A Strong, Simple Alternative to Dovetail Joints Using a Tablesaw JigWood Joinery with a Box Joint
As every carpenter or cabinetmaker knows, the secret to a strong wood joints is maximizing the contact surface area of the open grain of the wood. This is especially important with wood projects where you are making drawers or other components that sustain repeated movement.
While cutting dovetail joints by hand or with a jig might be intimidating to a DIYer that's just easing into furniture making, wood joinery with a box joint is a good place to start. This is a good technique to have in your “skill set toolbox” if you are remodeling vintage kitchen cabinets or restoring antique furniture.
History of the Box Joint
There was a time before cardboard and plastic, believe it or not, and farmers needed a way to package their fruits and vegetables to get them to market. Boxes were the method of choice because pine was cheap and abundant.
But the box corners had to be strong. Dovetail joints were the perfect solution except... they were time consuming and required more expensive cutting heads. Enter the box joint.
A box joint is based on the dovetail except there is no “flare”. Rather than a socket side and a tail side, there are merely straight fingers and opposing slots. To visualize this, just interlace your fingers at a 90 degree angle. Or, head on down to your local antique shop and look at one of those old pine boxes. They are very trendy.
Cutting a Box Joint
One of the good things about a box joint as opposed to a dovetail joint, is that you use a dado head rather than an expensive dovetail woodworking jig or router head. Use the dado on your table saw with enough chippers between the blades to make sure you end up with the desired finger width.
To do this, you will need to make a layout on one of your boards to determine how thick the fingers and slots need to be to make it “work out”.
Set the dado head to 1/16” thicker than your stock. This will give you something to sand off after the glue sets.
Make a Box Joint Jig for Your Table Saw
The jig can be made out of a chunk of 3/4” plywood that you will attach to your miter gauge. The plywood should be about 4” high and the length at least 8” past the dado head.
You'll need to attach a “guide pin” to it which is the same thickness as the finger of the joint and not quite as tall as the slot depth. Attach it just offset from the centerline of the plywood.
When you attach the jig to the gauge, put a spacer block between the head and the guide pin. It should be exactly the same thickness as the guide pin so that it will give you equal spacing when you cut the slots that accept the fingers.
Cut the Box Joints
Your first slot will be between the guide pin and the dado head. For the next slot just set the first slot over the guide pin. See how you get equal spacing?
To cut the slots in the board that will match up to the one you just slotted, hold the first board with its first slot straddling the guide pin. Now butt the second board up to it snug to the plywood and make the cut. Then continue the leapfrog cutting that you have been doing.
When done, all that's left to do is fit test, glue up, and clamp. You will be surprised at how strong your Box joint is.
