1 Building the jig
To rout dadoes that are straight and square to the edges of your stock, use a T-square jig like the one shown above. Make the jig from %-inch plywood, sizing the pieces to suit the stock you will be using and the diameter of your router base plate. The edge guide should be about 4 inches wide and longer than the workpiece’s width; the fence, also about 4 inches wide, should extend on either side of the guide by about the width of the router base plate. Assemble the jig by attaching the fence to the edge guide with countersunk screws. Use a try square to make certain the two pieces are perpendicular to each other. Then clamp the jig to a work surface and, with the base plate against the edge guide, rout a short dado on each side of the fence with your two most commonly used bits—often Уг and 3A inch. These dadoes in the fence will minimize tearout when the jig is used and help align the jig with the cut you wish to make.
2 Routing a dado
Clamp the jig to the workpiece, aligning the dado in the fence with the outline on the stock. When making the cut, press the router base plate firmly against the edge guide (above). Continue the cut a short distance into the fence before stopping the router.
T-square routing guide
A drafting T-square can be used to guide your router through dado cuts. To customize the jig for your tool, clamp the square to a scrap board, butting its crosspiece against the board edge. Ride the router base plate along – the arm of the square, cutting into the board and trimming the crosspiece. To use the jig, clamp it to the workpiece with the cut edge of the crosspiece aligned with the cutting mark on the stock. Rout the dado, keeping the base plate butted againstthe arm.
1 Assembling the jig
The jig shown at right is ideal for cutting equally spaced dadoes with a router. Dimensions depend on the size of the workpiece and the spacing between the dadoes. Begin by cutting a piece of %-inch plywood for the base, making it a few inches wider than the diameter of your router’s base plate and a few inches longer than the spacing between the dadoes. Set the base on a work surface and place your router near one end. Mark the screw holes in the router base plate on the base; also mark a spot directly below the tool’s collet. Bore holes for the screws and cut a hole at the collet mark large enough for the router bit. Remove the sub-base from the tool, screw the jig base to the router base plate, and install a straight bit the same width as the dadoes you wish to rout. Next, cut a spacer to fit snugly in the dadoes, making it slightly longer than the width of the workpiece. Screw the spacer to the bottom of the jig, making the distance between it and the bit equal to the space you want between your dadoes.
1 Assembling the jig
The jig shown at left makes it easy to rout dadoes with minimal tearout. The device consists of four strips of %-inch plywood attached to form two Ls. Rip all the pieces of the jig about 4 inches wide. Cut the edge guides a few inches longer than the cut you intend to make. The cleats should be long enough to overlap the adjacent edge guide by several inches when the jig is set up. Fasten the edge guides to the cleats, making certain the pieces are square; use four countersunk screws for each connection.
Cutting a dado
Slide the workpiece between the edge guides, aligning the marked outline with the reference dadoes. Secure the panel in position with the clamping block. Clamp the jig to a work surface. With the bit clear of the stock, turn on the router and start the cut at the reference dado in the end piece, making certain the router is between the edge guides. Feed the bit into the workpiece, keeping the base plate flat on the stock (left). To minimize tearout, wait until the bit enters the reference dado in the clamping block before raising the router clear of the stock.