Large glued-up panels draw attention. We woodworkers fuss over the details: arranging the boards for a pleasing appearance, achieving tight gluelines, planing and sanding the panel for a smooth-to-the-touch surface.
Another critical aim is making sure the panel is (and stays) flat. Embedded stress in the wood along with seasonal expansion and contraction conspire to thwart that goal. One of the tools at our disposal to maintain flatness is to add breadboard ends. These strips of wood are attached across the grain of the panel. The rigidity of the pieces is meant to constrain a panel from warping.
Breadboard ends perform a decorative role as well as a functional one. The strips conceal the end grain and the change in direction of the ends acts like punctuation for the panel. By varying the width and detailing, the breadboard end can look utilitarian or ornamental. Most of the time, a breadboard end isn’t strictly necessary. Including the detail in a project falls along a spectrum that balances its decorative and practical roles.
 |
| Large bolts (or lag screws) supported by washers provide one option to |
| attach a breadboard end to a panel like this bench or a workbench. |
When you decide to include breadboard ends, the method of attaching them to the panel needs to be considered. Since this is a cross-grain connection, a plain glue joint or a handful of screws or nails isn’t going to cut it. Seasonal wood movement will lead to early joint failure or to cracks in the panel. Instead what you need is an interlocking joint that combines strategically placed glue and some fasteners. Let’s look at a few of the options.
TONGUE & GROOVE.
For small panels like a cutting board (a.k.a. breadboard), a tongue and groove joint is often all that’s necessary to integrate the end with the panel. You can see this in Figure 1.
This method is the simplest to make. The longer the tenon, the stronger the joint. However, there’s a risk. Removing a lot of material from the breadboard end can release stresses that cause the walls of the breadboard end to spring open after a while, as show in Figure 1.
CLOSED MORTISE.
Solving this is accomplished by stopping the groove short of the ends. This is shown in Figure 2. The material at the each end of groove provides support to keep the sides from opening out.
In effect, you go from a tongue and groove joint to a wide mortise and tenon. The process to make a long mortise is more involved compared to a groove. Yes, the tenon gets cut narrower too, but that step is straightforward.
ROOM TO GROW.
The trick is to create a secure connection and allow the panel to move in response to changes in humidity. Rather than a snug fit between the sides of the tenon and the ends of the mortise, you need to cut the mortise so that it’s a little longer than the width of the tenon. The size of the gap depends on the width of the panel. In a small cutting board, 1⁄8" is all you need. A large dining table on the other hand calls for gaps up to 1⁄2".
PINNING THE JOINT.
An extra large mortise provides the room for expansion. We now need to secure the breadboard end in such a way that gives the panel the freedom to expand as well. That’s where the fasteners come into the picture.
Instead of just gluing the cap onto the panel, it’s also pinned with dowels, as in Figure 2. This is similar to a pinned mortise and tenon joint. You drill a hole through both pieces and then drive in a short length of dowel.
The difference with a breadboard end is that you need to elongate the outer holes in the tenon before driving in the dowels. This allows the panel to expand out in both directions, while the center pin anchors the end cap to the panel.
I still apply glue to the joint — just not the entire surface. The glue works to center the panel. So I glue the middle 6"-8" of the tenon. This strengthens the joint while still allowing the edges to move in and out.
LARGE PANELS.
A single, wide tenon on large glued-up tops requires the removal of a lot of material from the breadboard end. This can lead to the end splitting if it’s levered against (lifting the table, for example). The solution is to break up the tenon into a wide, short stub tenon interspersed with longer tenons.
Figure 3 shows an example of this. The breadboard end requires two steps. The long groove (mortise) we’ve already discussed. The other step is to make deeper mortises that align with the tenons. Like before, these mortises should be slightly wider than the tenons. photo
Each tenon gets a dowel to pin it in place. Once again, the holes in the outer tenons should be elongated. I usually glue the center tenon as well (belt and suspenders).
A FINAL OPTION.
Dowels aren’t the only way to attach a breadboard end. Long woodscrews, lag screws, or bolts can be driven in from the end. The lower photo on the previous page shows this. Elongated shank holes allow the panel to expand and contract.
YES, IT’S SUPPOSED TO LOOK LIKE THAT
Like a broken clock that’s right twice a day, a breadboard end and the tabletop may rarely be flush. Do not be alarmed. The panel is meant to expand and contract seasonally across its width. The length of the breadboard end doesn’t change. In addition to what’s shown here, there may be times when the panel is wider than the breadboard end.
