Backset is measured from the centre of the keyhole to the edge of the lock. Most backsets are commonly measured at either 44mm (for a 64mm (2½”) lock) and 56mm (for a 76mm (3”) lock). Typically a lock adjacent to a glass panel will be 2½” (44mm) and otherwise 3” (56mm), but you should always measure to be sure.
If the lock is still in the door it is possible to measure from the front plate of the lock to the centre of the keyhole. If the measurement is 45mm, you need a 64mm (2.5") mortice lock. If the measurement is 57mm, you need a 76mm (3") mortice lock. These measurements are approximate.
There are two sizes of mortice locks: 21/2” and 3”. If you are installing a mortice lock to a door with a narrow frame, or any door for that matter, it's very important to know what size lock you need. The size of the mortice lock refers to how far the keyhole will be from the edge of the door.
You can work out the size of the lock by measuring the distance from the edge of the door to the centre of the door handle or knob. This measurement will give you the approximate size of the backset which will allow you to identify which size lock or latch you have.
Case depth is also a common main concern when it comes to sash lock size, with the two most common being 64mm (2.5 inches) and 76mm (3 inches) for 3 and 5 lever sash locks.
One of the main factors to consider is the backset, which is measured from the center of the lock's hole to the edge of the door. The backset measurement of a door determines if a lock will fit it properly. Door handedness, or the direction the door swings when opened, is another crucial factor for lock installation.
What is the difference between a 3 lever and 5 lever lock? The difference between a 3 lever lock and a 5 lever lock is that a 3 lever lock is less secure because it has fewer levers which increases the risk of key duplication. Also, a 3 lever lock will NOT be BS3621 approved due to the poor security of the lock.
In the United States, there are two common backsets for residential door locks: 2-3/8 inches. 2-3/4 inches.
Two standard backsets are 2-3/8” and 2-3/4”. Other backsets include 2”, used by National and Lori Lock, and 5” used by Weiser, Weslock, Kwikset and others. There are also extensions for some brands, like Schlage, that can extend the latch enough to have the lock located in the center of the door.
Choose the Right Lock to Fit Your Door
Usually, the backset measures 2 3/8-inches or 2 3/4-inches. Cross (or edge) bore: The small hole along the edge of the door frame, usually measuring about 1-inch in diameter.
However, you will find them very easy to handle and a joy to use. Now available in sizes 1/8" - 1/2" by 1/16". It is perfectly acceptable to just have one mortise chisel ( 1/4" or 3/8" being the most common) and size all your mortises accordingly.
A pin-tumbler mortise lock is the most common type of mortise lock available. These Locks are very simple to operate and are fairly inexpensive. However, they are easily picked and are less secure than other types of locks. They are commonly found in older homes and apartments.
Whether your lock is broken and needs replacing or you're just ready for an updated look, mortise locks are generally simple to remove and replace; standard mortise lock replacement parts made by Emtek, Juralco, Pado, Papaiz or new-style Wright are easily interchangeable.
It is quite straightforward to fit a mortice lock to a wooden door but it does require accurate measurements and cutting so that the mortice lock and striker plate fit correctly. Two sorts of mortice lock are available: Sashlock - which has a door catch and lock bolt - so has a keyhole and door handle spindle.
A mortice deadlock is designed to be fitted into the timber edge of a door and allows the door to be manually locked from both sides with a key. A deadlock is a lock bolt only and does not have a latch/catch section for the operation of a door knob/handle.
The 3 Lever Sashbolt Mortice Door Lock is a classically designed, low cost sashlock, which offers additional security for internal doors and outside applications such as sheds. The sashbolt is to be operated by a handle. Available in 64mm (2 ½") and 76mm (3") and in both brass effect and satin finishes.
Mortise: Mortise. Pros: Very durable; locks have more features, and trim is easy to replace or upgrade because, unlike tubular locks, latch and lock fit in one hole. Cons: Costs about 50 percent more than tubular; usually requires a locksmith to install. A special-order item; allow up to 10 days for delivery.
Mortise locks are one of the most secure forms of residential hardware available today.
The Master Lock No. 5 Laminated Steel Padlock features a 2in (51mm) wide reinforced laminated steel lock body providing extra strength and a 1in (25mm) tall, 3/8in (10mm) diameter hardened steel shackle for excellent cut resistance.
Generally, the minimum door thickness requirement for mortice locks/latches is 35mm although some heavy duty types will require doors to be 45mm or over. A lock should have strength at least equal to the door on which it is fitted. Such fitting must not weaken the door in order to accommodate the lock.
Firstly, What Is A Backset? The backset of a door lock gearbox if the distance from the front of the gearbox to the centre of the spindle hole as shown in the image below. The most popular backsets are 30mm, 35mm, 45mm and 55mm.
The backset is the distance from the edge of the door to the center of the bore hole. There are two common backsets for residential door locks: 2-3/8″ and 2-3/4″.
It's important to remember that 5 lever mortice deadlocks won't be found on uPVC, aluminium or composite doors. It locks and unlocks from the inside and outside with a key. The words '5 Lever' should be engraved on the internal faceplate of the lock.
When choosing your 5 lever lock, make sure it is stamped or kitemarked with BS3621 - this is a lock standard rating given by British Standards for thief-resistant locks. 5 lever locks are also generally sold in two sizes: 2.5 inch and 3 inch case sizes. These translate to 44mm and 57mm backset measurements.
You can check this by looking on the faceplate of the lock, the number of levers should be stamped there. For optimum security the 5 lever mortice lock should be Kitemarked and conform to BS3621. If it is, these details should be stamped on the lock faceplate.