Curves are critical (sometimes)
Straight lines are the easiest to machine. Whether you're ripping on a table saw, crosscutting with a mitre saw, running a router along a straightedge, or jointing a board, straighter is simpler.
Curves, on the other hand, really slow a project down. They also offer a pleasing focal point in a piece of furniture or woodwork. There’s a balancing act between making something efficiently and making it beautiful that we all wrestle with now and then. For me, I know sometimes efficiency wins, while other times curves are critical enough to slow down and add them to the project.
Tools and machines
As you surely know, some tools specialize in making straight cuts, while others make it easier to add a curve to a workpiece. Laying out curves is often the first step. You can sketch a line onto a workpiece if you have a steady hand or don’t mind some imperfection. Alternatively, you can use a thin, straight piece of wood or a flexible ruler to create an even curve that you can trace.
Once the curve is laid out, you’ll need to machine it. A coping saw is a simple tool that can help, but if that’s your tool of choice, hopefully, the workpiece isn’t too large and you’re working with softwood; otherwise, you might spend all day making the cut, which isn’t a fun way to start adding curves to your work.
A jigsaw is a step up, and a bandsaw is another good option. Both of these tools, however, will leave you with an edge that needs to be faired and smoothed, but hand tools and sanders can go a long way in completing this task.
The almighty router
A router, thanks to the myriad of bits available, can cut curves into your work in various ways. For example, a flush trim or template bit can be used to trim a workpiece to match a template with a pre-cut curve, allowing you to create multiple parts of the same size and shape.
Another approach I’ve used is to attach the router to a length of material, drive a single screw through the material into the workpiece, and use a straight router bit to cut, resulting in an arc. A longer piece of material will create a gentle curve on a larger workpiece, like a tabletop, while a shorter piece will allow for a much tighter curve. You could even machine a full 360-degree arc, resulting in a circular workpiece.
The fanciest router of all
Today, CNC routers are quite widespread, especially in production settings. They are becoming increasingly common in small shops, where they can quickly handle not only curves with a set radius but also uneven curves and many other tasks. While their prices have decreased over the past five years, they still aren’t exactly cheap. Additionally, they require a fair amount of time to learn how to operate. One day, I hope to have a CNC router at my disposal. Until then, I’ll stick to a handheld router with a wide assortment of bits. Woodworkers often say you can never have enough clamps, but I think router bits deserve a place on that list too
An extra fancy approach
Cutting curves into flat workpieces is one way to incorporate curves into your next project. If you really want to elevate the design, you can create curved panels using either curved cauls and clamps or a vacuum bag. This is generally a more advanced technique, but, like most things, it can be approached in a simpler way.
Give it a try
If you gravitate toward the visual simplicity of straight lines, I understand—there’s nothing wrong with them. But if you’re avoiding curves because you think they’re too difficult to add, think again. There are many options for cutting curves, and they can significantly enhance the visual appeal of a project.
Arc Table
While the elliptical shape of the top was not cut with a router attached to a single length of material, it wasn't all that complex. The use of an ellipse cutting jig makes this easy. And the curved base was laminated with multiple layers of flexible plywood, veneer, and a vacuum bag. While this table might be more than some want to bite off when they're just starting to incorporate curves into their work, with a bit of learning it can be something to shoot for.
Fairing Gentle Curves
A block plane with do a surprisingly good job at fairing very gentle curves. For steeper curves, try a spokeshave, compass plane or a curved sanding block.
Following a Pattern
Template bits (left) have a single bearing between the cutter and shank. Flush trim bits (center left), have a single bearing at the end of their cutter. A combination bit (center right) includes both bearings. Although less common for most woodworkers, the bit on the far right is mainly used for tracing a template while mortising for a shallow hinge, like an interior or exterior door. Choosing among the four is mainly a matter of function. If, for logistical reasons, the operation is best performed with a flush trim bit, that’s what should be used, and vice versa. The combination bit is a great option, as it allows both approaches. A hinge mortising bit takes care of one main function.
A Simple Curve
Here I'm routing a curve into the edge of a piece of solid wood. The piece of wood is screwed to my worksurface, while a single screw allows the long piece of plywood my router is attached to to travel in an arc and leave an even curve in the workpiece.
Rob is a studio furniture maker and the editor at Canadian Woodworking & Home Improvement. Instagram at @RobBrownTeaches
Or you can use a piece of string or cable to cut/mark a curve. Very useful for chairbacks. An option for old routers was a rod with adjustable trammel point on it. My personal preference go to is a spokeshave.