Mortise and Tenon: The Essential Joint

The mortise-and-tenon joint has held furniture together for thousands of years. A projecting tenon fits into a rectangular mortise. Glue and mechanical interlock provide strength that outlasts the wood itself.

Why This Joint

Mortise-and-tenon handles stress in all directions. Racking, twisting, pulling—the joint resists them all. That’s why chair legs, table aprons, and door frames use this construction almost universally.

The large glue surface bonds securely. The mechanical fit prevents movement even if glue fails. Well-made mortise-and-tenon joints have lasted centuries in antique furniture.

Cutting the Mortise

Start with the mortise. It’s harder to adjust a mortise to fit a tenon than the reverse. Mark the mortise carefully—layout errors compound through the rest of the joint.

Several methods work. A dedicated mortiser makes quick work of square holes. A drill press with a fence removes most of the waste; chisels square the corners. Hand tools—mortise chisel and mallet—require more skill but no machinery.

Mortise depth should be slightly more than tenon length. This gap allows glue to pool at the bottom rather than preventing the joint from closing.

Cutting the Tenon

The tenon should fit the mortise snugly—tight enough to require light mallet taps, loose enough to assemble without force. Test fit dry before reaching for glue.

Table saws cut tenons efficiently. A dado stack removes cheeks in one pass. A standard blade requires multiple passes. The shoulder cuts define the joint’s visual line; make these carefully.

Hand-cut tenons require a backsaw and shoulder plane. The process takes longer but allows precise fitting. Many woodworkers find this method more satisfying.

Fitting and Assembly

Shoulders must seat fully against the mortised piece. Gaps here weaken the joint and look bad. Trim the tenon cheeks or deepen the mortise until shoulders close tight.

Apply glue to both mortise walls and tenon. The mortise absorbs more glue; coat it well. Clamp until dry, checking for square before glue sets.