Tips for Dowel Joinery

Is there a list of tried-and-true doweling rules? I want to edge-join a pair of ³⁄₄ ×7×48" ash boards for rocking horse rockers. How close to the ends can I place dowels, and how far apart can I space them?
—Charlie Stopcynski, Lawrenceville, Ga.

We recommend making that first hole about ³⁄₄ " from the end, as shown above, to avoid breaking out the end grain while muscling loose a dry-assembled joint in preparation for a glue-up.

For edge-gluing, the dowels align the pieces and keep their surfaces flush more than reinforce the joint. So space the dowel holes just close enough to correct any minor warping of the parts. For most edge joints, space the dowels roughly 10" apart, advises Jim Lindsay of O.M.S. Tool Co., maker of the Dowelmax doweling jig. Because you're cutting rockers from your glue-up, you'll also need to position the dowels away from your cutlines.

As for dowel diameters, use dowels half the thickness of the stock you're joining. For example, use ³⁄₈ " dowels for ³⁄₄ " stock, and ¹⁄₄ " dowels for ¹⁄₂ " stock. Drill each dowel hole ¹⁄₁₆ " longer than half the dowel's length —usually 1¹⁄₂ " or 2" for precut dowels—to ensure a tight fit and allow space for trapped glue.