A sheared screw, one that has broken off at or below the surface, can be removed using methods ranging from a pair of pliers to welding a nut onto the stub. The right approach depends on how much of the screw is still sticking out, what material it’s embedded in, and what tools you have available. Start with the simplest method that fits your situation and escalate from there.
If Any Metal Is Sticking Up
When even a small amount of the screw protrudes above the surface, you can often skip drilling entirely. Locking pliers (Vise-Grips) are the first thing to reach for. Clamp them tightly onto the stub and turn counterclockwise. If the screw is corroded in place, apply penetrating oil first and let it soak for 10 to 15 minutes before attempting to turn.
Screw removal pliers with both vertical and horizontal serrations on the jaws grip more securely than standard pliers and work faster than drill-and-extract methods. These are worth owning if you deal with broken fasteners regularly. For screws that sheared at the head but left a partial stub, these specialty pliers can often finish the job in under a minute.
Cut a New Slot With a Rotary Tool
If the break left a flat surface you can access, a rotary tool with a thin cutting wheel can create a new slot for a flathead screwdriver. Cut as close to the center line of the screw as possible, deep enough for the screwdriver blade to seat firmly but not so deep that you weaken what’s left of the fastener. This works best on smaller screws in softer metals where the screw isn’t seized by corrosion.
Soak It With Penetrating Oil First
Before you drill into anything, give penetrating oil a chance to do the hard work. The difference is dramatic. In one widely referenced comparison test, rusted fasteners required an average of 516 pounds of force to break free with no penetrant applied. PB Blaster cut that to 214 pounds. Kroil dropped it to 106 pounds, roughly one-fifth of the original force needed.
Apply the oil and wait. A single application needs at least 15 minutes. For badly corroded fasteners, apply it several times over the course of an hour or more. If you can access the back side of the hole, apply oil there too so it can wick through the threads from both directions.
Heat to Break the Corrosion Bond
Heat expands the surrounding metal, which can crack the rust bond between the screw and the hole. A small propane or MAP gas torch aimed at the material around the screw (not the screw itself) causes the parent metal to expand slightly, loosening the grip on the threads. Once heated, let it cool, then try turning. The expansion-and-contraction cycle is often more effective than heat alone.
For fasteners held with thread-locking compound, heat is especially useful because those adhesives break down at elevated temperatures. Blue (medium-strength) thread locker softens at lower heat than red (permanent), but both will release with a focused torch. Avoid this method near fuel lines, plastic components, or painted surfaces you want to keep.
Drilling and Extracting: The Core Method
When the screw has broken off flush or below the surface, you’ll need to drill into it and use a screw extractor (sometimes called an “easy-out”). This is the most common approach, and getting the preparation right matters more than the extraction itself.
Center Punch the Broken Surface
A drill bit will wander across a hardened, irregular broken surface unless you give it a starting point. A center punch creates a small dimple that guides the drill tip and keeps it centered on the screw. Use an automatic spring-loaded center punch if you have one, since it delivers a consistent strike without needing a hammer. Place it as close to the exact center of the broken screw as you can. Being off-center is the single most common reason extractions fail, because the extractor won’t grip evenly and the remaining screw wall on one side becomes too thin.
Drill the Pilot Hole
The pilot hole needs to match your extractor size. Drilling too large weakens the screw and can damage the threads in the surrounding hole. Drilling too small means the extractor won’t bite. Here are the standard pairings:
- No. 3 to No. 6 screws (up to 4mm): drill 5/64″, use a #1 extractor
- No. 6 to No. 12 screws (4mm to 6mm): drill 7/64″, use a #2 extractor
- No. 14 screws (6mm to 8mm): drill 5/32″, use a #3 extractor
- 1/4″ to 3/8″ bolts (8mm to 10mm): drill 1/4″, use a #4 extractor
- 3/8″ to 5/8″ bolts (10mm to 16mm): drill 19/64″, use a #5 extractor
Use a left-hand drill bit if you have one. Because it spins counterclockwise (the loosening direction), it sometimes catches and backs the screw out before you even get to the extractor. Run the drill at low speed with steady, moderate pressure. High speed generates heat that can harden the screw further and dull the bit.
Choose the Right Extractor Type
Spiral flute extractors are the most common and work best on hardened steel, where the twisting flutes can bite into the material. Straight flute extractors are better for softer metals like brass or mild steel. Spiral types can actually compress softer material rather than gripping it, which makes them spin uselessly in the hole. Some experienced machinists prefer four-sided square fluted extractors over both, finding they bite more aggressively in a wider range of materials.
Tap the extractor into the pilot hole with a firm strike from a hammer, then turn it counterclockwise with a T-handle or wrench. Go slowly. Extractors are made of hardened, brittle tool steel, and if one snaps inside your pilot hole, you now have a much harder problem (more on that below). If you feel the extractor bottoming out or the resistance suddenly spiking, stop. Apply more penetrating oil, try heating the surrounding area, and attempt again.
Welding a Nut Onto the Stub
For larger bolts or studs, especially those broken flush with the surface, welding a nut directly onto the broken end gives you something to grip with a wrench. This is one of the most reliable methods when you have access to a MIG welder.
Start by cleaning the broken surface and the area around it with a wire brush so the welder’s ground clamp makes good electrical contact. Place a washer over the stud first to act as a shield, preventing you from accidentally welding the stud to the surrounding material. Then center a nut over the stub. Use a nut slightly larger than the stud diameter, not one that just barely fits. A bigger nut lets you fill the gap between the nut’s inner wall and the stud with weld material, creating a much stronger bond and giving you more wrench leverage.
Weld around the inside where the nut meets the stud, let it cool, then test it with a wrench. If the nut pops off, clean the surfaces, increase your amperage and wire feed slightly, and try again with a fresh nut. After welding, heating the surrounding material with a torch before turning helps break any remaining corrosion bond.
If the stud is broken below the surface with nothing to grab, you can place a washer over the hole, weld down into it to build up a mound of new metal above the surface, then weld a nut onto that mound.
What to Do if the Extractor Breaks
A broken extractor stuck inside a pilot hole is one of the most frustrating situations in fastener removal. Extractors are hardened tool steel, so standard drill bits won’t touch them. Diamond hole saw bits are the most accessible solution for most people. They cut through the hardened steel slowly but effectively without requiring specialized shop equipment. Work at low speed, keep the bit cool with cutting oil, and be patient. The process can take a while, but it avoids the expense of electrical discharge machining, which is the professional-shop alternative for truly stuck broken extractors in critical parts.
Protecting the Threads
Throughout any extraction method, your goal is to save the threaded hole in the parent material. If you damage those threads, you’ll need to drill the hole oversize and install a thread repair insert. To minimize the risk, always stay centered when drilling, use the correct pilot hole size for your extractor, and resist the urge to use a larger extractor than the screw calls for. If the screw was set in aluminum or another soft metal, be especially careful, since the parent threads are the weaker component and easy to strip.
Once the broken screw is out, run a tap through the hole to clean up any thread damage before installing a replacement fastener. Apply anti-seize compound to the new screw’s threads so the next person who needs to remove it won’t face the same problem.