A Guide to Mortice Locks: Measurements and Functionality Explained.

Welcome to our blog where we aim to provide the answers to the most frequently asked questions about mortice locks, the most common type of door locking mechanism. While it may seem straightforward, mortice locks come with their own set of complexities. In this article, we will guide you through the various types of mortice lock cases, lock terminology, and the correct measurements required to replace or install a new mortice lock.

What Exactly is a Mortice Lock?

Simply put, mortice locks are installed on a door within a recess or pocket instead of being mounted on the surface. Only the forend of the mortice lock is visible when the door is open, as the lock itself is fitted into a recess or pocket. Mortice lock cases come with various functions, with the most common ones being 5 lever sashlocks and 5 lever deadlocks that are insurance-rated for external domestic properties. A sashlock is a mortice lock that combines a latch with a deadbolt operated by a pair of handles or doorknobs and a key. A deadlock, on the other hand, is only operated by a key and has a bolt that throws into a keep on the door frame. Latches, on the other hand, are beveled, spring-loaded bolts commonly found on internal doors that hold the door closed but do not lock.

How Can I Determine the Size of My Lock?

When measuring your existing mortice lock, it is best to remove it from the door if possible. However, before taking any measurements, it is essential to know the terminology associated with mortice locks.

Lockcase – The main part of the mortice lock, which is often square or rectangular in shape and houses all the movable components of the lock.

Forend – Also known as the faceplate, the forend is attached to the lockcase body but is not included when measuring the depth or height of the lockcase.

Follower – The part of the lock or latch that operates the bolt when turned by a spindle. The standard square hole for a spindle is typically 8x8mm. A thumbturn usually controls the deadbolt in a bathroom lock with another follower measuring 5x5mm. Some mortice sashlocks come with an escape function and a 9x9mm square follower.

Piercing for the cylinder – This can be euro profile, oval profile, or dual profile cylinder that accommodates both euro and oval cylinders.

Keyway – Refers to the location where the key is inserted in 3 lever and 5 lever lockcases when a lever-operated lock key is being used.

Bolt apertures – Found in the area of the lockcase pierced for the cylinder and around the handle follower. Commercial mortice locks usually come with a 38mm bolt fixing furniture.

We hope this guide helps you understand the basics of mortice locks. If you have any questions or need assistance with purchasing a mortice lock, we are always available to help!

The Importance of Accurate Lockcase Measurements

When it comes to selecting or replacing mortice locks, accurate measurements can save you a lot of time and hassle. Here's what you need to know:

Backset - This is the distance from the outside face of the forend to the centre of the keyway or cylinder, or to the centre of the follower on a latch. It's important to note that this measurement applies to both sashlocks and deadlocks.

Centres - Only found on sashlocks, this is the vertical distance from the centre of the follower to the centre of the keyway.

Lockcase Depth - Also known as case width, this is the distance from the outside face of the forend to the back edge of the lockcase.

Lockcase Height - This measurement only includes the body of the lockcase, not the forend.

Follower - On mortice sashlocks, the follower measurement is usually the same as the backset. However, horizontal mortice locks require measuring from the forend of the lockcase back to the centre of the follower.

Forend - This refers to the part of the mortice lock or latch case through which the bolt protrudes, and by which the lock or latch is screwed to the door. Be sure to measure the longest and widest parts and exclude the radius of the corners.

It's important to note that DIN lockcases differ from other types of lockcases in that they all have the same case dimensions despite different profiles or functions. For instance, a DIN bathroom lock would have the same case height and depth/width as a DIN sashlock or DIN escape lock. Their forends will all have the same height and width.

For smaller locks and latches like tubular latches and deadbolts, measuring the lockcase depth and backset to the follower is crucial. These latches are compact and efficient, ideal for internal doors which need to be closed but do not require locking.

Lastly, there are specialist mortice locks that can be operated by panic hardware, digital locks, or access control. These less common types of mortice lock still require accurate measurements, such as backset and centres, to ensure compatibility with other items of door hardware.

Uncertain? Never hesitate to seek our assistance. Our customer support team is readily available to respond to any questions or concerns you may have via phone, in-person consultation at our branch, or email.