Can you drill out a bolt? Yes, you can drill out a bolt if it’s stuck or broken. This guide will show you how to do it safely and easily. We’ll cover everything you need, from choosing the right tools to the final steps of cleaning up.
Image Source: i.ytimg.com
Why Drill Out a Bolt?
Sometimes, a bolt just won’t budge. It might be rusted solid, its head might have stripped, or it might have broken off during removal. In these situations, extracting broken bolts becomes necessary. Trying to force a stubborn bolt can damage the surrounding material, making the problem worse. Drilling out the bolt is often the best way to remove it without causing further harm. This technique is crucial for removing seized fasteners and drilling out stubborn bolts.
Gathering Your Tools and Materials
Before you start drilling, ensure you have all the necessary tools. Having the right equipment makes the job much simpler and safer.
Essential Tools:
- Drill: A powerful corded drill is usually best for its consistent power. A good cordless drill can also work, but make sure it has enough torque.
- Drill Bits: You’ll need a set of high-quality drill bits.
- HSS (High-Speed Steel) drill bits: Good for general use.
- Cobalt drill bits: Better for drilling into harder metals like stainless steel.
- Titanium-coated drill bits: Offer increased hardness and heat resistance.
- Left-handed drill bits: These are particularly useful because they can sometimes catch the bolt and unscrew it as you drill.
- Center Punch: Used to create a small indentation for the drill bit to start in, preventing it from wandering.
- Hammer: To strike the center punch.
- Safety Glasses: Absolutely crucial for eye protection from flying metal fragments.
- Gloves: To protect your hands.
- Cutting Fluid or Lubricant: Helps keep the drill bit cool and reduces friction, making drilling easier and prolonging the life of your drill bits.
- Wrench or Pliers (optional): If there’s a small portion of the bolt head sticking out, you might be able to grip it with these.
- Bolt Extractor Kit: A collection of specialized tools designed for removing broken bolts. These often include drill bits and reverse-threaded extractors.
Optional but Helpful Tools:
- Drill Guide or Drill Press: For ensuring straight and precise drilling. This is vital for drilling precision.
- Vise or Clamps: To secure the workpiece if it’s not already fixed.
- Grinder or File: To clean up the bolt head surface if it’s uneven.
- Penetrating Oil: To help loosen rust and corrosion before you start.
- Shop Vacuum: For cleaning up metal shavings.
Step-by-Step Guide to Drilling Out a Bolt
This detailed guide will walk you through each step to ensure a successful bolt extraction.
Step 1: Prepare the Area
First, assess the situation. Is the bolt head intact, or is it broken off? Is it flush with the surface, or is a portion protruding?
- Clean the Area: Remove any dirt, grease, or debris from around the bolt. This will give you a clear view and prevent contamination.
- Apply Penetrating Oil: If the bolt is seized due to rust or corrosion, apply a good penetrating oil. Let it soak for at least 15-30 minutes, or even overnight for severely rusted bolts. Tapping the bolt head gently with a hammer can help the oil penetrate deeper.
Step 2: Mark the Center
Drilling precision starts with a clear target. If the bolt head is intact but stripped, or if it’s broken off flush, you need to mark the exact center.
- Use a Center Punch: Place the tip of the center punch on the very center of the bolt head or the broken shaft.
- Strike with a Hammer: Give the center punch a sharp tap with a hammer. This creates a small divot. This divot will guide the drill bit and prevent it from slipping off-center. If the bolt is broken off flush or below the surface, you might need to grind a small, flat area first for the punch to sit on.
Step 3: Select the Right Drill Bit and Speed
Choosing the correct drill bit and setting your drill speed are critical.
- Drill Bit Size: You’ll typically start with a small drill bit and gradually increase the size. The goal is to drill a hole that is just large enough to accommodate a bolt extractor, or large enough to weaken the bolt so the remaining threads can be picked out.
- Drill Bit Material: For most common metals, HSS bits are fine. For harder metals, opt for cobalt or titanium-coated bits. If you have a bolt extractor kit, it will usually come with specific drill bit sizes recommended for its extractors.
- Drill Speed: Use a slow to medium speed. High speeds can overheat the drill bit, causing it to dull or break, and can also lead to inaccurate drilling.
Step 4: Pilot Hole Drilling
Starting with a small hole is key to controlled drilling. This is often referred to as pilot hole drilling.
- Choose a Small Bit: Select a drill bit that is significantly smaller than the bolt’s diameter.
- Drill Slowly and Steadily: Place the tip of the drill bit into the divot you created with the center punch.
- Apply Firm, Consistent Pressure: Let the drill do the work. Don’t force it.
- Use Lubricant: Apply cutting fluid or lubricant to the drill bit and the drilling area periodically. This is essential for smooth drilling and bit longevity.
Step 5: Gradually Increase Drill Bit Size
Once your pilot hole is established, you’ll progressively move to larger bits.
- Follow a Pattern: If the bolt head is stripped or broken off, you might drill through the center of the bolt. For a broken bolt, you’re drilling into the remaining shaft.
- Drill Straight: This is where using a drill guide or a drill press becomes highly beneficial. A guide ensures the drill bit stays perpendicular to the surface, preventing it from damaging the threads in the surrounding material. If you don’t have a guide, try to hold the drill as steady and straight as possible.
- Drill to the Correct Depth: If you are using a bolt extractor, drill to the depth recommended by the kit. If you are aiming to collapse the bolt threads, drill most of the way through the bolt but be careful not to drill into the surrounding material.
Step 6: Using a Bolt Extractor (When Necessary)
If your pilot hole is drilled to the correct size for an extractor, it’s time to use one.
- Select the Correct Extractor: Most bolt extractor kits have numbered or sized extractors. Choose one that matches the size of the hole you’ve drilled.
- Insert the Extractor: Gently tap the extractor into the drilled hole with a hammer. The extractor has reverse threads, designed to bite into the metal of the bolt.
- Turn the Extractor: Use a wrench or tap handle to slowly turn the extractor counter-clockwise. As you turn, the extractor should bite into the bolt and begin to unscrew it.
- Be Patient: If the bolt starts to turn but is still tight, apply more lubricant and continue turning slowly. If the extractor spins without gripping, you may need to tap it in a little harder or use a slightly larger extractor.
Step 7: Using Left-Handed Drill Bits
Left-handed drill bits can be a fantastic tool for this job.
- How They Work: When drilling counter-clockwise (the direction you’d normally loosen a bolt), the left-handed bit can sometimes bite into the bolt material and unscrew it on its own.
- The Process: Start with a small left-handed bit and set your drill to reverse (counter-clockwise). As you drill, if the bolt starts to turn, you’ve successfully removed it. If it doesn’t turn, you can continue drilling to prepare for an extractor.
Step 8: Drilling Out the Entire Bolt
If extractors fail or if the bolt is completely disintegrated, you may need to drill out the entire bolt.
- Drill Close to the Threads: Use a drill bit that is slightly smaller than the bolt’s minor diameter (the diameter at the bottom of the threads). This is where extreme drilling precision is needed.
- Drill Down the Center: Carefully drill through the bolt, trying to stay perfectly centered. You want to drill away the bolt material without touching the threads of the hole it’s in.
- Remove Remaining Threads: Once most of the bolt material is drilled out, the remaining thread fragments can often be carefully picked out with a pick or a small scribe.
- Re-tap the Hole (If Necessary): After removing all the bolt fragments, the threads in the hole might be damaged. You may need to use a tap to clean up the threads or re-tap the hole to a slightly larger size if the original threads are too damaged.
Step 9: Final Cleanup
Once the bolt is out, clean the area thoroughly.
- Remove Debris: Use a brush, compressed air, or a shop vacuum to remove all metal shavings and debris.
- Inspect the Threads: Check the threads in the hole for any damage. If necessary, use a tap to chase the threads and restore them.
Common Challenges and Solutions
Even with the best preparation, you might encounter some issues.
Stripped Bolt Heads
- Solution: Try using a rubber band between the screwdriver and the bolt head for extra grip. If that doesn’t work, use locking pliers to grip the head. If the head is completely rounded, you may need to grind a slot into it for a flathead screwdriver or proceed to drilling.
Broken Bolt Head
- Solution: If a small portion is protruding, try gripping it with locking pliers. If it’s flush or recessed, a center punch and drilling are your primary options.
Rusted or Seized Bolts
- Solution: Generous application of penetrating oil and allowing it to soak are crucial. Gentle heating with a torch (if safe for the surrounding material) can also help expand the material and break the rust bond.
Drill Bit Walking
- Solution: This is why a center punch is essential. A drill guide or drill press provides the best solution for preventing this.
Overheating Drill Bits
- Solution: Use cutting fluid or lubricant consistently. Drill in short bursts, allowing the bit to cool. Ensure your drill is set to an appropriate speed – slower is often better.
When to Call a Professional
While drilling out a bolt is a common DIY task, there are times when it’s best to seek professional help:
- Critical Components: If the bolt is in a critical component where failure could be catastrophic (e.g., engine parts, structural elements), it’s safer to let experienced professionals handle it.
- Delicate Materials: If the surrounding material is fragile, expensive, or difficult to repair (e.g., aluminum castings, antique machinery), a mistake can be costly.
- Lack of Confidence or Tools: If you don’t feel comfortable with the process or lack the necessary specialized tools like a drill press, a professional mechanic or machine shop can perform the task efficiently and accurately.
Frequently Asked Questions (FAQ)
What is the best drill bit to use for removing a broken bolt?
High-speed steel (HSS), cobalt, or titanium-coated drill bits are recommended. Left-handed drill bits are particularly useful as they can sometimes unscrew the bolt as you drill.
How do I prevent the drill bit from wandering when drilling a bolt?
Using a center punch to create a divot is the first step. For maximum accuracy, using a drill guide or a drill press is highly recommended.
Can I drill out a bolt without damaging the threads?
Yes, with careful drilling precision. Start with a small pilot hole and gradually increase the bit size. Drill directly down the center of the bolt. Avoid drilling into the existing threads in the workpiece.
What is a bolt extractor kit?
A bolt extractor kit is a set of specialized fastener removal tools designed to remove broken or seized bolts. They typically include drill bits and reverse-threaded extractors that bite into the bolt and help turn it out.
How much force should I use when drilling?
Apply steady, consistent pressure. Let the drill bit do the cutting. Forcing the drill can overheat the bit, break it, or cause the drill to wander, damaging the surrounding material.
What if the bolt extractor breaks off in the bolt?
This is a difficult situation. If an extractor breaks, it’s usually hardened steel and very difficult to drill. You might need to try to grind it out or use specialized EDM (Electrical Discharge Machining) services. It’s best to avoid this by using the correct size extractor and turning it slowly.
How deep do I need to drill for a bolt extractor?
Follow the manufacturer’s recommendations for your specific bolt extractor kit. Generally, you drill deep enough for the extractor to get a good grip on the bolt’s material.
What are left-handed drill bits good for?
Left-handed drill bits are beneficial for removing seized fasteners. When used in reverse, they can sometimes catch the bolt and unscrew it as you drill, making extraction easier.
My bolt is seized. What can I do before drilling?
Apply a penetrating oil and let it soak for an extended period (hours or even overnight). Gently tapping the bolt head can help the oil penetrate. Sometimes, applying heat (if safe for the material) can also help break the bond of rust or corrosion.
How can I tell if I’m drilling straight?
If you’re not using a drill guide or press, try to keep the drill body parallel to the direction the bolt should be coming out. Looking down the drill bit from above can help you maintain alignment. Consistent speed and pressure also help.