| In the United States, standards for grading hardwood
are set by the National Hardwood Lumber Assn. The standards are
voluminous, replete with exceptions, special rules for certain species, and many details.
Here we will only try to illustrate the principles behind the grading, with a few
indications of how the home woodworker can use them. For details, contact the association. Unlike softwood, most hardwood is used in applications where appearance is
crucial, such as furniture. Hardwood being a natural product, no two boards are alike, and
almost all contain defects like knots that would be unacceptable in a piece of fine
furniture. In most cases, however, only one side of the board will show. The grading of
hardwood reflects that; it is based on the number and size of the ※clear face cuttings§每rectangular pieces free of
defects on the graded side每that could be cut from the board
being graded. The other side of a clear face cutting may contain defects, as long as they
don't affect the strength of the cutting. The fewer and bigger the clear face cuttings,
the higher the board's grade. Grading a board doesn't involve actually sawing the clear
face cuttings from it; they are purely conceptual.
The three top grades are
The remaining grades每2A, 2B, 3A and 3B每rarely reach the retail market; manufacturers make flooring, pallets and
similar products from them.
The best way of grasping the puzzle-like nature of grading hardwood
is to consider a real example. Here is one from the Wood Handbook, by the Forest
Products Laboratory of the U. S. Department of Agriculture (Washington, 1974).
In this case, the grader gets a board 12 feet long and 12 inches
wide. He examines both sides and senses it will make No. 1 Common, so he turns to the
poorer side, pictured above. One end is cracked, bark shows along both edges, and there
are several knots. According to the standard for No. 1 boards between 11 and 13 square
feet, a maximum of 4 clear pieces may be cut, which, if 3 inches wide, must be at least 3
feet long, and if 4 inches wide at least 2 feet每and the
cuttings must take in 66 2?3% of the area of the board. Can the
grader do it?
Although the National Hardwood Lumber Assn. defines grades called ※Firsts§ and ※Seconds,§
in practice the best boards are almost always sold as a combined grade,
FAS (which stands for &dquo;firsts and seconds§). From 20
to 40 percent of the boards in a lot graded FAS must be Firsts; the actual percentage
required depends on the species. Boards must be at least 6 inches wide and from 8 to 16
feet long; in a lot no more than 30% of the boards can be shorter than 11 feet, and
only half of those can be 8 or 9 feet long.
FAS grading is based on the poorest side of the board.
The clear face cuttings must be no smaller than 4 inches by 5 feet, or 3 inches by 7 feet.
As many as 4 cuttings are allowed, depending on the board's area. For a 4 square foot
board to qualify as a Firsts, for example, only 1 cutting can be made, but 3 cuttings are
allowed in a board with an area of 15 square feet or more. For larger boards, a choice of
two numbers of cuttings is offered, but the larger number must take in a greater
percentage of the board's area. For example, if the grading of a particular 12 sq. foot
board as Seconds is based on getting 3 clear face cuttings out of it, those cuttings must
include 83 1/3% of the board; but if 4 cuttings are planned,
they must take in 91 2/3% of the board's total surface.(As
seen in the sample boards to the right)
Unlike the other hardwood grades, Selects are graded on the basis of
the best side. Minimum width is 4 inches and lengths run 6 to 16 feet. In a lot,
30% of the boards may be 6 to 11 feet long, but only one-sixth of those may be 6 or 7
feet long. Except for those restrictions, Selects over 4 square feet are graded by the
same criteria as Seconds. Since Selects are cheaper than FAS, the home woodworker should
seriously consider them for any use in which only one side of the board will be seen.
A No. 1 Common board need only be at least 3 inches
wide; the minimum clear face cuttings size drops to 4 inches by 2 feet, or 3 inches by 3
feet. In a lot, 10% of the boards may be 4 to 7 feet long, and half of those may be 4 or 5
feet long. Even in the larger boards, where as many as 5 cuttings are permitted, the clear
face cuttings will take in at least 66 2/3% of the board.
(As seen in the sample boards to the right)
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The more detailes can view on following website:http://pearl.agcomm.okstate.edu:16080/forestry/general/f-5041.pdf
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FAS - Highest grade in hardwood lumber. A board grading FAS must
be at least 6" wide and 8" long. All FAS boards must yield 83 1/3% in the
defined clear face cuttings. This grade is used mostly for moulding and millwork.
1C - Number 1 common is the "cutting" grade of hardwood
lumber and used extensively in furniture and cabinetry. Number 1 common boards must yield
66 2/3% in the designated clear face cuttings.
2C - Number 2 common boards must yield 50% in the designated cuttings.
In 2A grade, cuttings must be clear, 2B grade allows
sound cuttings. This grade is used in flooring, furniture, and cabinets.
3A - A hardwood grade used mainly in flooring, furniture frames and
pallets, 3A must yield 33 1/3% in the designated cuttings.
2C and Better - the entire grade mix of all Number 2 common and FAS
the log will yield.
WHAD - Worm holes a defect
WHND - Worm holes no defect (unlimited wormholes allowed in cuttings)
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Sel - Select cypress is the highest quality grade available. It
is ideal for use in paneling, moulding and other millwork.
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2C - Number 2 common cypress is used for all types of general
construction, trim, and pattern stock. This grade is determined by defect grading from the
standpoint of strength, thus allowing some knots, wane and split.
3C - Number 3 common cypress is used primarily for boxes, pallets, and
crates. This grade allows a considerable amount of knots, wane, split and other defects.
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4/4 - Lumber which is 1" thick.
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5/4 - Lumber which is 1 1/4" thick.
6/4 - Lumber which is 1 1/2" thick.
8/4 - Lumber which is 2" thick |
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