Light passes minimize tear-out
Carbide-tipped bits and high-horsepower routers may tempt you to make a habit of routing any profile on any type of wood in one pass. That's the quick way to produce tear-out. Shallow passes mean less chance of accidentally shredding an edge, so divide the cut into more manageable bites. Wood types prone to tear-out deserve especially careful handing. These include oak, ash, and some types of pine. Melamine-coated particleboard also benefits from shallow passes. If necessary, reduce your cutting depth to 3⁄32 " per pass and slow down the feed rate. Even without a backer board, dividing the cut into three passes of 1⁄8 " each left smooth edges in the rabbet on the top left. The 3⁄8 " rabbet on the bottom left was cut in a single pass with no backing. The profile in back shows this block has backed up one router bit already, but still has three more grain-supporting edges left.