Not many years ago, I would see keyhole saws in use almost daily; now, for many carpenters, keyhole saws have been relegated to the category of rarely used tools. The responsibility for this lies with the saber saw, which will perform most of the tasks for which the keyhole saw has traditionally been used—and does all the work with virtually no elbow grease required.
Nevertheless, the inexpensive and convenient keyhole saw has a place in the fully equipped carpenter’s toolbox.
These days, the keyhole saw is sometimes called a compass saw although a few years back the standard keyhole saw had a narrower blade (and could cut quite fine arcs) while the compass saw’s larger blade had coarser teeth and was better suited to curves with larger radii. Smaller keyhole saws were commonplace in years past, in part because they were traditionally made from the broken blades of larger saws. When they broke, the fractured blade would be chopped down and fitted to a suitable handle.
Despite the traditional names, what is sold today interchangeably as a keyhole or compass saw is a bit large for cutting keyholes. Still, the keyhole saw can be used to cut holes for large-diameter pipes, vents, plug or switch boxes, and other purposes. They are used away from the edge of a board, panel, or sheet of plywood, or for cutting in tight places where an ordinary handsaw could not be used.
The keyhole saw and its near relation the wallboard saw have wooden handles and thin, tapering steel blades. The teeth are usually coarse, in the eight- to ten-teeth-per-inch range. Blade length varies (some are as short as five inches) but can be up to 12 or 15 inches long. Some models are designed to use replaceable or interchangeable blades and are sometimes sold as utility saw sets. The handle comes complete with several blades, one of which may be designed to cut metal. The narrower the blade, the tighter the curve it can cut; finer blades are preferable for cutting plywood.
On different days, the average home craftsman wears different hats: plumber, electrician, carpenter, tiler, plasterer, whatever. On demolition day, this is the tool for you. The reciprocating saw is a larger, more powerful version of the saber saw. Though it is designed for cutting on the horizontal (with the blade moving backward and forward, unlike the saber saw’s up-and-down stroke), the reciprocating saw can be used at all sorts of angles for demolition and rough-cut purposes. It isn’t a high precision tool, though rough scrollwork can be done with it. More often, the reciprocating saw is used for its brute strength, to saw through walls or ceilings, creating openings for windows, plumbing lines, or other purposes.
The reciprocating saw, which is sometimes referred to by the proprietary name Sawsall, is a powerful tool and must be used with care. Two hands are needed for proper control, one at the pistol grip where the on-off trigger is located, and the other on the body of the saw to stabilize it while cutting. Some models come with variable speed controls, which make for more efficient cutting through various materials. Remember, metal-cutting is done at slower speeds, but softer materials like wood can be cut at a higher rate.
Blades for cutting wood, plywood, metal, plastic, and other materials are sold. They are available in various lengths ranging from about four inches (for scroll cutting) to as long as nine or even twelve inches (for rough cutting of wood). Metal-cutting blades are also sold that can cut through nails, bar and angle stock, and metal tubing.
Cordless reciprocating saws are also being introduced, though they are less powerful and less flexible. On a work-site with no electricity (or in an awkward position where a power cord would be in the way), the cordless models can make good sense.