Rebated Double Door Offset Cylinder Sizing: Meeting Stile Clearance Formula
Engineering Overview: Installation guide for measuring and sizing offset Euro profile cylinders in rebated double doors, French doors, and asymmetric meeting stile profiles.
Technical & Engineering Specifications
| Mounting | Aligned to M5 mortise axis inside rebate |
|---|---|
| Application | Rebated Double Doors, French Doors |
| Rebate Depths | 12 mm, 14 mm, 15 mm standard step |
| Typical Specification | 30/40 mm or 30/45 mm Asymmetrical |
The Rebated Door Sizing Problem
In French doors and architectural double-door pairs, the meeting stiles overlap via a stepped rebate (typically 12 mm to 15 mm deep). Because the lockcase is mounted inside the active leaf's rebate step rather than the door centerline, symmetrical cylinders (e.g. 35/35 mm) will sit misaligned.
Mathematical Sizing Formulas
$$\text{Dim A (Internal)} = \frac{\text{Door Thickness}}{2} + \frac{\text{Rebate Depth}}{2} + \text{Escutcheon}$$ $$\text{Dim B (External)} = \frac{\text{Door Thickness}}{2} - \frac{\text{Rebate Depth}}{2} + \text{Escutcheon}$$
Practical Example (50 mm Door, 14 mm Rebate, 5 mm Plate):
- $\text{Dim A} = 25 + 7 + 5 = 37\text{ mm} ightarrow \mathbf{40\text{ mm}}$
- $\text{Dim B} = 25 - 7 + 5 = 23\text{ mm} ightarrow \mathbf{30\text{ mm}}$
- Required Cylinder: 30/40 mm Asymmetric Offset.
Frequently Asked Engineering & Selection Questions
Q1: Why do French doors require asymmetric lock cylinders?
The overlapping rebate step shifts the lockcase off-center, requiring an offset split such as 30/40 mm to keep the cylinder flush with handle escutcheons.