Why will my key not turn in the lock?
Separating a worn key from a worn cylinder, a door under load and a lock that has simply dried out — with the cheapest and most likely causes checked first.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 4 min
- Safety
- warning
Short answer
Try the spare key. If the spare works, your everyday key is worn and needs cutting from the original. If neither works, take the load off the door by pushing or pulling it while turning. If it is still stiff, lubricate the cylinder with a PTFE or graphite lock lubricant — never an oily spray — and work the key gently.
A key that will not turn is usually one of four things, and they can be sorted in a few minutes without spending anything. Worn keys are by far the most common and the easiest to miss, because the key wears so gradually that the increasing effort feels normal until the day it stops working altogether.
Safety
Step by step
- Check the key goes fully in.If it stops short, something is in the keyway — grit, a broken tip from a previous key, or ice. Do not force it deeper. A short blast of compressed air or a gentle pick with a fine wire will often clear it.
- Try the spare, and try it from both sides.If a rarely used spare turns and the everyday key does not, the everyday key is worn. Keys wear where they do the work, and copies cut from copies wear out fastest of all. Get a new one cut from the least-used key you own.
- Take the load off the door.Push the door firmly closed, or pull it towards you, and try the key at the same time. If it turns under one of those conditions and not otherwise, the lock is being held under pressure by a misaligned door — nothing is wrong with the lock at all.
- Lift the handle first, on a multipoint door.On most uPVC and composite doors the key will not turn until the handle has been lifted and the bolts thrown. If the handle is not going fully up, the key never gets its chance and the fault is bolt alignment, not the cylinder.
- Lubricate the cylinder correctly.A PTFE-based lock lubricant or a puff of powdered graphite. Work the key in and out a dozen times, then try turning it. This alone cures a large share of stiff cylinders, particularly on doors that face driving rain.
- Do not use an oily aerosol.General-purpose penetrating and water-displacing sprays wash out what little lubricant is in a pin cylinder and leave a film that traps dust. The lock works beautifully for a fortnight and is worse than before within a year.
- Check for a frozen lock in winter.Warm the key in your hands or with hot water and insert it slowly. Never apply a naked flame to a key, never pour boiling water over a uPVC door, and never use antifreeze intended for a car cooling system.
- Test the cylinder out of the door if you can.If the door is currently open, take the cylinder out — one long screw through the door edge — and try the key in it on the bench. A cylinder that is stiff on the bench is worn or damaged and needs replacing. A cylinder that works perfectly on the bench proves the problem is the door or the gearbox.
Tips
- Never lend the only original key for copying. Copies of copies drift, and a key cut from a worn copy is born worn.
- If several different locks in the house have gone stiff at once, the common factor is the weather rather than the locks.
- A key that has to be jiggled to work is telling you it will fail soon. Sort it in daylight rather than on a wet evening.
If it doesn't work
Key turns a few degrees then stops hard
Cause: A bolt under load, or the gearbox is jammed — Fix: Relieve the pressure on the door and try again. If it still stops, do not force it — the gearbox is the part that will break, and it costs more than the cylinder.
Key is loose and rattles in the keyway
Cause: Worn key, worn cylinder or both — Fix: Cut a new key from the original. If a fresh key is also loose, the cylinder is worn out and should be replaced — it is a cheap part and a ten-minute job on a euro cylinder.
Stiff only in cold weather
Cause: Moisture in the cylinder freezing, or a contracted door tightening on its seals — Fix: Lubricate with a PTFE lock lubricant in autumn, and check the door's compression setting. A door wound tight in summer becomes very stiff in a cold snap.
Stiff on one side of the door only
Cause: The outside half of the cylinder has weathered — Fix: Replace the cylinder. Water gets in from the outside and the pins on that side corrode first, which is exactly this symptom.