How to Mortise a Door for a Mortise Lock？

A mortise lock is a hallmark of security, durability, and classic design. Unlike standard cylindrical locks, a mortise lock is recessed into the door itself, creating a robust and reliable mechanism. While the installation process—known as mortising—can seem intimidating to DIY enthusiasts, it is a highly achievable project with the right tools, patience, and guidance.

This comprehensive guide will walk you through the entire process of how to mortise a door for a mortise lock, transforming a daunting task into a manageable and rewarding weekend project.

Why Choose a Mortise Lock?

Before we dive into the "how," let's briefly discuss the "why." Mortise locks are prized for their strength. The lock body sits inside the door's core, distributing force more evenly and making it significantly more resistant to forced entry. They also offer versatility, often operating both a latch and a deadbolt with a single mechanism, and are available in a wide range of stylish designs to complement any home decor.

Tools and Materials You Will Need

Gathering the correct tools is 90% of the battle. Trying to cut a mortise lock pocket with inadequate tools will lead to frustration and a poor result.

Essential Tools:

• Mortise Lock Jig: This is the single most important tool. It guides your router or chisel for precise cuts. While you can do it without one, a jig guarantees accuracy.

• Router with a Sharp Drill Bit & Router Bit: A power drill and a sharp router are crucial for removing the bulk of the material.

• Sharp Chisels (Various widths: 1/2", 3/4", 1"): For cleaning up and squaring the corners of the mortise.

• Combination Square or Tape Measure: For precise marking.

• Utility Knife: For scoring outline marks to prevent wood splintering.

• Mallet: For using with your chisels.

• Pencil and Masking Tape: For marking and layout.

• Safety Glasses and Dust Mask: Always protect yourself.

Step-by-Step Guide to Mortising a Door

Step 1: Mark the Door

Start by consulting the template provided with your mortise lock. If one isn't available, use the lock itself.

1. Mark the Height: The standard height for a door handle is between 36" and 48" from the floor. Mark the centerline for the lock on the edge of the door.

2. Mark the Face: On the face of the door, mark the center point for the cylinder and the keyhole (or turnpiece). Use a combination square to extend these lines around the edge of the door to ensure everything is aligned.

3. Mark the Edge: Place the lock body on the door's edge, centered on your height mark. Use a sharp utility knife to carefully score the outline of the lock. This will create a clean edge for your chisel later.

Step 2: Drill Out the Main Mortise

This step removes the bulk of the wood for the lock body.

1. Set Your Depth: Measure the thickness of the mortise lock body. Set the depth stop on your drill to this exact measurement.

2. Drill Pilot Holes: Using a drill bit slightly smaller than the width of the mortise, drill a series of overlapping holes within the scored outline on the door's edge. Take your time and keep the drill level to avoid going too deep or at an angle.

Step 3: Chisel Out the Mortise

Now, it's time to clean up the drilled section and create perfect, square sides.

1. Clean the Sides: Using a chisel that matches the width of the mortise, begin paring down the sides. Work with the grain of the wood, using your mallet for gentle taps. Use the utility-knife-scored line as your guide.

2. Square the Corners: Use a narrower chisel to clean up the corners, making them sharp and square. Frequently test-fit the lock body. It should slide in snugly but without having to be forced.

Step 4: Cut the Faceplate Recess

The faceplate adds security and a finished look.

1. Trace the Plate: Place the faceplate into position on the edge of the door, centered over the mortise you just created. Trace its outline with a utility knife.

2. Chisel the Recess: Using a sharp chisel that matches the width of the plate, carefully chisel within the scored lines to the depth of the plate. The goal is for the plate to sit flush with the door's edge.

Step 5: Bore the Cross Bore (Cylinder Hole)

This is the large hole on the face of the door for the knob/lever spindle and the keyed cylinder.

1. Use a Hole Saw: Following the center marks you made in Step 1, use a hole saw attachment on your drill to bore the large-diameter hole through the face of the door. This hole must intersect perfectly with the mortise you created on the edge.

2. Clean the Hole: Sand the edges of the hole smooth.

Pre-Installation Checklist Table

Before you permanently install the lock, use this table to ensure you haven't missed any critical steps.

Step 6: Test and Install the Lock

1. Assemble the Lock: Insert the mortise lock into the pocket and secure it with the provided screws through the faceplate.

2. Install the Hardware: Insert the keyed cylinder and the interior knob/lever onto the spindle. Ensure all parts move smoothly.

3. Mark and Chisel the Strike Plate: Close the door slowly and turn the lock to mark the location of the latch and deadbolt on the door frame. Chisel out the recess for the strike plate on the frame, just as you did for the faceplate on the door.

Final Thoughts

Learning how to mortise a door for a mortise lock is a valuable skill that elevates the security and aesthetic of your home. While it requires more precision than installing a standard lockset, the result is a professional, heavy-duty installation that will last for decades. By following these steps, using sharp tools, and double-checking your measurements, you can confidently tackle this project and enjoy the unparalleled performance of a mortise lock.

Ansi 3 mortise lock

mortise lock

uninstall door lock