DIY GUIDE · HOME REPAIRS & HANDYMAN

How to fix a stiff lock or change a Euro cylinder yourself
An hour. £20–£60 for a cylinder; almost nothing for a stiff lock.

Diagnose the stiffness, lubricate properly, adjust the keep, and measure and fit a Euro cylinder — and when to call a locksmith.

DIFFICULTY
Easy
part of the job only
TIME
About an hour
ten minutes to diagnose, half an hour to adjust or swap, the rest testing with the door open and shut
MATERIALS
£20–£60
a standard or security-rated Euro cylinder; lubricant for a stiff lock
A PRO CHARGES
£70–£180
typically £100
  • Every step, start to finish
  • Checked October 2026 — sources at the end
  • Honest about when to call a pro

FIRST, THE HONEST ANSWER

Do it yourself, or get a repairer?

Do it yourself if…

  • The key turns stiffly but the lock works with the door open
  • You have the keys and want a new cylinder after a key was lost or you have moved in
  • The latch or bolt catches on the keep and the door has dropped a little
  • The door has a Euro cylinder held by a single screw in the edge of the door

Get a pro if…

  • You are locked out, or a key has snapped in the cylinder
  • The lock has been forced or the door frame is split
  • The door has a mortice lock or a multipoint gearbox that needs replacing
  • You rent your home and the tenancy agreement does not let you change the locks

Safety first

  • Always work with the door open and wedged, and test from inside first. A failed lock with you outside is a lockout.
  • Do not leave a front door without a working cylinder overnight; order the new one before you remove the old.
  • If the lock has been forced or the frame is split, treat it as a break-in: photograph it, report it if needed, and get a locksmith.
  • Lift a door off its hinges only with a helper; HSE's lifting filter puts the guide figure for a close lift at 25 kg for men and 16 kg for women, and many external doors weigh more.
  • Keep keys and the key card where children cannot hand them out.

Stop here: A whole lockset on an external door, and any lock in a rented home

Changing a cylinder like for like is a householder's job. Replacing the lock body, a mortice lock or a multipoint gearbox affects the door's security and your insurance, and a fire-escape door's lock must stay openable from inside without a key. In a rented home, most tenancy agreements in England, Wales, Scotland and Northern Ireland treat changing the locks as a change needing the landlord's permission, and the landlord is entitled to keep access for repairs and emergencies. Ask first, in writing. How to hire a lock repairer →

MATERIALCOVERAGEFOR THIS JOB
Euro cylinderSized to your two measurements; three-star or with security handles for a front doorOne per door
Graphite powder or lock lubricantA small tubeOne
Replacement keep or packingOnly if the keep is damaged or the door has droppedAs needed

Measuring a Euro cylinder

With the cylinder out, measure from the centre of the fixing screw hole to the outside end, then to the inside end. A cylinder measuring 40 mm to the outside and 45 mm to the inside is a 40/45 — 85 mm overall. On a front door, the outside measurement should leave no more than a few millimetres of cylinder standing proud of the handle or escutcheon.

Different sellers write the two sizes in different orders; check which number they mean is the outside before you order.

Euro, oval or rim cylinder

Most uPVC and composite doors and many timber ones take a Euro cylinder: a key-shaped profile through the door, held by a screw from the door's edge. Older timber doors often have a rim cylinder on the outside of a nightlatch, held by screws from the inside. Take the old one out, or look at its profile, before you buy anything.

Measure from the screw, not the ends

A Euro cylinder is sized by two lengths: from the centre of the fixing screw hole to each end. One security door maker explains that it is the split that matters, not the height or width, and that the external and internal sizes must not be swapped. A thumb-turn cylinder is marked with a T before the size of its thumb-turn side, which always goes inside.

Security grades

Cylinders sold for front doors are tested against attacks such as snapping, where the cylinder is broken at its weakest point. Look for a cylinder certified to the British kitemark standards with a three-star rating, or a one-star cylinder used with security handles that make up the protection. Check your home insurance wording too; many policies name the standard they expect.

Lubricant: dry, not oily

A cylinder works on small pins and springs. One cylinder maker recommends graphite powder for a key that has become stiff — put it on the key and work it in. Oil and general sprays attract dust and grit and can gum the pins over time. Use a product made for locks.

Keyed alike and spare keys

If you are replacing front and back cylinders, buy them keyed alike so one key does both. Register the key code if the maker offers it; a registered key cannot be copied without proof of ownership.

Measure twice and write both numbers down before ordering; a cylinder too long sticks out and is easy to snap, one too short will not engage the lock.
Keep the old cylinder until the new one has worked for a week.

THE PART THAT DECIDES THE FINISH

Before you start — the door and the lock

Find what your lock is doing. Each case begins with the door open and wedged, so you are never shut out while working.

Key stiff in the cylinder

Grinds or needs jiggling, door open or shut.

  1. Try the key with the door open: still stiff means the cylinder, smooth means the door alignment
  2. Try a spare key; a worn copy can be the whole fault
  3. Check the key for bends or burrs
  4. Have graphite powder or lock lubricant ready
Lock works open, sticks shut

Smooth with the door open, hard to turn once closed.

  1. Close the door slowly and watch where the latch and bolt meet the keep
  2. Rub pencil on the bolt, lock it, and look where the mark lands
  3. Check the hinge screws for looseness; a dropped door misaligns everything
  4. On a uPVC or composite door, this is often an adjustment, not a lock fault
Lost key — changing the cylinder

You have a working key but want the lock changed.

  1. Open the door and wedge it
  2. Find the fixing screw in the door edge, in line with the cylinder
  3. Have the key ready; the cylinder only comes out with the key turned a little
  4. Measure and order the new cylinder before you remove the old one
A rented home

You are a tenant.

  1. Read your tenancy agreement on locks and keys
  2. Ask your landlord in writing before changing any lock
  3. Offer the landlord a copy of the new key if they ask for one
  4. Keep the original cylinder to refit when you leave
Internal door latch

Bathroom or bedroom latch that sticks or will not catch.

  1. Check the latch tongue springs back freely with the handle
  2. Check the strike plate on the frame lines up with the latch
  3. Tighten the handle screws; a loose handle drags the spindle
  4. A broken latch is a cheap, like-for-like part
Signs of a break-in

Scratches round the cylinder, a snapped cylinder, a split frame.

  1. Do not tidy up if you need to report it
  2. Photograph the damage
  3. Secure the door temporarily from inside if you can
  4. Call a locksmith for a forced lock or a split frame

THE JOB

How to fix a stiff lock or change a cylinder, in order

  1. Diagnose with the door open

    10 min

    Open the door and wedge it. Turn the key in the lock and work the handle and the bolt. If it all moves smoothly with the door open but sticks when shut, the problem is alignment between door and frame, not the lock. If it is stiff even with the door open, the cylinder or the mechanism is the problem. Try a spare key as well. Read the case above that matches your door.

    • Never test a lock with the door shut and yourself on the outside
    • Note whether the stiffness is in the key turning or in the handle lifting
    • Listen for grinding; it often means grit in the cylinder

    Mistake to avoid: Spraying lubricant into a lock that only sticks when the door is shut. The lock was fine; the door has dropped.

  2. Lubricate the cylinder

    10 min

    Put a little graphite powder or lock lubricant on the key, or puff the powder into the keyway, then push the key in and out and turn it several times. Repeat once or twice. Work the lock with the door open until it runs smoothly. If the key still sticks badly or something feels caught inside, there may be debris in the cylinder, and a new cylinder is often the cheaper answer.

    • A little goes a long way; wipe the key afterwards
    • Do the outside cylinder face as well; it gets the weather
    • Lubricate the bolt and latch where they slide, with the door open

    Mistake to avoid: Using cooking oil or a heavy grease in the keyway. It holds dust, gums the pins and makes the lock worse within months.

  3. Find where the bolt catches

    15 min

    Rub pencil lead or lipstick on the end and top of the latch and bolt. Close the door gently and turn the key or lift the handle so the bolt shoots into the keep, then open the door. The mark on the keep shows exactly where it is binding. If the mark is on the top or bottom edge of the opening, the door is out of line with the keep.

    • Check the hinge screws first; tightening them often lifts the door back into line
    • On a multipoint door, check every hook and roller, not just the centre lock
    • Note whether the door needs to go up, down, in or out

    Mistake to avoid: Filing the bolt itself to make it fit. The bolt is part of the lock's security, and a shortened bolt is easier to force.

  4. Adjust or ease the keep

    20 min

    Many keeps on uPVC and composite doors have adjustment screws or cams; loosen them and slide the keep a millimetre or two towards the mark. On a timber frame, unscrew the keep, ease the edge of the opening with a small file or chisel where the mark is, and refit it. Test after each small change, with the door open first and then shut.

    • Small moves: a millimetre is often enough
    • If the door has dropped badly on its hinges, adjust the hinges instead — see the door and uPVC guides
    • Tighten all the keep screws firmly when done

    Mistake to avoid: Moving the keep a long way to chase a door that is sagging. The lock then works but the door no longer seals against the weather strip.

  5. Measure the old cylinder

    10 min

    To change a Euro cylinder, open and wedge the door, then measure the cylinder where it sits from the centre of the fixing screw to each end, or take it out first and measure it properly. Write down the outside and inside measurements separately. Order the new cylinder to match, at the same or a better security rating, and check whether you need a thumb-turn inside.

    • Measuring the cylinder out of the door is more accurate
    • Mark which end faced outside with a pen as soon as it is out
    • Order front and back cylinders keyed alike if you want one key

    Mistake to avoid: Ordering by the overall length alone. A 40/50 and a 45/45 share the same overall length, and only one of them fits your door.

  6. Remove the old cylinder

    10 min

    With the door open and wedged, undo the long fixing screw in the door edge, in line with the cylinder, and take it out. Put the key in and turn it a few degrees so the cam lines up with the cylinder body — usually about ten or fifteen degrees either way of the vertical. Then gently pull on the key and the cylinder slides out. If it will not, turn the key a little further and try again. Never force it.

    • Lay the screw where it cannot roll away; it is long and particular
    • If the cam is stuck, wiggle the key back and forth slightly while pulling
    • A snapped or seized cylinder is a locksmith's job

    Mistake to avoid: Pulling the cylinder hard with the cam not lined up. The cam catches inside the lock case and you damage the gearbox.

  7. Fit the new cylinder

    10 min

    Put the new key in, turn it so the cam sits in line with the body, and slide the cylinder in from the outside, the right way round, until the screw hole lines up with the hole in the door edge. Fit the fixing screw and tighten it until it is snug, not tight; overtightening can bend the cylinder and make it bind. Turn the key both ways and check the cam moves freely.

    • Check the outside end does not stand proud of the handle or escutcheon by more than a few millimetres
    • Test the thumb-turn, if there is one, on the inside
    • Keep the new key card somewhere safe

    Mistake to avoid: Fitting a cylinder that sticks well out of the door. A proud cylinder is exactly what a thief grips to snap it.

  8. Test everything with the door open, then shut

    15 min

    With the door still open, lock and unlock from both sides several times, and work the handle. Then close the door, step inside, and lock and unlock from inside. Only then test from outside, with someone inside to let you back in if anything goes wrong. Check every key you have.

    • Test each spare key, not just one
    • Lift the handle and lock a multipoint door fully, then check the hooks have thrown
    • Note any stiffness now; it will not improve with use

    Mistake to avoid: Closing the door behind you to test the new lock from outside with nobody indoors. If it fails, you have locked yourself out.

The mistakes that cost a call-out

  • Testing a lock from outside with nobody indoors
  • Ordering a cylinder by its overall length
  • Oiling a lock that only sticks because the door has dropped
  • Fitting a cylinder that stands proud of the door
  • Changing a rented home's locks without asking

Stop here and get a locksmith

  • You are locked out, or a key has snapped in the cylinder
  • The lock was forced or the frame is damaged
  • A mortice lock, nightlatch body or multipoint gearbox needs replacing
  • You rent and do not have the landlord's agreement to change the locks
How to hire a lock repairer →

Key stiff in front door lockDry or dirty cylinder, or a worn key. Use graphite or lock lubricant, try a spare key, and replace the cylinder if it stays stiff.
Lock only stiff with the door shutThe door has dropped or the keep is out of line. Tighten the hinges, then adjust or ease the keep.
Cylinder will not come outThe cam is not lined up. Turn the key a few degrees either way while pulling gently. A seized cylinder needs a locksmith.
New cylinder too longMeasured wrongly or sizes swapped. Return it and reorder; do not leave it sticking out.
Key turns but the door will not lockCam not engaging the gearbox, or the multipoint hooks not lining up. Check the cylinder is the right size; if it is, the gearbox may be failing — call a locksmith.
Key snapped in the lockIf a piece sticks out, grip it with fine pliers and pull straight. If not, call a locksmith; picking it out often damages the pins.
Internal latch not catchingThe strike plate is out of line or the latch spring has failed. Move the strike plate or fit a new latch.
Handle droops on a uPVC doorThe handle spring or the gearbox is worn. A new handle set may fix it; if the gearbox has failed, call a locksmith.

WHAT YOU SAVE

What it costs to do it yourself

Standard Euro cylinder£20–£26
Three-star security cylinder£54–£55
Lock lubricant£4–£8
Total, one door£20–£60
DIY total£20–£60
A lock repairer charges per job
LOW
£70
TYPICAL
£100
HIGH
£180
Lock Repair price guide →

Guide prices compiled by the Locufy team from published Irish and UK provider price lists and 2026/27 cost guides. Updated 2026.

A cylinder change is one of the best-value DIY jobs; a locksmith's price is for lockouts, forced entries and gearboxes.

RATHER NOT?

Lock repairers near you, with prices shown

The ones who cover your area, nearest first, with one score from every review. No account needed to look.

Or post the job free and let them come to you.

Keep the lock running

Lubricate the cylinder lightly once or twice a year, and the bolts and multipoint hooks with the door open.

Look after the keys

Store the key card or code safely; cut copies from an original key, not a copy.

Dispose of the old cylinder

An old cylinder is scrap metal: take it to the household waste recycling centre's metal skip, or put it in the general waste. If you are a tenant, return the original to the landlord or refit it when you leave.

Tell your insurer if the policy asks

Some home insurance policies name the lock standard they expect; check the new cylinder meets it.

Fixing a stiff lock or changing a Euro cylinder: questions people ask

From the centre of the fixing screw hole to each end, written as two numbers. Keep the outside and inside sizes the right way round; a thumb-turn is marked with a T on its side.

Graphite powder or a lubricant made for locks, worked in with the key. Avoid cooking oil and heavy grease.

The door or the keep is out of line. Tighten the hinges, then adjust or ease the keep so the bolt runs clear.

Usually only with the landlord's permission. Check your tenancy agreement, ask in writing, and offer a key.

A cylinder tested and rated to resist attacks such as snapping and drilling. Three stars on the cylinder alone, or one star used with security handles, is the usual front-door level.

On the Locufy UK price guide lock repair costs £70–£180 per job, typically £100. Lockouts at night and gearbox replacements sit at the top.

MORE GUIDES

More DIY guides

Adjusting and fixing a uPVC doorHanging an internal door or fixing one that sticksFixing a window that sticks, drops or will not lockRepairing a garden shedRegrouting tilesPainting a roomHanging wallpaperSpray painting small items outdoors
All 90 DIY guides →How to hire a lock repairer →Lock Repair price guide →Lock repairers on Locufy →

Sources — checked October 2026

  1. Latham's Steel Security Doors — how to measure a Euro cylinder lock (the split, external and internal sizes, T for thumb-turn)
  2. Avocet Hardware — cylinder FAQs (graphite powder for a stiff key)
  3. HSE — manual handling at work, a brief guide (INDG143)
  4. Citizens Advice — renting privately: tenancy agreements and repairs
  5. GOV.UK — dispose of household waste: scrap metal and the recycling centre
  6. Wickes — Euro cylinders, price check October 2026
  7. Wickes — lock lubricants, price check October 2026