Band saw

A band saw uses a blade consisting of a band of toothed metal, and may be powered by wind, water, steam, electrical motor or animal power. The band rides on two wheels rotating in the same plane. Band saws can be used for woodworking, metal working, or for cutting a variety of other materials, and are particularly useful for cutting irregular shapes. The radius of a curve that can be cut on a particular saw is determined by the width of the band and its lateral flexibility.

Metal-cutting band saws

When cutting metals or timber, a constant flow of liquid over the blade facilitates cutting by lubricating to keep the blade cool as well as preventing encrustation or smearing on the blade, prolonging blade life and making for greater cutting accuracy. Brushes or brushwheels are sometimes used to remove chips and encrustation from the blade as it exits the material. Band saws are available in vertical and horizontal designs. These units range from manually operated machines to fully automatic machines. Band speeds range from 40 feet per minute to 5000 feet per minute.

Machine shop bandsaws may also be horizontal or vertical. Small bandsaws may employ a gravity-fed blade or the rate of descent may be controlled by a hydraulic cylinder bleeding through an adjustable valve. When the saw is set up for a cut, the operator raises the saw by hand and the material is clamped in place and the saw is turned on, the blade slowly descending into the material, cutting it as the band blade moves. When the cut is complete, a switch is tripped and the saw automatically turns off.

Feed mechanisms

* Gravity feed saws fall under their own weight against a hydraulic cylinder which has a control valve. Common in small saws.
* Hydraulic feed saws use a positive pressure hydraulic piston to advance the saw through the work. Common in production saws.
* Screw feed employ a leadscrew to move the saw.

Fall mechanisms

* Pivot saws hinge in an arc as they advance through the work.
* Single Column saws have a large diameter column that the entire saw rides up and down on, very similar to a radial drill.
* Dual column saws have a pair of large columns, one on either side of the work, for very high rigidity and precision. The dual column setup is unable to make use of a miter base due to inherent design. Dual column saws are the largest variety of machine bandsaws encountered, to the point where some make use of a rotary table and X axis to perform complex cutting.

Automated saws

Automatic bandsaws feature preset feed rate, return, fall, part feeding, and part clamping. These are used in production environments where having a machine operator per saw is not practical. One operator can feed and unload many automatic saws.

Some automatic saws rely on NC/CNC control to not only cut faster, but to be more precise and perform more complex miter cuts.

Large band saws

Timber mills use very large band saws for ripping lumber; they are preferred over circular saws for ripping because they can accomodate large-diameter timber and 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 blades are mounted on wheels with a diameter large enough not to cause metal fatigue due to flexing when the blade repeatedly changes from a circular to a straight profile. It is 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 at regular intervals. Sawfilers or sawdoctors 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, as well as the type and condition of the wood. Frozen logs often require a frost notch ground into the gullet to break the chips. The shape of the tooth gullet is created when the blade is manufactured and its shape is automatically maintained with each sharpening. The sawfiler will need to maintain the grinding wheel's profile with periodic 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.

Resaws

A resaw is a large bandsaw optimized for cutting timber along the grain to reduce larger sections into smaller sections or veneers. Resawing veneers requires a wide blade - commonly 2" to 3" (52 - 78 mm) - with a small kerf to minimize waste. Resaw blades of up to 1" (26 mm) may be fitted to a standard bandsaw.

Double cut saws

Double cut saws have cutting teeth on both sides. They are generally very large, similar in size to a head saw

See also

* Portable Sawmill
* Chainsaw
* Circular saw
* Sawfiler

afety Information

* [http://www.safetyculture.com.au/procedures/Band_Saw_Safety_Procedure.php Band Saw Safety Procedures]

References

*Mark Duginske (1989). "The Bandsaw Handbook". Sterling Publishing. ISBN 0-8069-6398-0