Cutting dovetails on a router-based jig is certainly easier than cutting them by hand. Still, there's a little bit of a learning curve. Here are some tips to help you get the most out of your jig.
By George Vondriska
The easier it is for you to move your router across the jig, the better. If the
router base gets hung up at all the router can rock, ruining the joint. A little
lubricant goes a long way toward keeping everything going smoothly.
I routinely spritz the jig template and router base with a lubricant. Try it and
you'll find that, by reducing the friction between the router and jig, it's suddenly
easier to use the jig.
Be sure you're using a lubricant that's designed for these applications, such as
Empire Manufacturing's Table Top Lubricant. Once it's dry, there's nothing left
behind to migrate on to your wood and mess up your staining and finishing.
Know The Score
You'll reduce the likelihood of chipping if, before cutting the full tails, you
lightly score the face of the vertical tail board.
After your setup is complete, run the router left to right across the jig. Allow
only the corner of the dovetail bit to contact the face of the material. This creates
a slight shoulder. When the scoring cut is complete, cut the full dovetail.
Setting Bit Depth
The fussiest part of getting good dovetails from a router-based jig is setting the
dovetail bit to the perfect depth. When the bit is set too deep, the joint will
be too tight. When the bit is set too shallow, the joint will be too loose. The
mantra that's been stuck in my head for years is "Too tight-too deep. Too loose-too
shallow." I even wrote it on the board the jig is mounted on.
Once you've cut a perfectly fitting dovetail you can create a shortcut to make setup lots easier next time. Cut an extra dovetail joint and save the tail board. Mark
it so you know it's a setup board for your jig.
The next time you need to cut dovetails insert the setup board the same way you'd
normally insert a tail board. Set the depth of cut of the router bit by allowing
it to "kiss" the shoulder on the tail board.
This makes setting the bit depth significantly easier, and if you're careful you'll
be dialed in close on the first try, but you should still do a test cut in scrap
before working on parts from your project.