible.
2. Use a screw extractor with an extension if needed.
3. If the hole is large enough, try using needle-nose vice grips.
4. For very deep recesses, consider specialized extractors with longer reaches.

Using Heat to Remove Stubborn Bolts

Heat can break the bond between a bolt and its surrounding material, especially if there’s corrosion.

1. Apply penetrating oil first and let it soak.
2. Use a propane torch to heat the area around the bolt (not directly on the bolt).
3. Heat for 30-60 seconds, allowing the metal to expand.
4. Try to extract the bolt using one of the methods above while the metal is still warm.

Warning:

Do not use heat near flammable materials or on parts that could be damaged by heat (such as plastic components or electrical parts).

Tips for Success

– Patience is key. Rushing can lead to more problems.
– Always wear safety glasses when drilling or hammering on metal.
– Quality tools make a difference, especially when it comes to extractors.
– Apply penetrating oil multiple times over several hours for best results.
– Methyl salicylate (oil of wintergreen) is an excellent penetrating oil alternative.
– If one method fails, try another rather than forcing the current approach.

Frequently Asked Questions

How do I prevent bolts from breaking in the first place?

Always use the correct tools, apply penetrating oil to rusty bolts before attempting removal, and never force a bolt that won’t turn easily. Consider using anti-seize compound when installing bolts in areas prone to corrosion.

What’s the best penetrating oil for stuck bolts?

Commercial products like PB Blaster, Kroil, and Liquid Wrench work well. Some mechanics swear by a homemade mix of automatic transmission fluid and acetone (50/50 ratio), while others recommend oil of wintergreen (methyl salicylate) for its exceptional penetrating properties.

What if the screw extractor breaks inside the bolt?

This is unfortunately a common problem. Extractors are hardened steel and can be very difficult to drill out. You may need to consult a professional machinist who can use specialized equipment like EDM (Electrical Discharge Machining) to remove both the broken extractor and bolt.

How do I know what size extractor to use?

Extractors are sized based on the diameter of the bolt. Most extractor sets include a chart that recommends drill bit sizes and corresponding extractors. As a general rule, your pilot hole should be about 1/4 to 1/3 the diameter of the bolt.

Is it worth trying to remove a broken bolt myself or should I hire a professional?

For accessible bolts in non-critical applications, DIY removal is often worth trying. However, if the bolt is in a critical component (like an engine block), in an expensive part, or if your initial attempts fail, consulting a professional can prevent further damage and potentially save money in the long run.

By following these methods and tips, you’ll be well-equipped to tackle those frustrating broken bolts that inevitably appear during repair and maintenance tasks. Remember that sometimes the simplest approach works best, so start with the least invasive methods before progressing to more aggressive techniques.