A compass saw is a small hand or power saw featuring a narrow tapered blade used for cutting curves and inside profiles in timber paneling, PVC, and drywall sheets. These devices are also handy for use in small confined spaces where larger saws are impractical. Compass saws feature fixed or retractable blades which are typically interchangeable. This allows for the replacement of blunt blades and several blade lengths and tooth pitches to be used with one handle. Compass saws are similar to keyhole saws except they are slightly larger with typical blade lengths running between 5 and 15 inches (127 and 381 mm).
Compass saws are typically used to cut awkward shaped holes from the inner surfaces of a variety of common construction materials. They are also often used to cut PVC tubing or timber in small, cramped spaces. The compass saw may be used to cut most plastics, non-ferrous metals, soft timber panels, pressed wood, and drywall sheeting. Their narrow tapered blades allow easy cutting of circular holes and small radius curves. These saws are generally hand operated although electrical reciprocating compass saws are available.
The blade of a compass saw is either of a fixed or retractable design. They are typically interchangeable allowing for easy replacement of blunt or broken blades. This also allows a range of blade lengths and tooth pitches to be used with one handle catering for cuts in a selection of materials. The most popular blade lengths are 10 to 12 inches (254-304 mm) although different lengths are also commonly used for specific applications. Short blades, for example, allow the saws to be used to cut out shapes from one side of a drywall without penetrating the opposite sheet.
When cutting holes in soft materials such as dry walling, the narrow pointed blade allows the initial penetration to be achieved without having to pre-drill pilot holes. The ability to retract the blade to an optimal length on some saws also prevents undesirable blade flex and blade breakage when cutting harder materials. Most compass saw blades have teeth which only cut on the pull stroke, thereby helping to prevent the blades binding while cutting. This feature also ensures clean cuts even when working in confined spaces.
As with most saw designs, the compass saw blade should be matched to the material being cut. The general rule is the denser and harder the material, the finer the tooth pitch should be. A general purpose blade will feature a tooth pitch of between 8 to 10 teeth per inch (25.4 mm). A blade designed for harder timber and aluminum may feature tooth densities of up to 20 teeth per inch. Compass saw blades used for softer fiber boards or dry walling my have as few as five teeth per inch.