Band saw
From Wikipedia, the free encyclopedia
A band saw uses a blade consisting of a long, narrow, flexible band of toothed metal, and may be powered by wind, water, steam, electrical motor or animal power. The band rides on two wheels in the same vertical plane with a space between them. 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.
Contents |
[edit] Metal-cutting band saws
When cutting metals, coolant is often used to provide a constant flow of liquid coolant over the blade. The coolant keeps the blades cool, which prolongs blade life. Wire brushwheels are sometimes used to remove chips and encrustation from the blade as it exits the material. Metal-cutting 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 come in two styles - horizontal and vertical. Small, manual shop saws usually employ a gravity-fed blade that falls in an arc around a pivot point and are of the horizontal style. The rate of descent is controlled by a hydraulic cylinder that has an adjustable valve. When a manual saw is set up for a cut, the operator raises the saw by hand and leaves it in a 45 degree up position. The material is put into the saw, clamped, the saw is turned on, and the blade slowly falls 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.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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 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 with a grinding wheel. The sawfiler will need to maintain the grinding wheel's profile with periodic dressing of the wheel.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] See also
[edit] Safety Information
[edit] References
- Mark Duginske (1989). The Bandsaw Handbook. Sterling Publishing. ISBN 0-8069-6398-0
|
||||||||
