Design & DIY

How to sharpen your router bits

side view of a selection of red and blue woodworking router bits for router machine on a wooden surface Photo by PopFoto/Shutterstock

Using a router is a surefire way to add polish and character to your woodworking projects. But dull router bits will leave nasty burn marks on your wood, leaving you stuck sanding them out while your sunny weekend goes up in smoke.

Carbide router bits’ durability is legendary, but their reputation can lull us into thinking that a bit’s edge is still sharp long after it should have been refreshed. Traditionally, router bits are sent out to industrial sharpening centres to be reground for a fresh edge. But that’s not the cottager way. We save time, extend the life of bits, and maintain a more constant sharp edge by sharpening them on diamond hones, which are hard enough to abrade carbide. Honing removes a thinner layer of carbide compared to grinding, so you can hone more often to maintain sharpness.

Think of cutting edges as the intersection of two faces—in this case, the flat face of the router bit and the bevelled profile. This is the area of attention. If this edge is truly sharp, it looks like a one-dimensional line.

As a bit becomes dull, this edge wears and becomes a third face, which burnishes the wood as much as it cuts, creating heat, smoke, and those nasty burn marks.

Use a coarse, 45-micron hone, lubricated with water, to remove carbide quickly if the edge is nicked or very dull. With the flat face of the carbide against the hone, stroke to and fro until the cutting edge is only visible as a thin line. To keep the bit balanced, stroke each flat face the same number of times. Follow up with a fine, 25-micron honing until the edge is keen.

Sharpening your bits more frequently will keep the cottage air from turning blue—in more ways than one.

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