Wooden stair treads that have smooth, rounded leading edges are known as bullnose treads. The bullnose treatment is considered more elegant than a straight edge, and it is especially attractive on hardwood stairs. Creating a bullnose on a stair tread is not difficult when you use a handheld router with bits designed to cut wood into various decorative shapes. To make a bullnose stair tread, get a 1/2-inch bullnose or "round-over" bit.
Things You'll Need
1/2-inch round-over router bit
Set the wood for the stair tread on your work table. Adjust the wood so that the edge you will be rounding hangs over the work table by at least 6 inches. Clamp the wood in place so it will not slide as you work on it.
Set the base of the router onto the edge of the wood at one end. Move the round-over router bit so it rests right next to the edge.
Grip the router with both hands and turn it on by pressing the power button. Move the router in one direction, slowly and steadily along the edge of the wood. The round-over router bit will mill the wood and create a smooth, rounded edge.
Slide the router straight off the end of the wood when you reach the end. Avoid lifting the router up at the end, because doing so will mar the shape of the rounded edge.
Go over the edge of the wood a second time, from one end to the other, to ensure even milling and a uniform shape. Pay special attention to the ends of each stair tread. You may need to make a few extra passes at the ends to perfect the rounded bullnose shape.
If your stair tread will also have its short side exposed, use the router to give it a finished edge.
Don't press the router into the wood; that will create an uneven edge. Just hold it steady and move it along the edge without pressure.
Always wear eye protection when milling wood.