Science Fair Project Encyclopedia
A band saw is a certain type of saw that can be used for both woodworking and metal working, but which can be used for a variety of other materials as well. It gets its name because its blade consists of a band of metal with teeth on it. This band rides around on two large wheels stacked vertically with a space between them. Band saws are useful in that they can be used for cutting irregular shapes. The radius of a curve that can be cut on a particular saw is determined by the thickness of the blade.
Large Band Saws
Timber mills use very large band saws for ripping lumber; they are preferred over circular saws for ripping because of their smaller kerf (cut size), resulting in less waste.
The blades range in size from about (4" wide x 19' long x 22 ga thickness) to (16" wide x 62' long x 11 ga thickness). The saws are mounted on large mills and stretched very tight (with fatigue strength of the saw metal being the limiting factor). Band saws of this size need to have a deformation worked into them that counteracts the forces and heating of operation. This is called benching. They also need to be removed and serviced after every four hours of use. Sawfilers are the craftsmen responsible for this work.
The shape of the tooth gullet is highly optimized and designed by the sawyer and sawfiler. It varies according to the mill, type of wood being cut and the condition the wood is in. Frozen logs often require a frost notch be ground into the gullet to break the chips. The shape of the tooth gullet is created with a grinding wheel, which is shaped by hand, while running, with an abrasive brick. The sawfiler will need to maintain the grinding wheel's shape with periodic re-dressing of the wheel.
Head saws are large band saws that make the initial cuts in a log. They generally have a two to three inch tooth space on the cutting edge and sliver teeth on the back. Sliver teeth are non-cutting teeth designed to wipe slivers out of the way when the blade needs to back out of a cut.
Head saws may cut massive logs at up to five feet per second.
Resaws are small band saws (up to ten inches in width) that are optimized for a narrow kerf, and therefore low waste. They usually have about a one and three-quarter tooth space, 32' length and 16ga thickness (and a flat back).
Double cut saws
Double cut saws have cutting teeth on both sides (see sawfiler for a picture of a very small double cut). They are generally very large, similar in size to a head saw.
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