How to Remove a Broken Bolt | Without Damaging Threads

A broken bolt can be removed by center-punching, drilling a pilot hole, then backing it out counterclockwise with a left-hand drill bit or screw extractor.

Snapping a bolt off flush with the surface is one of the most frustrating moments in any repair. The good news: knowing how to remove a broken bolt correctly saves the threads and your sanity. The key is patience—center your pilot hole accurately, let penetrating oil do its job, and escalate only when a method stops working.

Removing a Broken Bolt: Prep and Setup You Need Today

Before you grab a drill, the fastener needs cleaning and lubrication. Rust, dirt, and old thread-locker can lock a bolt in place, so use a wire brush to clean the area thoroughly. Then apply a penetrating oil like WD-40, PB Blaster, Liquid Wrench, or Kroil. Let it soak for at least 15–30 minutes—overnight is better for severely rusted bolts. Tapping the bolt lightly with a hammer helps the oil wick into the threads, and several sources recommend repeating the oil application during the soak period.

You’ll need: safety glasses, a center punch, a hammer, a drill with variable speed, a set of left-hand drill bits, screw extractors (easy-outs), and vice-grips or locking pliers if any stub protrudes. For a full rundown of the best extractor kits and techniques, see our recommended broken bolt removal tools.

How to Remove a Broken Bolt Step by Step

Once the bolt is clean and oiled, the removal procedure is straightforward if you follow these steps in order. Work slowly—rushing is the main reason people damage threads.

1. Center punch the exact middle. A dimple prevents the drill bit from wandering off-center, which is the most common mistake. Take your time—being off by even 1/16 inch can damage the threads irreparably. If the bolt face is irregular, file it flat first so the punch has a clean surface.

2. Drill a pilot hole. Start with a small bit—about 1/8 inch—and drill slowly with steady, moderate pressure to prevent the bit from skating. Use cutting oil to reduce heat and keep the bit sharp. Increase bit size gradually if needed, but never jump more than 1/16 inch at a time.

3. Switch to a left-hand drill bit. These bits cut while spinning counterclockwise, and the reverse rotation often grabs the bolt and backs it out before you even reach for an extractor. If the left-hand bit goes through and the bolt doesn’t budge, the hole is already perfectly sized for a screw extractor.

4. Insert the screw extractor. Tap it lightly into the pilot hole, then turn it counterclockwise with a tap handle or T-handle. Apply steady, increasing torque—jerking or forcing can snap the extractor, which turns a bad situation worse. Follow the guidance from This Old House’s stripped bolt removal guide, which recommends matching extractor size to the pilot hole precisely.

5. If the bolt backs out, you’re done. Chase the threads with a tap to clean any debris before reinstalling. Run the tap through by hand, not with a power tool.

What Should You Try If the Bolt Won’t Budge?

Sometimes the extractor fails or the bolt is too seized. Here are the common escalations, each with a specific use case.

If you drill the bolt out completely, use a tap of the same size and pitch to clean or restore the internal threads. In deep holes, drilling out may be the only practical option, as Dormer Pramet’s technical notes confirm. For bolts that are deeply seized, heating the metal around the bolt—not the bolt itself—can expand the surrounding material and break the corrosion seal. Let it cool naturally before trying again; rapid cooling can crack the surrounding metal.

The most important rule: do not force an extractor. If it feels like it’s about to snap, back off and switch to drilling out the bolt. Broken extractors are notoriously hard to remove and may require carbide bits or electrical discharge machining. When all else fails, a machinist or automotive shop can handle the job with specialized equipment.

FAQs

Can you remove a broken bolt without a screw extractor?

Yes. A left-hand drill bit often backs the bolt out on its own during drilling. Vice-grips work if any stub is exposed, and welding a nut onto the broken end is another extractor-free method that mechanics use regularly for seized fasteners.

How long should penetrating oil soak before removal?

Most guides recommend at least 15 to 30 minutes for light corrosion. For heavily rusted or seized bolts, letting the oil soak overnight dramatically improves success rates. Tapping the bolt after applying oil helps it penetrate deeper, and reapplying oil during the soak keeps the threads wet.

What size drill bit do you use for a broken bolt?

Start with a small pilot bit around 1/8 inch. The final drill size depends on the extractor you plan to use—extractor kits specify the matching bit sizes for each extractor. Stepping up gradually in 1/16-inch increments gives you the best control and reduces the risk of drilling off-center.