In short:
- A stiff lock has three possible culprits: the key, the lock itself, or the door and frame pulling the bolt out of line.
- The quickest test is to try the lock with the door open. If it's smooth then, the door is the problem, not the lock.
- Try another original key. A worn or poorly made copy is a common cause and costs nothing to rule out.
- Lock makers disagree on lubricants. One recommends graphite; another says never use graphite. Follow the maker of your lock.
- Never lever the key with pliers or a screwdriver. A snapped key turns a stiff lock into a lockout.
Work out what kind of stiff it is
"The key won't turn" describes several different faults. Pay attention to exactly how it behaves, because that points to the cause:
| What happens | Likely cause |
|---|---|
| Key slides in but won't turn at all | Wrong or badly worn key, or a fault inside the cylinder |
| Key is hard to push in or pull out | Dirt or grit in the keyway, a bent key, or a cylinder that needs care |
| Key turns part of the way, then stops | The bolt is rubbing on the strike plate or frame; often a door alignment problem |
| Stiff only when the door is shut | The door has dropped or moved, so the bolt or latch binds |
| One key works, another doesn't | The difficult one is worn or was copied inaccurately |
| Gets worse with the seasons | A wooden door or frame swelling and shrinking |
| Turns, but the door still won't open | A broken part inside the lock; this one needs a technician |
The door-open test
This is the single most useful check, and it takes seconds. Open the door, then lock and unlock it with the key while it stands open, watching the bolt come out and go back.
- Smooth when open, stiff when closed: the door or frame is out of line. Look for loose hinge screws, a door that scrapes the floor or frame, or shiny rub marks on the strike plate. Lock makers warn about this: Mul-T-Lock says a misaligned door causes load and friction that can damage cylinders, and ASSA ABLOY says faulty hinges and warped doors or frames put excessive load on other components.
- Stiff either way: the problem is the key or the lock itself.
On a multipoint door (common on aluminium and uPVC doors), the handle usually has to be lifted fully before the key will turn. If you have to lift harder than you used to, that's the same alignment problem in a different form.
Check the key before blaming the lock
- Try a different key, ideally one of the originals that came with the lock.
- Lay two keys side by side and compare the cuts. Rounded, shiny peaks mean wear.
- Look along the key for a bend or twist. A bent key will drag in any lock.
- Check for grime, rust or bits of keyring stuck to the blade.
- If only a copy is stiff, put it aside and use an original.
We don't cut or copy keys, so we can't replace a worn copy. If every key you have is worn, the usual fix is a new cylinder, which comes with fresh keys from the manufacturer.
Lubricants: why there's no single answer
The usual advice is "spray something into it". Lock makers don't agree on what that something should be, which is why you should check yours before reaching for a can:
| Maker | What it recommends | What it warns against |
|---|---|---|
| ASSA ABLOY (Union, Yale) | Graphite powder on the key blade, at least once a year or when the key feels rough | Silicone-based lubricants on exposed mechanisms, which go tacky; cleaning fluids getting into the lock |
| Mul-T-Lock | Only its own special lubricant, at least twice a year, more often on external doors | Painting cylinders; hosing or chemically washing them |
| BASI | Its own oil-based care product | Graphite, which it says should never be used on its cylinders |
So graphite is right for one maker and wrong for another. Using the wrong product can leave residue that attracts dust or gums up, and with some brands it may affect the warranty. Look for the brand stamped on the face of the cylinder or on the key, and follow that maker's guidance. If there's no name, or the lock is still stiff after care, stop and get it looked at.
Lubricant can't fix a misaligned door, a worn key or a broken part. If the door-open test points at the frame, adding more lubricant just hides the problem for a while.
What makes it worse
- Levering the key with pliers, a screwdriver or a second key. Keys snap, and a broken piece in the cylinder means broken key extraction before anything else.
- Jiggling a key that's nearly the right one. If it doesn't go in and turn cleanly, it's the wrong key or too worn.
- Kicking or slamming the door shut to get the bolt to line up. That loosens hinges and moves the frame further.
- Filing the key or the strike plate yourself. A filed strike can stop the bolt holding properly, and a filed key wears the lock.
- Putting it off. A lock that's getting stiffer usually fails at the worst moment, often with you outside.
Repair, adjust or replace?
What fixes a stiff lock depends on what the technician finds:
- Adjustment. When the door has dropped or the strike is out of line, adjusting hinges or the strike can be all it needs.
- Cleaning and servicing the lock or cylinder, using the right product for that make.
- Repair. Replacing a worn or broken part inside the lock where one is available. See lock repairs.
- Replacement. When the cylinder or lock is worn out, damaged, or every key is worn. See lock replacement.
The technician tells you which one applies and quotes on site before starting; nothing is done until you agree. The R250 call-out brings them to you, we're open 24/7, and payment is by EFT, cash or card. Our guide to what a mobile locksmith costs in Kempton Park explains how the quote is worked out.
When to call, and what to send
Phone us if the lock is still stiff after the checks above, if the key turns but the door won't open, if a key has broken off, or if it's the only lock on an outside door and you're worried it will fail shut. Before the visit, send:
- A photo of the lock from outside, close enough to see the keyway and any brand name.
- A photo of the edge of the door with the faceplate, if you can open it.
- A short video of the key turning, with the door open and closed.
- Your keys laid side by side.
If the stiff lock is on a security gate rather than a door, read security gate lock problems, which covers the faults particular to gates. For our other services, start at the Kempton Park mobile locksmith homepage.
Questions
Should I spray WD-40 or oil into a stiff lock?
Only if your lock's maker recommends it. Makers disagree: ASSA ABLOY recommends graphite, Mul-T-Lock wants its own lubricant, and BASI says never to use graphite. Check the brand on the cylinder first. If you can't tell, it's safer to ask than to spray.
The lock is stiff only in the afternoons or in rainy weather. Why?
That usually points to the door, not the lock. Wooden doors and frames can swell and shrink with moisture and temperature, which shifts the bolt against the strike. Use the door-open test: if the lock is smooth with the door open, the fix is adjusting the door or strike.
Our copied key sticks but the original works. Can you make a better copy?
No, we don't cut or copy keys. Use the original. If you need more keys that work well, a new cylinder with a fresh set of factory keys is the reliable option.
Need a locksmith to look at it?
If this hasn't solved the problem, our lock repairs service covers it. We're a mobile locksmith in Kempton Park, so we come to your door.
Sources and further reading
- ASSA ABLOY South Africa: Product Care and Maintenance (PDF) — Graphite powder (Yale UnJam-It) for cylinders, lever locks and padlocks at least yearly; no silicone-based lubricant; keep cleaning fluids out of the lock; faulty hinges and warped doors or frames overload components.
- Mul-T-Lock: Mechanical product maintenance — Use only Mul-T-Lock lubricant, at least twice a year and more often on external doors; never paint, hose or chemically wash cylinders; a misaligned door causes load and friction that damages cylinders.
- BASI: Fitting and care advice for locking system cylinders — Do not re-lubricate BASI cylinders with graphite; use the maker's own oil-based care product.