How do I remove a screw or bolt that will not turn?

Stuck fasteners are held by corrosion or by thread-locking compound. Force alone usually rounds the head, which turns a difficult problem into a much harder one. Patience with penetrating oil is what actually works.

Safety

What you'll need

• Penetrating oil
• Correctly sized driver
• Impact driver (optional)
• Screw extractor (optional)
• Eye protection (optional)

Step by step

1. Apply penetrating oil and wait.Twenty minutes minimum, longer for badly corroded fasteners. Reapplying every few minutes helps it wick into the threads. This step does most of the work.
2. Clean the head out before applying any force.Paint, rust and debris in the recess prevent the driver seating fully, which is what causes rounding. A pick or a small brush.
3. Use the largest driver that fits properly.A driver that is slightly too small chews the head immediately. It should fill the recess completely with no wobble.
4. Push hard into the head while turning slowly.Most of the force should be downward pressure rather than rotation. Slipping out of the head is what rounds it.
5. Try tightening very slightly first.A small movement in the tightening direction often breaks the corrosion bond and makes loosening possible. Counter-intuitive and frequently effective.
6. Use an impact driver for stubborn screws.A manual impact driver converts a hammer blow into rotation while pressing into the head. It is remarkably effective and inexpensive.
7. For a rounded head, cut a slot or use an extractor.A small cut across the head with a rotary tool lets a flat driver grip. Otherwise a screw extractor bites into a drilled pilot hole.
8. Consider heat as a last resort on metal.Expansion breaks corrosion bonds. Never near fuel, plastics, wiring or anything flammable, and never on anything you cannot afford to damage.

Tips

• Bolt heads are easier than screws because you can use a spanner or socket for far more leverage without slipping.
• Rubber band trick: a wide elastic band between the driver and a rounded screw head sometimes gives just enough grip.
• When reassembling, a little grease or anti-seize on the threads means it will come out easily next time.

Common mistakes

• Applying force before the penetrating oil has worked — It rounds the head, which removes your ability to grip it at all. Twenty minutes of waiting saves an hour of extraction.
• Using a driver that is slightly too small — It chews out the recess within a couple of turns and turns a stuck screw into a rounded one.
• Turning without pushing hard into the head — The driver cams out and destroys the recess. Downward pressure matters more than rotational force.

Questions people ask