A saw capable of cutting curves must have a narrow blade, and the actual width of the blade determines the sharpness of the curve that a particular saw can cut. Blades become less rigid and more breakable as they get thinner, however, so it can be difficult to cut sharp curves accurately in hard or thick wood. Jigsaws and rotary tools are useful for utility purposes when accuracy isn't the main concern.
Hand Saws for Cutting Curves
Anyone skilled in the art of marquetry, or wood inlay, knows how important it is to cut precise curves. When working by hand, artisans use either a coping saw or fret saw to make the shapes for their inlays. Both tools have elongated U-shaped frames that hold thin blades that are less than 1/4 inch wide. Fret saws are capable of more precision than coping saws, but the blades are also more delicate. Both types of saws become less useful as the thickness and hardness of the wood increases, because the blades tend to bend and break.
Using a Coping or Fret Saw
Woodworkers usually use coping and fret saws in conjunction with a V-board. It is a length of wood with a "V" shape cut into one end. They clamp it to the workbench with the "V" hanging over the edge and place the piece of wood over the "V" so the saw blade can pass freely through the cut line. Sawing in a steady up-and-down motion, they rotate the work or the saw as the blade follows the cut line. For especially tight curves, they loosen the blade, rotate it in the direction of the cut and tighten it before proceeding.
Bandsaws and their more accurate relatives, scroll saws, are the shop tools that woodworkers use most frequently to cut curves. The blades of both saws are bands with toothed edges wound around a pair of wheels that rotate in the same plane. The toothed edge intersects a work table, and the worker cuts the curve by placing the wood flat on the table, feeding it into the blade and rotating it as the blade cuts. Choosing the right blade is often a tradeoff between accuracy and stability. Narrow blades cut sharper curves, but they bend more easily than wide ones when cutting thicker stock.
Handheld Power Saws
The most common handheld tool for cutting curves is the jigsaw. A type of reciprocating saw, it has multiple uses in cabinetry and carpentry alike, but lacks the finesse needed for many precision jobs. Larger reciprocating saws with longer blades are even less precise, and are mostly used in heavy construction. A rotary tool with a cutting accessory doesn't produce the same amount of vibration as a jigsaw and is capable of more accurate cuts, but it can do more damage if the operator loses control. Using one is a realistic option only after practice has bestowed the confidence to use it properly.