band saws

BAND SAWS

Band saws should be used when curves are cut in flat sheets or when formed parts are rough trimmed. They are also used for making straight cuts in thick sheets of Chemcast® GP. For production work, large saws with a 30" to 36" throat are best, although smaller band saws are satisfactory for small work. The saw should have provision for adjusting the speed of the blade to suit the work. The blade should run at a speed of 2,300 to 5,000 feet per minute. As a general rule, as the thickness of the Chemcast® GP increases, the speed of the saw should decrease. Speed, feed, and thickness of the Chemcast® GP should be balanced so that each tooth cuts a clean chip. If the speed is too high in proportion to the feed, the teeth will rub and overheat the material instead of cutting freely.

Metal cutting blades stay sharp longer than blades designed for cutting wood and are better for use on Chemcast® GP. They are supplied by several manufacturers in 100 foot coils and can be cut to the proper length and brazed or welded. The weld must be annealed and dressed.

Blade thickness, width, and the number and type of teeth depend on the size of the band saw, the thickness of the material to be cut, and the minimum radius to be cut. Band saw blades of 1/4 "to 3/8" width should be used for cutting curves; blades of 1/2" to 3/4" width should be used for straight ripping or cutting large radius curves. The diameter of the band saw wheels will determine the maximum thickness of the blade. The thickness of the blade increases as the diameter of the wheels increase.

Special band saw blades, called "skip tooth" or "buttress" blades, have been developed for soft materials such as plastics, and are available with 2, 3, 4 or 6 teeth per inch. These blades are hardened and will retain their sharpness for long periods when used only for cutting Chemcast® GP acrylic sheet.

BAND SAW OPERATION

The tension on the saw blade should be just enough to prevent slipping on the wheels but not enough to stretch the blade and cause misalignment. The guide rolls or blocks should be set so they just miss the teeth but support the rest of the blade width. They should be set so that their rotation can be stopped with pressure from the thumb and forefinger when the saw is turned by hand. The backup roll should be adjusted so that it does not turn when the saw is idling, but will provide support while the saw is cutting. The upper guide should be placed within ½" of the Chemcast® GP. When cutting formed sections, it may be necessary to raise the upper guide. When this is done, extra care is neces sary to insure proper alignment. For added safety, the upper guide should be as low as possible.

The action of the saw carries sawdust from the Chemcast® GP and the masking paper onto the wheels. The dust builds up on the wheels and may cause the blade to run off, therefore, this accumulation of dust must be removed. Stiff bristle brushes can be placed so that they touch the tires and clean them as they revolve. The brushes should be held with a light spring tension so that they will make contact, yet not cause excessive wear on the tires.

Internal cuts may be made by drilling a hole through the Chemcast® GP and cutting and welding the blade inside the hole. Once the internal cut is made, the blade must be re-cut, removed from the hole, and re-welded. This technique may be useful for special jobs but is too time consuming for production use.

When cutting unmasked Chemcast® GP on a band saw, special care must be taken to prevent scratching. The saw table must be kept clean and should be free of nicks or burrs. Kraft paper or cardboard should be placed on the table under the unmasked Chemcast® GP. Tape or rubber cement can be used to hold the paper and the Chemcast® GP together to assure that both will move through the saw together. When trimming flanges on formed parts, the flange will slide on the saw table so any scratching will not be objectionable for most applications. For other curved work, a piece of wood about 1/2" thick by 1"wide can be run partially through the saw and clamped to the saw table at the ends. The main portion of the Chemcast® GP part will be raised slightly above the saw table while the kerf is supported by the wood strip.

MX-2: Cutting Chemcast GP and Vical Sheet