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Repair and Maintenance of Mortise Locks on wooden doors

This advice may be slightly boring but is designed to help you save money and differentiate between a sash lock, dead lock and 5 lever locks or 3 lever locks, it may also help you maintain and repair the mortise sash type lock or mortise dead type locks.

Video showing how to fit a mortice dead lock:

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Mortice 5 Lever Security Locks - Repair and Maintenance for locks fitted to timber doors

All external Sash or Dead locks must be 5 lever and to BS 3621 for insurance purposes within the UK.Both lock types are sold in two varying depths 65mm and 75mm and in a brass or chrome style of face plate, they generally have a "box" type frame keeper for the lock to sit securely within when the door is closed, the face of each individual lock type is the same as any other lock of the same type by any manufacturer.

The 3 lever type locks look very similar to 5 lever but are generally lighter and do not have a box type keeper, they do not comply for insurance purposes, the word lever relates directly to the assembly mechanism within the lock, more levers = more security.

A sash lock is a lock that has a latch and a lock, the latch is operated by handles and thereby allows you to close the door on the latch without locking it, see image directly below.

View 5 Lever Sash Locks

The Dead lock is a lock that does nothing (dead) until you turn the key to throw the lock bolt, see image directly below.

View 5 Lever Dead Locks

The removal of the lock from the door and dismantling it for maintenance requires a small selection of screwdrivers, plain and star (Philips) type as well as some release agent and 3 in one oil or similar. 

For a sash type lock you will need to.......

1. Firstly remove the handle from one side of the door and remove the spindle (metal bar) that connects both handles through the lock, for a dead type lock there will not be a handle connected in any way to the lock.

2. Remove the front (face) plate from the lock that is visible on the edge of the door.

3. After (2) above you can then access the fixing screws that hold the lock in place and need to be removed but be aware that some front (face) plate screws are the fixing screws, either way, it really will be obvious.

4. Look at the face of the door and place a screwdriver through the spindle hole in the lock, and gently pull the lock horizontally towards the edge of the door until you can access it well enough to pull the lock from the door.

5. Now for the maintenance, remove the back cover from the lock, two screws should be holding this in place, be very careful as some internal parts known as "levers" or "detainers" are spring loaded and could jump out, see image below.

6. Remove the "levers" but BE CAREFUL and lay them out in a set order as they and any spacers between them must go back in the exact same order, the levers are shaped so that they match the key shape, these shapes are what give locks their individual security by up to 5000 different variations.

7. Clean each moving part of the lock with WD40 or similar and then a spot of oil on each of the same parts.

8. Reassemble the lock making sure to test the key operation at before you begin the installation process which is the reverse of the above processes.

9. A spot of oil on the handle mechanism will also help keep things running smoothly.

10. After reinstalling the lock and handle it is best to carry out a test of the lock operation before closing the door to do so, if all is well, close the door and test the lock operation from inside and outside the house.

Job done!

Mortise Dead locks need virtually the same process except there are no handles.

Info supplied by Chippy for

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