How to Cut Curves in Wood

Whether you're building a frame for an arched opening, making curved brackets or fashioning arch-top casing, marking and cutting curves is part of the process. In this article, we'll show you several techniques and tips for marking, cutting and fine-tuning curves. Some methods are best suited for rough curves. Others are refined enough for furniture making. Choose the technique that works best for the project at hand.

This simple router trammel is easy to build and allows you to cut a perfect

circle. For circles up to 6 ft. across, use a piece of 1/4-in. plywood, MDF or hardboard that's about 4 ft. long and at least as wide as your router base. Start by removing the base plate from your router and clamping it to one end of the trammel material. If you want your trammel to be stylish, trace around a coffee cup to make a nice-looking rounded end. Then draw tangent lines connecting the circles and cut the sides. If you don't care about looks, simply make a long rectangular trammel.

Trace around the base plate and use the mounting holes as a guide for drilling holes in the trammel (Photo 1). Cut out the trammel and drill a 1-1/2-in. hole in the center of the router end to clear the router bit. Countersink the mounting screw holes so the screw heads won't tear up your workpiece. Attach the router to the trammel with the base plate screws.

Screw the trammel to the workpiece, centering it on the circle you want to cut out. Mount a straight plunge-cutting bit in your router and set the router bit to cut about 3/8 in. deep for the first pass. A plunge router works best, but if you don't have one, hold the router above the wood and start it. Carefully plunge it into the wood and begin moving it counterclockwise around the circle (Photo 2). Complete the circle, then readjust the depth and make another pass until you cut all the way through.

Bent plastic wood makes a perfect curve. Clamp blocks to a 2x2 and spring-fit a length of 1x2 plastic wood between them. Adjust the position of the blocks to change the curve.

Often you can simply “eyeball” the best curve for the job by bending a piece of wood and using it as a template. But variations in wood grain can result in inconsistent curves. Here's a tip to make this technique even better. Use plastic wood or a plastic molding instead. It bends very uniformly and yields near-perfect symmetrical curves. Azek, Fypon, Kleer and Versatex are several brands available at home centers. Choose a thickness that'll bend to the curve you need. For gradual bends or wide curves, use 3/4-in.-thick material. For tighter bends (those with a smaller radius), use a 1/2-in. x 1-1/4-in. plastic stop molding or something similar. Support the ends of the plastic wood with blocks attached to a strip of wood. Adjust the position of the blocks to change the curve.

Grab any narrow board or strip of plywood and drill a few holes—voilà, instant compass. Drill a pencil-size hole a few inches from the end of the board. Then drill a screw-size hole at the pivot point. The distance between them should be the radius of the curve, if you know what that measurement is. Otherwise, just use the trial-and-error method, drilling a series of pivot holes until you can swing the trammel and draw the right-size arch. It's easy to draw parallel curves too. Just drill two pencil holes spaced the desired distance apart.

There's no limit to the size of the arch you can draw. If your plan calls for a 10-ft. radius, find a long stick and use the floor as your workbench.

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