FITTING A MORTICE LATCH
If you are reading this because you are about to hang a door, please check you have the door round the right way. See our hanging a door project first.
A mortice latch is the most common of door furniture being fitted to internal and external door alike. It is simply a catch with a handle either side.
Flush doors and lightweight hollow panel doors have lock blocks fitted inside them to allow for the lock or other door furniture you wish to fix. The cut away picture of a door below shows the frame and lock block which usually extends about 200mm either side (up and down) from the centre of the door.
First of all mark the position on the door where you want your handle and using a carpenters square, draw a line around the edge and both sides of the door, extending about 3 inches into the centre of the door. Draw the line lightly so it can be rubbed off later before painting.
The image top right shows the line extending toward the middle of the door. This serves as a marker for every operation while fitting a mortice latch. On the edge of the door, mark the centre of the line. Using a suitable drill, either a flat wood bit or an auger bit, ( The diameter of door latches varies so either measure yours, or see the fitting instructions on the packet. Common sizes are 18mm and 22mm) drill into the door. Keep the drill absolutely level while you drill and if you are using a panelled door as shown above, mark your drill bit with a piece of tape to make sure you do not drill too deeply. You can see how to do this in our fixing to masonry project. Measure the length of the barrel of the latch, including the latch plate itself.
When you have drilled the hole, which should be a couple of mm bigger than the barrel diameter, slide the barrel in so the latch plate sites against the edge of the door. The plate needs to be “let into” the door edge and this is done by marking round the latch with a sharp pencil. Pull out the barrel again and chisel out the insides of the mark you have made to the
depth of the latch plate (usually 2mm). Be very careful as you are chiselling as the latch plate will almost always be very close to the edge of the door. Most hollow doors have a very thin cover and it is easy to dislodge this as you cut away. The easiest, surest way to get an even cut is to chisel the latch recess as you would a hinge while hanging a door, lots of little cuts to the correct depth. Don’t forget to leave the pencil line in place or your recess will be cut too large.
When the recess is chiselled out, push in the barrel to fit. The latch plate on some barrels has raised edges behind the screw holes. If they are not too deep they can be sunk into he timber by tapping the latch plate with a mallet. The best way however is to push the latch plate into the recess as shown above right, and mark the centre of the screw holes, then pull it out again and drill lightly on the marks, with a 8mm wood bit. This allows the hole edges to sink into the timber leaving the latch plate to sit absolutely flush with the edge of the door.
Pull the barrel out again and hold to the side of the door along the line you have marked. Make sure the front of the latch plate is flush with the edge of the door and push your pencil through the hole in the barrel. Do this on both side of the door.
Drill through the door, from both sides. The handle securing plates will be large enough to cover a hole which is larger than the bar going through it and in most cases the same drill bit can be used which weas used to drill out for the barrel. DO CHECK THIS.
When the hole is through the door, the barrel can go back in and, using pilot holes, be screwed in. The bar is pushed through and the handles slid onto either side. Again, using pilot holes, fix the handles. Be extra careful when fixing these handles as, more often than not, the screws are slotted heads rather than cross heads and the driver can slip quire easily, scratching the handle.
Now push the door into the opening of the frame. Extend the mark on the door to the front of the frame and round into the frame. This line is also the centre of the keep which is the small plate which catches the latch as you close the door.
Put the keep up against the frame, with the centre of the keep in the centre of the mark and marl all round the keep with a pencil. Cut out for the keep plate justr as you did for the latch plate. Screw the keep into position. Using a 6mm chisel, cut out the centre of the keep, through the keep plate, to allow the catch to click in when the door is closed. The fixed keep can be seen in the right hand image of those above.