How do I get out a screw that has snapped off?

This is a different problem from a screw whose head has rounded out. There is no drive left to work with at all, so every method is about getting a grip on the shank, on the outside or on the inside. Work through them in order, because each one destroys a little more of the surrounding material and you cannot go back.

Safety

What you'll need

• Eye protection
• Locking pliers or mole grips
• A screw extractor set (optional)
• Left-hand drill bits (optional)
• A plug cutter or hardwood dowel and PVA (optional)
• A rotary tool or a sharp chisel (optional)

Step by step

1. Look at how much shank is showing.Any protruding stub at all changes the job completely. This is the first thing to establish before reaching for anything.
2. Method one: grip the stub.Lock a pair of mole grips onto the shank as tightly as they will go and wind it out anticlockwise. Steady, continuous rotation — a jerk snaps what is left. This works far more often than people expect.
3. Method two: expose a stub.If it is flush, pare a shallow crater around the screw with a sharp chisel or a rotary tool burr, 2 to 3mm deep and just wide enough for the grips. In visible work you are trading a small repairable hollow for a solved problem.
4. Method three: cut a slot.With a rotary tool and a thin cutting disc, cut a straight slot across the top of the shank and try a flat-blade driver. It works on screws that are not seized, and it needs the slot to be deep enough not to burr over.
5. Method four: a left-hand drill bit.Centre-punch the middle of the shank, then drill with a left-hand bit running in reverse. Very often the bit bites and the screw simply winds itself out before the hole is even finished. This is the most elegant method and the one professionals reach for.
6. Method five: a screw extractor.Drill a pilot down the centre of the shank at the size the extractor specifies, then wind the extractor in anticlockwise. Its reverse taper bites harder as you turn. Go slowly and stop if it starts to feel springy — that is the extractor about to shatter.
7. Method six: drill it out entirely and plug.Drill the screw away with a bit slightly larger than its shank, then bore the hole out to a clean round size, glue in a hardwood dowel or a cut plug with the grain running the same way as the workpiece, and redrill once the glue has cured.
8. In masonry, consider leaving it.A snapped screw in a plug in a wall is often best driven or drilled a few millimetres below the surface, filled over, and a fresh fixing made 75mm away. Excavating it usually damages more than it saves.

Tips

• Heat from a soldering iron applied to the stub for a minute or two breaks the corrosion bond on a seized screw in metal, and it works on some in timber too.
• Penetrating oil is worth trying on anything rusted, but give it time — twenty minutes, not twenty seconds — and tap the area to help it travel.
• If the screw was snapped by over-torque rather than corrosion, it usually comes out easily once you have anything to grip, because nothing is actually seized.

Common mistakes

• Drilling off-centre when starting an extractor pilot — The pilot wanders into the surrounding timber or into the side of the screw, and you end up with an oval hole and a screw still in it. Centre-punch first, and start with a small bit.
• Using an ordinary right-hand drill bit at speed — It tightens the screw as it cuts and heats the shank. If you are drilling, drill slowly, and prefer a left-hand bit.

Questions people ask