Today I am finally continuing the series on the dining table that I built for my friends. Previously I have gone through ripping common lumber for the table, adjusting the design to account for seasonal wood movement, routing the tenons, and glueing the table top together. This week I’ll walk through the steps I took to route the mortises in the breadboards.
Breadboards are the long boards attached to the sides of the table top to hide the joints of each panel. Sometimes called a rail, these have to allow for seasonal wood movement. For my table, I decided to create mortise and tenon joints that allow the table top to expand and contract within the breadboards. Below is a great picture of the mortise and tenon joints that go into a breadboard or rail.
Specific to my design, there are nine mortise and tenon connections within each breadboard. The middle mortise is sized to fit the tenon perfectly, while the others to each side of the middle are slightly wider than the tenon, to allow it to expand and contract freely.
I began by ripping the breadboards down to 5” wide to get rid of the rounded lumber edges. Then, because this was my first time making a mortise, I decided to use a spare board to test out the joint. First, I measured out and marked exactly where I wanted to route out the mortise. In this case, my mortises are ½” thick (⅓ of the total thickness of a 2×4). The middle mortise is 5” wide to fit the tenon perfectly, while the rest are slightly wider, with the furthest mortises from the middle being about 6” wide (allows for ½” of movement in either direction). Each mortise is 2.5” deep, half the width of the breadboard and conveniently the deepest my router can cut.
For both the test mortise and actual breadboard, I clamped the board to the side of my assembly table, with the edge level to the top. I then set up a guide parallel to the edge of the board. This was measured based on the distance from the edge of my router to the middle of the router bit and allowed for a straight surface to run the router along. Finally, I added stops perpendicular to the board that kept me from making the mortise too wide. Below is my setup after routing a mortise.
And the moment of truth, my first test fit with an extra board from the table top.
Not bad! It did take a fair bit of sanding on the tenon thickness to get it to fit into the mortise. That was completely fine with me, as I’d rather have to take off a bit of material to get a tight fit than have taken too much off initially and have to deal with a loose joint.
After getting the jig setup dialed in, it was relatively simple to make the rest of the mortises. Time consuming, as I had to do 9 different mortises per breadboard, but simple. I also had to sharpen my router bit a couple of times through the process. The last step was the route a ½” deep mortise along the entire length of the breadboard. I did this using the same jig as before, but without the perpendicular stops. This “haunch” adds strength and stiffness to the final table and can be seen in the example picture from the beginning of this post. Here’s a picture of one of the breadboards next to the table top with the tenons and mortises cut and ready to be joined.
One final note that I realize I didn’t cover in my previous post about the tabletop glue up. After getting the top assembled, I used an 8’ straight edge (a piece of mdf trim in this case) to create a guide along each edge. Then, using my router, I created a perfectly even edge across all 19 boards on each side. Finally, I cut back every other tenon with a jigsaw, leaving behind a ½” “haunch” that will fit into the groove cut along the entire breadboard. The picture above shows the tabletop with the final tenon configuration.