Sometimes it makes sense to go in the opposite direction of prevailing wisdom. Such is the case with climb cutting—he practice of running a handheld router in a clockwise motion around the edge of a workpiece.
As shown below, when you feed a router in the "typical" (counter-clockwise) direction, the bit's cutting edges lift the grain of the workpiece. But, in a climb cut, the bit pulls the grain down as its cutting edges enter the workpiece.
So with a climb cut, you don't get the splintering that you often get with a bit fed counter-clockwise. And climb cutting has a burnishing effect on the wood, leaving an exceptionally smooth routed surface. For those reasons, we climb cut most of the time we rout an edge with a handheld router.
Climb cutting takes a little getting used to, so practice this technique with small router bits and scrap softwood. Remove no more than 1⁄8 " of stock when using small bits, and restrict yourself to about 1⁄16 " of stock removal when using larger bits such as 1⁄2 " cove bits. Use sharp bits, and never climb cut with bits over 2" in diameter.
When you climb cut, your router will want to run away from you, so hold on firmly with both hands. The workpiece should be clamped down—not simply sitting on a router mat.
Because a climb-cutting bit does not tend to pull into the workpiece, you don't have to lower your bit to increase its cut for each successive pass. Simply set the bit to its full cutting depth and remove a little more stock with each cutting pass. You'll be surprised at how quickly you can rout edges, and how much control you have over this freehand process provided you take light cuts.
Although you get little splintering with a climb cut, it still makes sense to follow the traditional wisdom of routing the ends of a workpiece before routing the edges. If you see some fuzzing of the grain when you climb cut, you probably have a dull bit. (Some woods, such as butternut and willow, will fuzz even with sharp bits.)
Under many circumstances, it still makes sense to feed a router in a counter-clockwise direction. That's because a bit fed that way tends to pull into the workpiece, template, or straightedge that you guide it against. This tendency to hug whatever you guide the router against serves you well when it's essential that the router not wander off course. For example, when cutting a dado or the groove for holding a tambour door in the example, the cut must exactly follow its guiding edge.
Always remember to feed a workpiece in the typical right-to-left direction when using a router table. If you try to climb cut, the bit will pull the workpiece away from you, creating an unsafe situation, and poor-quality cuts.
However, if you have the luxury of owning a power feeder mounted to your router table or shaper, climb cutting produces silky smooth moldings with these stationary tools. That's because the power feeder controls the workpiece for a rock-steady cut, and your hands never come close to the cutting edges.
With manufactured materials such as Corian or medium-density fiberboard (MDF), there's no advantage to climb cutting. Because these materials have no natural grain that might tear out.