Trimming Plywood By Inclined Cutting Using a Disk

A problem sometimes encountered in plywood production is chipping of the surface veneers at the edge when the ends of sheets are saw-trimmed. When a saw is used, the edge of the tooth that cuts across the fibers has very little inclination to its direction of motion, and the edge and motion are both perpendicular to the grain. Experiments were conducted using mountain ash plywood comprising three veneers nominally 1/8- inch thick. A rotating disk was used in the experiments of 11-l/2 inches diameter, and the edge had a rake angle of 50? and .a clearance angle of 5?. At 50 rpm, which produced a rim speed of 150 feet per minute and a feed speed of 1/5 feet per minute, the line of feed at which there was minimum force component normal to the sheet was found to be offset 3-1/2 inches from the center line. For this condition the range of no break-out was small, and a small amount of break-out did occur on both edges. When the spindle speed was raised to 200 rpm the range of no break-out was increased to nearly 2 inches. Thus a disk could be used advantageously following an ordinary trim saw in cases where breaking out cannot be brought to an acceptable level by optimum sawing practice.

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