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    How to Build a Router Jig for Perfect Dadoes

    A handheld router is an incredibly versatile tool, and when you're just starting out, it's among the four most useful handheld power tools you can have in your arsenal. A cordless drill, circular saw, jig saw, and router will get you well on your way to producing beautiful, well-built furniture that will serve you well.

    Routers do two things very well: they profile edges with a variety of shapes, and they plow out grooves. In woodworking terms, any groove running "with the grain" is called just that: a groove, while any groove running "across the grain" is called a dado.

    Routers really shine when building bookcases, perhaps one of the most common projects novice woodworkers take on. When constructing a bookcase, the shelves are usually made to fit into a dado cut into the side of the bookcase, thus resting within...you guessed it...a dado. The questions is: how do you cut a perfectly straight dado that is square to the front edge of the bookcase? The answer is: you use a guide, or jig like the one featured at the top of this post.

    Here's how to build a simple router jig for cutting straight, square dadoes:



    • Wood glue
    • Four screws
    • Two pieces of plywood or hardwood scraps, about 3-1/2-in. wide
    Building a router guide
    click to enlarge
    Clamp on a Square
    I begin by clamping a square onto the base of what will become the router guide-or "jig." Remember, in order for this jig to provide perfectly straight and square dadoes, you'll need to ensure that the "cross" shape you're building is dead-on square.
     How to build a router guide
    click to enlarge
    Glue on the Second Piece
    Apply glue on the end of the second piece and place it atop the first piece, butting it right up against the square, to ensure that you've got a cross piece set at exactly 90-degrees.
     How to build a router guide
    click to enlarge
    Clamp and Screw
    Clamp the two pieces tightly together and screw them down. I used four screws to make sure there would never be any "play" or movement between the two pieces. Screws and glue make for a rock-solid joint that won't ever move on you.
     How to build a router guide
    click to enlarge
    Rout Away!
    To use the jig, slide it up against the workpiece you wish to rout dadoes into. Make sure you clamp the workpiece down to the bench, and the jig to the workpiece - and bench. Rout from left to right. If you're routing a deep dado, it's best to rout in multiple passes, increasing the depth of cut by 1/8-in. with each pass.

    How to make a router guideHere's what you'll be left with: a clean cross-grain groove - or "dado" that's ready to accept a shelf. Notice how I started the cut in the actual router guide? By doing this, I know exactly where on the workpiece my router will cut when I line the jig up against it. Going forward, all I've got to do is slide the jig alongside the workpiece, aligning any pencil marks indicating my shelf dados (on the workpiece) with the cut-out in the actual jig. Click the photo to enlarge.