How to Replace a Mortise Lock With a New Style Door Knob

Residential door locks typically fall within two categories – the lock is either mortised or bored into the door. Mortise locks were widely used until the early 1950s, when new homes were fitted with bored locks. The challenge when replacing a mortise lock with a modern bored lock is concealing the large hollowed-out space the mortise lock requires. Lock conversion kits commonly include a set of decorative escutcheon plates designed to conceal this space. These kits come with all of the necessary hardware and are usually straightforward to install.

Tape measure
Hex wrench
Screwdriver
Nail or screw
Hole saw
Drill

Instructions

- 1
  Measure the distance from the edge of the door to the middle of either the interior or exterior door knob with a tape measure. This distance is referred to as “backspace.” Although the standard backspace is 2 3/4 inches, backspace does vary. It's important to purchase a new lock with the same backspace as the mortise lock.
- 2
  Measure the thickness of the door. As with the backspace, you must purchase a lockset that matches the door's thickness.
- 3
  Open the door.
- 4
  Remove the recessed set screw from the base of the interior door knob with a hex wrench.
- 5
  Pull the knobs off the door. Note that a square spindle is attached to the back of the exterior-side knob. The spindle will slide out of the door when you pull the exterior knob away from the door.
- 6
  Remove the two screws that secure the lock mechanism to the edge of the door with a screwdriver and pull the mechanism out of the door.
- 7
  Use the template supplied with the new knob to mark the location of the center of the lock on the door. Align the perforation marks on the template with the edge of the door. Tape the template to the door to keep the template stationary. Push the tip of a nail or screw through the template to mark the door.
- 8
  Drill a hole through the door to accommodate the new lock with a hole saw attached to a drill. Ensure that the shaft in the middle of the saw rests against the mark on the door before beginning the cut.
- 9
  Insert the new latch unit into the edge of the door. Install and tighten the unit’s retaining screws with a screwdriver to secure the unit to the door.
- 10
  Remove the screws that secure the mortise lock’s strike plate to the door frame with a screwdriver and pull the plate away from the frame.
- 11
  Position the latch plate supplied with the new lock against the door frame. Install and tighten the latch plate’s retaining screws with a screwdriver to secure the plate to the frame.
- 12
  Position the escutcheon plates included with the new lock against the door, ensuring that the large hole in each plate aligns with the knob hole drilled through the door. Mark the location of each plate’s retaining screw holes on the door by pressing the tip of a screw or nail through the holes and into the door.
- 13
  Drill a starter hole through each of the escutcheon plate’s screw hole marks on the door.
- 14
  Position the escutcheon plates against the door and install and tighten the plate’s retaining screws.
- 15
  Insert the exterior door knob into the door with the serrated portion of the keyhole facing up.
- 16
  Position the interior door knob against the door and install the knob’s retaining screws.

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