How do you get dados square to the edges of the workpiece? That's one of the first questions people ask when I show them my jig. The answer is easy. If you start with a workpiece that's cut square, then use its sides and edges to position the various jig parts.
Start by resting the workpiece on your bench, raised above the benchtop's surface on a couple of scraps of 2-by lumber. This set-up lifts up the whole jig so you can reach underneath with your fingers to tighten the locking knobs. Pinch the workpiece between the two slotted baseboards, with your guide strips sitting on top of the workpiece in no particular position. Next, slide the ends of the two baseboards and the edge of one guide strip so they're all flush with one end of your workpiece. Tighten the two locking knobs to hold these parts together before marking dado locations on your workpiece in pencil. Position other pairs of guide strips using these marks, then use a wood spacer to orient the other guide strips parallel to the first strip that you tightened down along the end of the workpiece. As you do this, place the particular piece of wood that will ultimately reside in the dado itself between the guide strips. Remember, it's the thickness of this wood that determines the precise width of the grooves milled with this jig.
Double-check the tightness and position of all guide strips, then place a couple of clamps across the joint between your workpiece in the slotted base strips. These clamps are critical because they stop the workpiece from sliding sideways as grooves are milled.
Routing multiple parts with the same dado or rabbet spacing? Just lift the jig off one workpiece and fit it over the next one, then re-clamp and rout again with the same guide-strip arrangement. You can speed up production even more if you rout grooves in a workpiece that's twice as wide as you need, then saw the wood in half to make a matching set of grooves. Any way you tackle the job, your dados and rabbets will always match the thickness of wood that's supposed to fit into them.
The best style of router bit to use with my jig is usually sold as a hinge-mortising bit. This means it has a bearing on the shaft and relatively short cutters-about 1/2" long- extending down below it. You should be conscious of diameter when selecting a bit. Each groove is always cut in two passes, so the bit needs to be smaller than the width of the groove you're creating. I find a 1/2"-diameter works best for routing dados and rabbets of about 3/4" in width. My favourite bit is the Freud 16-560. It's made entirely of carbide, with angled cutters that create a downward slicing action as they move through the wood. The result is ultra-crisp edges with no splintering even when plowing through fragile veneers. This little bit isn't cheap (about $44), but it is designed to last a long time, even if you're routing something as abrasive as veneered particleboard.
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1 Comment
In regards to the video clip on creating dados, the sound was coming through, but the picture was not playing. Cheers