Kerf bending can be a powerful tool when creating curved pieces. This online calculator will help you figure out the kerf spacing.
There are myriad ways to bend wood–steam-bending, bent lamination, hot-pipe bending–but one method that doesn’t get very much attention is kerf bending. Kerf bending is a technique where you remove wood to allow the outer surface of the wood to bend more easily into the shape you want. Most often, this is done by cutting sawkerfs or slits into a piece of solid wood at a given spacing and depth, bending the piece and holding it all together with veneers or splines.
We covered the technique in 2013 when David Haig wrote Curved Panels for Furniture in issue #231. The cover of issue #292 features Philip Morley’s wall cabinet with kerf-bent sides. Both David and Philip are incredible woodworkers but it seems as though they both shoot from the hip and rely on their hard-won experience and skill when it comes to the spacing and depth of the kerfs. Well, some of us hobbyists don’t have the experience or the skill they have, and need more information when it comes to our projects.
In step the coders and engineers! Hooray for coders and engineers!
If you’re looking for specific dimensions to guide you through a kerfed bend, check out blocklayer.com/kerf-spacing. On the page, you can input the radius of your curve, the sweep angle, blade width, stock thickness, and the minimum thickness (how much meat you want to leave on the bone) after cutting. The website leans metric, but thankfully they’ve ported the calculators over to imperial for those who are fans of the fraction.
Now, keep in mind that both Haig’s and Morley’s projects featured tapered curves, which this calculator won’t output, but I’m willing to bet that it’ll get you closer than guessing!