If you are installing a new lock on an exterior door, you are probably going to opt for a deadbolt for security reasons. However, if you simply want to replace an entrance or passage lock, it is basically the same process of installing a deadbolt. The difference being instead of putting in the key cylinders, you will put in the doorknobs.
If you are putting a new door in, your best bet is to get a door that is predrilled for the knob and latch. In that case, the job could not be simpler. You simply put the lock together and screw it in place.
Selecting a DeadBolt
The most important decision you will have to make when choosing a deadbolt is how you want to open the door. Single cylinder locks can be opened from the inside with a thumb latch. Double cylinder locks require a key from either side.
In most applications, a single cylinder lock is fine. On one side, a key will unlock it while the other side can be locked or unlocked with a thumb latch.
However, if you have a door with a small window in it, or it has a window next to it, a double cylinder will provide more security because if someone breaks the window, they will still need a key to unlock the lock from the inside, rather than simply turning the lock with their hand.
The downside to double cylinder locks is that if you do not store the key nearby, you would not be able to get out in the event of an emergency such as a fire. Over time, most people solve that by leaving the key inside the lock, however that defeats the whole purpose of installing a double cylinder lock in the first place.
All door locks have what is called a setback which is the distance from the edge of the door to the center of the knob or cylinder. There are two standards commonly used: 2 3/4 and 2 3/8 inches.
If you are drilling the holes yourself to install a new deadbolt in an existing door, a lock using either setback will be fine. If a the door already has the holes predrilled, measure the setback and buy a lock that matches that distance. However, even that is not a big deal because locks come with the ability to adjust to either setback.
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Installing a Door Lock
For this discussion, I will assume that you are installing a new deadbolt in a new location in a door, not simply replacing an existing one. Replacing an existing deadbolt is a simple project, but installing a new one in a separate location is more difficult because it requires precise drilling.
- Measure the deadbolt location from the edge of the door. Most locks you purchase will have a cardboard template to use for drilling. However, you can purchase a separate hard plastic mold that is better to guide the drill for a straighter cut. If you do not have a steady hand with a drill, consider purchasing one of those lock guides from any home improvement store for around $15. For the purpose of this discussion, I will assume the harder installation once again using the cardboard template.
- Tape the cardboard template to the door in the location where you want to installthe deadbolt. Use a sharp instrument such as a nail to mark the center of the cylinder on the face of the template and the side latch bolt hole on the edge of the door. Simply poke the nail through the template directly in the center of each side. This will be the point to set your drill.
- Bore hole on each side of the door with a power drill. To avoid splintering, drill through one side until the drill bit is almost through to the other side of the wood. The go to the other side of the door and finish the hole from the other side.
- Bore the latch bolt hole using a spade bit (usually ½ inch) from the edge of the door into the cylinder hole you just drilled on the other side on the door. Be sure to keep the drill absolutely perpendicular to the edge while drilling or you will have issues later when you install the lock cylinder. Again, this is where it might be wise to buy one of those separate lock mold drilling guides.
- Chisel out the edge of the door to mount the plate by screwing the plate with locking mechanism in place, then holding it tight to the door’s edge, trace around the brass plate with a utility knife. Now remove the screws and the plate from the door.
- Cut the outline of the recess by holding the bevel side of a chisel facing the inside ofthe recess. Using a hammer, tap the end lightly to start the cut. Only goes as deep as the thickness of the plate. If necessary as you progress, drop the plate into the groove you are creating to make sure you are not going too deep. Make a series of parallel cuts across the recess at a 45 degree angle to remove more of the wood from the door. Each time you will need to hammer the end of the chisel a bit to drive it into the wood.
- Remove the waste wood from the recess you are creating for the lock plate by holding the chisel at a low angle with the bevel side toward the door side. Push the chisel by hand to dig out the remaining waste.
- Insert the lock tailpiece through the latch bolt mechanism and test fit the cylinders. If the tailpiece is too long, adjust it at the indentations by bending it with a set of pliers while holding with another set of pliers.
- Put the strike in place and trace around the hole. Mark the center and drill the latch bolt hole with a spade bit. Again, you will have to dig this out a bit with a chisel to get the fit correct so that it allows the deadbolt to be inserted smoothly into the hole in the door frame. Close the door and lock the deadbolt to insure it goes into the hole correctly before screwing the strike plate in place.
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It is critical that you drill the holes absolutely straight in order to fit the locking mechanism correctly. Any devious from holding the drill absolutely perpendicular to the door on both cuts will results in issues later when you go to put the lock and mechanism together inside the holes. Believe me, I have experienced this and the lock will stick or simply not open or close if it is not perfectly straight. For that reason, I do recommend you buy one of the separate lock kits to guide the drill in place.
Once the holes are drilled correctly, the hardest part of the project will be chiseling out the side so that the plate fits flush with the door. However, this is not a difficult project and it can be done in under an hour for someone that is experienced, a little more for the novice.
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