Screw or bolt will not come out, or its head is damaged

A screw spins without moving, the tool slips, the head is round, or a bolt snaps off. This happens most with steel cross-head screws in aluminium engine cases, and with old bolts in rusty parts. The right tool and a gentle first approach save the part.

Is it safe to ride?

Ride only if the fastener holds nothing important. A loose or damaged fastener on a wheel, brake, steering or engine mount: do not ride until it is fixed.

Quick checks first

• Is the tool the right size and fully seated, with the recess clean?
• Is it a screw into an engine case, a bolt through a part, or a bolt that holds a brake or wheel?
• Is the head rounded, or still sharp?
• Has the bolt rusted into place, or was it over-tightened?
• Do you have penetrating oil, an impact driver and a drill?

Diagnose it step by step

1Is the head still square or has a clean recess?

• Yes: soak with penetrating oil. Try the correct size 6-point socket or bit: Choose and use spanners and sockets without rounding fasteners. Go to step 2 if it still does not move.
• No, rounded: go to step 3.

2Is it a cross-head or hex screw into an aluminium case?

• Yes: use an impact driver with the right bit: Loosen a tight screw with an impact driver. Support the part behind it.
• No (a bolt through a bracket or frame): heat and oil may help; use a longer handle and a steady pull.

3Can you grip the head?

• Yes: try grinding paste in the recess, a slightly smaller socket tapped on, or locking pliers.
• No: go to step 4.

4Has the head snapped off, with the thread inside?

• Yes: Remove a rounded, seized or broken fastener: drill and extract.
• If an extractor breaks, stop. Take it to a workshop.

5Is the fastener on a brake, wheel, steering or engine mount?

• Yes: stop. Take it to a workshop. See Check engine mounting bolts.

What happens if you force it: the head rounds more, a cast part cracks, or a hardened extractor snaps and cannot be drilled out.

Causes, most likely first