MACHINE STRENGTH GRADING OF GREEN SAWN TIMBER

850 pieces of structural timber (European spruce, Picea abies) with cr oss-sections 50 to 95 mm thick and 85 to 295 mm wide were machine grad ed at three different stages of production, using a bending/radiation type grading machine: Immediately after sawing (green, sawn surface), after kiln-drying to approx. 12% (dry, sawn surface) and after planing (dry, planed). They were then subjected to strength and stiffness tes ts in bending and tension according to EN 408. Machine grading of gree n sawn timber resulted in correlation coefficients between 0.73 and 0. 80 and approximately the same yield as compared with machine grading o ff dried and planed timber. In all cases yield was higher than that ob tained with conventional visual grading according to DIN 4074.