Dynamometer Tests on . . . Cutting Action of Chain-Saw Teeth

Little research has been done on multiple cutters for continuous cross-cutting under controlled conditions, which could lead to improvements in chain saws. A 38-inch saw disk driven by an accurate dynamometer with stable speed control was used to cut samples held on a lathe carriage and fed at a controlled rate by the lead screw. Ponderosa pine cants 12 by 12 inches square and 16 feet long were cut. For each cutting speed, a maximum cutting rate occurs at a different feed rate. This results in an optimum bite, which is the theoretical thickness of each chip just before it is formed. With adequate chip removal, stable cutter behavior, and no friction losses in the drive, cutting rate at a given power is the same for high speed and few teeth as it is for low speed and many teeth. The procedure for rating the machinability of test samples permitted a definite rating of cutting efficiency for various cutters. Plotting corrected cutting rate against bite gave a rating which could be used to predict performance at any given speed and feed. The cutting efficiency decreased with small bites, and vibration was extremely wasteful of power. Chain cutter action was affected by the mass of the supporting bar; the effect of kerf width on cutting efficiency varied greatly with bite; and feed pressure requirements were much lower with moderately high cutter velocities.

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