Climb-cutting Explained

Some articles on router techniques advise against climb-cutting, but then say it can produce excellent results. What exactly is climb-cutting, and how can I determine when to use it?
—Joe Bogatich, Akron, Ohio

Joe, climb-cutting is when you feed your work into the router bit with, instead of against, the rotation of the bit. It'll feel like the router is pulling itself along the edge of the wood, which is how the technique gets its name—the bit pushes itself away from the edge of the board and climbs out of the cut. When you're using a hand-held router along the edge of a board, for example, moving the router from left to right is a climb cut. To climb-cut on a router table, feed the workpiece from left to right.

While the standard feed direction produces faster cutting, it sometimes becomes too aggressive and tears out chunks of wood when the bit lifts up the grain. But when you combine a climb direction with a shallow cut and a light touch, tear-out is far less likely, even with woods that have unruly grain patterns. Some woodworkers use climb cuts in several passes to take off small amounts of wood along areas with tricky grains that are likely to tear out. Following up a climb cut with a conventional pass at the same depth setting smooths any unevenness left behind by climb-cutting without removing an additional layer.

A few words of warning: Although you can safely climb-cut with small-diameter bits at the router table, NEVER attempt a climb cut with a large one, such as a panel-raising bit. The surface of the profile is what matters, but a ¹⁄₂ " quarter-round bit is as large as you'd want to use. Also, NEVER attempt a climb cut with a shaper cutter. When using a router table, remember that it's the tendency of a climb-cut to pull your hands toward the router bit, so position your hands carefully and away from the bit.