Study on Visual Grading of Dimension Lumbers of Chinese Fir

摘要

As one of the main plantation species and widely distributed in 17 provinces in southern China, Chinese fir is suitable for the construction of housing and many traditional houses in Southern are built from it. It can promote utilization of domestic dimension lumbers economically and efficiently by studying on visual grading of dimension lumbers of Chinese fir. In this study, the stumpages of 1577 pieces of dimension lumbers were collected from four main Chinese fir regions: Anhui, Hunan, Sichuan and Fujian, and they were graded into three groups: SS, No.1, and No.2 according to NLGA. The results showed that knots, wanes and skips were the main maximum strength reduced defects for dimension lumbers of Chinese fir, while knots were the only main maximum strength reduced defects for grade No. 1 and wanes, skips, and knots were the common maximum strength reduced defects for grade No.2; The dimension lumbers from different regions had different types of defects. It is believed that the growing situation of Chinese fir was the main reason for dimension lumbers in Sichuan having obvious skips and slope of grain for grade No.1 and No.2 separately.