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Mortise locks Night latch Cupboard locks Tips and Tricks

Mortise locks
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Fitting a new lock
  1. Mark the position of the strike plate on the “lock block” side of the door.

  2. Remove the door and carefully measure and mark the middle of the thickness of the door at the lock position. One way to do this is to set your marking gauge to approximately half the thickness, make small indents from both sides of the door and keep on adjusting the marking gauge until the two indents are at exactly the same distance from the sides. That is the middle line. Or use the handy little centering tool described in "How to mark and measure". Accurate marking and sharp tools are essential

  3. The results of bad marking and blunt tools

  4. Mark the width of the body of the lock as well as the width of the face plate on the door and make the mortise by drilling 13 mm holes close to one another along the whole length of the lock body to the depth of the lock body. Clean out a hole for the lock body with a sharp chisel.

  5. Chisel away the wood around the hole to a depth of 2 mm to accommodate the face plate. The lock should now be a comfortable fit in the hole with the face plate flush with the side of the door.

  6. Check that the curved side of the latch is facing towards the door. If necessary turn the latch as follows. Open the lock body by undoing the screw(s) on the side and removing the cover plate. Make sure the springs are retained in the lock. Push the latch back into the body, lift it out, turn it over and replace.

  7. Hold the body to the side of the door and, through the body, mark the position of the key and handle holes with a bradawl. Drill holes large enough to accommodate the key and the handle bar, after clamping a piece of waste wood to the opposite side of the door to prevent splintering when you have drilled right through.

  8. Place the lock in the hole and fit the handle bar and key to ensure that they can move freely. Now screw down the lock and fit the handles.

Repairing a mortise lock

A faulty body mechanism cannot be repaired. It is better to replace the body.
  1. Remove door handle on one side of the door.

  2. Extract the handle bar.

  3. Undo the two screws holding the face plate and remove the lock body.

  4. Insert the new lock body and replace the screws. Screw down using either longer screws or fit a few match sticks into the existing screw holes.

  5. Replace the handle bar and handle.
Night latches (Yale locks)
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Fitting a new lock
  1. Drill a 34 mm hole in the door 60 mm from the edge using an expansion bit and brace or a spade bit.

  2. Fit the key mechanism (cylinder) into this hole and screw it to the plate provided. Rebate the door at the height of the lock to accommodate the face plate.

  3. Check that the lock bar and retaining screws are the correct length. Lock bars and retaining screws have small indents along their length where they can easily be broken off to allow for different thicknesses of doors.  

  4. Screw the lock to the inside of the door.

  5. Fit the strike plate to the frame.

Repairing a night latch

Night latches can only be repaired by a locksmith. Replacement cylinders can, however, be bought separately. If the cylinder needs replacement:
  1. Unscrew the lock from the door.

  2. Unscrew the cylinder from the plate.

  3. Remove the old cylinder.

  4. Check the length of the lock bar and fit the new cylinder.

Cupboard locks
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These are mostly one or two lever locks surface mounted on the inside of the door.

To fit a new lock:
  1. Carefully mark the position of the lock and key hole.

  2. Drill a 7 mm hole for the shaft of the key extending the hole downwards with a keyhole saw until the key fits through the hole.

  3. With the key in place, position the lock and screw it to the door.

  4. Fit an escutcheon plate to the front of the door over the keyhole.

Cupboard locks can not be repaired and have to be replaced.

Tips and tricks
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When replacing screws in existing holes, put a few matchsticks or toothpicks in the hole to give the screw a better grip.

Lubricate a lock with graphite powder or spray. Never use oil as this gathers dust and literally gums up the works.

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