How to Cut a Mortise and Tenon Joint in Wood

What You'll Need
Power drill
Table vice
Masking tape
A straight edge

If you are looking to produce a strong joint for a piece of wooden furniture, a mortise and tenon joint is considered to be the best available option. By following a few simple steps, you should find that this type of joint is relatively easy to construct.

Step 1 – Prepare Wood

The pieces of wood that you will use to construct the intended item will need to be cut and prepared in readiness for the mortise and tenon joint to be cut. Make sure that your measurements are precise so that the joint fits properly. After undertaking any cutting, finish the edges by smoothing them with sandpaper.

Step 2 – Measure Tenon

The tenon is the peg section of the joint that is inserted into the slot within the edge of the adjoining piece of wood. These should be measured out by laying the relevant piece of wood out flat and using a straightedge to mark a pencil line. This should be 1/2 inch back from the edge and is known as the shoulder line. Following this, you should measure the width of the piece of wood to enable you to work out what a third of this will be. The result can then be marked on the board with a pencil so that it is centered and will display how thick the tenon will be. These are known as the cheek lines.  

Step 3 – Cut Tenon

Once it has been marked up, you will be in a position to cut out the tenon to begin to create the mortise and tenon joint. This will be easier if you secure the piece of wood in a vice before cutting along the cheek lines to the shoulder line. The next step is to cut around the shoulder line to form the base of the tenon.  

Step 4 – Mark Out Mortise

The next step required to create a mortise and tenon joint is to mark out the position of the mortise. This is the slot into which the tenon will be fitted. Lay the section of wood that comprises the tenon atop the piece from which the mortise will be cut so that the edges are directly adjacent. Mark the position of the shoulder to determine the length of the mortise. Do the same by marking off the cheek lines with a pencil. This will show how thick the mortise needs to be.

Step 5 – Cut Mortise  

Begin the process of removing the wood within the mortise slot by drilling a hole at either side of the marked position. Ensure that the drill bit is the same width or slightly smaller than the width of the recess. After drilling the holes, carefully use a chisel to break up and withdraw the wood from the slot. Use some masking tape to mark the length of the mortise on the chisel so that you do not go deeper than needed.    

Step 6 – Finish and Test

After completing both component of the mortise and tenon joint, slot them together to ensure that they fit together properly. If any adjustments are needed, always undertake these to the tenon.