Can you drill out a broken screw? Yes, you absolutely can drill out a broken screw, and this guide will show you how to do it safely and easily. When a screw breaks off flush with the surface or its head strips, it can feel like a woodworking or metalworking disaster. But with the right tools and techniques, extracting a broken screw is a manageable task for DIYers and professionals alike. This comprehensive guide will walk you through the process, covering everything from preparing your workspace to cleaning up afterward. We’ll explore various methods and provide tips to ensure you can tackle this common problem effectively.
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Why Do Screws Break?
Before we dive into solutions, it’s helpful to consider why screws often break. This knowledge can help prevent future issues.
- Over-tightening: Applying too much torque can stress the screw, especially if it’s made of a brittle material.
- Stripped Heads: When the screwdriver bit slips, it can chew up the screw head, making it impossible to turn. This often leads to a need for removing a stripped screw.
- Material Fatigue: Older screws or those subjected to vibration and stress can weaken over time, making them prone to snapping.
- Corrosion: Rust and other forms of corrosion can seize a screw, requiring excessive force to remove, which can lead to breakage.
- Incorrect Tool Usage: Using the wrong size or type of screwdriver can damage the screw head and make removal difficult.
Preparing for the Task
Proper preparation is key to a successful screw extraction. It ensures safety and maximizes your chances of success.
Gathering Your Tools and Materials
Having the right equipment readily available will make the process much smoother. You’ll likely need a selection of the following:
- Safety Glasses: Absolutely essential to protect your eyes from flying metal shards.
- Drill/Driver: Corded or cordless, with variable speed control.
- Center Punch: To create a starting dimple for your drill bit.
- Hammer: To strike the center punch.
- Drill Bits: A set of various sizes. We’ll discuss the drill bit size for screw selection later.
- Screw Extractor Kit: These are specialized tools designed for this purpose.
- Penetrating Oil: Like WD-40 or a rust penetrant, to help loosen stubborn screws.
- Pliers: For gripping and turning if any part of the screw is exposed.
- Wire Brush: For cleaning the area around the broken screw.
- Protective Gloves: To protect your hands.
- Workpiece Support: Clamps or vises to keep the material stable.
- Rag: For cleaning up oil and debris.
Assessing the Situation
Before you start drilling, take a moment to look closely at the broken screw.
- Is the screw head completely gone, or is a small portion still protruding? If it’s sticking out, you might be able to grip it with locking pliers or a vise grip.
- What material is the screw made of? Hardened steel screws are tougher to drill than softer brass or aluminum screws.
- What material is the screw in? Wood is much softer than metal. Drilling into metal requires more care and the right drill bits.
- How deep is the break? Is it flush with the surface, or is there a gap?
Method 1: Using a Screw Extractor Kit
A screw extractor kit is the go-to solution for most broken screw situations. These kits typically contain a series of specialized bits and extractors.
How to Use a Screw Extractor
This method generally involves two main steps: drilling a pilot hole and then using the extractor.
Step 1: Preparing the Screw
- Clean the Area: Use a wire brush to remove any dirt, debris, or rust from around the broken screw.
- Apply Penetrating Oil: Spray a generous amount of penetrating oil onto the broken screw and let it soak for at least 15-30 minutes, or even longer for severely seized screws. This helps loosen the threads.
- Center Punch: Place the tip of the center punch on the exact center of the broken screw. Gently tap it with a hammer to create a small indentation. This prevents the drill bit from wandering off-center.
Step 2: Drilling the Pilot Hole
This is a critical step. The size of your pilot hole depends on the size of the screw and the extractor you plan to use.
- Drill Bit Size for Screw: Most screw extractor kits come with recommendations for pilot hole sizes. If not, a general rule of thumb is to choose a drill bit that is smaller than the diameter of the screw shank. For example, if you have a 1/4-inch screw, you might start with a 1/8-inch or 5/32-inch drill bit.
- Drilling:
- Set your drill to a slow speed and in a reverse (counter-clockwise) direction for the initial drilling. This is important because we want to avoid further tightening the screw.
- Carefully drill a hole directly into the center of the broken screw. The depth of the hole should be about half the length of the screw shank, or deep enough to accommodate the extractor.
- Keep the drill as straight as possible. A crooked pilot hole can make the extractor less effective.
Step 3: Using the Screw Extractor
Screw extractors have a tapered, reverse-threaded flute. When you insert and turn them, they bite into the metal of the broken screw and, with luck, unscrew it.
- Select the Right Extractor: Choose an extractor that fits snugly into the pilot hole you drilled. The kit usually provides a range of sizes.
- Insert the Extractor: Place the tip of the extractor into the pilot hole.
- Engage the Extractor:
- For manual extractors (often T-handled or square-headed), use a tap wrench or adjustable wrench to slowly and steadily turn the extractor counter-clockwise.
- For drill-compatible extractors, attach them to your drill. Ensure the drill is set to reverse (counter-clockwise) and a slow speed.
- Extract the Screw: Apply firm, steady pressure. As you turn, the extractor should bite into the screw. Continue turning slowly and carefully. If the extractor starts to slip, you may need to try a slightly larger pilot hole or a different size extractor. The goal is for the extractor to grab the screw and turn it out.
Important Considerations When Drilling a Hole in a Screw:
- Drill Material: For harder screws, especially those in metal, you might need cobalt or titanium-coated drill bits. Regular HSS (High-Speed Steel) bits can work for softer materials like wood.
- Lubrication: For drilling into metal, using a cutting fluid or oil can help keep the drill bit cool and prevent it from dulling.
- Left Hand Drill Bits: In some cases, using left hand drill bits can be very effective. These bits spin counter-clockwise. As you drill into the screw, the friction and the spinning action of a left-hand drill bit can sometimes catch the broken screw and back it out on its own, especially if you’ve drilled deep enough. This can be a fantastic way to extract a drilling out seized screw.
What if the Extractor Breaks?
This is a common fear. If an extractor breaks off inside the screw, it’s a much harder problem to solve because the extractor is typically made of hardened steel and is very difficult to drill through.
- Prevention is Key: Ensure you’re using the correct size pilot hole and extractor. Don’t force it if it feels like it’s not biting.
- If it happens: You might need to try grinding the top flat, using a carbide burr, or even resort to more aggressive methods like EDM (Electrical Discharge Machining) if the part is valuable. For most DIY situations, it’s best to avoid this scenario by being methodical.
Method 2: Using Left-Hand Drill Bits
As mentioned, left hand drill bits can be a clever alternative or a precursor to using an extractor.
The Advantage of Left-Handed Rotation
The primary benefit of left hand drill bits is their ability to potentially remove the screw during the drilling process. As the bit spins counter-clockwise (the same direction you’d turn to loosen a screw), it can grip the broken screw and unscrew it as you drill.
Steps for Using Left-Hand Drill Bits
- Preparation: Just like with the extractor method, clean the area, apply penetrating oil, and use a center punch to mark the center of the broken screw.
- Choose Your Bit: Select a left-hand drill bit that is slightly smaller than the diameter of the screw shank. You want it large enough to bite but small enough that it doesn’t damage the surrounding threads.
- Drill Slowly: Set your drill to a slow speed and ensure it’s set to reverse (counter-clockwise) rotation.
- Apply Steady Pressure: Begin drilling into the center of the broken screw. Apply firm but steady pressure.
- Watch and Listen: As you drill, pay attention to any signs of the screw beginning to turn. If the bit bites into the screw and starts backing it out, continue slowly and steadily. If it just drills without any turning action, you might need a slightly larger bit or you’ll need to switch to a screw extractor.
- Depth: Drill deep enough to get a good bite on the screw, but avoid drilling all the way through the workpiece if possible, unless that’s part of your plan.
This method is particularly effective for drilling out seized screw situations where the screw is tightly held in place.
Method 3: The “Drill and Tap” or “Drill and Re-thread” Approach
If the above methods fail, or if the original screw hole is damaged, you might need to drill out the screw completely and then repair the stripped screw hole or create a new one.
Step 1: Drilling Out the Entire Screw
This is a more destructive method, aiming to remove all traces of the broken screw.
- Center Punch: Accurately mark the center of the broken screw.
- Choose Drill Bit Size: Select a drill bit that is the same diameter as the screw shank, or slightly larger, depending on your goal. The goal here is to obliterate the screw material.
- Drill Carefully: Set your drill to forward (clockwise) rotation and a slow to medium speed. Drill straight down the center of the screw. As you drill, you will be removing the screw material.
- Progression: You might need to step up to progressively larger drill bits to completely remove the screw material. Be very careful not to enlarge the original screw hole in the workpiece excessively. The aim is to drill out the screw, not out of the hole it was in.
- Clean Out Debris: Once the screw material is gone, use a pick or a small screwdriver to clear out any remaining metal shavings or debris from the hole.
What If You Drill Too Big?
If you accidentally drill the hole too large, you’ll need to repair it.
- Thread Repair Inserts: For metal, you can use thread repair inserts (like Helicoils or similar products). These are small coils that you thread into a slightly larger hole, and then they provide new, strong threads that are the original size of the screw.
- Epoxy and Dowels: For wood, you can fill the hole with wood epoxy or wood filler and then drill a new pilot hole once it’s cured. Alternatively, you can glue a wooden dowel into the oversized hole and then drill a new pilot hole into the dowel.
Step 2: Re-tapping the Hole
After drilling out the screw, you’ll likely need to create new threads in the hole.
- Select a Tap: Choose a tap that matches the size and thread pitch of the original screw. Taps are cutting tools used to create internal threads.
- Use a Tap Wrench: Secure the tap in a tap wrench.
- Lubricate: Apply cutting fluid or oil to the tap and the hole.
- Tap the Hole:
- Start the tap straight in the hole.
- Turn the tap wrench clockwise, applying gentle pressure.
- After a half to full turn, back the tap out a quarter turn to break the chip. This prevents the tap from binding and breaking.
- Continue this process until you’ve tapped the full depth of the hole.
- Clean: Remove the tap and clean out the hole.
This method is particularly useful when you need to drill out a stripped bolt that is stuck in a threaded housing.
Method 4: The “Patience and Force” Method (When Something Protrudes)
If a portion of the broken screw is sticking out above the surface, you have a few more options.
Gripping and Turning
- Locking Pliers (Vise Grips): If there’s enough of the screw head or shank exposed, grip it tightly with a pair of locking pliers. Slowly and steadily try to turn the screw counter-clockwise. Wiggle it gently back and forth if it’s very tight.
- Hammer and Chisel: For very stubborn cases where pliers might slip, you can use a sharp chisel and hammer. Place the chisel at an angle against the edge of the broken screw, aiming to turn it counter-clockwise. Tap the chisel with the hammer gently but firmly. Be careful not to damage the surrounding material.
Drilling Around the Screw (More Advanced)
This is a last resort if the screw is truly stuck and you can’t use extractors. It’s often used when you need to drill out a stripped bolt without damaging the surrounding bolt threads if the bolt is part of a larger assembly.
- Precise Drilling: This requires a very steady hand and good control. The idea is to drill a series of small holes around the periphery of the broken screw, essentially weakening it and breaking it apart.
- Small Drill Bits: Use very small drill bits, and drill around the edges of the screw, trying to stay within the diameter of the screw itself.
- Pecking Action: Use a “pecking” motion (drill for a second, pull out, repeat) to clear metal chips and keep the bit cool.
- Prying: Once you’ve weakened the screw, you might be able to use a small pry bar or awl to break it up and remove the pieces.
Special Considerations for Different Materials
The material you’re drilling into will affect your approach.
Wood
- Softer Material: Wood is generally easier to drill than metal.
- Pilot Holes: Pilot holes for screws in wood are often smaller than in metal.
- Damage: It’s easier to accidentally enlarge a hole in wood, so be cautious. If you do, repairing a stripped screw hole in wood is relatively straightforward with wood filler, dowels, or specialized wood screw repair kits.
Metal
- Harder Material: Metal requires sharper drill bits and slower speeds.
- Lubrication: Cutting fluid or oil is highly recommended to prevent overheating and extend the life of your drill bits.
- Thread Damage: Damaging threads in metal is more problematic. Thread repair inserts or re-tapping are often necessary.
- Drill Out Stripped Bolt: When dealing with bolts, especially in automotive or machinery applications, ensuring you don’t damage the mating threads is crucial.
Frequently Asked Questions (FAQ)
Q1: What is the best drill bit size for a broken screw?
A1: The best drill bit size for a screw depends on the size of the broken screw and the type of extractor you’re using. Generally, you’ll use a bit that is smaller than the screw’s shank diameter. Screw extractor kits usually provide guidance on pilot hole sizes for their specific extractors. Always consult the kit’s instructions if available.
Q2: Can I use a regular drill bit to remove a stripped screw?
A2: While a regular drill bit won’t directly remove a stripped screw, it’s essential for creating a pilot hole if you plan to use a screw extractor. If the screw head is stripped but the screw itself is intact and the head is accessible, you might try gripping it with locking pliers. For a broken screw, a regular drill bit is used to prepare for extraction.
Q3: How do I prevent a screw from breaking in the first place?
A3: To prevent screws from breaking:
* Use the correct size and type of screwdriver for the screw head.
* Apply firm, consistent pressure on the screwdriver to prevent slippage.
* Avoid over-tightening screws, especially in softer materials.
* Use lubrication when screwing into dense materials or metal.
* Ensure screws are not rusted or corroded before attempting to remove them.
Q4: What are left-hand drill bits used for?
A4: Left hand drill bits spin in a counter-clockwise direction. They are useful for drilling into tough materials and can sometimes be used to extract broken screws. As they spin counter-clockwise, they might catch the broken screw and unscrew it during the drilling process, effectively combining drilling and extraction.
Q5: How do I repair a stripped screw hole?
A5: To repair a stripped screw hole:
* In Wood: Fill the hole with wood filler or epoxy, let it cure, then drill a new pilot hole. Alternatively, glue a wooden dowel into the hole and drill a new pilot hole into the dowel.
* In Metal: Use a thread repair kit (like Helicoils), which involves drilling out the damaged hole to a specific size, tapping it for the insert, and then installing the insert to provide new, correct-sized threads.
Q6: Is it better to drill or use an extractor?
A6: It’s generally better to try an extractor first if possible. Drilling out the entire screw is more destructive and requires more precision to avoid damaging the surrounding material or threads. An extractor is designed to grip and remove the screw without excessive damage. However, if the screw is severely broken or rusted, drilling might be the only option.
Conclusion
Dealing with a broken screw can be frustrating, but by approaching the task with the right tools, preparation, and techniques, you can successfully extract a broken screw. Whether you’re using a dedicated screw extractor kit, left hand drill bits, or a more involved drilling and tapping method, patience and precision are your best allies. Remember to always prioritize safety by wearing eye protection. With a little practice, you’ll be able to tackle these common repair jobs with confidence.