Turn your drill press into an effective mortising machine with this simple fence and a Forstner bit.
One challenge to boring mortises with a drill press is keeping leg workpieces firmly pinned against the drill press table. Often, when you raise the bit to extract wood chips, it tends to lift the workpiece along with it. But, you can avoid that hassle with this quick and easy mortising jig. It consists of a fence fastened to a base that clamps to your drill press table. A pair of hold-downs on top allow you to slide the leg along the fence for each mortising pass while preventing it from lifting up when clearing the chips. The jig works best on square-profile legs, as you can cut mortises on adjacent faces by flipping and feeding the blank in from opposite ends. Here’s how to make a mortising fence for your drill press.
Step 1: Cut the jig base from a piece of plywood, MDF or other scrap. Make it about as long as the legs you’ll be mortising and 3 to 4 inches wider. That will allow room for attaching the fence to the base and clamping the jig to your drill press. Now rip a strip of scrap about 1/32 in. wider than the leg thickness to form the fence. The extra bit of width provides “slip space” under the hold-downs for sliding the leg more easily. Use glue and nails or screws to fasten the two parts together, leaving about 2 in. along one edge of the base for clamps (see Photo 1, below).
Step 2: Create a pair of hold-downs from another piece of scrap. Make these wide enough to cover the top edge of the fence and overlap at least half the width of the legs. Cut the hold-downs to a length that will leave an open window at the center of the fence. Fasten them to the fence’s top edge with screws (see Photo 2).
Step 3: Set your first leg blank in the jig so the mortise area is within the window between the hold-downs. Install the Forstner bit you’ll use for mortising, and adjust the jig on the drill press table until the bit lines up evenly between the long mortise layout lines. Clamp the base in place (see Photo 3).
Set your bit depth as needed, and you’re ready to bore your mortises! Here’s a handy jig to add to your collection—and another way to put scrap to good use.