How to Cut Mortise and Tenon Joints

One of the oldest and most common joints found in furniture-making is the mortise and tenon joint. This sturdy joint interlocks two wood pieces, usually at right angles, by a "tongue" (tenon) cut into one piece slipping into a hole (mortise) made in the other piece of wood. It'll take practice, but soon you'll be making a mortise and tenon joint that will stand the test of time.

Things You'll Need

• Measuring tape
• Vise
• Back saw
• 2 boards
• Drill
• Chisel
• Masking tape
• Wood glue

Instructions

Making the Tenon

1. Measure out tenon width, length and thickness. Measure the tenon 1/2-inch back from the edge of one end of the board and mark with a pencil for the length of tenon. These are called shoulder lines. Then measure the width of the board and determine 1/3 of that measurement.

2. Use the measurement arrived at for 1/3 the width of the board and measure from the face on each side of the board. Mark with a pencil. This will determine the thickness of the tenon and are called cheek lines.

3. Repeat with that same measurement by measuring from each edge and marking with a pencil. This will determine the width and are also called cheek lines.

4. Place the board in a vise and cut from the cheek lines to the shoulder lines using a back saw. Then cut along the shoulder lines around the entire board. This will shape the tongue, or tenon, as the wood around the tenon is removed.

Cutting the Mortise

1. Place the tenon on the flat side of the mortise board with edges of each board flush. Mark width of tenon with a pencil. Then stand board on edge and transfer those marks using a square to the edge of the board. This will determine length of mortise.

2. Determine width of mortise by measuring in 1/3 from each edge of the mortise board. Mark with a pencil. You will now have an outline of the mortise.

3. Drill along the tenon width marks on the edge of the mortise board. Use a drill bit that is approximately as wide as the outline of the tenon. Mark drill bit 1/2-inch to set depth of mortise.

4. Chisel out mortise. Measure 1/2-inch from tip of chisel blade and mark with tape to equal mortise depth. Clear out all debris from inside mortise to leave a clean hole.

5. Fit the tenon into the mortise to see if they fit snugly. Trim tenon with a saw, if needed, until the two pieces fit together. Then apply wood glue to the tenon and inside the mortise and join the pieces. Clamp together until glue dries.

Tips & Warnings

• Always wear safety goggles or glasses when cutting wood.

• Do not try to cut the mortise if the pieces do not fit together. Always trim the tenon.