CUTTING RESISTANCE OF HINOKI LUMBER CONTA INING A KNOT

Monochrome photographs of the surfaces of lumber of hinoki (Chamaecypa ris obtusa Endl.) containing single knots were taken under sunlight fr om three different incident directions to estimate the grain angle. Th e gray level profiles of these photographs were scanned along the long itudinal direction at 1.25 mm or 2.5 mm intervals in the tangential di rection. Cutting resistances were measured at the same places. The dar k and light parts of a knot due to the heartwood and sapwood of a bran ch, branch/trunk interface, and trunk area were detected from the gray level profiles with the variations of light reflections. Thus when th e cutting direction was from the upper to the down side of the knot, t he cutting resistance was more in the areas with sloped grain around t he knot and most in the dark parts of the knot. But when the cutting d irection was from the down to the upper side of the knot, the cutting resistances were a little different between the areas with sloped grai n around the knots and in the trunk area.