Preliminary evaluation for quality of dimension lumber in four common softwoods in Mongolia

Journal of Wood Science

Official Journal of the Japan Wood Research Society

Table 5 Downgrading factors in the visual grading of lumber in each species

Factor	Grade	Quantity of downgraded lumber in each species (%)
Factor	Grade	Pinus sylvestris (n = 61)	Pinus sibirica (n = 39)	Picea obovata (n = 67)	L. sibirica (n = 37)
Knot	SS	1.6	2.6	37.3	10.8
	No. 1		2.6	7.5	5.4
	No. 2
	No. 3
ARW	SS–No. 2
ARW	No. 3
Wane	SS–No. 1	6.6	7.7	13.4	48.6
	No. 2	6.6	5.1	6.0	27.0
	No. 3	6.6	5.1	4.5	13.5
Fiber orientation	SS			1.5
	No. 1			1.5
	No. 2			1.5
	No. 3
Crack	SS			1.5	2.7
	No. 1			1.5	2.7
	No. 2				2.7
	No. 3
Crook	SS–No. 1		5.1	4.5	8.1
Crook	No. 2–3		5.1	4.5	8.1
Bow	SS–No. 1		2.6
	No. 2		2.6
	No. 3
Twist	SS–No. 1			25.4	32.4
	No. 2			9.0	18.9
	No. 3			3.0	13.5

n, number of lumber; ARW, annual ring width; SS, select structural. The value was calculated from the ratio of the lumber downgraded to total lumber number in each species. When the threshold values of the JAS for structural lumber and finger jointed structural lumber for wood frame construction [25] are the same in several visual grading classes in a factor, the classes were combined