Scroll saw
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A scroll saw is a small electric or pedal operated saw useful for cutting intricate curves where a jigsaw or coping saw is not appropriate; it is capable of creating curves with edges. It is somewhat similar to a band saw, but unlike band saws, in which the saw blade is a continuous loop, scroll saws use saw blades similar to those used by coping saws and operate through a quick reciprocating up and down motion. Its advantages compared to a bandsaw are that the blade can be removed and placed in situ into a pre-drilled starting point, allowing for cuts within surface boundaries, and the scroll saw is able to cut much more intricate curves.
There are many different brands of scroll saws on the market today. Notable ones include Excalibur (made in Taiwan), RBI (made in the USA), Hegner (made in Germany), Eclipse (made in the USA), and DeWalt (originally made in Canada, but now made in Taiwan). There are also a number of less expensive scroll saws manufactured in Asia including: Delta, Dremel (Bosch), Craftsman, Ryobi and others.
Size
Scroll saws are referred to by throat. This is the distance from the blade to the rear frame of the saw, which determines how large of a piece of wood can be cut. The smaller saws have a throat of as little as twelve inches, while the larger commercial saws are approaching the thirty-inch mark. Industrial saws have been used before computer automation to make even larger objects by hanging the top mechanical linkage to a ceiling providing indefinite throats. Scroll saws vary in price from under a hundred dollars, to close to two thousand dollars. The more costly ones are generally much more accurate and easier to use, as the vibration in the machine is minimal.
Uses
Scroll sawing is a very popular hobby for many woodworkers. The tool allows for a substantial amount of creativity and takes comparatively little space. In addition, many scroll saw projects require little more than the saw itself, reducing the investment in tools. One main purpose for using a scroll saw is the ability to cut intricate curves and joints, very quickly, and with great accuracy. They can also be used to cut dovetail joints quickly, and are a common tool for thicker intarsia projects. Using a very fine blade, the saw kerf is all but invisible.
Scroll saws are comparatively safe meaning that children, under close adult supervision, can enjoy creating crafts, and realizing the pride generated when completing a mechanical task. Inadvertent contact between the blade and the operator's fingers is unlikely to result in serious injury.
Mode of operation
There are different types of scroll saws. The most common design is the parallel arm in which a motor is attached near the back of the arms, and the two arms always remain parallel to each other. The C-arm has a solid "C" shape with the blade being mounted between the two ends of the "C". The parallel link, used by Excalibur and DeWalt, has rods in the upper and lower arms that are "pushed" by the motor to move short (about 4 inches – 100 millimetres– long) articulated arms and the end which hold the blade. The rigid arm scroll saw, which was very popular up until the 1970s, but is no longer made, has a single-piece cast iron frame. The blade is attached to a pitman arm on the bottom which pulls the blade down, and a spring in the upper arm pulls the blade back up again. This resulted in a significant weakness in that tension on the blade changed with every stroke of the blade. Modern scroll saws are all "constant tension" saws. Uncommon and larger industrial type scroll saws, included spring or vacuum sprung scroll saws, didn't have arms. Instead they had the reciprocation mechanism at one end of the blade and a tension device on the other to return the push stroke, their advantage being the tension/spring device could be hung from the ceiling of a building and large parts that otherwise could not be cut on arm-style scroll saws could be cut, e.g., aircraft frames of the past. This single-sided force of reciprocation had its advantages (speed, size of object) for rough work but had its limitations for delicate work.
Blades
Scroll saw blades come in many different types. With the exception of blades made for very light duty saws, typical blades are five inches long. The major types are:
- Skip tooth (or single skip tooth) which has a tooth, a gap then another tooth;
- Double skip tooth (two teeth, a gap then two teeth);
- Crown or two-way which has teeth facing both up and down so it cuts on both the down-stroke (as with all other blades) and on the up-stroke;
- Spiral blades which essentially are a regular flat blade which is twisted so that there are teeth sticking out on all sides.
- Metal cutting blades using hardened steel;
- Diamond blades (a wire coated with diamond bits) for cutting glass.
Blades come in many different sizes ranging from #10/0 for making jewelry (about the size of a coarse hair) to #12 which is like a small band saw blade.
There is also a variation called a reverse tooth blade. On reverse tooth blades, the bottom 3/4" of the teeth are reversed (point up). This helps reduce splintering on the edges of the bottom of the cut. It does not clear sawdust out of the cut as well, making the cutting slower, producing more heat in the blade which reduces blade life, and making burning of the cut more likely. Reverse tooth blades are especially useful when cutting softwood, and plywood such as Baltic birch plywood.
External links
- Scrollsaw Association of the World website
- Craftsmanspace - Free scroll saw, marquetry, intarsia and fretwork patterns Large free patterns collection.
