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How to Make a Jig for Cutting Dado Joints

Routing dado joints can be a nuisance when making several at a time. This simple homemade jig can make the job easier and more accurate.

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make a jig for cutting dado joints

Step 1: Position and Cut the Hardwood

Position the two 20" x 4" x 1" pieces of hardwood so that the base of the router will fit snugly between them. Measure the distance between the outside edges of the two pieces of hardwood.

position and cut the hardwood

Step 2: Attach the Boards

Use 1-1/4" drywall screws to attach those two boards perpendicular across either end of the longer two boards (Image 1). Use a framing square to make sure the boards are perfectly perpendicular (Image 2). The four pieces will create a hollow rectangle.

Step 3: Mount the Rectangle, and Cut the Plastic

Mount the rectangle to a worktable with the two shorter strips of wood facing down. Using a table saw, cut the 3/16" thick piece of clear plastic or Plexiglas the width of the router base and the length of the rectangle's inside length. Place the plastic in the center of the rectangle.

Step 4: Scribe a Center Line in the Plastic

With a V-bit in the router, scribe a center line through the length of the plastic. The line will act as a guide. You'll place the work piece underneath the plastic and line up the spot on the work piece to be cut with the center line of the plastic.

scribe center line through length of plastic

Step 5: Clamp the Rectangle, and Make the Cut

Once the work piece is aligned, clamp the right and left sides of the rectangle in place. Remove the plastic. Insert the appropriate bit into the router, and make the cut, using the rectangle as a guide for the router.

clamp rectangle and make cut