The Relation of Mechanical Properties of Wood and Nosebar Pressure in the Production of Veneer

Research reported in this paper attempts to establish what takes place when wood is cut into veneer by the rotary-cutting process, particularly the relationships between the mechanical properties of wood and nosebar pressure. Checking frequency, depth of check penetration, veneer thickness, and surface quality were observed for 20 machining conditions. The effect of cutting temperature was demonstrated. Strength in compression and tension perpendicular to the grain and rolling shear were determined at four temperatures. Veneer was produced by an experimental method suggested by Franz, which involves orthogonal cutting perpendicular to the grain with knife edge and nosebar perpendicular to the direction of relative motion of the cutting fixture and the work piece. This generates a plane surface parallel to the original work surface. If a small segment of the outer periphery of a large veneer bolt is considered to approach a straight line, orthogonal cutting may be considered analogous to rotary cutting. Results led to the following conclusions: 1) The veneer-cutting process is characterized by two extremes: a) veneer formed by a splitting and bending process, containing severe lathe checks and rough surface qualities, and b) veneer formed by a peeling process, with superior surface qualities and an absence of lathe checks. 2) The nature of wood failure ahead of the knife determines the quality of veneer formed, and surface quality is a function of this wood failure. 3) The type of wood failure is a function of wood properties and force relationships in the veneer particle. 4) Mechanical properties of the wood define the nature of the failure under a given force system. 5) Nosebar pressure influences veneer quality by establishing additional forces within the veneer particle. 6) Frictional forces at the knife are important because they affect force relationships within the veneer particle. 7) Compression and tension perpendicular to the grain and rolling shear appear to have the most significant effect on veneer quality. 8) An increase in the temperature of the veneer reduces tension perpendicular to the grain more than compression or rolling shear.

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