Effects of Sawtooth Edge Defects on Cutting Forces and Sawing Accuracy

Forces induced on the teeth of a saw blade when the edges are damaged were measured by means of a single-tooth cutting apparatus. If the edge of a tooth departs by 12.5 degrees from the perpendicular to the cutting direction, lateral forces of up to 23 percent of the corresponding force measured in the cutting direction (the principal force) can be generated. The species were green red pine (Pinus resinosa Ait.), white spruce (Picea glauca (Moench) Voss) and yellow birch (Betula alleghaniensis Britt.) cut at right angles to the annual rings. When a tooth corner is broken, and the magnitude of damage is of the order of the bite per tooth (0.050 inch in our case) the lateral force is 27 percent of that of the principal force and the principal force increases by 33 percent. In the case of similar damage to two or more successive teeth, these percentages become 25 percent and 65 percent. When sawing a random sample of 24 white pine, white spruce, and red pine, cants 12 to 16 feet long, a 12-inch wide band saw blade was found to yield average thickness variation of 0.119 inch when 25 successive tooth corners were similarly damaged. With intact teeth, the variations were only 0.065 inch.

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