Make dazzling moldings with an indexed miter gauge fence and a dado blade.
Dentil molding consists of a series of matching pins and slots. The repetitive geometry can add interesting shadow lines to a picture frame, box or the built-up crown on a cabinet. You can buy manufactured dentil molding, but it's simple to make in any species of wood you like. All you need is an auxiliary fence attached to your table saw's miter gauge to index the slot cuts. Here's how to make that fence and cut this attractive molding yourself.
Step 1: A dentil molding miter gauge fence works exactly like the fence you'd use for cutting box joints. It's simply a wooden key affixed to a fence facing. The key serves as an index to register each slot of the molding while you cut the next slot. The space between the fence key and the blade creates the matching pins. To make the jig, cut a piece of scrap about 2-1/2 in. wide and long enough to adequately support the strips of molding you plan to make. Sixteen to 24 in. is a good general length to use. Dentil molding typically has a 1/4-in.-wide slot-and-pin pattern, and that's what we're making here. To create the fence key, plane a piece of stock to 1/4-in. thick, and rip a 1/4-in.-wide strip from one edge (see Photo 1).
Step 2: Install a 1/4-in.-wide dado blade in your table saw, raise it to 1/4-in. and cut a notch into one edge of your dentil fence. Center this notch on the length of the fence. You may want to make a test cut in another scrap piece first to check your blade setup; the notch you cut in the fence must fit your indexing pin snugly. Add shims between the blades if necessary so the blade's width matches the key stock. Once you've cut the notch, cut the key to a length of 1-1/2 in. Spread glue into the fence notch, and press the key into place so its back end is flush with the back face of the fence (see Photo 2).
Step 3: You're now ready to install the fence. Set a long strip of the extra key stock against one side of the dado blade to create a "pin" space between the blade and the dentil fence key. Hold the fence against your miter gauge, and slide it over until the key just touches the pin index piece. Attach the fence to your miter gauge with a couple of screws, being careful not to change the spacing of the key and index piece (see Photo 3).
Step 4: If you are making several pieces of dentil molding, it's a good idea to machine the molding from a wider workpiece, then rip the strips of dentil off of this blank afterward. It speeds the process along. To cut the first slot, set the end of your workpiece against the side of the key as shown in Photo 4. Slide the workpiece and miter gauge over the blade to cut the first slot and form the first pin.
Step 5: Fit the first slot over the fence key to lock it in place, and you're ready to cut the second slot and pin. Repeat this process across the workpiece to form the dentil pattern. Simple, isn't it? But, despite the repetition, make sure to press the workpiece down firmly over the pin each time so that all of the dentil slots will have uniform depth. And, by all means, remember to keep your fingers clear of the blade's exit point through the fence.
Step 6: Carefully smooth the top surfaces of the pins with a sanding block before ripping the molding strips to width. That's all there is to it! Be sure to save your dentil fence for the next time you need to make more molding. If you needed to shim the dado blade to work properly, make a few notes on the fence to refresh your memory about the number and type of shims required for a good fit.