Fitting door locks is a skill that most people don’t have but learning to fit a lock can save you time waiting for locksmith and money as they can charge not only to the fit the lock, but often a minimum callout fee as well which can soon add up, and you get the benefit of a having a secure home which is always a good thing.
I recently had to fit a couple of mortice locks and decided to share my tips on how so that you can learn a new skill and save a few bucks in the process and it’s not as hard as you might think.
Fit a mortice lock using the lock as a template and mark out the door. Drill out the center of the mortice to the correct depth and width, mark out and cut the door for the faceplate with a chisel or router. Mark and drill the keyhole through the door and fit the lock, then mark the door frame and fit the striker plate.
That’s the simplified version to get you started, now check out my full method and tools you will need along with some time-saving Pro tips in the post below:
Tools For Fitting a Mortice Lock
How to Position and Set Out a Mortice Lock
To install a mortice lock into a wooden door, and to get the right heights the door must be already fitted to the frame. This makes aligning the lock and striker plate easier, you can do this using a tape measure and transferring the dimensions across, but that can lead to errors.
To hold the door in the right place use a wedge or door-stop to prevent it from swinging on the hinges as you are working on it.
For the best results the mortice lock should be fitted in the middle of the cross rail, this is where the door is strongest. and will have the most material to work with and secure the lock in place.
This will also put the door handles at a height that works for most people.
How to Mark Out the Mortice Lock on The Door
The first step is to scribe a line centrally on the edge of the door with a marking gauge or pencil, this needs to be at roughly the height required for the lock. I use a center gauge to do this quickly but a tape measure pencil and straight edge work well, just double check by measuring from both sides of the door.
Use the lock body as a template and offer it up to the door, then using a sharp carpenters pencil mark the top and bottom of the mortice which needs to be removed from the door, I like to mark the waste area with a bit of cross-hatching, this makes it clear which areas need to be removed, even if you come back to the job at a later date, you will clearly see which bit is scrap.
How to Drill Out the Mortice For The Door Lock
The best way to cut out the mortice is by using a drill bit that matches the width of the lock body and a power drill and some sharp chisels
I use a Hikoki 18V cordless drill which has served me well for many years, drill into the centre of the door and remove the majority of the waste wood for the mortise, keeping between the lines you have marked out.
With drilling complete, square up the edges of the mortise with a sharp chisel, checking that the lock fits snugly in the mortice.
How to Mark Out the Faceplate of the Mortice Lock
Once again use the lock mechanism as a template and hold the faceplate of the lock against the door, in line with the mortice and with a marking knife, carefully mark around the edge of the faceplate, The knife will break the wood fibres on the surface helping to give a clean-cut,
I use some masking tape to protect the surface of the faceplate, this also gives you a little clearance around the edge as you mark it out with the knife.
Carefully cut out the waste material creating a series of shallow cuts with the chisel, then pare out the faceplate recess until it sits flush with the edge of the door.
If you are comfortable using power tools, you can use a trim router to cut this material away, using the faceplate as a depth gauge, and set the router tool to the correct height. I would recommend a small trim router like the Bosch GKF range of palm routers, as they are smaller and easier to handle on narrow surfaces like doors, unlike full-size routers which need more surface area to sit correctly on for a good, flat cut.
How to Mark Out the Keyhole
Once you have cut the edge of the door it’s time to drill out the keyhole.
This is where the lock comes back into use again, hold the lock against the side face of the door, inline with the mortice you have just cut out, and mark the center point for the keyhole, use a sharp bradawl or pencil, or you can use a small drill bit if you don’t have one to hand.
You can also do this by measuring the lock and transferring the measurements and marking the distance on the door. I often use this method to double-check the position of the keyhole.
How to Drill a Keyhole through a Door
To drill the hole through the door, it’s a good idea to clamp a sacrificial block on the far side where the drill bit will come out, position it and hold it in place with a speed clamp, take care not to over tighten the clamp as this could mark or damage the door,
Once the clamp is set you can then drill right through the door, the sacrificial block will stop the drill bit from tearing out the face of the door as it goes through the other side, leaving a nice, clean hole.
Then use a smaller drill to open up the lower part of the keyhole, these two holes need to be joined together to create a big enough space for the key to fit easily but not too big so the lock covers won’t cover it.
The keyhole needs to be shaped with a small slot to allow the key to fit, this slot is cut out on both sides with a pad saw or you can use a power jigsaw.
How to Fit the Mortice Lock into the Door
Clean up any loose wood and stray edges or strands with a sharp chisel then offer up the lock,
Using the fixings supplied with the lock, screw the lock into its recess that you have made and check it works properly and the key can easily engage with the lock from both sides of the door, if there are any tight spots, remove the lock and trim the areas that are required with a chisel.
Screw on the cover plate and then use the key to throw the lock into its locked position so that the bolt is sticking out.
How to Install the Lock Striker Plate
Carefully close the door against the frame, so as not to mark it and use a pencil to transfer the position of the bolt from the door to the frame.
Then unlock the door and close it fully, some mortice locks have markers on the ends of the bolt, and operating the lock whilst the door is closed, will mark the door frame where the lock will be positioned.
If the lock you are using does not have markers, use a steel rule to measure the size and position of the lock bolt, using the closing face of the door as the datum face, and transfer these dimensions onto the door frame, using the marks you transferred in pencil as your guide.
The striking plate can then be used to mark the door frame, using it as a template just as we did for the lock.
Cutting the Door Frame for the Lock Striker Plate
Again I wrap the striker plate in some low tack masking tape to prevent any damage and then cut around the striking plate with the marking knife and drill out the hole for the lock keep with the cordless drill and drill bit.
This doesn’t need to be very deep but check the depth by measuring how far the lock bolt throws when the key is turned.
You can then clean away the material for the striking plate either with a set of sharp chisels or by routing the wood away using a palm router and a small cutting bit.
I like using the sharp chisel for this as its too small for the router really, I have a good set which I got for Christmas a few years ago, these are made by Irwin tools,
If you use a router to cut these areas remember that the corners will need to be cleaned up with chisels to allow the square corners of the striking plate to fit properly.
You can then fit the striking plate and check the door closes and lock fully.
If the door is too tight or too loose against the door frame the striker plate and keep will need to be adjusted to correct this either by carefully removing some material with a chisel or adding shims that will need to be glued in place
It’s always better to be too tight so you can sneak up on the correct fit, rather than removing too much material and then having to glue shims back in, so take your time when measuring and setting things up.
Once you have the lock and striker plate adjusted, double-check all the screws are tight and check the lock works from both sides of the door.
Make your home safer with our guide to home security and get lots of tips.
This article was written by: Richard Quinton – The DIY Help Desk Owner, Engineer & technical specialist.
Richard is one of the key partners in The DIY Help Desk team. He is a qualified Engineer, writer, and publisher, educated to Master’s level. He is a keen advocate of DIY and home improvements.
Richard enjoys helping others to learn new skills and reach their goals and believes that passing his knowledge and experience on through his writing is an effective way to positively impact the lifestyles and well-being of others on a larger scale.