Full Product Manual

8
of 0.250-inch to 0.375-inch width should be used for cutting
curves; blades of 0.50-inch to 0.75-inch widths 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 increases.
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 should
be used when cutting thicknesses greater than 0.472 inches. These
blades are hardened and will retain their sharpness for long periods
when used only for cutting Plexiglas
®
acrylic sheet.
Variable pitch (number of teeth per inch) blades work well in
reducing chipping when cutting sheet 0.472 inches thick or less.
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. When cutting formed sections, it may be neces-
sary to raise the upper guide. When this is done, extra care is
necessary to insure proper alignment. For added safety, the
upper guide should be as low as possible (within
1
⁄
2 inch of the
Plexiglas
®
acrylic sheet).
The action of the saw carries sawdust from the Plexiglas
®
acrylic sheet 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 Plexiglas
®
acrylic sheet and cutting and welding the blade inside the hole.
Once the internal cut is completed, the blade must be recut,
removed from the hole, and rewelded. This technique may be
useful for special jobs but is too time-consuming for production use.
When cutting unmasked Plexiglas
®
acrylic sheet 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 sheet. Tape or rubber cement can be used to
hold the paper and the Plexiglas
®
acrylic sheet together to ensure
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-inch thick by
1.0 inch wide can be run partially through the saw and clamped
to the saw table at the ends. The main portion of the acrylic
part will be raised slightly above the saw table, while the kerf is
supported by the wood strip.
For Plexiglas
®
MC acrylic sheet, band saw blades should be of
the edge-hardened metal-cutting type with raker set or broach-style
teeth. Blades should have 10 to 14 teeth per inch. Speeds should
be between 2,300 and 5,000 feet per minute. In general, the thicker
the stack of material, the slower the blade speed should be to
avoid overheating. Blade speed and material feed and thickness
should be such that each saw tooth cuts a clean chip. The welded
joint of the blade should be smooth and carefully aligned to prevent
chipping or cracking of the material during the cutting operation.
A band saw cut should not be considered a finished edge and, if
not a rough cut, should be further finished by scraping.