Let us understand some materials for door construction before we go on to door locks. Doors are usually made of a wood, metal or a hybrid of the two.
Metal Doors
Metal doors are constructed using angles, tubes and flats of mild steel or stainless steel. They can be made artistic and are usually installed as an extra protection to wood doors. Door locks are usually welded onto such doors.
The Anatomy of a Wooden Door
Wood doors are generally constructed depending on the size of the wooden panel available. A single panel wood door is the strongest but also has a problem of bending, warping or shrinking if not seasoned properly. Availability of panels 3 to 4 feet in width is scarce and pushes the construction cost of the door up. Multi-panel doors made of three or more panels are the most common due to wide availability of narrow panels. Multi-panel doors though cheaper are weaker and need reinforcement. This is achieved in 2 ways - with the reinforcement reapers placed on the outside of the door or with cross braces on the inside of the door. The skill of the craftsman also plays a significant role in the construction of the door as the quality of the joints is very important for its strength. Also metal fasteners cannot be used in the joinery of such doors, instead wooden dowels are recommended - again laying emphasis on the skill of the carpenter. In the hands of such a craftsman, the door becomes a single solid unit. Equally important is the construction of the door frame. A door installation is completed using hinges, door locks and other hardware such as handles, tower bolts and stoppers. Most door locks are generally manufactured keeping a wooden door in mind. A wooden door is not only strong, it is also preferred due to the ease of fitting hardware onto it and also due to the aesthetics of the wood grains.
Hybrid Doors are usually a sandwich of a metal sheet between two wood panels. The metal gives added strength to the door, thus allowing for slimmer doors. The wood panels allow for fitting of hardware using regular fasteners such as screws. These doors are fast gaining popularity due to lower cost and improved strength.
The requirements for a good entrance door lock are as below :
. An entrance door lock has to be strong, trouble free and convenient to use.
. Keys that should not be easily duplicated or cannot be duplicated at all.
. Strong locking bolts.
. Crowbar attack resistant.
. Strong locking shackle/clamp.
. Drill Resistant.
. Concealed fitting.
. Ease of use.
. Long Life and trouble free service.
It should have all of the above features and functions and also look good.
Major Components of a Door Lock. Locking tumbler or cipher.
. Key or the decipher.
. Locking Bolts.
. Locking Shackle.
. Lock Body.
What kind of door lock must one buy?
A few major factors that influence the choice of a door lock are listed below:
Lever Technology, Pin Cylinder technology or Dimple Key Pin Cylinder
Abstraction is what must be considered in the choice of technology. The more abstract or unique the manufacturing techniques used to manufacture the lock, the safer it is. Knowledge or the lack of is definitely the key to the safety of door locks. Another factor for safety is the accuracy or "resolution" of the locking tumbler and key. The higher the resolution, the harder it is to replicate. Higher resolution locks require more sophisticated machinery such as CNC lathes often costing crores of rupees, making duplication prohibitive. The number of key combinations per lock also matters in the overall safety.
One of the oldest technologies in door locks is lever technology. It involves a toothed key and a set of levers set inside the lock. The knowledge of this technology is wide spread and can be easily duplicated. The keys can be made easily using a set of files. Although very dependable, locks using this technology are low in safety.
Pin cylinder locks on the other hand have a jagged key with higher resolution than a toothed key. These locks are popular among buyers looking for an economical and safe lock. Duplication is difficult, but not impossible.
Dimple Key tumbler locks are the next level of locking technology in which the cipher has one or more rows of pins that engages the lock when the dimples in the key match the pin pattern. These locks require accurate, high precision sophisticated machinery to manufacture. The number of key combinations that can be generated for a given lock using this method is in the millions, making each key one in a million.
Advances in technology are producing even higher key resolutions and key combinations. As the key resolution and key combinations go up, the price goes up due to increased cost of manufacturing. It is wise to think of the trade off between safety and price before taking a decision.
One Sided or Two Sided Key Operation:
A door lock with one sided key operation will have a hand operated knob on the inside and a key hole for key operation on the outside. This feature reduces cost due the use of 1 less pin cylinder in the lock and has the convenience of key-less operation from the inside. This kind of lock has one major drawback - the lock can be manually unlocked by reaching in from a window near the door. Also anyone wanting to leave the premises need not have a key to unlock the door.
A two side key operated lock will not have the above drawbacks but will lack the convenience of key-less operation from inside.
Auto-Latch or Dead Lock
Auto latch locks will lock as soon as the door is closed. These locks have a latch which springs into the lock shackle when the door is fully closed. The advantage of such a lock is that one need not worry about the door being locked after exiting the premises. Just pull the door on the way out and it is locked. The auto latch mechanism can also be a bane. Lock out is possible. In the case of absence of keys and no one inside the premises, there is no way to open the lock other than to break open the door.
On the other hand a dead lock is locked manually and lacks the convenience of auto locking.
The above three are the major factors influencing the purchase of an entrance door lock. Any combination of the above three are available in the Indian market today.
Other factors to consider :
Style & Aesthetics and finish also play a role in the choice of a lock. The lock must match the hardware used on the door and should also match the interior decor.
Locking Bolts
Number of locking bolts plays a role and is a matter of personal preference and convenience. More bolts give better security. A locking bolt of minimum 1" length is recommended. Locking bolts that have a double throw are smoother to operate.
Striking Plate or Locking Shackle
Screws used to fasten the locking shackle onto the door should not only be perpendicular to the door plane but also parallel. This applies to the locking shackle and the lock.
Fastners
It might seem trivial to think about screws, nuts and bolts but they are the ones that attach the lock to the door. Good quality stainless steel fastners are recommended for strength and resistance to corrosion. Screws of length 3" are recommended for the lock shackle and lock.
Balcony/Terrace Entrance
Balcony or terrace locks need not have a key hole on the outside. The absence of the key hole not only leads to lower cost but also added safety. There is no risk of the lock being picked.
Hope this helps you to pick out a lock !! Happy locking!
Here is a great place to have a look at a range of entrance door locks available in the Indian market.
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