Cosen C-620NC, Instruction Manual, Page: 77 / 122

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Material size and shape
The optimum material width for a band saw blade is 1 inch wide by 0.35 inch thick and is about 5
inches long. Below this width tooth loading may become excessive and the cutting rate must be
reduced. Above this width blade control begins to be lost, as discussed below. Since the blade "sees"
only that material it is cutting, the shape of the stock being cut will also affect cutting speeds,
particularly if the piece is excessively wide or if it varies in the dimensions being cut.
Guide spacing
The rigidity of the blade is a function of guide spacing, with rigidity being reduced to the third power
as the distance between the guides increases. For example, with guides spaced 2 inches apart, blade
deflection might be approximately 0.2. Under the same conditions, but with the guides spaced at 4
inches apart, blade deflection would be approximately 0.8.
This is a much simplified version of the formula, because it does not consider band tension or guide
design. It is important to recognize, for example that rollers are considered as a pivotal contact.
Whereas carbide faces could be considered as anchored supports. A more complete deviation,
including band tension and guide design, is included in Roark's handbook, "Formula for stress and
strain".
Blade selection
There are different types of blades available. Please contact a bandsaw blade manufacturer for
advice.
Blade speed and feed
Blade speed is generally limited by vibration and the ability to keep the blade sufficiently cool to
avoid dulling the teeth. A blade which is running fast and taking a very light cut will dull quickly
because the tips of the teeth will overheat from the rubbing action. If, however, we force the blade
teeth deeper into the material, the blade will be less sensitive to heat, because the teeth are cutting
more and rubbing less.
Tooth form and spacing
The selection of a tooth form generally is determined by the material to be cut. There are three
general factors to consider: tooth form, style or shape of the teeth; tooth spacing, the number of
teeth to the inch; and tooth set, which provides clearance for the body of the blade. Three styles of
tooth are shown in Fig. 7.3 below:
Fig. 7.3 Three Styles of Tooth