How to Mortise Tennon
- 1). Mark the four edges outlining the mortise onto the mortise board. Position this board face up on a work table.
- 2). Align a sharp chisel with one edge of the mortise, and tap the end of the chisel with a mallet to score the edge of the mortise. Continue around the perimeter of the mortise until all edges are scored.
- 3). Make a series of chisel cuts across the face of the mortise, approximately every 1/8 inch. Remove the waste created by these cuts with the chisel. Repeat scoring and cutting until the entire mortise is completed. Clean up the edges of the mortise, making sure they are square and even.
- 4). Measure the exact dimensions of the finished mortise. Transcribe these measurements onto the end of the tenon board with a pencil to mark the outline for the tenon.
- 5). Clamp the tenon board into your bench vise, with the end of the board receiving the tenon cuts facing upwards. Cut out along each vertical line with a hand saw to make the cheek cuts of the tenon. Stop cutting when you reach the desired depth of the tenon.
- 6). Release the vise and reposition the board horizontally so you can make the shoulder cuts on the sides of the tenon. Cut downward on the marks until you reach the edge of the cheek cut, and remove the waste. Rotate the board in the vise until the tenon is completed.
- 7). Test fit the tenon into the mortise. It should fit snugly without being too tight. If the tenon needs to be trimmed to make it fit a little better, clean up the tenon with a sharp chisel.
- 8). Apply glue to all four faces of the tenon and insert it into the mortise. Clamp the assembly to hold the joint until the glue dries.
Source...