Servicing and Retrofitting Mortise Locks

The purchase price of a mortise lockset is significant and usually is less expensive to repair than to replace.

These two entrance function locksets are available with or without deadbolt. They can be ordered as Office Vestibule, Vestibule, Entrance or Dormitory function.

The difference between the Series 91 and 114 is the hub. The hub transfers the rotational force of the knob or lever to retract the latch, and, if configured, the deadbolt. The hub is spring loaded and when rotational force of the lever or knob is released, the hub rotates back and the latch extend.

Different versions of the hub and spindles drive the hub. The Series 91 lock has a two part hub. One part transfers the force from the exterior lever or knob and the second part from the interior. This hub uses a swivel spindle that enables each lever to operate independently. The spindle has an enlarged portion on the exterior side that prevents it from being forcibly removed.

The Series 114 lock uses a hub with steel security separator. The separator is a solid wall within the hub requiring two separate spindles. Each spring loaded spindle is secured to an escutcheon. The outside mortise cylinder keeps the exterior escutcheon from being removed and removing the exterior spindle.

Mortise lock of the Series 91 and 114 sizes are common in many homes in the Northeast as well as other parts in the country. These residential mortise lockset are not ANSI or UL tested and cannot be installed onto fire rated openings.

The modern mortise lock is manufactured of stamped metal for the body (case). Earlier mortise locks were manufactured with cast metal bodies. When the case cracked after many years of wear, repairs were very difficult. An additional difficulty was these mortise locks were individually built at the factory. Each part would be hand filed in order to fit. There was no part interchange between any locks. If a mortise lock broke, it was not easy fitting replacement parts from another broken lock as sometimes the parts were too small or would not fit the lock.

The modern mortise lock has been improved with armored fronts, hardened bolts, through bolting, protection against vandalism and adjustable front. For example, many mortise locksets have handing and the latch that can be changed without having to remove the cover plate. These include Corbin-Russwin, Marks, Sargent and Schlage locks.

Another improvement is convertible mortise locks whose function can be changed. The Sargent Lock Multi-function Mortise Lockbody and the Schlage L9050 Universal Case each can be changed to become one of nine different functions.

With the standards enacted, case size and backset are now standardized making the pocket dimensions universal and the location of the knob or lever. One of the reasons for standardization is modification is not permitted to the mortise pocket in a Fire Rated Door.

Mortise locks are available electrified, providing the ability to control access remotely. Mortise locks can be electrified using a solenoid or motor and can be configured for Fail Secure (when power is not provided, the lock is in the locked condition) or Fail Safe (power is required to keep the mortise lockset in the locked condition).

Mortise Locksets comply with exit door, lobby door and stairwell door security needs and fire life safety code requirements. They can be installed into any wood or hollow metal door application, including applications where electric strikes and magnetic locks are not permitted.

Most brands of mortise locks are available electrified or existing mortise locksets can be electrified. Once a mortise lock has been electrified, it will still fit into the same door prep with the addition of a wire raceway. And as an added benefit, electrification of a mortise lock enables optional features including REX output, door status, and latched and locked status.



Servicing a mortise lock is relatively easy as the body can be removed from the door and disassembled without manipulating the lock cylinder. If there is a problem, the customer will normally tell you what it is. Whether it is the latch will not retract from the interior or the deadbolt will not throw.

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