Euro profile cylinder in a mortise case (DIN)
The most standardised lock family on earth. A 17 mm × 33 mm profile cylinder sits in a mortise case built to DIN 18251, driven by an 8 mm square spindle, with a 72 mm centre distance on interior doors. If you design one adapter well, you cover most of continental Europe.
Also called: Euro cylinder · DIN cylinder · Profilzylinder · PZ cylinder
Anatomy
- Profile cylinder — the replaceable keyed barrel, keyed both sides or with a thumb-turn inside
- Mortise case — the box mortised into the door edge, holding the latch and deadbolt
- Cam — the tab on the cylinder that throws the deadbolt
- Follower — the 8 mm square hole the spindle passes through to retract the latch
- Faceplate — the strip visible on the door edge
- Strike plate — the pocket in the frame
Parameters to measure
Measure in this order: Centre distance, spindle-to-cylinder (Entfernung / PZ) → Backset (Dornmaß) → Cylinder total length and halves (e.g. 35/35) → Faceplate width × length → Spindle (follower) size → Door thickness
| Parameter | Typical values | Tolerance that still fits | How to measure |
|---|---|---|---|
| Backset (Dornmaß) | 55 mm (interior), 60 mm; 65 / 70 / 80 mm on exterior and older doors | ±1 mm still fits most cases | Door edge to the centre of the cylinder hole. |
| Centre distance, spindle-to-cylinder (Entfernung / PZ) | 72 mm interior, 92 mm exterior; 78 / 85 mm on older doors | None — this is the number that decides handle fit | Centre of the spindle hole to centre of the cylinder hole. |
| Faceplate width × length | 20 × 235 mm or 24 × 235 mm; 24 × 280 mm on fire doors | ±2 mm | Width and length of the strip on the door edge. |
| Cylinder total length and halves (e.g. 35/35) | 30/10, 35/35, 40/40, 45/45 mm halves; total 60–90 mm | Must be exact, in 5 mm steps | From the centre screw to each end, measured on the installed cylinder. |
| Spindle (follower) size | 8 mm square (7 mm exists on older hardware) | None | Calliper across the square. |
| Door thickness | 38–50 mm interior, 40–68 mm exterior | — | Measure at the lock, not at the corner. |
Retrofit architectures that work
- Motor on the thumb-turn — A geared motor clamps over the existing cylinder body on the inside of the door and turns the thumb-turn (or a key left in the cylinder). The lock case, cylinder, faceplate, keys and door prep are all untouched.
- Electronics integrated in the cylinder — The cylinder itself is replaced by a cylinder with the motor, battery and radio inside. The outside keeps a mechanical keyway; the inside is a motorised knob. Nothing else on the door changes.
- Motor replacing the interior handle — The interior lever or knob is replaced by a motor unit that drives the 8 mm spindle directly. The outside keeps the original key cylinder and handle. This is the cleanest fit for mortise locks where the bolt is thrown by the key and the handle only retracts the latch.
This is the best-served family for retrofit because the cylinder is a separate, standardised, replaceable part. Check two things first: does the cylinder have an emergency (double-clutch) function, and does the thumb-turn protrude enough to clamp.
Related standards
DIN 18251 · DIN 18252 · EN 12209 · EN 1303 · EN 1634-1
Reference devices
Recorded as engineering examples, not endorsements.
- Nuki Smart Lock — Motor on the thumb-turn ✓ verified
- Yale Linus L2 — Motor on the thumb-turn ✓ verified
- SwitchBot Lock Pro — Surface motor on a deadbolt turn-piece ✓ verified
- Aqara Smart Lock U200 — Motor replacing the interior handle ✓ verified
- Tedee smart lock — Electronics integrated in the cylinder ✓ verified
- 1Control DORY — Electronics integrated in the cylinder ✓ verified
Questions
Why does 72 mm matter so much?
Because the handle is drilled at that spacing. A 72 mm handle on a 92 mm case cannot be fitted without redrilling the door, which on a fire door is not allowed.
What does 30/10 mean on a cylinder?
The distance from the central fixing screw to each end: 30 mm outside, 10 mm inside. Order the two numbers separately, never just the total.
What is an emergency function cylinder?
A double-clutch cylinder that can still be opened from outside with a key even when a key is inserted inside. Every retrofit motor that leaves a key in the cylinder needs one.