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Cutting the Mortise Joint

Cutting the Mortise

Mortise and Tenon Joints. One of the frequently used joints in Woodworking. Methods to make them range from common hand tools, to elaborate machinery. Any way you choose to make these joints, the desired result is a snug fit between the two parts.

Drawing of mortise and tenon joint

Drawing of Haunched Mortise and Tenon

The mortise, or female component to the joint, is basically a recess, cut into one of the pieces to be joined. It receives the mating tenon, which is the male part of the joint, and it actually a stub sticking out from the end of the adjoining piece. These pieces fit snuggly together to create a very strong joint.

A good rule of thumb in determining the size of the tenon is one half the thickness of the board. While you can go as light as one third, the greater thickness in the tenon will add considerable strength to the joint. Sometimes these joints have a peg driven through a hole, which goes through both the mortise and the tenon. It is cut off flush with the surface on both sides. The peg adds to the strength of the joint by preventing it from pivoting, and therefore breaking off the tenon. This is called a pegged Mortise and Tenon Joint. I rarely use this pegged method unless I'm reproducing a period piece, or if it is on a bread board edge of a table.

There are many variations to this joint. If the tenon pertrudes through the work piece it is called a through tenon. I personally don't use this joint much, as the tenon expands and contracts at a different rate than that of the board it extends through. Sometimes it will be flush, other times it will be recessed or even sticking out.

The mortise and tenon is a woodworking joint that is used to connect two pieces of wood together, usually at a angle, most common of which is a ninety degree angle. There are many methods to making these joints, and the technique used boils down to the equipment available, the quantity of the joints needed, and even the woodworkers preference. We use the Powermatic mortiser as shown in the picture, and it provides a quick, accurate method to producing the mortise.

Tools used in Mortise and tenon joints

There are some basic tools involved in laying out the joint. These consist of marking tools, which are used to mark both pieces of the joint. Some of these tools have two scribing devices, which will mark both edges of the joint, while others have a single markers. The thumbnail shown below has the best of both world's, as one end has a single scribe, while the other end has two scribes. This is a very convenient set up. Other types have rollers, which are tapered one edge to pull the tool into the wood, to keep it from following the grain of the wood. Either type actually scratches the lines into the wood and helps to place the chisel into the proper position.

Rosewood Marking Gauge

 This gauge is available from Lee Valley Tools

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