What is a half-mortise lock?
A half-mortise lock is a reproduction antique style used to secure drawers or cabinet doors. It fits into a cutout recess in the wood within the interior of the drawer or door. Once installed the lock plate is all that is visible from the inside. A keyhole is all that shows on the outside of the drawer or door.
How to choose a half-mortise lock for a drawer or cabinet door?
For new furniture, choose a lock that fits the available space and wood thickness. Plan the recess and keyhole position around the chosen lock, noting that the key pin may not be centered in the lock body.
When replacing an existing lock, start by matching the backset so the key pin aligns with the existing keyhole. Then compare the lock’s body and plate dimensions with the existing recess. An exact match to an antique lock is rarely available, so the recess may need adjustment.
For cabinet doors, also check whether the lock suits a right- or left-hand door.
Which half-mortise locks work with drawers?
- When the key is turned to the locked position, the bolt extends upward into a notch in the rail above the drawer, securing it closed.
- A strike is rarely used with this application.
- Keyhole is all that is visible on drawer front.
- Use with keyhole cover for a finished appearance.
Which half-mortise lock do I need for a cabinet door?
- Half Mortise Door Locks are handed, meaning specific right-hand or left-hand types are required. When looking for door locks be sure lock is handed according to your needs. Please note: some half mortise locks are not available in both left and right options.
- Doors hinged right - bolt shoots left.
- Doors hinged left - bolt shoots right.
How do I measure the backset for a half-mortise lock?
The backset is the distance from the lock’s selvedge edge to the center of the key pin, as shown in the lock diagram above. A replacement lock’s backset must match the existing keyhole position.
How do I measure for a replacement if I have the original lock?
Measure from the selvedge edge to the center of the key pin. Also compare the lock body and plate dimensions with the replacement to check whether it will fit the existing recess.
How do I measure if the original lock is missing?
For a drawer, measure from the top edge of the drawer front to the center of the round portion of the keyhole, where the key pin would sit.
For a cabinet door, measure from the door’s closing edge to the center of the round portion of the keyhole.
What should I check before fitting a half-mortise lock?
If you’re replacing a lock, check that the key pin aligns with the existing keyhole and that the lock fits the existing recess.
If there’s no existing keyhole or recess, plan their positions before drilling or cutting. The key pin may be off-center in the lock body, so use the lock itself to check alignment. If you’re adding a keyhole cover, allow room for it too.
How do I install a half-mortise lock?
- Adjust position to allow for location of keyhole as it is often off center in lock
- Mark location of lock on drawer or door interior
- Hold lock at desired location against drawer or door interior
- Selvedge edge should be level with top of drawer or edge of door
- Trace outline of lock on drawer or door interior
- Trace outline of selvedge on drawer top or door edge
- Inspect outline for accuracy , straighten lines where necessary
- Again holding lock in position, trace lock-body
- Cut shallow mortise for lock plate and selvedge with router or chisel
- Selvedge and lock-plate should be flush with the interior wood surface once installed
- Cut lock-body-mortise. Okay if off slightly as lock-plate will cover lock-body once installed. Be sure there is ample room for mounting screws to attach lock
- A strike is rarely used on drawers and doors. Traditionally a simple mortise was cut in the wood to accept the lock bolt.
Keyhole Placement
- Measure distance from top of lock-plate to center of key pin
- Measure distance from side of lock-plate to center of key pin
- With these two measurements locate keyhole on furniture front, make sure key pin is aligned with keyhole location
- Drill small pilot hole at key pin location, hold lock in position and check to make sure hole lines up with key pin
- Drill hole larger to accommodate key barrel
- For a finished appearance: mount an escutcheon/keyhole plate, on furniture front.
