The NHLA grading rules used in the US hardwood industry are based on imperial (inches and feet) units. But most export markets are more familiar with the metric system. In addition, the grading rules do not specify the width and length of the board.
Standard thickness of rough sawn timber
The standard thickness of rough sawn timber is expressed in quarters of an inch. For example: 1 inch = 4/4 inch. Most American hardwood sheet saws are between 1 inch and 2 inches thick, although there are other thickness specifications, but the number is limited. The following are standard thickness specifications and corresponding metric sizes: 3/4 (3/4" = 19.0mm) 6/4 (1 1/2" = 38.1mm)
4/4 (1" = 25.4mm) 8/4 (2" = 50.8mm)
5/4 (1 1/4" = 31.8mm) 10/4 (2" = 63.5mm)
Board ruler
The ruler (BF) is the basic unit for measuring hardwood boards.
One ruler unit is 1 foot (length) x 1 foot (width) x 1 inch (thickness). (1 foot = 0.305 meters, 1 inch = 25.4 mm)
The formula for measuring the plate ruler is: [width (inches) x length (feet) x thickness (inches)] ÷ 12
The proportion of the net facet in each grade is measured in this 12-digit unit of measure.
Thousands of feet as the name suggests is a thousand feet (BF), the English abbreviation is MBF, 1MBF = 2.36M3
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