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.
•The features of the workpiece, 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
Width
Band saw blades come in different standard widths, measured from the back edge of the blade to the tip of the tooth. Generally, wider blades are used for ripping or making straight cuts, such as resawing. 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 drift (see “Blade Lead”).
Pitch
Pitch is measured in “teeth per inch” (T.P.I.) and can be constant or variable. Figure 53 shows blades with different pitches.
A fine pitch (more teeth per inch) will cut slowly but more smoothly. A coarse pitch (fewer teeth per inch) will cut faster but more roughly.
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 clean cuts.
Using a blade with too few teeth may cause vibration and a rough cut, while too many teeth may cause the gullets to fill with sawdust and overheat the blade.
As a general rule, use a blade that will have from 6 to 12 teeth in the workpiece at any given time.
Figure 53 – Blade Pitch
Shape
Figure 54 shows common types of tooth shape, or form. Tooth shape has an effect on cutting rate.
The Regular, or standard blade, has evenly spaced teeth that are the same size as the gullets, and a zero-degree rake (i.e. cutting angle). These offer precise, clean cuts at slower rates. It is usually a good choice for cutting curves and making crosscuts.
The Skip type has fewer teeth and larger gullets with a zero rake. It allows faster cutting rates than the Regular type, with a slightly coarser finish. It is useful for re-sawing and ripping thick stock, as well as cutting softwoods.
The Hook type blade has larger teeth and gullets and a positive rake angle for more aggressive, faster cutting when re-sawing or ripping thick stock, especially hardwoods.
Variable-tooth blades combine features of the other shapes, with tooth style and spacing varying on the same blade. This produces smooth cuts while dampening vibration.
Figure 54 – Blade Tooth Shape
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