Gage
Use the standard gage (blade thickness) except when the increased thickness of the workpiece decreases accuracy and width cannot be increased to compensate.
Examples of heavy gage applications:
1.When radius cutting in thick materials.
2.When the maximum width usable on the machine still provides insufficient beam strength for the blade. (Beam strength is the blade’s resistance to compression caused by strong feeding or the type of material being cut).
Pitch
Pitch is measured in “teeth per inch” (T.P.I.) and can be constant or variable. Figure 23 shows blades with different pitches. A fine pitch (more teeth per inch) will cut slower 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 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 shavings and overheat the blade.
As a general rule, use a blade that will have no fewer than 6 and no more than 12 teeth in the workpiece at any given time.
The chart on page 23 will aid in determining pitch for a particular job.
Shape
Figure 24 shows common types of tooth shape. Tooth shape has an effect on cutting rate.
The Regular blade, sometimes called a “raker” blade, has evenly spaced teeth that are the same size as the gullets, and a 0-degree rake angle. This is a good general-purpose blade, and often works well with ferrous metals.
The Skip type has fewer teeth and larger gullets, providing the added chip clearance needed for cutting softer, nonferrous materials, as well as non-metallic applications such as wood, plastic, cork, and composition materials.
The Hook blade has larger teeth and gullets and a positive rake angle which permits better feed and chip removal. It is useful for both cast iron as well as hard, nonferrous alloys.
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Figure 23
Figure 24
