Carpentry Guides DIY Spotlight

Fitting a New Door Lock

fitting a door lock

There are two main options available when fitting a new lock to a solid wooden door. The most common for heavy traffic entrances such as the front door of the house is the Cylinder Rim Lock, which features a key hole on the outside and a simple handle on the inside. The inside of a cylinder rim lock also features a deadlocking button and sometimes a secondary keyhole so the deadlock cannot be opened.

Rear entrance doors and internal wooden doors are more likely to suit a Mortice (or Mortise) Lock. The body and mechanism of a mortice lock is embedded inside the wood of the door and is locked or unlocked from either side using a key. Mortice locks feature a latch which is operated using the handle or doorknob, and a deadlock operated with the key.


Fitting a Mortice Lock

There is an old saying in DIY, “Measure twice and cut once”. With a job like this, measurement and marking out needs to be accurate. The better the lock mechanism fits into the mortise, the more secure the door will be. Taking the time to be accurate when measuring and marking will also save time overall.

Marking the Position of the Lock

Once you have bought the lock mechanism, the first thing you need to do is mark where the lock will go. If you are installing the lock into a new door, the best place for it to go is directly in line with the centre rail (the solid strip of wood running across the middle of the door). If you are adding the mortise lock to a door that already has a standard lock fitted, fit the Mortice just above the existing lock, as close to the rail as possible. Hold the body of the lock against the edge of the door and use it as a template to mark the top and bottom of the mortice you need to cut. Now measure the width of the door edge and draw a line down the middle or the mortice mark you just made.

Drilling Out the Recess

Take a Drill Bit the same width as the body of the lock and using a strip of electrical tape, mark the depth of the lock on the drill bit. Now drill a series of overlapping holes along the middle line you marked (the tape will let you drill them all to the correct depth). With a sharp Chisel, take out the small ridges of wood not removed by the drill until you have a nice straight mortise.

Fitting the Lock

mortice-lockInsert the lock into the mortise and mark around the faceplate. Remove the lock and carefully Chisel out a recess for the faceplate to sit in. This will need to be no more than 3-4mm deep. Re-insert the lock to check everything fit nicely. Now hold the lock against the side of the door, lining it up carefully with the mortise and with the edge of the door. Mark the position of the key and spindle holes by pushing a sharp point through the keyhole in the lock mechanism and, using a drill bit the same width as the shaft of the key, drill out the keyhole. If you have a Pad Saw, you can use this to shape the hole, if not, three carefully drilled holes will do the job.

Slide the lock mechanism back into the mortise and check that the hole for the lock lines up with the mechanism. If it does, you can mark the screw holes in the faceplate and drill guide holes for the screws using a 3mm drill bit. Screw the lock mechanism firmly into place using 50mm or longer screws.

Fitting the Striking Plate

With the bolt (and latch if there is one) open, close the door against the frame and mark where the top and bottom of the latch and bolt touches the frame. Extend those marks around onto the face of the frame. Now measure from the edge of the door to the centre of the bolt, and use that measurement to mark where the centre of the mortice needs to be on the doorframe. Cut out the mortise in the same way you did on the door, only using a drill bit the width of the bolt. Chisel out any excess wood once the drilling is done. Close the door and make sure the bolt lines up with the hole.

Line up the Striking Plate with the mortice on the frame and mark around it. Chisel out a rebate so the striking plate will sit flush in the frame. Finally, mark the screw holes in the striking plate and drill guide holes. Screw the plate into place and the job is done.


Fitting a Cylinder Rim Lock

Cylinder Rim Locks fit on the inside face of the door, with the Staple (the part that the latch sits in when the door is closed) sitting on the face of the door frame. Because of this, cylinder rim locks are only really suitable for solid wooden doors.

Positioning the Lock

The first thing you need to do is decide where the lock will be positioned on the door. It should be placed roughly halfway up the door for the sake of security, but it is worth placing it slightly higher if you have small children who could reach a lower placed lock.

When you have decided where to position the lock, mark a straight horizontal line in from the edge of the door using a Combination Square. Continue the line around the edge and front face of the door. This will be your guide for drilling the hole for the lock cylinder.

On the back of the lock, measure the distance from the front edge to the hole that takes the connecting bar (it should be the only hole you can see on the back of the lock mechanism). Transfer this measurement onto the lines you marked on the inside and outside face of the door. You now have the position of the cylinder hole.

Fitting the Lock

Using your mark as a guide, drill a hole through the door with a flat or auger drill bit. The instructions that came with the lock may recommend a size to use. If not, use a 15-20mm wide bit. Drill from both sides of the door to avoid splitting the wood surrounding the hole.

Slide the cylinder into the hole from the outside, with the connecting bar extending in through the hole. The flat plate on the front of the cylinder should sit flat against the outside face of the door. Place the mounting plate over the hole on the inside of the door with the connecting bar passing through it. Fix this to the door (making sure it is straight and level) using the screws provided.

Depending on the thickness of your door, you may now have to trim the connecting bar using a hacksaw. Make sure that you leave enough bar sticking out to engage the hole in the lock mechanism. Slide the lock mechanism onto the mounting plate and fix it in place using the mounting screws provided.

Fitting the Staple

Close the door and use a straight edge and pencil to mark the position of the top and bottom of the lock on doorframe. This will be your guide when positioning the staple. Open the door and hold the staple in position on the door frame. Draw around it to mark out exactly where it needs to go. The front face of the staple (that faces the lock) needs to be flush with the edge of the doorframe. Use the outline you have just drawn to chisel out a thin recess to accommodate the face of the staple.

Finally, secure the staple in place using the screws provided and then test the lock to make sure that it closes and locks properly. It is worth considering adding extra security bolts to a door if the Cylinder Rim Lock is the only locking mechanism in place.


Added Security – Fitting Rack Bolts

rack-boltThere are several reasons why you might want to fit Rack Bolts to your door rather than other types of bolt. They are very secure whilst being unobtrusive and because the mechanism is embedded in the wood of the door, they are difficult for an intruder to tamper with. They can be used on both doors and windows and are particularly good when used in conjunction with a properly fitted Mortice or Rim lock.

The first thing you need to do is measure the size of the bolt (although it should be stated on the packaging) and find a wood drill bit to exactly match. You want the hole to be as closely fitting as possible so that there is little movement when the bolt is in the hole.

Drill your hole at the required height to the depth of the bolt. measure from the front of the faceplate of the bolt to the keyhole in the shaft of the bolt and transfer that measurement onto the face of the door using a Try Square. Take your time to make sure that the hole for the key is going to line up with the keyhole in the bolt.

With the keyhole measured and marked correctly, drill the keyhole (usually with a 10mm drill bit). Slide the bolt into place and make sure the key meets the keyhole in the bolt. Leave this in place for a moment while you mark the position of the faceplate. chisel out the recess for the faceplate with a small woodworking chisel. Now re-insert the bolt and screw the faceplate into the recess. Mark the holes for the keyhole plate and screw the keyhole plate into place.

Now close the door and operate the bolt to make a mark on the door frame. This will show you exactly where you need to drill the hole (16mm usually) in the frame which will take the bolt in its locked position. Drill out this hole and fit the lock plate over it. This should also be recessed for the best finish. Once this is done test the bolt again with the door in the closed position.

If fitting a rack bolt to a window, follow the instructions above but consider fitting the bolt so that it locks into the top or bottom of the frame rather than the middle rail, as this will be more secure. Window rack bolts are usually smaller than those designed for doors, but are essentially the same.