The short answer
Four things cause almost every stuck key, and only one of them is a broken lock.
The key is worn. Brass is soft, and a key that has been copied from a copy, or carried on a ring for a decade, no longer matches the cuts the lock was built for. The pins get dragged instead of lifted. This is the most common cause and the least suspected.
The door is binding. If the door has swollen or dropped on its hinges, the bolt is under load and cannot move. The lock is working perfectly; it simply cannot overcome the weight of a door pressing on it. Take the pressure off and it turns.
The cylinder is dry, dirty or corroded. Dust, old lubricant gone to paste, or in damp parts of Delaware, corrosion on the pins and springs.
Something inside has actually broken. A spring, the cam, the tailpiece. This is real, and it is the least common of the four.
Work through them in that order and you will identify the problem most of the time without any tools at all.
The long answer
What is actually happening inside the lock.
A pin tumbler cylinder is a simple machine, and once you know how it works, the symptoms stop being mysterious.
Inside the cylinder are pairs of small pins sitting in vertical channels, pushed down by springs. Each pair straddles the line between the rotating plug and the fixed housing around it. With no key in, the lower pins sit across that line and block rotation completely.
The right key lifts each pair to exactly the height where the gap between the two pins lines up with that shear line. All of them at once. Then, and only then, the plug turns. The cuts along your key are a set of heights, and every one of them has to be right, which is why a key can be one cut wrong and feel utterly dead in the lock.
That explains the wear problem immediately. If a peak on your key has worn down by a fraction of a millimetre, one pin sits slightly low. The gap does not quite reach the shear line. The plug will not turn, or turns only if you jiggle and force it into position. People describe that as "the lock is going" when what is going is the key in their hand.
It also explains why forcing is so destructive. Torque applied to a plug that cannot rotate goes straight into the key blade. Brass has a limit, and the blade is thinnest exactly where the cuts are deepest. When it snaps, the half with the cuts stays in the cylinder holding the pins in the wrong position, and now the lock cannot be picked or turned by any key at all.
Corrosion is the same story from a different direction. Springs that have rusted lose tension and stop returning pins cleanly. Grit and old oil turn into a paste that holds pins where they land. The lock is not broken in either case; it has simply stopped doing what it was built to do smoothly.
Diagnose it
Which of the four do you have?
Match your symptom to the left column. This gets it right the large majority of the time.
| What you're experiencing | Most likely cause | What that means |
|---|---|---|
| Key enters fully, will not rotate at all, feels solid | Wrong key, worn key, or a seized cylinder | Try any other copy of the key first. If a different copy works, the key was the problem, not the lock. |
| Turns partway then stops dead | Bolt under load from a binding door, or debris | Push or lift the door and try again. If it turns, you have an alignment problem. |
| Turns only with jiggling, wiggling or upward pressure | Worn key, or worn pins | A new key cut to code usually solves it. This is the stage before it stops working entirely. |
| Feels gritty or crunchy through the turn | Dirt, dried lubricant, or internal corrosion | Cleaning and a dry lubricant. If the grit is corrosion, the lock is on a countdown. |
| Turns freely but nothing happens | Broken cam or tailpiece, the cylinder is spinning without driving the bolt | Genuine internal failure. This is a repair or replacement. |
| Only sticks in cold weather | Moisture inside the cylinder freezing | Warm the lock body, never pour hot water. Treat before winter rather than during it. |
| Key turns, door won't open | Not the lock at all, the door is stuck in the frame | Hinges, swelling or a frame that has moved. New hardware will not help. |
What to do
In this order, and no other.
- Stop turning it. First and most important. You have already established it will not turn under normal pressure. More pressure does not change that; it only decides whether the blade survives.
- Try a different copy of the key. The spare in the drawer, the one your partner carries. If another copy works, you have your answer and it costs nothing to find out.
- Take the load off the door. Push it firmly closed, or lift it slightly by the handle, and turn again. A surprising share of "broken locks" open immediately at this step.
- Look at the key in daylight. Rounded peaks where there should be points, a bright polished shine along the cut edges, or a visible bend all mean the key is worn or distorted.
- Check the same key in another lock it should fit. If it works there and not here, the fault is in this cylinder. If it struggles everywhere, it is the key.
- Use a dry lubricant, not oil. A PTFE or graphite product made for locks. Never WD-40, never a household oil, never cooking spray, each of those makes the next twelve months worse in exchange for one good afternoon.
- Do not heat, hammer or lever anything. A flame near a uPVC door melts it. A hammer cracks the cylinder housing. A screwdriver in the keyway destroys the pins you need intact.
- Call before it fails completely. A lock that is difficult is far cheaper to fix than a lock that has stopped, and vastly cheaper than one with a snapped key inside it.
Cost
What decides whether this is cheap or expensive.
No figures here, but these are the factors, so you can weigh any quote you are given, ours included.
| Factor | Effect |
|---|---|
| Whether the door still opens | An adjustment on a working door is the cheapest job in this trade. A door nobody can open is a lockout first and a repair second. |
| Whether the key snapped | Extraction is its own job, and the cylinder frequently needs work afterwards. This is the single most expensive consequence of forcing. |
| Whether the fault is the frame | Strike adjustment is minutes. Rehanging a door that has dropped badly is not, though it is still cheaper than replacing hardware that was never faulty. |
| The type of lock | A standard residential cylinder, a mortise case, a multipoint mechanism and a high-security cylinder are four different jobs with four different parts. |
| Whether a key code exists | If we can decode the lock or find a code, cutting a fresh accurate key is straightforward. Where it does not, the route is different. |
| The hour | A door that still locks can wait for a weekday afternoon, which costs less. If the property is not secure, it cannot. |
The upgrade to refuse
If a locksmith looks at a sticking door and immediately quotes a new deadbolt without checking the strike alignment or the hinges, ask what specifically they found. On Delaware's older housing the frame is the fault far more often than the cylinder, and a new lock on a misaligned door will bind exactly the same way by next season, except you will have paid for hardware as well.
Delaware specifics
Why this happens more here than you'd expect.
Two things make this the single most common call we take, and both are about the housing rather than the hardware.
The age of the stock. Wilmington's row homes, the pre-war streets through Elsmere and Edgemoor, the mill-village core at Marshallton, the old towns of Kent County, a great deal of what we work on was built before 1940. Those doors are solid timber hung in timber frames, and they have moved through eighty to a hundred and twenty Delaware summers and winters. Timber swells in August humidity and contracts in a January freeze, hinges settle, and the gap where the bolt meets the strike is not where the builder left it.
The moisture. Delaware is a coastal plain state and the humidity is in everything. Near the river and the marsh, Newport, Edgemoor, Leipsic, Little Creek, Delaware City, salt-laden damp works on the inside of a cylinder year-round, and locks there simply do not last as long as identical hardware five miles inland. Add road salt spray on doors that open straight onto a street, which is most of Wilmington and Elsmere, and the corrosion clock runs faster still.
The practical consequence is a seasonal rhythm we can almost set a calendar by. Doors that bind in the humid weeks of late summer. A second wave on the first hard freeze, when marginal locks stop being marginal. And the pattern of people forcing a key through both, until it breaks.
Related
If this turns out to be something else.
Diagnosis often lands somewhere other than where people expect. These cover the neighbouring problems, and the guide to door frames covers the one nobody checks.
Lock Repair
Strikes, hinges, latches and cylinders, and an honest answer about which one actually failed.
If it snappedBroken Key Extraction
Removing the blade without wrecking the cylinder, and cutting a fresh key on the spot.
Most requestedLock Rekeying
Same hardware, new key, every old key dead. Often the right answer when keys are the problem.
24 hoursHouse Lockout
If it has already stopped turning and you are standing outside.
UpgradeLock Replacement
When the hardware genuinely is finished rather than simply tired.
All home workResidential Locksmith
The full picture on locks at home across New Castle and Kent.
Where we do this
Across both counties.
Sticking locks are the most common call we take, and the housing that causes them is concentrated in the older towns.
Questions
About keys that won't turn.
My key turns but the door won't open. Is that the same problem?
No, and the distinction matters. If the key turns freely through its travel, the lock is doing its job, the bolt has retracted and the door is stuck in the frame instead. That is swelling, a dropped hinge, or a frame that has moved. Try lifting the door slightly by the handle while you turn. If it opens, you have a hinge or alignment problem, not a lock problem, and no amount of new hardware will fix it.
Should I use WD-40 on a stiff lock?
No. It will free a lock for about a week and then make it considerably worse. WD-40 is a water-displacing solvent, not a lubricant, it strips whatever grease is in there, then leaves a residue that collects dust and grit until the pins are moving through paste. Use a dry PTFE or graphite lubricant made for locks. If somebody has already used oil, the cylinder needs flushing before a dry lubricant will help.
The key goes in but won't turn at all. What's most likely?
In rough order: the key is worn, the key is the wrong one for that lock, the door is binding so the bolt is under load, the cylinder has debris or has seized, or something inside has broken. On an older Delaware house the door is the culprit more often than the lock. Take the pressure off by pushing or lifting the door and try again, if it turns then, the lock is fine.
Can a key wear out?
Yes, and it is one of the most common causes of this problem and one of the least suspected. Brass is soft. A key copied from a copy from a copy has drifted from the original cuts, and a key carried on a ring for fifteen years has worn its peaks down. Either way the pins are being dragged into position rather than lifted cleanly. A key cut fresh to code often fixes a lock nobody needed to touch.
It only sticks when it's cold. Is that normal?
It is common, and it is a warning rather than a quirk. Cold alone stiffens grease; cold plus moisture inside the cylinder means ice, and ice does not stiffen a lock, it stops it. If a lock is marginal in November it will fail in January. The fix is a dry lubricant before the season starts, and on an exposed door, a cover or a storm door if one can be fitted.
Is it safe to keep forcing it if it eventually works?
No. A key that needs force is a key that is about to snap, and it snaps at the worst possible moment, in the dark, in the rain, with the broken half inside the cylinder. That turns a service call into an extraction plus, quite often, a new cylinder. If a lock needs persuading, it is telling you it has a fault that has not finished developing yet.
How do I know whether to repair or replace?
Look at what actually failed. Alignment, debris, dry pins and worn keys are all repairs, and cheap ones. A cracked cylinder housing, a sheared cam, a broken spring in a lock that is already forty years old, or hardware that was never adequate for the door, those are replacements. Anyone who arrives, glances at the door and quotes new hardware without checking the strike and the hinges has not diagnosed anything.
Can you cut a new key if I can't get the door open?
Yes. We open it non-destructively in the great majority of cases, then decode the lock and cut a key to it on site. That is often the right outcome anyway, a fresh key cut to the lock's actual code rather than copied from a worn original solves the problem at its source instead of postponing it.
The small checks worth doing before you call
Before assuming the lock is broken, run through a few quiet checks. Make sure you are using the right key, because duplicates sometimes look nearly identical and a ring of similar keys is easy to mix up. Try pushing the door gently toward the frame while you turn, since a door that has shifted can put pressure on the bolt and stop it from retracting. Also try lifting the handle slightly. If the key turns when the door is held a certain way, the lock may be fine and the alignment may be the problem. Stop at the first sign of resistance.
Look at the key itself. A key with bent shoulders, worn teeth or a visible crack is a poor tool, and turning it harder risks snapping it inside the cylinder, which turns a nuisance into a bigger job. Compare it with a spare if you have one, holding them side by side in the light. If the spare works and the main key does not, you have learned the key is the weak link. Keep the worn one safe, since a technician can sometimes use it as a reference, and do not try to straighten a bent key with pliers.
Think about what changed recently. Cold snaps, heavy rain, a recent paint job, a loose handle or a fresh coat of door finish can all affect how a lock behaves. If you have sprayed anything into the keyway, say what it was when you call. Describe when the problem happens, whether it is every time or only some times, and whether the key goes in smoothly. Those clues help the technician arrive prepared. We explain the scope and any quote before work begins, and we confirm availability by phone for your address.
What the technician does at the door
The technician begins by watching you try the key, if the lock is still usable, because how the key enters and turns says a great deal. A gritty feel suggests dirt or worn pins, a sudden hard stop suggests a bent component or a bolt binding against the strike, and a loose, floppy turn suggests the cylinder has separated from the mechanism. After that, the technician examines the strike plate, the latch alignment and the door position, since many sticking locks are door problems rather than lock problems. This step matters because replacing a good cylinder does nothing when the real trouble is a sagging hinge.
If the cylinder itself is at fault, the choices include cleaning and lubricating with a suitable product, replacing worn components, rekeying to new pins, or swapping the whole cylinder. Each has costs and tradeoffs, and the technician explains them before work begins. A cleaning is the lightest option and may be enough for a lock that is gritty but sound. A worn cylinder usually wants replacing, since lubricating a failing mechanism only delays the problem. If the key has broken off inside, the technician will describe how it will be extracted and whether the lock can be saved afterward.
Afterward, test the lock yourself. Turn the key repeatedly from outside and inside, with the door open and closed, and confirm the bolt moves fully into the strike. Ask whether any other doors in the house use the same hardware and may be showing early signs of wear. It is also reasonable to ask for a spare key to be cut or checked while the technician is there. Keep the old key aside until you are sure the repaired lock behaves well for a few days, then ask what the technician recommends about it.