Deadbolts: Home Security Improvements

Police and insurance experts say that in more than 40 percent of residential burglaries, thieves will enter a home through an unlocked door or window.

A determined burglar can smash his way into your home even when you do keep it locked, but experts also say burglars don’t like delays, noise, or other attention-getting risks.

Obstacles you can put in a burglar’s path, such as locks and deadbolts, increase your home’s security and your peace of mind.

The simplest and least effective locks are the kinds which are included as part of the door knob assembly. They are a great place to start, since most doors need knob/latch assemblies anyway; however, they should be used in combination with more effective locks for exterior applications.

Privacy lock, key-in-knob lock

A privacy lock has a lock on the inside knob only, and is usually used for installation on bathroom or bedroom doors.

A key-in-the-knob lock, on the other hand, characteristically has a key slot on the outside knob and a button, or thumb turn, on the inside. Key-in-the-knob locks are most often used on exterior doors, although they may also be used on closets or storage room doors where security is a concern.

Assemblies for these locks are called locksets, and consist of knobs or handles, a latch bolt assembly, and any associated trim. They are easy to replace, but an original installation is a bit more challenging since it requires precisely cutting and mortising holes into which the assembly will fit.

Surface mount, rim mount or vertical deadbolt

These names all refer to a single type of lock which bolts flush against the inside face of the door. Vertical bolts from the lock slide up and down through a strike attached to the door frame. This is the most easily installed type of supplemental security lock. They are, however, bulkier and visually more obtrusive than deadbolts that are mounted inside the door.

Internal deadbolts

Deadbolts are an inexpensive and effective way of adding security to exterior doors, and make a great supplement to key-in-knob locks. The best deadbolts have at least a 1-inch bolt with a hacksaw resistant steel pin. They are mounted inside the door and, with reasonable care, can be installed easily using a template provided by the lock manufacturer.

Mortise lock

Mortise locks are installed in a slot cut into the edge of the door. These locks include both a deadbolt and latch bolt in a single assembly, and come complete with knobs or handles. Because of the need for precisely mortising the slot for these types of locks, professional installation is usually recommended.

How to install an internal deadbolt

Tools and Materials List

Wood chisel (3/4-inch)

Hammer

Torpedo level

Carpenter’s square

Adjustable hole saw bit (or appropriate size)

7/8-inch spade or Forstner bit (or appropriate size)

1/8-inch and 3/16-inch drill bits

Electric drill

Tape measure

Pliers

Awl

Phillips-head screwdriver

Utility knife

Masking tape

Internal deadbolt

1. For maximum effectiveness, deadbolts should be installed 10-12 inches above, or at least 6 inches below, the existing lock. Make sure that your deadbolt placement will not interfere with screen or storm door handles.

2. Your deadbolt will include a template for installation placement. Tape the template to the door, following the manufacturer’s instruction. Check the placement with a square and level to make sure it is straight on the door.

3. Locate and mark the pilot hole position for the screws with an awl. Also mark the center of the cylinder hole on the door face, and the bolt hole on the door’s edge.

4. Using a 1/8-inch bit, drill the pilot holes for the screws about 3/4-inch deep. Use care to keep the drill level. Then, using an adjustable hole saw set at the appropriate size for the cylinder hole (consult manufacturer’s instructions), begin drilling the cylinder hole through the door face. Use the center punch mark as the pilot hole, and drill as straight as possible until the pilot bit protrudes from the far side of the door. To prevent splintering the wood, finish drilling the hole from the other side.

5. Next, use a 7/8-inch (or appropriate size) spade or Forstner bit to drill the hole for the bolt through the edge of the door. Hold the drill level, and drill straight through to the center of the cylinder hole. Then continue drilling into the far side of the cylinder hole about 3/8-inch.

6. Insert the latch bolt into the bolt hole. To recess the latch plate and
make it flush with the edge of the door, score around the latch plate with a utility knife. Remove the bolt assembly and use a chisel to shave away thin layers of the wood to the depth of the plate. If you cut too deeply, you can shim behind the latch plate to bring it up flush with the door’s edge.

7. Install the bolt assembly to the doors edge with the provided screws. Insert the cylinder into the hole on the outside face of the door, sliding the connecting bar through the slot in the bolt latch. The bar will extend to the inside of the door.

8. Install the thumb latch assembly to the inside of the door, aligning it with the connecting bar. Secure the assembly with the mounting screws. Check to make sure that the bolt projects and retracts easily.

9. Turn the thumb latch to project the bolt. Then, hold the door closed
against the door frame. Trace the position of the bolt onto the door frame, using a square and level to continue the marks around the inside edge of the door jamb. Measure and mark the center point where the bolt will strike the jamb.

10. Prepare the hole in the door jamb where the latch bolt will project.
Some locks will require only a drilled hole, while others will require an elongated, square-edged hole be chiseled to accept a metal strike box.

11. Align the strike plate on the door jamb and mark around it with the
utility knife. Chisel out enough wood to allow the strike plate and box to fit into the jamb with its face flush with the surface of the jamb.

12. Install the strike plate and box. Mark pilot hole locations for the
strike plate attachment screws. Drill the pilot holes with a 3/16-inch bit, then install 3-inch screws driven through the jamb and into the framing stud.

13. Test the operation of your new lock.

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