An Overview of Cylindrical Deadbolts

The bolt is the heart of the deadbolt. Bolts will vary in diameter, material, construction, length and backset. Smaller bolts will generally be found on lower grade residential locks.

Finally, the backset of the deadbolt must match the door preparation.

The two most common deadbolt applications are two and three-eighths and two and three-quarters of an inch backset. With this in mind, many manufacturers have designed deadbolt mechanisms that are adjustable between the two measurements.

Another bolt-related design change is a metal shield designed to cover the top edge of the deadbolt when it is in use. The metal shield is attached to the lock housing and prevents someone from using a sharp pointed instrument from attacking the activating finger of the deadbolt.

In this type of attack, an awl or ice pick is pushed through the door, just above the outer deadbolt trim ring. The tool can be used to manipulate the activating finger to a neutral position allowing the bolt to be withdrawn, unlocking the door. The shield covers this sensitive area from attack.



Often overlooked during the installation is the strike plate. When an existing deadbolt is replaced, the existing strike is often re-used if is properly aligned and the bolt throws and retracts smoothly.

The problem with this habit is that you may be short-changing the customer on security. Most Grade 1 and 2 deadbolts are now packaged with a security or heavy duty strike plate and extra long (3” long) screws in order to secure the strike plate into the inner stud of a wooden frame. Other over-sized and aftermarket security strikes are available as well. All are intended to increase security.

If the gap between the lock side of the door and the jamb is large, surface mount the strike plate. Explain to the customer that by surface mounting the strike plate, the deadbolt has more material to push against provided a more secure installation.



Mortise locks may incorporate deadbolts in the mechanism, but they aren't considered auxiliary deadbolts.

Some cylindrical deadbolts are incorporated into a knob or lever lock by the trim. Usually these appear to be a separate knob and deadbolt from the exterior, but are interconnected with an interior trim plate. When the deadbolt is locked, turning the inside knob retracts both the dead latch and deadbolt in one motion.

East Coast locksmiths still deal with a lot of surface-mounted or rim deadbolts. These are usually installed above the knob or mortise lock and use a rim cylinder on the outside and a surface-mounted deadbolt lock body with a thumb turn for inside control. The bolt throws into a surface-mounted strike.

The final consideration when selling and installing a deadbolt lock of any type is to look at the door and the area surrounding the jamb. If the door is not solid core, a deadbolt will probably not provide the desired security. A single pane window large enough for a person to walk through adjacent to the door lessens security dramatically. A non-graded deadbolt with a 5/8” throw is probably not worth installing. A quality deadbolt lock properly installed onto a solid core door can provide the end user with many years of confidence and security. Remember the cost of residence must be considered when selling a deadbolt.          

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