Effect of Induced Lateral Vibration of a Saw Tooth on the Cutting of Wood

The research reported is part of a program at the Ottawa Laboratory to conduct basic studies aimed at improving the log breakdown process. A single-point cutting apparatus was used. The introduction of lateral vibrations to the cutting tool, analagous to the back and forth motion of a hand knife, could reduce the heat caused by cutting and, thus, reduce the amount of cutting force required or improve cutting accuracy. Two types of vibrating devices were used: a mechanical vibrator for frequencies up to about 130 cps; and an electrodynamic shaker for frequenices over 130 cps. Wood samples were end-grain hard maple at 4 percent moisture content; specific gravity ranged from 0.69 to 0.78. Depth of cut was 0.010. Cutting speeds were of the order of 0.4 to 0.75 inch per second. Cutting direction was at right angles to the annual rings, except where this angle was studied as a variable. Two types of wood sample were used, one in which the cutting tooth became embedded in the wood, and one in which the cutting tooth was wider than the 0.150 inch wide wood sample. Lateral vibration double amplitudes of 0.013 to 0.015 inch were studied. With the electrodynamic shaker, no reduction in cutting force was detected above a cutting speed of 0.7 inch per second. In the narrow wood samples cutting force reductions of 50-70 percent were witnessed in the range of 120-300 cps. Reduction in cutting force begins only when the double amplitude in the cut reaches a value of 0.004 inch. It was found that an increase in the depth of cut to 0.012 and 0.016 inch reduces sharply the percentage of parallel cutting force reduction for given conditions. A general increase in cutting force was noted for higher density specimens, but there was no significant change in the percentage cutting force reduction. A slight increase of 10 to 20 percent occurs as the annual ring orientation varies from 90 degrees to the cutting direction to zero degrees. The surface finish is improved by lateral vibrations.

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