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    Mortise and Tenon Joinery Basics

    While the dovetail joint is the strongest way to join wide pieces to form a box of some kind, the mortise and tenon is the most solid way to join narrower pieces, like the frame of a door. Tenon is an old-timey name for a square piece of wood that sticks out from the end of a board, and the mortise is the square hole that the tenon fits into. Cut and fit a few of these joints, add glue, and you have a table and chair you could throw off a roof and still use for breakfast.

    The other great thing about the mortise-and-tenon joint is all the variations. A normal tenon ends inside the mortise, so it is invisible on the outside of the pieces, but there are also through-tenons, which poke through the other side, where they can be wedged for extra strength or shaped for a decorative touch. Another technique that adds strength and beauty is pegging the tenons, by driving in small round or square wood pins from the side.

    The last variation you need to know is the slip tenon, also called a “floating” or “loose” tenon. In this case you cut two similar mortises in the mating pieces, and then cut a separate tenon piece that fits into both of them.

    There are as many ways to cut mortises and tenons as there are varieties of the joint, and there are options for all budgets and skill levels. Probably the most common way to cut tenons is on a tablesaw, using some kind of tenoning jig that holds the pieces upright. But you can cut them with a handsaw too, or on a bandsaw for that matter.

    Mortises are usually cut in any of three ways: simply by drilling out the waste and then chopping the mortise square with a chisel, by using a router and a straight bit, or with a hollow-chisel mortiser, which is a dedicated mortising machine. And since woodworkers cut so many mortises, there are even pricier jigs and machines that make the process even faster and easier.



    Mortise and Tenon Methods and Styles

      The standard mortise and tenon. The sides of the tenon (and mortise) are called the “cheeks,” and the narrow shoulders around the tenon are called (finally, a straightforward woodworking name) “shoulders.”
      These are through-tenons. Notice how the woodworker has shaped the ends rather than leave them square. Shaping the ends of the tenons like this, using a block plane, is called "chamfering."
      A tenon can also be made to stick out far enough for a wedge to be driven through it, as on the base of this trestle table. In this example, the stretcher has not been glued into place. Instead, it's held in via the friction fit of the wedge.
       You can also drive pegs into a mortise and tenon, which adds strength and decoration. Woodworkers will often use a wood of contrasting color for these pegs as an extra visual element. Strength and beauty.
      Finally, this is a "slip tenon." It is for a door, so there is also a groove for the door panel. If you have an easy way to cut matching mortises, like a router jig or horizontal mortiser, slip tenons are faster to make than normal ones, since you don't have to cut a tenon and perfect shoulders on the end of the board.
      Usually, you cut the mortises before the tenons. Drilling is an easy way to rough out a mortise, and then you use sharp chisels to square the sides and ends. The drilled surfaces guide the chisel work.
      You make the tenons second, fine-tuning them to fit the mortise. This is a store-bought tenoning jig for the tablesaw, but you can make a simpler version. The woodworker is cutting the cheeks here, and then he will lay the pieces down on the saw table, and use a miter gauge to help him cut the shoulders.