How to Make a Stair Nosing With a Router

Set the table saw's rip fence to the desired width of your nosing, usually 3 1/2 inches wide. Activate the saw and run both sides of the finish-grade lumber through the spinning blade. If you are using tongue-and-groove hardwood flooring, only rip the tongue side of the plank.

Set the table's saw rip fence to the desired width of the bottom portion of the nosing piece; this dimension determines how far the nosing protrudes beyond the riser, usually 1 1/2 inches. Run a second piece of finish-grade lumber or hardwood flooring through the saw. If you are using tongue-and-groove flooring planks, rip both the tongue and groove side from the plank to create this piece.

Multiply the depth of your round-over bit by 2. The result equals the desired overall thickness of your nosing; the round-over bit cuts from both bottom and top to create a half circle. Subtract the thickness of the wide nosing board from the overall nosing thickness to determine the desired thickness of the bottom nosing board. Set the table saw to the desired thickness of the bottom board. Set the board on edge and run the board through the saw.

Squeeze wood glue along one edge of the wider board. Position the face of the bottom board over the glue and align the edges of the boards. While the glue is still wet, fasten the boards with a finish nail gun and finish nails, approximately 2 to 4 inches apart. Wipe excess glue from the boards and allow the glue to dry.

Clamp the boards to a work bench or sawhorses with the glued portion protruding over the work surface's edge. Mount a round-over bit to the router. Set the router's plate on the end of the boards and align the bit with the glued edge. Activate the router and pass the router across the glued edge.

Loosen the clamps and flip the board. Clamp the board to the work surface with the opposite side facing up. Align the bit with the board's edge and pass the router through board. Cut the routed nosing to the width of the stair tread with a circular saw or chop saw.

Scoop wood filler into its canister with a putty knife and spread filler into the gap between the glued boards. Smooth the filler with the putty knife and allow the filler to cure. Sand the routed edge and the wood filler with sandpaper to create a smooth, semicircular nosing.