Cross-grain construction tends to freak out most beginning woodworkers, but it’s a viable construction method in many cases. Wide tables and chest lids often employ breadboard ends to keep things flat, as well as cover end grain. If it’s done right, expansion and contraction problems can be nearly eliminated.
There are many methods to attach breadboard ends, but only a few actually accomplish the primary goal of keeping things flat. It takes a little understanding, sound joinery practices, proper planning and patience to avoid disaster.
Understanding Wood Movement
Before you jump into to making breadboard ends you need to understand what’s happening and why. That begins with a basic knowledge of wood movement.
Boards expand and contract at a greater rate across their width than they do along the length. How much they expand and contract is more a matter of species and final resting place than anything else.
Also, wood tends to expand and contract more actively toward the bark side of the tree than toward the heart side. When you look at the growth rings on the ends of the board, the convex side of the rings is generally more active than the concave side. When one face moves more than the other, the board ends up bowed across its width – this is what we refer to as cupping.
Straight away you should know that, structurally, breadboard ends are strictly used to control cupping; they are not meant to stop shrinkage or expansion. There is no way to keep a board from changing dimensionally.
Breadboard ends are a mechanical means to overcome a board’s natural tendency for one side to expand or contract at a greater rate than the other. Whenever you try to overcome the nature of wood, you run the risk of cracking, splitting or breaking something.
Acceptable Joinery Practices for Breadboard Ends
Dowels are acceptable, but they provide limited hold and completely restrict wood movement. Screws or nails are also an option when attaching breadboard ends, but they’re only marginally better than dowels in most respects, and have the same drawback.
Better Joinery Options
In the end, the best way to keep the primary board from cupping is to capture it in the breadboard end as much as possible. This narrows your joinery choices to sliding dovetails, tongue-and-groove joints, loose tenons or true mortise-and-tenons.
If you decide to go with true mortise-and-tenon joinery, you have several options available. You can use pocketed mortises and tenons that are haunched (combining tongue-and-groove with a mortise-and-tenon joint) – or not.
There’s also the possibility of using through-mortise-and-tenon joinery, also haunched – or not. The advantage to either version is that you get the hold you need to keep things aligned while having the flexibility to withstand expansion and contraction cycles.
The above post is just an excerpt from Chuck’s full article on this topic in the October 2014 issue of Popular Woodworking Magazine. Subscribe to the magazine today and start receiving all our full articles directly in your digital or paper inbox!