What is a breadboard in woodworking?

It’s a cutting board intended for cutting bread. It’s also the technique in how to prevent a wide panel from cupping that doesn’t require large cross grain battens fixed to the surface of the panel.

Description

Using breadboards on a wide panel, such as a tabletop, helps reduce the likely hood of the panel cupping during seasonal wood movement. Often used on table tops, bread cutting boards, doors, etc that are thick enough to support the tongue and groove joinery required to implement the joint. The breadboard joint appears to be a child of tongue and groove and mortise and tenon joinery, with a little bit of doweling thrown in for good measure. This joint excels because it allows the wood to naturally expand and contract but does not allow it to cup.

While, from the finished product, it appears to be a tongue and groove joint, a normal one would run the risk of not being strong enough to resist the wood movement in the long run. Resulting, of course, in a ruined panel as it rips itself apart.

When the breadboard is taken apart, the tongue and tenon end is easily examined and understood. The tongue and tenons have the same thickness, generally about 1/3 the thickness of the panel. The tongue runs the width of the panel and the tenons emerge from the tongue at intervals. A ‘normal’ breadboard will have 3 or more tenons along the length. There will be a tenon in the middle of the panel. This tenon will be the only one that is tight on all four sides of the mortise and the only tenon is glued completely in place. The ‘outrigger’ tenons will be tight in the thickness but be gapped in the width to allow for the board to expand and contract. These tenons will also not be glued to allow for movement. All tenons will be pegged with a through dowel.

As far as I can tell, there are no ‘rules’ for the number of tenons or their size. They can either be through or blind tenons, although through tenons are more difficult to execute because of the accuracy needed in making the mortises exact.

The dowels hold the breadboard on the panel. The center tenon gets a dowel that is glued all the way through. The outrigger tenon dowels require a bit more work. The holes in the tenon are wallowed out to allow for the panel to expand and contract but are tight so the breadboard will not come loose. Generally, the wallowed hole will be twice as long as it is thick. The dowels on the outriggers are only glued on the breadboard piece, allowing the tenon to float free(ish).

Creation Step-through

As always, there are many different ways to go about different techniques. This is merely one of them.