JET Tools JWBS-18-3 User Manual - Page 23

Resawing, Blade lead, Saw blade selection, Width, Pitch

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Figure 9-3 9.4 Resawing Resawing is the process of slicing stock to reduce its thickness, or to produce boards that are thinner than the original workpiece. Figure 9-4 demonstrates resawing. The ideal blade for resawing is the widest one the machine can handle, as the wider the blade the better it can hold a straight line. When resawing thin stock, use a push block, push stick, or similar device to keep your hands away from the blade. Figure 9-5 9.6 Saw blade selection Using the proper blade for the job will increase the operating efficiency of your band saw, help reduce necessary saw maintenance, and improve your productivity. Thus, it is important to follow certain guidelines when selecting a saw blade. Here are factors to consider when selecting a blade: ˆ The type of material you will be cutting. ˆ The thickness of the workpiece or part. ˆ The features of the workpiece or part, such as bends or curves with small radii. These factors are important because they involve basic concepts of saw blade design. There are five (5) blade features that are normally changed to meet certain kinds of sawing requirements. They are: 1. width 2. pitch (number of teeth per inch) 3. tooth form (or shape) 4. the "set" of the teeth 5. the blade material itself. Figure 9-4 9.5 Blade lead Blade lead, or drift, is when the blade begins to wander off the cutting line even when the band saw fence is being used. Figure 9-5 shows an example of blade lead. It is more common with small, narrow blades, and is almost always attributable to poor blade quality, or lack of proper adjustments. Inspect the band saw for the following: • Fence not parallel to miter slot and blade. • Blade not tensioned correctly. • Blade is dull. • Teeth have excessive "set" on one side of blade. • Workpiece being fed too quickly. 9.7 Width Band saw blades come in different standard widths, measured from the back of the blade to the tip of the tooth. Generally, wider blades are used for ripping or making straight cuts; narrower blades are often used when the part being cut has curves with small radii. When cutting straight lines with a narrow blade, the blade may have a tendency to wander, causing blade lead. (refer to sect. 9.5). 9.8 Pitch Pitch is measured in "teeth per inch" (TPI). Figure 96 shows blades with different pitches. A fine pitch (more teeth per inch) will cut more slowly but smoother. A coarse pitch (fewer teeth per inch) will cut rougher but faster. As a rule of thumb, the thicker the workpiece, the coarser will be the blade pitch. If you have to cut a hard or very brittle material, you will probably want to use a blade with a finer pitch in order to get good clean cuts. 23

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23
Figure 9-3
9.4
Resawing
Resawing is the process of slicing stock to reduce
its thickness, or to produce boards that are thinner
than
the
original
workpiece.
Figure
9-4
demonstrates resawing.
The ideal blade for resawing is the widest one the
machine can handle, as the wider the blade the
better it can hold a straight line.
When resawing thin stock, use a push block, push
stick, or similar device to keep your hands away
from the blade.
Figure 9-4
9.5
Blade lead
Blade lead, or drift, is when the blade begins to
wander off the cutting line even when the band saw
fence is being used. Figure 9-5 shows an example
of blade lead. It is more common with small, narrow
blades, and is almost always attributable to poor
blade quality, or lack of proper adjustments. Inspect
the band saw for the following:
•
Fence not parallel to miter slot and blade.
•
Blade not tensioned correctly.
•
Blade is dull.
•
Teeth have excessive “set” on one side of
blade.
•
Workpiece being fed too quickly.
Figure 9-5
9.6
Saw blade selection
Using the proper blade for the job will increase the
operating efficiency of your band saw, help reduce
necessary saw maintenance, and improve your
productivity. Thus, it is important to follow certain
guidelines when selecting a saw blade.
Here are factors to consider when selecting a blade:
±
The type of material you will be cutting.
±
The thickness of the workpiece or part.
±
The features of the workpiece or part, such
as bends or curves with small radii.
These factors are important because they involve
basic concepts of saw blade design. There are five
(5) blade features that are normally changed to meet
certain kinds of sawing requirements. They are:
1.
width
2.
pitch (number of teeth per inch)
3.
tooth form (or shape)
4.
the "set" of the teeth
5.
the blade material itself.
9.7
Width
Band saw blades come in different standard widths,
measured from the back of the blade to the tip of the
tooth. Generally, wider blades are used for ripping
or making straight cuts; narrower blades are often
used when the part being cut has curves with small
radii. When cutting straight lines with a narrow
blade, the blade may have a tendency to wander,
causing
blade lead
. (refer to
sect. 9.5).
9.8
Pitch
Pitch is measured in "teeth per inch" (TPI). Figure 9-
6 shows blades with different pitches.
A fine pitch
(more teeth per inch) will cut more slowly but
smoother. A coarse pitch (fewer teeth per inch) will
cut rougher but faster. As a rule of thumb, the thicker
the workpiece, the coarser will be the blade pitch. If
you have to cut a hard or very brittle material, you
will probably want to use a blade with a finer pitch in
order to get good clean cuts.