While routing a juice groove into a cutting board with a core-box bit, I made some serious burn marks. Without fouling up the half-round shape of the groove, how can I fix it, and how do I prevent burning in the future?
The first and fastest method is to set the bit a hair deeper and re-rout the contours. Because it doesn’t have to hog away as much material, the second pass has fewer tendencies to burn. If you still see burn marks, sand or scrape them away using a contoured scraper or sanding pad. The scraper comes with interchangeable blades that fit into contours and corners and remove material quickly for serious burn marks. Depending on the wood, end grain may require a follow-up with some sandpaper. For a contoured sanding pad, wrap sandpaper around the contour and grip it while you sand. Sand with 120 grit until the marks mostly fade; then follow up with 180 and 220 grit. To avoid future burn marks, make sure you use clean, sharp bits. If you have a variable-speed router, decrease the revolutions per minute (rpm) and increase your feed rate slightly. Finally, practice the cut on scrap first, working to eliminate any pauses.