Quick answer
If your key won't turn, first check you've lifted the handle fully — multi-point locks need this every time before the cylinder will rotate. If it still won't turn, suspect a worn cylinder, a failed gearbox cam, or a key that has worn out of tolerance. Never force it; a snapped key costs far more to fix.
Overview
A key that won't turn falls into three buckets: cylinder problem, gearbox problem, or you haven't lifted the handle. Force is the enemy - a snapped key inside the barrel turns a £15 job into a £150 one.
Symptoms
- Key goes in fully but won't rotate.
- Key rotates partway then stops solid.
- Key rotates but nothing happens.
- You have to jiggle the key to make it work.
Common causes
- Handle wasn't lifted first - multi-point locks need this every time.
- Cylinder pins are worn or dirty.
- Gearbox has failed and the cam won't drive.
- Wrong key, or key has worn out of tolerance.
- Cylinder has been partially snapped by an intruder attempt.
The single most common cause we find on arrival
More call-outs than you'd expect turn out to be exactly this: the handle wasn't lifted fully before the key was turned. On a multi-point mechanism, the handle drives the hooks and bolts into the frame, and the cylinder cam only engages the gearbox pawl once that lift is complete — turn the key too early and it simply won't rotate, or will feel like it's fighting something.
It sounds obvious once explained, but on a new-to-you house, or after someone else has adjusted the handle tension, this catches people out regularly enough that it's always the first thing we ask about over the phone.
Three genuine mechanical causes, ranked by likelihood
Beyond the handle-lift issue, the next most likely cause is a worn cylinder — the pin stacks inside a Euro cylinder wear down over years of use, especially with a heavily-used front door key that's been copied from a copy one too many times, degrading tolerances slightly with each generation.
Less common but more serious is a failed gearbox cam, where the internal drive mechanism that the cylinder is supposed to turn has itself seized or broken — in this case the key can rotate slightly but never completes a full turn, or turns with a grinding resistance that shouldn't be there.
- Handle not lifted fully — check this first, every time
- Worn or poorly cut key — try a spare if you have one
- Cylinder pin wear — gradual, gets worse over months
- Gearbox cam failure — sudden, often with a grinding feel
- Attempted lock snapping — check the cylinder face for gouges
Why forcing a stuck key is the worst move you can make
A key blade is deliberately the weakest part of the whole locking system by design — it's cheaper and easier to replace a key than a cylinder. Apply steady extra force to a key that won't turn and you're very likely to snap it flush with the cylinder face, which converts a simple call-out into an extraction job.
We've attended jobs where a customer used pliers to force a stuck key, which not only snapped the key but bent the cylinder's internal cam, meaning the whole cylinder had to be replaced rather than just cleared.
Distinguishing a cylinder fault from a gearbox fault
Remove the key entirely and try turning it with your fingers held on the outer face of the cylinder alone, without the door engaged (this only applies where the cylinder can be tested loosely — don't attempt to remove it yourself). If a locksmith or installer tests the cylinder in isolation and it turns freely, the fault sits further along, in the gearbox itself.
This distinction changes the repair cost significantly: a cylinder swap is a fifteen-minute job, while a gearbox replacement involves more careful matching of backset and hook configuration to the specific door.
Security risk of a key that intermittently won't turn
An intermittent fault is arguably worse than a total failure, because it lulls people into believing the door is properly secured when the mechanism may only be partially engaging. If the key sometimes turns and sometimes doesn't with no clear pattern, that's consistent with a cam or pawl that's close to complete failure.
For holiday let owners in particular, an intermittent lock fault discovered by a guest at 11pm on a Friday is a genuinely bad outcome. It's worth having these checked proactively between bookings rather than waiting for a guest to report it.
Getting the right person out first time
For a modern composite door, we'd always suggest calling the original installer or a composite-door specialist before a general locksmith. A locksmith unfamiliar with multi-point systems may default to drilling the cylinder, which is sometimes unnecessary and can void any remaining warranty on the door.
We carry a full range of Euro cylinder lengths and the major gearbox brands used across Cornwall, so in the majority of cases the job is diagnosed and resolved in the same visit.
How we triage this fault over the phone
Before we even book a visit, we'll ask you to try the spare key if one exists, and to describe exactly where the resistance appears — right at the start of the turn, halfway round, or only at the very end. Each answer points somewhere different: early resistance usually means the pin stack, mid-turn resistance points to the cam, and end-of-turn resistance often means the gearbox itself hasn't fully picked up.
This quick triage means that by the time we arrive, we've usually already narrowed the fault down to one of two likely causes, which keeps the visit efficient and the invoice predictable rather than open-ended.
How an intermittent turning fault develops
A key that occasionally won't turn rarely improves on its own. What typically happens is the intermittent occurrences become more frequent over a matter of weeks, moving from 'once a fortnight' to 'most mornings' as the underlying wear or seasonal movement worsens.
The genuine risk here is habituation — after enough encounters with a stubborn lock, people develop a workaround (extra force, jiggling the handle, trying the key upside down) without registering that the fault is actively getting worse underneath the habit.
Coastal salt exposure and cylinder wear
Euro cylinders on coastal-facing doors take in a fine mist of salt-laden moisture every time wind drives rain against the door face, and that moisture works its way past the cylinder face into the pin chamber over time. The result is a specific kind of gritty, uneven resistance that inland cylinders rarely show in the same way.
We see this pattern reliably in properties from St Ives round to Mousehole, where a cylinder replaced every three to four years is genuinely more cost-effective than one nursed along for a decade, given the accelerated wear salt air causes.
What we check before quoting a repair
Before quoting, we always test whether the fault sits in the key, the cylinder, or the gearbox by isolating each component in turn, because quoting for a full mechanism replacement when a £45 cylinder swap would fix it isn't a mistake we're willing to make.
We'll also check the door's overall condition — hinge security, drainage, and general alignment — since a key that won't turn is sometimes the first visible symptom of a door that has dropped slightly, and fixing only the lock would leave the underlying cause to reappear within months.
Describing the fault accurately when you ring
The most helpful description includes whether the fault happens with the door open as well as closed, how long it's been happening, and whether it affects one key or all copies. If only a specific key is affected, mention which one — it saves us bringing a cylinder to replace when the real fix is simply cutting a fresh key.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Diagnostic call-out (handle/cylinder check) | £45-£75 | Often resolves as a simple adjustment |
| Cylinder replacement | £45-£120 | Depends on standard cylinder vs 3-star anti-snap |
| Gearbox replacement | £180-£320 | If the cam or pawl has failed |
| Emergency lockout assistance | £85-£150 | Out-of-hours rates apply |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- Key has partially snapped inside.
- Cylinder shows any sign of tampering.
- Nothing has worked and you're locked out.
Prevention
- Lubricate the cylinder twice a year with a graphite or PTFE lock spray - never WD-40 or oil.
- Grease the hooks and rollers on the door edge every 6 months.
- Always lift the handle to engage the multi-point locks before turning the key - this takes load off the gearbox.
- Never force a stiff key - book a service call before the mechanism snaps.
