As I discussed in Episode 52, I’m currently building a doll wardrobe as a Christmas present for my daughter. I’m using 3/4” birch plywood for the main carcass, and 1/2” birch plywood for the interior dividers. The interior dividers will be housed in stopped dados.
My original plan was to use a plywood-sized router bit and an edge guide to cut the stopped dados. Unfortunately, my test cuts showed that even my plywood bits provided a very loose fit for my 1/2” plywood. My fallback in situations like this is usually a dado stack on the table saw, but that doesn’t work in this case because the dados are stopped. I had to find another alternative.
A quick Google search and a few hours in the shop provided me with the perfect solution: an adjustable dado jig.
This jig allows me to cut perfect-fitting dados for any work-piece using only a handheld router and a 3/8” straight bit. The jig has three basic components: A fence to register the jig against the work-piece, a fixed router support, and an adjustable router support.
Using the jig is really easy. First, take the work-piece that you need to fit into a dado and place it between the two router supports. Move the adjustable half until the work-piece is held snugly in the jig and tighten down the wing-nuts. Now place the jig on the board that you plan to cut the dado in and clamp it down. The fence holds the jig square to the board. On my jig, I drew a square on the fence that is calibrated to be precisely perpendicular. Now you’re ready to cut the dado. Notice the runners on both sides of the jig. Run the router along one runner and then back along the other runner. This gives you a dado that will fit your work-piece exactly.
There are two important facts to note. First, notice the arrows that I have drawn on the fixed router support. I have a corresponding arrow drawn on my router base. When using this jig, the arrow on my router must always point at the runner with the arrows drawn on it. This ensures that the router is used in the same orientation every time, which eliminates any slop that might be introduced by a router bit that is not exactly centered in the router base. Second, this jig is calibrated to work with one specific router bit. In my case, that’s a 3/8” straight bit. That bit must always be used.
This jig is by no means original. You can find plans for similar jigs all over the internet. It’s a handy tool to have in your arsenal, though, and it’s an elegant solution to a tricky problem.