What Is A Mortise Lock?

Mortise Lock Cylinder

A Mortise lock by definition is any lockset where the edge of the door has to be mortised out in order to accept the lock. Still not clear? Mortise means to hollow out or remove material, usually wood from the edge of a door. Enough wood is removed from the door edge to accommodate the mortise lock set.

A Mortise lock usually looks like a box that measures approximately 5 inches in height about 4-1/2 inches in depth and is about 1 inch thick. The entrance type of Mortise lock usually includes a spring latch and deadbolt combination in one package. There are different functions available for this type of lock including, entrance, passage and storeroom among others.

This type of lock usually includes a lock cylinder that enables you to operate the lock from the outside of the door with a key. The area of the lock that accepts the lock cylinder is threaded as is the lock cylinder. The lock cylinder is actually screwed into the lock body and then held in place using a set screw.

There are many older homes in the Toronto area that still have this type of lock installed on the front door. They were very popular locks in the 1940’s and 1950’s and the parts are getting harder and harder to locate as the years go by. Manufacturers have not produced these locks for many years so there really is no source for new parts. As of this writing, the only part that is still available for these locks is the Mortise lock cylinder. They are very expensive to buy because they are no longer mass produced.

Mortise style lock cylinders however, can be found in newer applications than the old Mortise locks. Today these cylinders are used in storefront aluminum doors. You may have noticed that many stores have a front entrance door that is basically nothing more than a large plate of glass with a small aluminum frame around the glass. The style of lock found in this type of door usually accepts a Mortise lock cylinder.

There are even some deadbolt manufacturers that employ this type of lock cylinder in their standard deadbolt design. Many of the high security lock manufacturing companies also manufacture this type of lock cylinder although the cylinder can be used in two different applications, either as a Mortise or rim cylinder.

A rim cylinder is commonly found on garage doors. It usually has a spring latch associated with it. The cylinder is held in place on the door by 2 screws that screw into the Rim Cylinder body. It is much the same design as today’s most common deadbolts. The only difference between the Rim Cylinder and a standard deadbolt is the tail piece. The tail piece is at the end of the cylinder opposite to where the key hole is and is what actuates the deadbolt or spring latch. We will cover the rim cylinder and it’s applications further in depth in a future post.

Security Article Written by: Toronto Locksmith



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