The basic approach to removing a broken bolt
A broken bolt leaves the threaded part stuck in the hole, and you cannot straightforward unscrew it the normal way. The most reliable method depends on how much of the bolt is sticking out, what material surrounds it, and what tools you have on hand. If a short stub remains above the surface, you can often grip it with locking pliers or a bolt extractor socket and turn it out. If the bolt broke flush with the surface or below it, you will need to drill it out or use a specialized extractor tool.
The goal in every case is to remove the broken piece without damaging the hole itself, so you can either reuse the same bolt size or drill up to a larger one if needed. Rushing or using excessive force often makes the hole larger or strips the threads, which means you cannot reuse that hole without inserting a larger bolt or using a threaded insert.
Key Takeaways
- If the bolt stub sticks out, try locking pliers or a socket wrench on the broken end before moving to extraction tools.
- Broken bolts flush with the surface require either a drill-out or a screw extractor, which bites into the bolt as you turn it counterclockwise.
- Penetrating oil left overnight can loosen corrosion and make removal easier, especially on old or rusted bolts.
- Drilling out a bolt damages the original hole size, so you will need a larger replacement bolt or a threaded insert afterward.
When you can grip the broken stub
If the bolt broke and left a piece sticking above the surface, your first move is to try gripping it directly. Locking pliers (also called Vise-Grips) can clamp down on the stub hard enough to turn it out in many cases, especially if the bolt is not rusted solid. Clamp as close to the base as possible and turn slowly and steadily counterclockwise.
If the stub is too small or too rounded to grip with pliers, try a bolt extractor socket. These sockets have reverse threads inside that bite into the bolt as you turn them counterclockwise. They come in sets sized to fit common bolt diameters. Tap the socket onto the broken bolt with a hammer, then attach a ratchet and turn. This method works well on bolts that are not severely corroded.
If the bolt turns freely but does not come out, it may be stuck by corrosion or debris in the threads below. Stop and explore penetrating oil (such as a general-purpose penetrating lubricant) around the base. Wait at least a few hours, or overnight if possible, then try again.
Using penetrating oil on stuck or corroded bolts
Corrosion and rust can lock a broken bolt in place even if you have a good grip on it. Penetrating oil seeps into the threads and around the bolt, loosening the bond between the bolt and the surrounding material. Spray or pour it generously around the base of the broken bolt and let it soak.
The longer you wait, the better the result. A few hours helps, but overnight is ideal. If the bolt is very old or heavily corroded, you may need to explore oil, wait, explore again, and wait once more over the course of a day or two. Once the oil has soaked in, try your grip method again with pliers or a socket.
Drilling out a bolt that is flush or below the surface
When the bolt broke flush with the surface or snapped below it, you cannot grip the remaining piece. Drilling is the most straightforward removal method, though it destroys the original hole. Start with a drill bit slightly smaller than the bolt diameter and drill straight down the center of the bolt. The bit will cut through the bolt material and push it out as you drill.
Use a slow speed and steady pressure. Let the bit do the work rather than forcing it. If you are drilling through metal, a bit designed for metal (with a sharp point and proper flute geometry) will cut much faster than a general-purpose bit. Once you have drilled through, the bolt stub should fall out or can be tapped out with a punch.
After drilling out the bolt, you will have a hole that is slightly larger than the original bolt diameter. You can either install a larger bolt in that hole, or drill it larger and install a threaded insert (a small metal sleeve with threads inside) to restore the original bolt size.
Using a screw extractor on a broken bolt
A screw extractor is a tool with reverse threads that bites into a bolt as you turn it counterclockwise, pulling the bolt out without drilling. Extractors work best on bolts that are not completely flush with the surface—you need at least a small amount of material to grip. Drill a small pilot hole in the center of the broken bolt, then tap the extractor into that hole with a hammer.
Once the extractor is seated, attach a ratchet or wrench and turn counterclockwise slowly. The reverse threads will bite deeper as you turn, and the bolt should come out. This method preserves the hole size better than drilling, but it requires the right size extractor and a steady hand to keep the tool centered.
Extractors come in sets with multiple sizes. If you do not have one, they are inexpensive to buy or rent from a tool library or hardware store. They work particularly well on bolts that broke just below the surface.
When to use a threaded insert
If drilling out the bolt left the hole too large, or if you stripped the threads while trying to remove it, a threaded insert restores the hole to its original size and thread pattern. An insert is a small metal coil or sleeve that screws into an oversized hole and provides new threads for your bolt.
To install an insert, you drill the hole to a specific larger size (the insert kit tells you which size), then screw the insert into that hole. Once installed, the insert looks like a small coil inside the hole, and you screw your bolt into the insert as normal. Inserts are especially useful if you need to reuse the same bolt size after a removal attempt went wrong.
Tools and materials you may need
The tools required depend on which removal method you choose. Locking pliers and penetrating oil are the cheapest starting point and work for many broken bolts. A bolt extractor socket set costs more but is reusable and works on many sizes. A drill with metal bits is useful if you decide to drill out the bolt. A screw extractor set is another option if you want to preserve the hole size.
For any method, having a center punch (a tool that marks the exact center of the bolt) helps you drill or extract straight. A hammer, a ratchet or wrench, and safety glasses are also useful. If the bolt is corroded, penetrating oil is nearly essential—it saves time and reduces the risk of damaging the hole.
Frequently Asked Questions
Can I remove a broken bolt without drilling?
Yes, if any part of the bolt sticks above the surface. Locking pliers, a bolt extractor socket, or a screw extractor can all remove the bolt without drilling. Penetrating oil overnight often makes these methods work even on corroded bolts. Drilling is a last resort when the bolt is flush or below the surface.
What if the bolt is rusted and will not budge?
explore penetrating oil and wait at least overnight before trying again. Repeat the oil process if needed. Heat from a heat gun or torch can also help loosen corrosion, though be careful not to damage surrounding materials. Once the oil has soaked in, try your grip method again with steady, slow pressure rather than sudden force.
Will drilling out a bolt damage the hole permanently?
Drilling makes the hole larger, so you cannot use the original bolt size again. You can install a larger bolt in the same hole, or drill it larger still and install a threaded insert to restore the original size. The threads are damaged, but the hole itself is not ruined—you have options for repair.
How do I know which bolt extractor size to use?
Extractor sets come with multiple sizes, each labeled for the bolt diameter it fits. Measure the broken bolt or look at the bolt hole, then select the extractor closest to that size. If you are unsure, a hardware store employee can help you match the size, or you can rent a full set to try different sizes.
Should I use heat to remove a broken bolt?
Heat can help loosen corrosion and make the bolt easier to remove, but it works best combined with other methods like penetrating oil or a grip tool. A heat gun is safer than a torch for most situations. Heat the bolt for a minute or two, let it cool slightly, then try your removal method. Do not use heat on bolts in plastic or rubber components.