Band saw
Band Saw - can be used for both woodworking and metal working. Other materials that can be cut with a band saw include cardboard, styrofoam, and plexiglass, depending on the type of blade it is equipped with.
A Basic Description of a Band Saw
A band saw 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. Some band saws made for cutting metal bars have two horizontally stacked wheels which move up and down while the material to be cut is clamped in a vise. As the blade spins it comes down off the top wheel and out of the machine's casing. The blade is exposed here and then disappears again as it passes into a slot on the table portion of the saw. Then it goes around the bottom wheel and back up the top again.
Overview of how to operate a Band Saw
Before turning the saw on, adjust the guard to about 1/4 of an inch above the workpiece. The workpiece is placed on the table and can be maneuvered to cut it to the desired size or shape. Cutting material that is not flat on the table is dangerous.
- Read all warning labels and the owners manual before operating a band saw.
- When not in operation, the blade guard should be lowered to the table.
- It is good practice to release blade tension when the saw is not in use. This increases blade life.
- Make sure the guard is adjusted to reveal as little of the blade as practical.
- Use a push stick when making cuts that would otherwise require fingers to be close to the blade.
- Disconnect power when changing blades or performing maintenance.
Band saws 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.
So the blade determines two things, what material can be cut and how.
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, 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.
Tooth kerf for these saws are usually made from the saw's base metal by a swaging-shaping-grinding operation, although stellite and carbide teeth are sometimes used.
Band saws for timber mills are either left or right handed, depending on which way they are run and which side of the log the plank falls from. To determine which, lay the saw down, with the teeth pointing toward the sky, step inside the saw, and see which hand fits into the tooth gullet. Double cut saws always need to have their right hand teeth ground first, since the left hand teeth are an even reference surface.
Fitting is the forming, grinding and sharpening of the teeth, generally done after every four hours of operation. The gullet of the tooth is also ground at this time to prevent fatigue cracking. When a mill has only right handed grinding equipment, a double cut or left handed saw needs to be turned inside-out. This is quite an experience with a saw weighing several hundred pounds.
The shape of the tooth gullet is highly optimized, 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
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
Resaws are small band saws (up to eight 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.
See also
