How to Measure a Euro Cylinder

A euro cylinder is the oval or oblong barrel that sits inside the lock case on most uPVC, composite, and aluminium doors. You will see it face-on as a small oval plate with a keyhole, usually with a thumb-turn on the inside. The cylinder is held in place by a single retaining screw accessed from the edge of the door. When you turn your key, the cylinder rotates a cam or tailpiece that operates the multipoint lock mechanism — the system of hooks and bolts that run up and down the door edge and engage with keeps in the frame.

Euro cylinders are not universal. They come in a wide range of sizes, and fitting one that is even a few millimetres too long on the outside face is enough to make snapping significantly easier for a burglar. Cylinder snapping is a well-documented method used by opportunist burglars across the UK: they grip the exposed part of the cylinder with a tool and apply sharp downward force, shearing the cylinder at its weakest internal point and disengaging the lock entirely in seconds. Streets around Station Road and Orpington High Street have not been immune to this — it is a nationwide problem that good cylinder choice and correct measurement directly address.

You will need a flat-head screwdriver to remove the door handle if it obscures the cylinder face, a tape measure or steel rule, and a pen and paper. Begin with the door open and standing on the inside. Measure from the centre of the retaining screw hole (or the centre of the cylinder itself, which is the same point) outward to the outside face of the door — this is your external measurement. Then measure from the centre of the retaining screw hole inward to the inside face, which is your internal measurement. The two figures together give you the cylinder size, written as external x internal — for example, 35x45mm. Always double-check by measuring the cylinder itself if you can remove it, rather than relying solely on the door thickness, because the cylinder may already be an odd size from a previous replacement.

The critical number for security is the external (outside) figure. As a rule of thumb, the outside of the cylinder should sit flush with the outer face of the door furniture, or no more than 3mm proud of it. If your existing cylinder protrudes 5mm, 10mm, or more, it is presenting a snap point. When you go to change a door lock or order a replacement cylinder, choose the smallest external measurement that still allows the key to turn freely — typically this means the external side is shorter than the internal side, which carries the thumb-turn. Anti-snap cylinders, particularly those carrying the TS007 3-star rating, have a deliberate snap point built into the external section so that if someone does apply force, the outer portion breaks off cleanly while the internal mechanism and thumb-turn remain fully intact and the door stays locked. This rating is now widely recommended by insurers, and it is the standard Chelsfield Locksmith fits as a matter of course during any door lock replacement Orpington appointment.

Cylinder snapping rarely features in evening news reports the way a smashed window does, but it accounts for a substantial proportion of residential break-ins involving uPVC and composite doors across the UK. The reason it is so prevalent is straightforward: it is fast, quiet, and requires no specialist skill. A burglar does not need to know how to pick a lock or how to pick a door knob lock — they simply need a pair of pliers and a protruding cylinder. The whole process can take under thirty seconds on an unprotected door, leaving no broken glass and sometimes no immediately obvious sign of forced entry.

If you have recently moved into a property in Orpington, St Mary Cray, Petts Wood, or Chelsfield and you are unsure what grade of cylinder is fitted, it is worth checking before you need an emergency locksmith Orpington in the middle of the night. Look for a logo or rating stamp on the cylinder face — a 3-star TS007 mark or a kite-mark alongside it indicates an anti-snap product. If there is no marking, or if the cylinder is an older brass-coloured barrel that protrudes noticeably, treat it as a priority to replace. Our team can assess and change the lock in a single visit, confirming the exact price before any work begins.

Once you have your measurements, you are looking for three things in a replacement cylinder: the correct size, the correct finish to match your door furniture, and the correct security rating. For most homes in the Orpington area, a TS007 3-star anti-snap cylinder in a size where the external measurement is flush or very slightly recessed is the right choice. If your door has a thumb-turn on the inside (common on back doors and flats with communal entrances), confirm whether you need a key-and-thumb-turn or a double-key cylinder — the latter requires a key on both sides and is typically only appropriate in specific circumstances such as glazed doors where a burglar could otherwise reach in and turn the thumb-turn.

Replacing the cylinder yourself is straightforward if you are comfortable with basic DIY: open the door, locate the retaining screw on the edge, loosen it, insert your key partway to release the cam, and pull the cylinder out. Installation is the reverse. However, if the cylinder is seized, the door has dropped on its hinges, or the multipoint lock is not operating correctly, the job becomes significantly more involved. uPVC door lock repair Orpington calls are among our most common — a door that will not lock or unlock is not always the cylinder itself; it can be a failed gearbox in the multipoint mechanism, worn keep plates, or a misaligned door that is putting stress on the whole system. If you are not certain of the cause, calling a professional before you start pulling components out avoids turning a straightforward repair into a larger one. You can reach Chelsfield Locksmith any time on 020 3757 6199 — we are available 24 hours a day, every day of the year.

If you are locked out in Orpington and reading this on your phone, skip straight to the bottom of this page and call us — we send a locksmith straight away and are usually with you in about 30 minutes. For everyone else planning ahead, the question of whether to change a lock cylinder alone or opt for a full lock change is worth thinking through properly. Moving into a new property is the most obvious trigger: you have no way of knowing how many copies of the previous keys exist, and fitting a fresh cylinder is the fastest way to establish control of who can enter your home. The same applies after a tenancy ends — landlords and letting agents in the Orpington area regularly ask us to change the lock between occupants as a straightforward precaution.

A full door lock replacement Orpington appointment covers more than just the cylinder. We check that the multipoint lock body is functioning correctly, that all hooks and bolts are engaging their keeps cleanly, and that the door is sitting in the frame without undue resistance. On timber doors, we also look at the 5-lever mortice deadlock if one is present — many insurers, including those covering properties in BR5 and BR6, specifically ask for a BS3621-rated mortice lock on the main entrance. We confirm all of these details and give you an exact, agreed price before we begin. Factors that affect the final quote include the type and size of lock, the number of cylinders being replaced, the time of day (evenings, weekends, and bank holidays are considered), and travel distance — but there are no surprises on the invoice. As a 24 hour locksmith Orpington homeowners and tenants have come to trust, we are on call regardless of when you need us.

If you find yourself locked out Orpington-side, run through these checks first: try every other door and window on the ground floor, check whether a neighbour or family member holds a spare key, and if you are a tenant, contact your letting agent's out-of-hours line to confirm whether they hold a key. These steps take under five minutes and occasionally save a call-out altogether. Do not be tempted to look up how to pick a lock or attempt to force a window — apart from the risk of injury, you may cause damage that costs considerably more to repair than a locksmith visit, and in a rented property you may be liable for that damage.

If none of those options resolves the situation, call 020 3757 6199. We will confirm your address, verify that you have a right to access the property, and dispatch a skilled locksmith straight away. We cover Orpington, Chelsfield, Farnborough, Green Street Green, St Mary Cray, Petts Wood, and surrounding areas — if you are within reach of an BR postcode, we can almost certainly help.