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.
Applies to these lock types
Euro profile cylinder in a mortise case (DIN) · Singapore HDB main-door mortise set and metal gate lock · Australian deadlatch and deadlock · Korean push-pull digital lock base (mortise)
Measurements this architecture needs
- Spindle (follower) size
- Centre distance, spindle-to-cylinder (Entfernung / PZ)
- Backset (Dornmaß)
- Handle fixing screw spacing
- Door thickness
- Escutcheon / rose diameter
Adapter interfaces to design
- Spindle coupler for 8 mm square (EU), 7 mm / 5/16 in (US), and worn or chamfered spindles
- Handle screw-spacing plates covering 38–70 mm pitch
- Clutch that decouples the motor from the outside handle in the locked state
Design targets
Targets marked "from standard" come from the cited document. Targets marked "practice" are our engineering guidance and must be verified for your design.
| Target | Value | Basis |
|---|---|---|
| Spindle torque | ≥ 1.5 N·m |
practice |
| Spindle travel | 45–90° for latch retraction |
practice |
| Lever force equivalent | A156.36 caps lever force at 3.6 N; the motor must stay under the door hardware's own limit |
from standard |
Known blockers
- Does not throw the deadbolt on locks where only the key can — so it is a latch opener, not a full lock.
- Split-spindle or free-turning outside handle changes the clutch design entirely.
- Fire doors with panic hardware: never interfere with the escape function.
Design checklist
- Decide the security model explicitly: does the motor lock, or only unlock?
- Test with a worn spindle — chamfered corners slip in a fresh coupler.
- Verify the escutcheon footprint hides the old handle's screw marks.