To get a broken bolt out, you should try a center punch followed by a pilot hole and a bolt extractor bit. This is a sensitive process that requires precision and special tools. Extremely corroded bolts may even require welding a nut to the bolt to provide your socket wrench with something to grip.

A broken bolt can be a frustrating roadblock. You’re eager to move forward, but you’re facing a broken bolt that just won’t budge. Maybe there is corrosion, or perhaps you got the diameter of the bolt wrong. Perhaps there is a broken screw or broken stud that is mysteriously immovable.

So, is your DIY project a bust, or is it possible to get a broken bolt out?

Luckily, you’re not the first person to encounter this problem!

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How to remove a broken bolt

When an automotive bolt is forced or overtightened, it can break slightly and become stuck. The broken bolt’s external threads no longer work properly, so it will stubbornly stick in position—unless you find a way to remove it.

To remove a broken bit, you can try a simple solution like a hammer and chisel. However, it’s more likely that you will need a more extreme tool, like a screw extractor or bolt extractor kit. Don’t expect an easy out in this situation!

Here are some of the tools you may require to remove a bolt:

a center punch

a chisel

vise pliers

a screwdriver

a left-handed drill bit to reverse-drill a pilot hole

a bolt extract or with an extraction bit

or some other type of extraction set or bolt extractor set

A magnet may also come in handy when you’re done to gather up the metal shavings left behind by your drilling.

The guiding principle of broken bolt removal is to preserve the threading on the bolt hole so that the bolt itself can be easily removed. If the threaded hole becomes damaged, you will need a product such as a Heli-Coil insert to replace them.

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Steps for bolt removal via extraction

If a basic chiseling and unscrewing do not work, then you can move on to extraction with a bolt extractor kit.

Be aware that corroded metal is very difficult to remove. Take extreme caution when dealing with seized plugs, as a single slip could permanently destroy the casting.

Here are the basic steps for bolt removal with a bolt extractor kit.

Drill a hole dead center with a left-handed bit

Why do you need a left-handed bit? This bit is actually threaded in the opposite direction to a standard drill bit, which allows it to torque in the opposite direction as the broken bolt.

Start with a center punch in the exact middle of the broken fastener. Then, very slowly reverse drill a small ⅛-inch pilot hole in the center of the bolt head to a depth of approximately ¼-inch.

Next, you can replace your ⅛ bit with a ¼ bit and repeat. Progressively enlarge the bolt extraction hole until there is minimal shank left.

If this has allowed the bolt to loosen slightly, you can try using locking pliers to remove the damaged part.

Still stuck? Insert the bolt extractor bit into the hole you made

If you still cannot remove the broken bolt, try switching out your standard drill bit for an extracting bit.

This super-coarse, super-strong bit will either have a hex head or a T-handle head, depending on the kit you bought. The instructions in your kit will also tell you which size bit you need for the bolt size.

Once the new extraction bit is in place, repeat the process described above. Gently tap the drill and bit into the pilot hole with a hammer. Then, reverse drill into the hole.

Heat and penetrating lubricant can be used here to help with expansion around the bolt shank.

Be very, very careful. Do not break off the extractor in the fastener. The extraction bit is tough metal, and if it gets broken off inside the hole, it will prevent you from ever removing the broken bolt.

Remove the broken bolt

Now, you can attempt to remove the broken bolt.

Take your time. To start, very gently work the steel extractor out with the bolt attached. Delicate precision will pay off at this step of the bolt removal.

At this point, the bit has ideally latched onto the broken bolt, which should allow you to unscrew it just enough to grab the broken bolt with vice grips or pliers.

Clean up the bolt hole with a chaser and penetrating oil

Congratulations on removing the bolt! But first—before you install a new bolt and washer—take the time to clean up the threads and make installation easier.

Begin by removing the filings and shavings. Use a thread chaser (aka thread cleaner) in the bolt hole with a penetrating lubricant. Then, use a magnet or compressed air to remove all remaining tiny metal remnants.

If you’re working with a spark plug hole in your car and the spark plug hole threads were damaged beyond repair during the extraction process, use Heli-Coil or another type of coil threaded insert. Then, proceed with replacing the bolt.

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Bolt removal via the welder method

If your bolt is proving to be extremely resistant or it’s corroded, you can try welding a bolt to a nut to assist in removal.

There are a few caveats. Only attempt this method if you are a skilled welder or if you have hired a professional. Only attempt welding if some of the fastener is sticking out of the casting. Finally, with the welder method, there is a risk that the bolt could become welded to the iron casting, which could make things even worse.

Here are the basic steps of the welder method of bolt removal:

Center punch the broken bolt

Drill out the center with a bit ¼ the diameter of the bolt

Thread a hex nut onto the bolt, backed off a half turn so it is not flush

Weld the nut to the bolt

Once it is cool, use a ratchet or socket wrench to grasp the nut

Slowly wiggle the bolt to loosen the corrosion

Attempt to remove the bolt

Weld again if the corroded bolt breaks, and repeat until the bolt is removed

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FAQs

What are the best tools for removing a broken bolt?

Buy a bolt extraction kit with a left-handed bit. You will also need a center punch and pliers. Penetrative lubricant and a thread chaser may come in handy as well.

Can you hammer out a broken bolt?

In some situations, yes, you can hammer out a broken bolt. Try using a hammer and chisel to lightly get the bolt to move. If you can loosen the bolt enough, you may be able to remove it without the need for an extraction kit.

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