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Bad Shear Locks
Electromagnetic "shear locks" are a popular choice of architects because the lock mechanism can be completely concealed with the door frame. Unfortunately, our experience with these types of locks has been almost entirely negative. First of all, the door must align perfectly in order for these locks to work. If the door doesn't fully close and seat properly in the opening, the lock will not bond properly. It's tough to get a door to align perfectly when its new, and nearly impossible to keep it aligned properly as the door ages.
Second, many of our clients have reported that electromagnetic shear locks are very noisy. When the door closes, the electromagnet in the door frame pulls the armature mounted at the top of the door against the lock. This metal on metal contact can make a loud "clunking" sound that many users find annoying. This noise can be particularly pronounced in places that have hard acoustical surfaces such as building lobbies.
We strongly urge our clients not to use electromagnetic shear locks. In several cases, these locks were installed during new construction but proved to be so unreliable that the building owner decided to replace them with frame mounted electromagnetic locks. The shear locks were left in the door frame so that there wouldn't be a need to install a filler plate. This creates a condition where there appears to be two locks on the door, even though the shear locks are no longer operational.
Here are a couple of actual examples of where frame mounted locks were used to replace shear locks:
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