How to Change a Euro Cylinder (UPVC Door)

Handles & Hinges UPVC Maintenance Ltd helps UK homeowners and trades swap euro cylinders quickly and safely. Follow the steps below to remove the old cylinder, measure correctly, and fit the new one (key/key or thumbturn).

Security note: Consider an anti-snap (TS007 3-Star or 1-Star + security furniture) cylinder for best protection against common attack methods.

Tools & parts

Pozi/Phillips screwdriver
New euro cylinder (key/key or key/thumbturn)
Measuring tape or ruler
Optional: graphite lock lubricant (non-oil)

Measure before you buy

Euro cylinders are sized from the centre of the fixing screw hole to each end. Record both halves (outside/inside):

A = Centre of screw → outside end
B = Centre of screw → inside end

Common examples: 40/40 (80mm), 35/45 (80mm), 45/50 (95mm), etc. Choose the size so the cylinder sits flush or just shy of the escutcheon outside — not proud.

Step-by-step: replace the cylinder

Open the door
It’s easier with the door open so the latch isn’t under pressure and you can access the edge screw.
Remove the retaining screw
On the lock faceplate (door edge), undo the long screw in line with the cylinder. Keep it safe.
Align the cam and withdraw
Insert the key and turn it a few degrees to align the cam with the cylinder body. Gently pull the cylinder out while wiggling the key until it slides free.
Measure A/B
From the centre of the retaining screw hole to each end. Note which side is outside (usually the shorter projection on many doors).
Fit the new cylinder
Slide the new cylinder in (correct orientation: thumbturn usually on the inside). Use the key to align the cam if it snags. Refit the retaining screw; do not overtighten.
Test operation
With the door open, lock/unlock from both sides. Ensure the key withdraws in both positions as expected and the cam engages the gearbox smoothly.

Quick reference

What	How	Why it matters
Size (A/B)	Centre screw → each end	Flush fit; correct cam engagement
Type	Key/Key or Key/Thumbturn	Convenience vs. external key control
Security	Anti-snap / TS007 rating	Resists snapping, drilling, picking
Projection	Cylinder shouldn’t sit proud outside	Reduces attack surface

Browse Euro Cylinders Need sizing help?

FAQ

The new cylinder won’t slide in — why? The cam is probably not aligned. Insert the key and turn a few degrees while gently pushing.

Key turns but doesn’t lock the door? The cylinder may be the wrong size or not centred; loosen the retaining screw, reseat, and retighten.

Thumbturn outside or inside? Thumbturns go on the inside for emergency egress and ease of use.

Do I need anti-snap? Strongly recommended for front doors and exposed locations; it’s a major upgrade over basic cylinders.