How To Drill Broken Bolt Out Safely: Easy Guide to Damaged Bolt Removal

Can you drill out a broken bolt? Yes, you can drill out a broken bolt, and this guide will show you how to do it safely and effectively. Removing a broken bolt is a common problem for DIYers and professionals alike. Whether a bolt snaps off due to overtightening, corrosion, or material fatigue, dealing with it requires patience and the right approach. This guide aims to provide you with the knowledge and steps necessary to tackle this frustrating situation, helping you to remove stuck bolt situations and extract stripped screw issues with confidence. We will explore various techniques, tools, and precautions to ensure you can successfully perform damaged bolt removal without causing further harm to your workpiece.

How To Drill Broken Bolt Out
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Why Bolts Break and What to Do

Bolts can break for several reasons. Understanding these causes can help you prevent future occurrences.

Common Causes of Bolt Failure

Overtightening: Applying too much force can stretch the bolt beyond its yield strength, leading to a fracture.
Corrosion: Rust and other forms of corrosion weaken the bolt material, making it brittle and prone to snapping, especially under stress.
Material Defects: Internal flaws within the bolt metal can create weak points.
Vibration: Constant vibration can fatigue the bolt over time, leading to a break.
Improper Tool Usage: Using the wrong size or type of tool can damage the bolt head, making it difficult to turn and increasing the risk of it breaking.

Initial Steps Before Drilling

Before you even think about reaching for a drill, take these preliminary steps:

Assess the Situation: Look closely at how the bolt broke. Is it flush with the surface, or is a portion still sticking out? This will dictate your approach.
Clean the Area: Use a wire brush to clean away any dirt, rust, or debris around the broken bolt. This gives you a clear view and helps prevent debris from getting into your drill.
Apply Penetrating Oil: Spray a good quality penetrating oil onto the broken bolt. Let it soak for at least 15-30 minutes, or even overnight if possible. This oil can help loosen rust and make the bolt easier to remove. Tap the area gently with a hammer after applying the oil to help it penetrate.

Methods for Broken Bolt Removal

There are several effective methods to remove a broken bolt. The best method often depends on how the bolt broke and what tools you have available.

Method 1: Using a Bolt Extraction Tool (Easy Out)

This is often the go-to method for damaged bolt removal. A bolt extraction tool, commonly known as an “easy out,” is designed to bite into the broken bolt and twist it out. This method is particularly useful when the bolt is broken flush or slightly below the surface.

What is a Bolt Extraction Tool?

A bolt extraction tool is a specialized drill bit or screw that has a reverse spiral flute. You drill a pilot hole into the center of the broken bolt, then insert the extractor and turn it counter-clockwise. The extractor’s reverse threads bite into the bolt, and as you continue to turn, it should unscrew the broken piece.

Steps for Using an Easy Out Bolt Remover:

Center Punch: Use a center punch to create a small indentation exactly in the center of the broken bolt. This is crucial to guide your drill bit and prevent it from wandering.
Drill a Pilot Hole: Select a drill bit that is smaller than the diameter of the broken bolt. Start with a small bit and gradually increase the size if needed. Drill a hole into the center of the bolt. The depth of the hole depends on the size of the extractor you’ll be using, but typically 1/8 to 1/4 inch is sufficient for smaller bolts. Ensure you drill straight and true.
Insert the Extractor: Choose a bolt extraction tool that matches the size of your drilled hole. Gently tap the extractor into the pilot hole with a hammer to seat it firmly.
Turn Counter-Clockwise: Use a tap handle, wrench, or your drill set to a very slow, reverse setting to turn the extractor counter-clockwise. Apply steady, even pressure.
Patience is Key: If the bolt doesn’t immediately budge, try gently tapping the extractor again to help it grip. You can also try working the extractor back and forth slightly (a small turn forward, then back, then forward again) to break the rust seal.

When an Easy Out Might Not Work:

Bolt is Extremely Tight: If the bolt is seized with significant force, the extractor might strip out of the bolt.
Extractor Breaks: If the extractor breaks inside the bolt, you have a much harder problem, as drill bits often can’t penetrate hardened extractors.

Method 2: Drilling Out the Entire Bolt

If an easy out fails or isn’t suitable, you may need to drill out seized bolt entirely. This method requires precision to avoid damaging the threads in the surrounding material.

Steps for Drilling Out a Seized Bolt:

Center Punch: Just like with the extractor method, accurately center punch the broken bolt.
Start with a Small Bit: Begin drilling with a very small, sharp drill bit. Keep the drill speed slow and steady. The goal here is to create a precise hole through the center of the bolt.
Increase Drill Bit Size Gradually: As you drill deeper, incrementally increase the drill bit size. You are essentially drilling away the bolt material. The final drill bit size should be just slightly smaller than the diameter of the bolt’s threads. For example, if you’re removing a 1/4-inch bolt, you might drill up to a 7/32-inch or 15/64-inch bit.
Drill to the Depth of the Bolt: Continue drilling until you reach the depth of the broken bolt.
Remove Remaining Material: Once you’ve drilled out the core of the bolt, you may be able to pick out the remaining bolt threads with a small pick or a scribe. Sometimes, a few carefully placed taps with a punch on the remaining thread remnants can help dislodge them.
Clean and Re-tap: After removing the bolt fragments, clean the threaded hole thoroughly. You may need to use a tap and die set to chase the threads and clean them up, or if the threads are damaged, you might need to re-tap them to a larger size or use a thread insert.

Safety Considerations for Drilling:

Wear Safety Glasses: Always wear safety glasses to protect your eyes from flying debris.
Secure the Workpiece: Ensure the item you are working on is securely clamped down.
Drill Straight: This is paramount. If you drill off-center, you risk damaging the threads in the surrounding material.

Method 3: Using a Reverse Drill Bit

A reverse drill bit (also known as a left-handed drill bit) can sometimes be effective without needing an extractor. When you drill with a reverse bit, it spins in the opposite direction of a standard drill bit.

How Reverse Drill Bits Work:

As the reverse drill bit spins counter-clockwise, its cutting action can sometimes catch the broken bolt and unscrew it. It’s like an automatic extractor if it bites just right.

Steps for Using a Reverse Drill Bit:

Center Punch: As always, create a center mark.
Select the Right Bit: Choose a reverse drill bit that is smaller than the broken bolt.
Drill in Reverse: Set your drill to reverse. Begin drilling into the center of the broken bolt.
Apply Steady Pressure: Keep steady pressure and allow the bit to do the work. If the bolt is not too seized, the reverse action might be enough to back it out.

Advantages of Reverse Drill Bits:

Can sometimes remove the bolt without needing a separate extractor.
If it doesn’t remove the bolt, the hole it creates is already prepped for an extractor.

Method 4: Using Bolt Removal Pliers

For bolts where a portion is still protruding from the surface, bolt removal pliers can be a lifesaver. These specialized pliers have serrated jaws designed to grip rounded or damaged bolt heads securely.

How Bolt Removal Pliers Work:

The jaws are angled and have aggressive teeth to grip the bolt head. When you clamp down, they dig into the metal, providing excellent traction.

Steps for Using Bolt Removal Pliers:

Clean and Lubricate: Clean the area around the bolt and apply penetrating oil.
Grip the Bolt Head: Position the jaws of the bolt removal pliers around the protruding bolt head. The deeper the grip, the better.
Apply Force: Squeeze the handles firmly to engage the jaws.
Turn Slowly: Apply a slow, steady counter-clockwise turning motion. You might need to reposition the pliers to get a better grip if the head starts to round off further.

Limitations of Bolt Removal Pliers:

Only effective if there is enough of the bolt head to grip.
Can further damage a soft bolt head if not used carefully.

Method 5: Using a Tap and Die Set

A tap and die set is primarily used for cutting new threads or cleaning existing ones. However, it can be part of the process for damaged bolt removal, especially after drilling.

How a Tap and Die Set Aids Removal:

Thread Cleaning: After drilling out most of a bolt, you can use a tap of the same thread size to clean out any remaining metal fragments or minor damage to the original threads.
Enlarging Threads: If the original threads are too damaged to salvage, you might use a larger tap to re-cut the threads to a slightly larger diameter. This requires drilling the hole out to the correct size for the new tap.

When to Use a Tap and Die Set:

After successfully drilling out most of a broken bolt to clean up the existing threads.
When the original threads are damaged and need to be re-cut to a larger size.

Method 6: Welding a Nut Onto the Broken Bolt

This is a more advanced technique but can be very effective for stubborn, broken bolts, especially if a good portion of the bolt is still accessible.

How Welding Works for Bolt Removal:

You weld a new nut onto the exposed part of the broken bolt. The heat from the welding process can help break the bond between the bolt and the surrounding material, and the nut provides a new gripping surface.

Steps for Welding a Nut:

Prepare the Area: Ensure the area is clean and free of flammable materials.
Place a Nut: Position a new nut (ideally the same size as the original bolt or slightly larger) over the broken bolt stud.
Weld the Nut: Carefully weld the inside of the nut to the top of the broken bolt. Aim for a strong weld.
Cool Down: Let the weld cool for a few minutes.
Attempt Removal: Once cooled, use a wrench to slowly turn the welded nut counter-clockwise. The heat from the weld should help release the bolt.

Precautions for Welding:

Requires welding equipment and skill.
Risk of damaging surrounding materials with heat and sparks.
Not suitable for all materials or situations (e.g., plastic, aluminum if not careful).

Choosing the Right Tools

The success of damaged bolt removal often hinges on having the right tools. A good broken bolt extractor kit is invaluable.

Essential Tools for Broken Bolt Removal:

Center Punch: For marking the bolt’s center.
Hammer: For tapping the center punch and extractors.
Drill: Corded drills offer more consistent power, but cordless drills are convenient.
Drill Bits: High-speed steel (HSS) bits are standard. Cobalt bits are harder and better for drilling harder metals. Reverse drill bits are a specialty item worth having.
Penetrating Oil: Essential for loosening seized bolts.
Bolt Extraction Tools (Easy Outs): Available in various sizes and types.
Tap and Die Set: For cleaning or re-cutting threads.
Bolt Removal Pliers: For bolts with protruding heads.
Safety Glasses: Non-negotiable for eye protection.
Wire Brush: For cleaning.
Wrenches and Ratchets: For turning nuts and extractors.
Welding Equipment (Optional): For advanced removal techniques.

Table: Tool Selection Guide

Situation	Recommended Tool(s)	Notes
Bolt broken flush or below surface	Broken Bolt Extractor Kit (Easy Out), Reverse Drill Bit	Requires drilling a pilot hole for extractors.
Bolt head stripped or rounded	Bolt Removal Pliers, Socket Set (if head is still intact), Nut Splitter (if removing nut)	Pliers grip rounded heads; sockets require some head integrity.
Bolt broken with enough sticking out to grip	Bolt Removal Pliers, Vise Grips	Pliers offer better grip on rounded or damaged heads.
Bolt seized very tightly	Penetrating Oil, Heat (torch), Hammer (shock), Welding a nut	Heat can expand metal and break corrosion bonds. Welding provides a strong grip and heat.
Threads damaged after bolt removal	Tap and Die Set, Thread Repair Kit (e.g., Helicoil)	Taps clean or recut threads; repair kits fix damaged threads.
Bolt is very small (e.g., electronics, glasses)	Small precision extractors, very fine drill bits, sharp awl	Requires extreme care and magnification.
Bolt broken flush and extractor fails	Drill Out the Entire Bolt using progressively larger bits, Tap and Die Set for thread repair if needed	This is a destructive method, requires precision to avoid damaging the housing.

Advanced Techniques and Tips

When standard methods don’t work, a few advanced tricks can save the day.

Using Heat for Stubborn Bolts

Applying heat to the area around the broken bolt can cause the surrounding metal to expand, potentially breaking the bond of rust or thread locker.

Methods: A propane torch or a heat gun can be used.
Caution: Be mindful of the material you are heating. Excessive heat can warp or damage sensitive components, especially aluminum or plastic. Always protect surrounding areas with heat shields.

Freezing Sprays

Conversely, some specialized freezing sprays can be used to contract the bolt. This rapid cooling can also help break corrosion bonds.

Precision and Patience

The most crucial element in damaged bolt removal is patience. Rushing the process often leads to mistakes like drilling off-center, breaking extractors, or damaging the workpiece. Take your time, double-check your work, and use the right amount of force.

Post-Removal Steps

Once the broken bolt is out, your job isn’t quite finished.

Cleaning the Threads

Use a wire brush to clean any debris or rust from the threaded hole.
If the threads are slightly damaged, use a tap and die set to chase them. Select a tap of the same thread size and pitch as the original bolt. Lubricate the tap with cutting fluid and slowly turn it counter-clockwise to clean the threads.
If the threads are severely damaged, you may need to drill the hole out to the correct size for a larger tap or a thread repair insert like a Helicoil.

Replacing the Bolt

Use a new bolt of the correct size and grade.
Consider using an anti-seize compound on the new bolt’s threads to prevent future seizing, especially in corrosive environments.

Frequently Asked Questions (FAQ)

What is the best way to remove a broken bolt?

The best way depends on the situation, but a broken bolt extractor kit (easy out) is often the first and most effective method. If that fails, carefully drilling out the bolt is the next common approach.

Can I remove a broken bolt without drilling?

Yes, if a portion of the bolt head is still sticking out, you might be able to use bolt removal pliers or even a pipe wrench. For very stubborn bolts, welding a nut onto the broken stud can also work without direct drilling.

How do I prevent bolts from breaking in the future?

Use the correct torque specifications.
Apply anti-seize compound to threads, especially in corrosive environments.
Use quality bolts appropriate for the application.
Ensure proper alignment when installing bolts.
Avoid overtightening.

What if the extractor breaks inside the bolt?

This is a difficult situation. You may need to try drilling it out with a very hard drill bit (like cobalt or carbide), or you might need to resort to more aggressive methods like carefully drilling out the entire bolt. Sometimes, grinding the broken extractor flush and then trying to drill out the bolt can work.

How do I know which size extractor to use?

Extractors are typically sized to correspond with the size of the bolt you are trying to remove. The packaging for a broken bolt extractor kit will usually provide a guide. The pilot hole you drill should also be the correct size for the extractor to bite effectively without cracking the bolt.

Is it safe to use heat to remove a broken bolt?

Yes, heat can be very effective in breaking corrosion bonds. However, it’s crucial to be aware of the materials around the bolt and to use heat cautiously to avoid damage. Always ensure the area is clear of flammable materials.

Conclusion

Successfully performing damaged bolt removal is a skill that every DIYer and mechanic should possess. By following these step-by-step guides, utilizing the correct tools such as a bolt extraction tool or reverse drill bit, and exercising patience, you can overcome the challenge of a broken bolt and get your project back on track. Remember to always prioritize safety, work methodically, and choose the removal method that best suits the specific situation. With practice, you’ll become adept at tackling even the most stubborn broken fasteners.