Removing a screw with a broken head can be a frustrating task. The head is needed to grip the screw and turn it, so when it breaks off, the remainder of the screw is very difficult to remove. There are several methods you can try to extract a broken screw, depending on how much of the head is still attached.
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Assessing the Damage
The first step is to inspect the damage and see how much of the screw head remains. This will determine which method will work best for removing it.
Completely Sheared Off Head
If the head is completely sheared off, leaving nothing protruding from the surface, you’ll need to use an extractor tool. Extractors grip the threads of the screw so you can unscrew the remainder.
Partially Broken Head
If part of the head is still intact, you may be able to grip it with locking pliers or a vice grip. Applying tight pressure with one of these tools can allow you to turn the screw counter-clockwise and back it out.
Stripped Head
If the head is not fully sheared off but is stripped so a screwdriver cannot grip it, you can try using a screw extractor, slotting the head with a rotary tool, or gripping it with locking pliers.
Preparing the Work Area
Before taking any measures to remove the screw, prep the area to give yourself the best working conditions:
– Clear away any obstructing objects to allow free access to the screw.
– Have good lighting on the screw to see what you are doing.
– Protect any nearby surfaces from damage. Extracting a screw can sometimes cause debris or metal shards to fly.
– Have your extracting tools and supplies at the ready. Time is of the essence once you start trying to remove it.
Using an Extractor
Hardware stores sell sets of screw extractors, also known as easy outs. These work on the principle of gripping and turning. To use an extractor:
Selecting the Right Size
– Determine the diameter of the broken screw. Measure it if possible, or estimate based on the size of the hole.
– Choose an extractor bit slightly smaller in diameter than the screw. You want it to wedge tightly into the screw.
Drilling a Guide Hole
– Use a drill bit that is the same size as the extractor bit’s diameter. Drill into the center of the exposed screw. Go in at least 1/8 inch deep.
– Keep the drill as straight as possible so the extractor can follow the same path.
Inserting the Extractor
– Fit the extractor bit into the guide hole you drilled. Give it a few light taps with a hammer if needed to seat it.
– Attach an adjustable wrench, locking pliers, or T-handle wrench to the square end of the extractor.
Turning Counter-Clockwise
– Turn the wrench counter-clockwise to essentially back the screw out.
– Apply firm, steady pressure. Quick jerking motions can cause the extractor to slip.
– If the extractor starts slipping, you can apply penetrating oil around it to lubricate.
Removing the Screw
– Keep turning counter-clockwise until the screw is completely disengaged.
– Pull the screw out of the hole with tweezers or pliers.
Using Locking Pliers
If enough of the screw head remains for gripping, locking pliers can sometimes supply enough grip and torque to turn the screw out.
Choosing the Right Pliers
– Standard locking pliers, or vise-grips, work best for this task.
– Go for a medium to large size, around 10 inches long.
– Make sure the pliers’ jaws have ridges that will grip the screw head.
Clamping the Jaws
– Fit the open jaws around what remains of the screw head so the ridges catch it.
– Close the pliers until the jaws are gripping the head as tightly as possible.
Turning Out the Screw
– With one hand holding the pliers handle, use your other hand to turn the entire pliers counter-clockwise.
– Keep a firm grip and apply steady, even force. Jerking too hard can cause the pliers to slip.
– You may need to periodically re-clamp the jaws as the ridges lose purchase.
Finishing Removal
– Once the pliers have turned the screw far enough, it should release from the material it is screwed into.
– You may need needle-nose pliers to fully remove and pull out the screw.
Slotting with a Rotary Tool
If a small part of the screw head remains, you can use a rotary tool like a Dremel to cut a slot for a flat-head screwdriver.
Selecting the Right Bit
– Use a reinforced cut-off wheel or metal grinding bit. These are made to cut through metal.
– Choose a bit width that matches the size of the screw head’s remains. You want to slot across its diameter.
Cutting the Slot
– Position the rotary tool bit at the center of the screw head fragment.
– Turn on the tool and gently feed the bit straight down into the screw.
– Cut down just deep enough to form a slot for the screwdriver without cutting too far into the screw shaft.
Removing with a Screwdriver
– Turn off the rotary tool when you have an adequately sized slot.
– Fit a flat-head screwdriver into the slot you cut.
– Turn the screwdriver counter-clockwise to back the screw out like normal.
Using Penetrating Oil
With metal parts that are stuck together by rust, corrosion, or grime, penetrating oil can work wonders to break them free.
How it Works
– Penetrating oils contain solvents that seep into tiny gaps in the metal.
– They dissolve the gunk holding the parts together. This releases the tension gripping them together.
Choosing the Oil
– Look for penetrating oil specifically formulated for freeing stuck parts. Popular brands are Liquid Wrench, PB Blaster, and WD-40.
– Avoid household oils like vegetable, mineral, or motor oil. They don’t have the solvents needed to penetrate stuck metal.
Applying the Oil
– Remove any dirt, grease, or debris from the area so the oil can reach the metal beneath.
– Spray or drop the penetrating oil liberally in and around the screw head. Give it time to penetrate.
– Reapply more oil every 15-30 minutes as needed, until you see results.
Extracting the Screw
– Once the penetrating oil has worked at dissolving the metal-to-metal connections, try your extraction method again.
– The oil will lubricate the parts for smoother twisting extraction.
Preventing Broken Screw Heads
While removing a broken screw is a headache, prevention is the best medicine. Here are some tips for avoiding sheared-off screw heads:
Use the Proper Size Screwdriver
– Make sure your screwdriver head exactly fits the screw head size and type.
– Ill-fitting drivers can slip and damage screw heads.
Apply Steady Pressure
– Turn screws at moderate speed using steady force. Jerking too hard risks twisting off the head.
Lubricate the Screw
– A little penetrating oil or general lubricant makes turning easier and prevents binding.
Use Quality Fasteners
– invest in good screws made of hardened steel. Softer screws strip and shear more easily.
Conclusion
Removing broken screw heads takes patience, perseverance, and the right techniques. First assess how much of the head remains. Use an extractor if the head is completely sheared off. Locking pliers can grab partial screw heads to unscrew them. And a rotary tool cuts a slot in remnant heads for a screwdriver. Penetrating oil helps loosen stubborn screws. With the proper methods, you can defeat the challenge of extracting broken screw heads.