Lathe Check Formation in Douglas-Fir Veneer

High-speed motion pictures of veneer cutting with a roller-bar production lathe were analyzed to determine the effect of production variables, such as nosebar pressure and cutting, speed, on veneer smoothness and depth of lathe cuts. The camera was mounted on framework normally supporting the veneer knife. The camera had a built-in timing device that made exposures on the edge of the film by means of a neon light flashing at 60 cycles per second. The following conditions were used: 1) low pressure, standard speed, 2) standard pressure, standard speed, 3) standard pressure, high speed, 4) high pressure, standard speed. The term standard refers to conditions the production lathe operator would use if he were peeling the log in regular production. The results indicate a modified type “A” veneer is produced by cutting at a steady rate for much of the distance between lathe checks. A lathe check is produced by an unstable “snap action” in an area stressed under tension normal to the break. In the range of the cutting speeds investigated (250 to 600 feet per minute), increasing the speed produced veneer with a slight improvement in smoothness. High pressure applied to nosebar produced a smoother veneer with shallower and more numerous lathe checks and with compression damage to the springwood structure.

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