Using a router to cut dadoes and rabbets

The most basic kinds of woodworking can happen with little more than a handsaw, hammer, nails, and glue, but the core of the craft is joinery. Making specialized cuts and contours in wood surfaces lets you join parts more accurately and create a much stronger result, but it takes more tools and techniques to step up to that level. Traditional hand tools still get the job done, though they require an investment of time and skills that isn’t an option for every woodworker today.

Outfitting your shop with a table saw will, in one step, bring a new dimension of versatility and accuracy to your woodworking efforts, and it’s probably the best first investment in power machinery. But don’t overlook portable power tools, especially routers. These small powerhouses spin a wide range of interchangeable cutters (called bits) at high speeds, letting you mill decorative edges as well as cut precise joinery such as rabbets, dadoes, and dovetails.

Cross-grain dadoes can be cut by aligning a jig or straightedge guide with your layout marking and clamping it in place. A dado is nothing more than a flat-bottom groove machined to accept another part, such as a shelf or a stiffening brace. Straight-cut router bits are sold in common fractional widths (1/4, 1/2, 3/4-inch, and so on) and so with a single pass can cut shallow and precise dadoes; for deeper or wider dadoes, you can make multiple passes.

The particular mechanics of a router cut mean that tearout and splintering are often far less problematic than when making a similar cut with a circular saw blade. Better still, the bottom face of the groove is smooth and flat, resulting in a better glue bond when you fit a mating part into place. But this technique illustrates one of the common requirements of router use: having a guide board, jig, or template to control the router base so the cutter doesn’t drift randomly off-course.

Some router bits feature built-in guide bearings that ride against the edge of a workpiece and cut away a portion of that edge. Many of these are decorative bits that cut curved profiles, but a rabbeting bit is different. A rabbet is an L-shape notch cut along the edge of a workpiece, again to make room for another part that will nest there. The size can be varied by using different bit and bearing diameters, and the depth adjustment is provided via the router base; typically the cut is made in several lighter passes rather than one heavy cut. This produces less strain on the cutter and the router motor, and typically yields a cleaner cut on the workpiece.

The same straight cutters used for dadoes can also cut rabbets, but an edge guide or other accessory must be used to control the cutter path so it cuts straight along the edge as desired.