How do I stop a bolt spinning when I cannot get at the other end?
Eight ways to hold a nut, a captive fitting or a carriage bolt that has started to turn — from the simple to the last resort.
- Difficulty
- beginner
- Time
- 25 min
- Read
- 3 min
Short answer
Work out which end is turning first. A carriage bolt is spinning because its square collar has stripped its seat — jam a screwdriver under the head or tap it back in. A captive nut that has come loose usually needs to be reached, gripped or replaced. If nothing can hold it, cutting the bolt is often quicker than persevering.
A fastener that turns endlessly and never tightens or loosens is one of the most frustrating repairs there is, and the productive first step is always the same: identify which end has failed. Everything after that follows from the answer.
What you'll need
- Locking pliers or mole grips
- A second spanner or a socket set
- A flat screwdriver or a small pry bar
- A hacksaw, a rotary tool or a mini grinder (optional)
- Two-part epoxy or threadlock (optional)
Step by step
- Work out which end is turning.Hold the head and turn the nut, then the reverse. If the head turns with the nut held, the head end has failed. If neither will hold, both are spinning and the fastener has lost its anchorage entirely.
- Carriage or coach bolt: re-seat the square collar.The square under the domed head has worn its seat in the timber. Tap the head firmly with a hammer while pulling on the nut, so the square bites into fresh material. Very often this alone fixes it.
- If the seat is destroyed, grip the head.Lock mole grips onto the domed head, or clamp a screwdriver blade or pry bar against the head so it cannot rotate, then turn the nut.
- Metal fitting: get a second tool on the other end.A ring spanner, a socket on an extension, a stubby spanner, a spanner ground thinner. Most captive nuts can be reached with the right shape of tool even where there seems to be no room.
- Grip a captive nut through the access you have.Long-nose locking pliers through a hole, a magnet to hold the nut against a face, or a piece of wire or tape to stop it rotating. Improvised, but it works.
- Flat-pack fitting: check the cam or the insert has not spun in the board.A cam lock that turns forever, or a threaded insert rotating in its hole, is not a bolt problem — the fitting has stripped its seat in the chipboard and needs epoxy or a larger fitting.
- Bond it as a last resort.Epoxy the nut to the surrounding metal, or use threadlock on the thread, let it cure fully, then undo from the other end. This obviously commits you to a permanent joint if you are trying to tighten rather than remove.
- Cut it if you are removing.A hacksaw blade in a pad handle, a rotary tool with a cutting disc, or a mini grinder. Cutting the bolt is frequently faster than an hour of trying to hold it, and if it has spun the fastener needs replacing anyway.
- Replace with something you can hold next time.A hex-headed bolt instead of a carriage bolt, a nyloc nut instead of a plain one, or a threaded insert instead of a captive nut in board.
Tips
- A spinning fastener you are trying to remove is a different problem from one you are trying to tighten. If it is coming off, cutting is always an option and it saves a lot of time.
- Where a carriage bolt has spun in timber, a large penny washer under the head on reassembly spreads the load and stops the seat wearing again.
- Spraying penetrating oil at a spinning fastener does nothing — it is not seized, it is unsupported.
Common mistakes
- Turning harder in the hope it will bite — Every rotation wears the failed seat a little larger, so the fastener gets less likely to hold rather than more.
- Cutting into the surrounding item to reach a nut — Almost always avoidable. Try a thinner spanner, a longer-reach grip, or cutting the bolt shank at the exposed end instead.