To correctly measure a composite door lock, you need to determine specific dimensions related to the handle, spindle, keyhole, and the lock body itself. Based on standard practices and the provided reference, the key measurements required are the handle/spindle centre and the backset.
Let's break down these essential measurements:
Key Measurements for Your Lock
Understanding these two critical dimensions is vital for selecting the correct replacement lock or identifying the specifications of an existing one.
1. Handle/Spindle Centre (Dimension A)
The Handle/Spindle Centre, often denoted as 'A', is a crucial measurement for aligning your door handles and keyhole.
- Definition: Taken from the centre of the keyhole to the centre of the handle/spindle.
- How to Measure: Position your measuring tape from the exact centre of the keyhole to the exact centre of the handle's spindle (the square bar that turns the lock mechanism).
- Practical Insight: Note that on some locks, as illustrated in the reference description, there might be two possible spindle points. Ensure you measure to the correct spindle point for your handle type or note both if present and applicable.
2. Backset (Dimension B)
The Backset, denoted as 'B', determines the distance from the edge of the door (where the lock faceplate sits) to the centre of the spindle and keyhole.
- Definition: The distance from the middle of the spindles to the front face of the lock.
- How to Measure: Measure from the middle point of the spindle(s) straight across to the front face of the lock body (the part that is visible on the edge of the door when the door is open).
Summary of Measurements
These two measurements are fundamental when dealing with composite door locks, particularly multi-point locking systems.
| Measurement | Description | How to Measure (as per reference) |
|---|---|---|
| Handle/Spindle Centre | Distance between keyhole centre and handle/spindle centre. | From the centre of the keyhole to the centre of the handle/spindle. (Note possible multiple spindle points). |
| Backset | Distance from spindle middle to lock face. | From the middle of the spindles to the front face of the lock. |
By accurately measuring the handle/spindle centre and the backset, you gain the necessary information to specify or identify the correct lock body for your composite door.
