How To Drill Out A Bolt Safely & Easily

Can I drill out a bolt? Yes, you can drill out a bolt. This guide will show you how to safely and easily remove a stubborn bolt.

When a bolt refuses to budge, whether it’s rusted, cross-threaded, or has a damaged head, drilling it out is often the best solution. This process might sound daunting, but with the right tools and techniques, it’s quite manageable. This article will walk you through everything you need to know to tackle a stuck bolt, remove a stripped bolt, drill a broken bolt, and even how to unbolt a stripped screw.

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Why You Might Need to Drill Out a Bolt

There are several common scenarios where drilling out a bolt becomes necessary:

• Rusted Bolts: Over time, metal bolts can rust, fusing them to the material they’re holding. This rust can make them impossible to turn.
• Stripped Bolt Heads: If the head of a bolt is damaged (stripped or rounded off), a wrench or socket can no longer grip it.
• Broken Bolts: Sometimes, a bolt can break off at the shaft, leaving a portion embedded in the material.
• Cross-Threaded Bolts: When a bolt is screwed in at an angle, it can damage the threads of both the bolt and the hole, making it very difficult to remove.
• Seized Fasteners: Similar to rusted bolts, other environmental factors or extreme heat can cause a fastener to seize, preventing its removal.

Essential Tools for Bolt Extraction

Before you start drilling, gather the necessary tools. Having the right equipment makes the job safer and more effective.

Must-Have Tools:

• Safety Glasses: Always protect your eyes from flying debris.
• Drill: A variable-speed drill is ideal. A corded drill offers more consistent power than a cordless one.
• Drill Bits: You’ll need a set of metal drill bits. Start with smaller sizes and gradually increase.
• Center Punch: This tool marks the center of the bolt, preventing the drill bit from wandering.
• Hammer: Used with the center punch.
• Penetrating Oil: Helps loosen rust and corrosion. Let it soak in.
• Wrench or Pliers: For initial attempts to loosen the bolt.
• Bolt Extractor Kit: Highly recommended for removing stripped or broken bolts.
• Work Gloves: For better grip and protection.
• Wire Brush: To clean away rust and debris.
• Cutting Oil or Lubricant: To keep the drill bit cool and improve cutting.

Optional but Helpful Tools:

• Vice Grips: For gripping stubborn bolts.
• Dremel or Rotary Tool: Can be useful for cutting a new slot in a stripped bolt head.
• Tap and Die Set: For cleaning or re-threading the bolt hole after extraction.
• Magnet: To pick up metal shavings.

Preparing for the Drilling Process

Proper preparation is key to a successful and safe bolt extraction.

Step 1: Assess the Situation

Look closely at the bolt. Is the head intact but just stuck? Is it stripped? Is it broken off below the surface? Your approach will depend on this assessment.

Step 2: Apply Penetrating Oil

Generously spray penetrating oil onto the bolt. Allow it to soak for at least 15-30 minutes, or even longer for severely rusted bolts. You can reapply it periodically. Tapping the bolt lightly with a hammer can help the oil penetrate deeper.

Step 3: Clean the Area

Use a wire brush to clean any rust or debris from around the bolt head and threads. This gives you a clearer view and can help tools grip better.

Techniques for Removing Stubborn Bolts

Let’s dive into the actual methods.

Technique 1: The Standard Drilling Method (for when the head is mostly intact but stuck)

This method involves drilling through the center of the bolt.

Choosing the Right Drill Bit Size for Bolt

The goal is to drill out the bolt’s shaft without damaging the surrounding threads.

• Start Small: Begin with a drill bit that is significantly smaller than the bolt’s diameter. This creates a pilot hole.
• Gradual Increase: If the bolt doesn’t loosen, you can gradually increase the drill bit size.
• Final Size: The final drill bit size should be close to the minor diameter of the bolt’s threads (the diameter at the bottom of the threads). You want to remove the bolt material without touching the female threads.

Drilling Through a Bolt: The Process

1. Center Punching: Place the tip of your center punch directly in the middle of the bolt head. Give it a sharp tap with a hammer to create a small indentation. This is crucial to prevent the drill bit from wandering.
2. Start Drilling: Place the tip of your chosen drill bit into the center punch mark.
3. Low Speed, Steady Pressure: Begin drilling at a slow speed with consistent, steady pressure. Let the drill do the work.
4. Use Cutting Oil: Apply cutting oil or lubricant to the drill bit as you drill. This cools the bit, prevents it from overheating, and helps it cut more smoothly.
5. Drill Straight: Aim to drill perfectly straight down the center of the bolt. If the bolt is long, you may need to drill most of the way through.
6. Remove Remaining Material: Once you’ve drilled through, you might be able to break off the remaining bolt shank or use a pick to pull out the drilled-out material. Sometimes, the bolt will simply fall out or can be tapped out.

Technique 2: Using a Bolt Extractor Kit (for stripped or broken bolts)

Bolt extractor kits, also known as screw extractors or easy-outs, are specifically designed for this purpose.

How a Bolt Extractor Kit Works

These kits contain hardened steel bits with reverse threads. You drill a pilot hole into the damaged bolt, then thread the extractor into the hole. As you turn the extractor counter-clockwise (using a tap wrench or a drill on its reverse setting), its reverse threads bite into the bolt, and hopefully, unscrew it.

Steps for Using a Bolt Extractor Kit:

1. Prepare the Bolt: Ensure the bolt head is relatively flat or that you’ve drilled a clean hole into a broken bolt.
2. Drill a Pilot Hole: This is critical. The size of the pilot hole depends on the extractor size you’ll use. The kit instructions will specify the correct drill bit size.
   • Pilot Hole for Bolt Extraction: The hole should be drilled straight and centered into the bolt.
3. Insert the Extractor: Select the appropriate size extractor from your kit. Place it into the pilot hole.
4. Engage the Extractor: Using a tap wrench or a drill set to reverse, slowly and firmly turn the extractor counter-clockwise.
5. Apply Steady Pressure: As you turn, the extractor’s reverse threads will bite into the bolt material. Continue applying steady pressure.
6. If it Doesn’t Budge: If the bolt doesn’t turn, you might need to:
   • Try a slightly larger extractor.
   • Reapply penetrating oil.
   • Gently tap the end of the extractor to help it seat deeper.
   • Consider heating the area around the bolt (use caution!).

Technique 3: Cutting a Bolt Head Off

If the bolt head is completely mangled or you can’t get a good grip or drill center, you might need to cut the head off.

Methods for Cutting a Bolt Head:

• Angle Grinder: For larger bolts, an angle grinder with a cutting disc can quickly slice off the bolt head. Ensure you have a stable work surface and wear appropriate safety gear, including a face shield.
• Hacksaw: A good old-fashioned hacksaw can work for smaller bolts, though it’s more time-consuming.
• Rotary Tool (Dremel): With a cutting wheel, a rotary tool can be effective for precise cutting on smaller bolts.

After Cutting the Head:

Once the head is removed, the item held by the bolt should be free. You can then often grip the remaining bolt shank with pliers or vice grips to unscrew it. If the shank is still seized, you might need to resort to drilling it out using one of the methods above.

Technique 4: Dealing with a Stripped Screw

The process of how to unbolt a stripped screw is similar to removing a stripped bolt.

Methods for Stripped Screws:

• Rubber Band: Place a wide rubber band over the stripped screw head. Then, insert your screwdriver firmly and try to turn. The rubber can provide extra grip.
• Screw Extractor Bits: These look like drill bits but have reverse threads. You drill a small hole into the screw head, then flip the bit to its extractor end and use your drill in reverse to back out the screw.
• Cutting a New Slot: Use a Dremel or a hacksaw to cut a new, deeper slot into the screw head. This allows you to use a flathead screwdriver.
• Pliers/Vice Grips: If enough of the screw head is exposed, try gripping it tightly with locking pliers and turning.

When to Use Which Method: A Quick Guide

Problem Scenario	Best Method	Notes
Bolt is just stuck/tight	Standard Drilling (small pilot hole)	Use penetrating oil first. Goal is to weaken the bond.
Bolt head is stripped	Bolt Extractor Kit	Requires drilling a pilot hole for the extractor.
Bolt is broken off	Bolt Extractor Kit (if flush or proud)	Drill precisely into the broken shank.
Bolt head is mangled	Cutting the bolt head	Allows you to remove the part, then deal with the shank.
Stripped screw	Screw Extractor Bits, Rubber Band, Dremel	Choose based on screw size and how mangled the head is.
Seized fastener	Standard Drilling or Bolt Extractor Kit	Similar to stuck or rusted bolts, focus on controlled material removal.

Advanced Tips and Tricks

• Heat: Sometimes, applying heat to the area around the bolt can help expand the surrounding material, breaking the bond. Use a heat gun or a propane torch, but be extremely careful not to damage surrounding components or cause a fire.
• Impact Driver: For bolts that are just stuck, an impact driver can sometimes shock them loose.
• Left-Handed Drill Bits: These bits are designed to drill in reverse. As they drill, they might catch the bolt and unscrew it.
• Left-Handed Extractors: Some bolt extractor kits include left-handed drill bits specifically for this purpose.

Safety First!

Drilling metal can be dangerous. Always prioritize safety:

• Wear Safety Glasses: This is non-negotiable. Metal shavings are sharp.
• Secure Your Work: Ensure the piece you are working on is stable and won’t move during drilling.
• Use the Right Tools: Don’t force tools or use them for purposes they weren’t designed for.
• Be Aware of Surroundings: Ensure no flammable materials are nearby, especially if using heat.
• Go Slow: Patience is key. Rushing increases the risk of accidents or damaging the workpiece.

Frequently Asked Questions (FAQ)

What is the best way to remove a seized bolt?

The best way to remove a seized bolt often involves a combination of penetrating oil, patience, and then either careful drilling or the use of a bolt extractor kit. Start with the least invasive methods and escalate if necessary.

Can I drill out a bolt without damaging the threads?

Yes, with careful drilling and the correct drill bit size, you can drill out a bolt without damaging the surrounding threads. The key is to drill precisely in the center and use a bit size that matches the bolt’s minor diameter.

How do I drill out a broken bolt if it’s below the surface?

If a bolt breaks off below the surface, you’ll need to drill a pilot hole into the center of the broken shank. Then, use a bolt extractor sized for that pilot hole. A center punch is essential to ensure your drill bit starts in the middle.

What if the bolt extractor breaks off in the bolt?

This is a frustrating but not uncommon problem. If an extractor breaks off, it’s usually because it was made of hardened steel. You’ll likely need to drill out the broken extractor itself, which is more difficult. Sometimes, a carbide-tipped drill bit is needed. Alternatively, you might need to use more aggressive methods like carefully chipping away at the bolt and extractor or even using a welding torch to heat and break the bond.

How do I clean up the bolt hole after drilling?

After successfully drilling out a bolt, you may need to clean up the threads in the hole. A tap of the correct size can be used to chase the threads, removing any remaining metal fragments and restoring them. If the threads are too damaged, you might need to drill the hole out larger and use a thread insert or a larger bolt.

By following these steps and prioritizing safety, you can confidently tackle the task of drilling out stubborn bolts and getting your project back on track.