BHMA/ANSI standards cover three basic lock grades based on tests for strength, operation, construction and finish durability. Grade 1, the highest performance rating, is given to locks capable of performing through 800,000 cycles without failure. This means the lock can be latched and unlatched at least 800,000 times and still operate as intended. Locks given a Grade 1 rating must also withstand 300 lbs. of force per inch for knobs, or 700 lbs. of force per inch for levers.
Grade 2 locks must be capable of operating through 400,000 cycles while withstanding 150/450 lbs. of force per inch for knobs/levers. Locks rated as Grade 3 should operate for at least 200,000 cycles and should be able to withstand 120/225 lbs. of force per inch for knobs/levers.
Why Lock Grades are Significant
Grade 1 locks are designed to outperform Grades 2 and 3 in strength, durability and performance. Locks of a higher grade make it more difficult to pry the door open during a break-in. It is also more difficult to damage the lock using torque or cylinder wrenching, as locks of a higher grade can withstand greater levels of force.
A Grade 1 lockset can be expected to function properly through twice as many cycles as a Grade 2 lock. The Grade 2 lock, in turn, is designed to operate through twice the number of the cycles as the average Grade 3 lock.
Choosing the Appropriate Grade
Only Grade 1 or Grade 2 locksets should be used in commercial applications, except for situations in which the cost of the lock is the only concern. Grade 1 locks are the most popular choice for any building exposed to heavy traffic, including schools, offices and shopping centers. These higher-grade locks are the best option for resisting vandalism and for ensuring continued operation under frequent use. Choose Grade 2 locks for light-duty commercial applications, such as interior office or closet doors.
Grade 2 locks are generally sufficient for residential settings. In areas where break-ins are fairly common, a Grade 1 lockset can offer additional protection and help deter thieves. Grade 3 locks are sometimes appropriate for interior doors in the home that are used infrequently, such as those in an attic or storage space.
While there is a negligible cost difference between higher and lower lock grades, this cost is insignificant compared to the added life cycle and protection offered by higher-quality locks.