Double-Cylinder Locks: Design and Function

For commercial buildings and certain residential applications, double-cylinder locks and deadbolts offer an additional level of security. This type of lock has two cylinders and requires a key for locking and unlocking the door from the outside or inside. Unlike a single-cylinder lock, there is no thumb-turn lock mechanism.

Single-Cylinder vs. Double-Cylinder Locks

Single-cylinder locksets are locked and unlocked using a key on the exterior side of the door, but they don’t require a key for locking or unlocking on the interior side. A single-cylinder device can be locked and unlocked by simply turning or pushing the thumb lock on the inside knob; this engages or detracts the bolt.

Double-cylinder locksets are keyed on both sides; they function with a key from both the exterior and the interior of the door. This means that a home or business owner would need to use a key to engage or retract the lock bolt even from the inside.

 

Advantages of Double-Cylinder Locks

The main advantage of installing double-cylinder locks is enhanced security. That’s because doors with adjacent windows or glass panels can be broken, allowing intruders to reach inside and unlock the door manually. This is a significant weakness in terms of commercial break-ins and residential burglaries.

Double-cylinder locks are an extra layer of protection for home and business security. Without a button lock mechanism, intruders cannot unlock the door manually. Replacing single-cylinder locks with double-cylinder models may reduce successful break-ins by 50% or more. One important disadvantage is the extra safety concern. With double-cylinder locks, it’s crucial that an extra key is kept handy in case occupants need to exit the building in an emergency.

Double-Cylinder Lock Manufacturers

Kwikset, Medeco and Sargent are leading manufacturers of reliable, high-quality double-cylinder locks.

The Medeco Maxum residential deadbolt is rated as ANSI grade 1. It’s highly resistant to hammering and prying with its hardened steel inserts and rotating pins. Its hardened steel bolt in heavy-gauge steel provides maximum protection from forced entry. And it comes with locking technology to protect against unauthorized duplication.

Sargent deadbolts are engineered and built with top-quality materials to provide maximum security, performance, and durability. Customers can choose styles with either single-cylinder or double-cylinder mechanisms. These locks can be purchased both with, or without, a deadbolt.

Determining Quality & Security of Double-Cylinder Locks

Purchasing a high-quality lock product and installing it properly are two important steps in effectively increasing the level of security.

Quality Factors

Home and business owners should verify the American Nation Standards Institute (ANSI) grade of the door lock. The ANSI grading system is based on three factors: material strength, latch length and durability of the lock product. The highest grade is 1, and the lowest grade is 3. For the most secure result, look for a lock where the bolt is be made of hardened steel, a minimum of 1 in. in diameter.

Grade 1

This is often used for commercial applications. Grade 1 locks is tested to ensure that it withstands a million cycles, and 10 strikes with 75 pounds of force.

Grade 2

This is typically used for residential applications; it can stand up to 800,000 cycles and five strikes using 75 pounds of force.

Grade 3

Double-cylinder locks in the grade 3 category are generally used as an additional security measure. While they can withstand 800,000 cycles, it is only certified to resist two strikes with 75 pounds of force.

Security Factors

Proper installation is crucial to ensuring high-security lock performance. Be sure that:

• Screws used to secure the lock or deadbolt should be made of solid steel and penetrate from the inside of the door with no exposed screw heads.
• Connecting screws are a minimum of ¼ inch in diameter and are inserted into a solid metal shock.

It should be noted that no lock is 100% guaranteed to protect your home or business from intruders. However, you can lower the risk of a break-in by using double-cylinder locks and deadbolts.

Learn about a growing security risk for homeowners with cylinder locks: Lock Bumping.

Reliable Residential & Commercial Locksmith Services

If you’re seeking to secure your residence or commercial business, talk with the locksmith experts at Great Valley Lockshop, in Chester County, Pennsylvania. Our services include lock installation, repair, and replacement. We are also specialized in more advanced keyless and electronic access control systems.

Since 1973, we have been the go-to locksmith for local residents and business owners. Call our office at 610-644-5334 or request a quote online.