Router Dado Guide

I’ve been searching for an easy to build, cheap router dado guide. What I found is a very simple router dado guide that I can build for making the dado’s in the book shelves I’m going go make for the basement storage room.

As you can see this router dado guide is really simple. I’m going to make the jig out of 3/4″ MDO plywood scrap that I have from a previous project. The most important step here is to ensure that the guide is build as square as possible. I’ll screw and glue the bottom rail to the two side guides as shown. The upper rail will have 1/4″ x 1-1/2″ slots so that I can adjust the width of the dado’s I cut. This router dado guide will be set up to use on standard 12″ wide book shelves. The guide is simple enough that if I need a different width I can make another one quickly.

Once the router dado guide is built the next step is setting it up to cut the dado’s. I’m going to be building the shelves out of 3/4″ MDO plywood. However, 3/4″ MDO is actually 23/32″ thick. I could use a 3/4″ router bit but then the dado would be loose. It’s a much more effective joint if it fits snug. Therefore, I’ll use a 1/2″ router bit and adjust the width of the guide to cut a perfect 23/32″ wide dado. The easiest way to set up the guide to cut the dado that width is to create a spacer block in combination with a piece of the shelf material.

The base of my router is 6″ in diameter. I’m going to use a 1/2″ router bit. Therefore I’ll cut a spacer that is 6″ – 1/2″ = 5-1/2″ wide. I’ll place the 5-1/2″ wide spacer between the rails with a piece of the 23/32″ MDO and clamp the upper rail in place. This way I can run the router base between the rails and cut a perfect 23/32″ wide dado.

Check out the finished Router Dado Guide.