Scroll saw
A scroll saw is a small electric or pedal-operated saw that is useful for cutting intricate curves in cases where a jigsaw or coping saw is not appropriate. It is capable of creating curves with edges. It is named after its traditional use in making scrollworks, which are sculptural ornaments that feature scroll-head designs.
Comparisons
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 of coping saws and operate through a quick reciprocating up and down motion.
A scroll saw has two main advantages when compared to a band saw. The first is that the blade can be removed and placed in situ through a pre-drilled starting hole. This feature allows interior cutouts to be made without creating an entry slot for the blade through the edge of the workpiece. Second, a scroll saw can cut significantly more intricate curves.
Brands
Many different brands of scroll saws are on the market today. Notable (made in Germany), Eclipse (made in the USA), and DeWalt (originally made in Canada, now in Taiwan).
There are also a number of less expensive scroll saws manufactured in Asia, including those from Delta, Dremel (Bosch), Craftsman, Ryobi, and others.
Size
Scroll saws are classified according to the size of their throat, which is the distance from the blade to the rear frame of the saw. The throat depth determines how large a piece of wood can be cut. Smaller saws have a throat of as little as 12 inches, while commercial saws can approach 30 inches. Before the era of computer automation, industrial saws were sometimes used to make even larger objects by hanging the top mechanical linkage from the ceiling, thus providing an arbitrarily deep throat.
Scroll saws vary in price from under $100 to close to $2,000. The more costly saws are more accurate and easier to use, usually because they minimize vibration.
Uses
Scroll sawing is a popular hobby for many woodworkers. The tool allows a substantial amount of creativity and requires comparatively little space. In addition, many scroll saw projects require little more than the saw itself, reducing the investment in tools.
Scroll saws are often used to cut intricate curves and joints, a task they can complete quickly and with great accuracy. They can also be used to cut dovetail joints and are a common tool for thicker intarsia projects. When a fine blade is used, the kerf of a scroll saw is all but invisible.
Scroll saws are comparatively safe. In particular, inadvertent contact between the blade and the operator's fingers is unlikely to result in serious injury.
Mode of operation
There are several 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 variant uses a solid "C" shaped arm, with the blade being mounted between the two ends of the "C". The parallel link type, used by Hawk, 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 which hold the blade.
The rigid arm scroll saw was popular until the 1970s but is no longer made. It has a single-piece cast iron frame. The blade is attached to a pitman arm on the bottom, which pulls the blade down. A spring in the upper arm pulls the blade back up again. This design has a significant weakness in that the tension on the blade changes with every stroke; modern scroll saws are all "constant tension" designs.
Blades
With the exception of blades made for very light duty saws, typical scroll saw blades are five inches long. The major types are:
- Skip tooth (or single skip tooth) which have a tooth, a gap, and then another tooth;
- Double skip tooth (two teeth, a gap, then two teeth);
- Crown or two-way, which have teeth facing both up and down so that the blade cuts on both the down-stroke (as with all other blades) and the up-stroke;
- Spiral blades, which are essentially regular flat blades with a twist, so that teeth project on all sides;
- Metal cutting blades made of hardened steel;
- Diamond blades (wires coated with diamond fragments), for cutting glass.
Blades come in many weights, ranging from #10/0 (for making jewelry - about the size of a coarse hair) to #12, which is similar to a small band saw blade.
Another variation is called a reverse tooth blade. On reverse tooth blades, the bottom 3/4" of the teeth are reversed (point up). This arrangement helps to reduce splintering on the bottom edges of the cut. However, it does not clear sawdust out of the cut as well as a regular blade, so cutting is slower and produces more heat. This heat reduces blade life and makes scorching of the workpiece more likely. Reverse tooth blades are especially useful when cutting softwood and plywood such as Baltic birch.
The latest variation is called "ultra-reverse". These blades are configured with 4-5 teeth down and then one up and is repeated through the length of the blade. The blade clears dust very well and leaves a much cleaner back (very few "fuzzies"). These blades sizes range from #1 through #9.
References
Further reading
- Jensen, Laurits: Billedskærerbogen, 1986, ISBN ISBN 87-7490-263-6
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