Joinery Class: Attaching Tabletops

Three solid fasteners that allow for wood movement

Show me a woodworker who has glued or screwed a solid wood tabletop to its base, and I’ll show you a person who has learned a painful lesson in wood movement. Mother Nature doesn’t strike right away, but in time an overly-secured top is doomed to shrink and crack during the dry season, or expand and bow (or damage the base) during the humid months.

The solution is simple: tabletop fasteners. These tiny clips and blocks offer a solid means of attachment and allow for some seasonal give and take. Here’s a brief overview of three commonly used options, utilizing inexpensive hardware or scrapwood, plus some selection and installation advice to help you choose the right solution for your next project.

Drill before assembly. Bore the recess 3⁄16" in from the rail’s inside edge and a hair deeper than the fastener.
Perfect pivoter. Drive the screw so that the clip can pivot slightly, and then check that its head sits flush with the rail.

Figure-8 fasteners

Figure-8 or “desktop” fasteners are screwed to both the apron and the tabletop, and pivot to accommodate wood movement. These fasteners are inconspicuous and easy to install. Because they don’t allow for much wood movement, they’re best suited to tabletops under 18" wide. To maximize movement, widen the recesses as shown above. Also, slightly angle the fasteners installed on rails running parallel with the top’s grain. 

Installation is quickly accomplished with a drill press and Forstner bit, followed by a touch of chisel-work. Just remember to drill the recesses before attaching the legs.

Put the squeeze on. To determine the location of the slot or groove, measure the height of the clip’s tip and add 1⁄32".
Simple slotter. For post-assembly clip slots, clamp a board to the rail’s outer face, and rout the inner face with a 1⁄8 × 3⁄8"-deep slot cutting bit. 

Z-clip fasteners

With one end screwed to the tabletop, and the other sitting freely in a groove or slot cut on the inside face of the rail, Z-clips allow more movement than figure-8’s. They also offer more installation options. The rails can be slotted at the tablesaw before assembly, or after, using a either a biscuit joiner or a router.

When attaching clips, be mindful of wood movement direction. Set the clips that will experience side-to-side movement fully in their slots. For the clips dealing with in-and-out movement, leave a gap during wet weather, or set them tight during drier months.

Dado a strip. Cut a dado in each end of the strip and then use a 15⁄8" spacer to reset the fence and stopblock for the next cut.
Bore the buttons. Use the spacer/stop trick when drilling the screw clearance hole in the center of each button-to-be.

Free at last. Align the blade with the button’s rear edge and make the cut. Stop the blade before removing the button.

Shop-made wood buttons

Wooden buttons are installed in dadoes or slots, much like Z-clips, but are stronger and infinitely more attractive. They take a little time to make, but you can mill a batch from scrap in less time than it takes to run to the store.

To make the buttons shown below, start with a strip of hardwood 3⁄4 × 1 × 24" long. Set up a dado head for a 5⁄8"-wide cut, and outfit your miter gauge with an auxiliary fence that reaches the blade. Clamp a thick stopblock to your tablesaw’s fence, a few inches in front of the blade.

Saw a 3⁄8"-deep dado 1" in from each end of the strip, then use a 15⁄8" spacer to reposition the fence and cut the next set. Repeat the set-up process until you’ve finished the strip.

I use same the spacer for drilling the screw clearance holes, and then saw the buttons from the strip by eye. Chamfer the sharp outer edges, and finish up with a light sanding.

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