When cutting hardwood lumber into a usable piece of wood, often referred to as parts, the ratio of the volume of parts to the volume of lumber is called yield, and is usually expressed in percentages. In general, the higher the grade of lumber, the higher the yield. However, Select and 1Face lumber usually have a yield (clear on both faces) that is the same as No. 1 Common lumber.
Unlike softwood lumber, where the grade reflects the strength and therefore the load carrying capacity and safety of a particular piece when used in construction, hardwood lumber grading does not require a certified or licensed grader. Anyone can grade; however, a trained grader will probably be more accurate and quicker than an untrained grader.
Also, unlike softwood lumber, hardwood lumber is not marked with a uniform system of symbols or stamps indicating the grade, although there may be some crayon marks that make sense to a grader or a particular mill.
The grading rules are quite complex and require study. Some of the basic concepts and grading requirements or rules are given in Table 1. The steps for grading a piece of lumber are straightforward. For example, consider a piece of lumber that is 6 and 7/16 inches wide and 10 feet 9 inches long (Figure 1).
Figure 1. Shown are two possible clear cuttings of a hardwood board.
Step 1. Determine the species. Some species have special rules that must be considered.
Step 2. Determine the surface measure (SM) of the lumber. SM is the width, in inches and fractions, times the standard length in feet with no fractions or rounding, and then divided by 12, and this answer rounded to the closest whole number. For our example, SM=(67/16 x 10)/12=5.36=5 feet.
Step 3. Determine the poor face, which is the side with the lowest grade, or if both sides are the same, the face with the least clear area when grading.
Step 4. Assume a trial grade for the piece of lumber and then see if all the conditions for that grade are met. For our example, assume No. 1 Common.
Step 5. Determine if the lumber size requirementslength and widthare met for the chosen grade. For our example, the minimum lumber size of 3 inches x 4 feet is met.
Step 6. Determine the number of clear cuttings (or sound cuttings for No. 2B and 3B Common and certain other cases) that are permitted. Note that often you can take an extra cutting, but then the yield requirement is increased. Always drop any fractions; do not round up. In our example, the number of cuttings permitted is (5+1)/3=2 at 66 2/3 percent yield. You can take 3 cuttings if you increase the yield to 75 percent.
Step 7. Determine the cutting yield required by multiplying the SM by 10 (FAS), 8 (No. 1), 6 (No. 2), 4 (No. 3A), or 3 (No. 3B). These numbers increase to 11, 9, and 8 for FAS, No. 1 and No. 2 respectively, if you take an extra cutting. The yield required is expressed in cutting units. A cutting unit is 1 inch wide by 1 foot long. In our example, the cutting units required is SMx8=5x8=40 units in two cuttings or 5x9=45 units in three cuttings.
Step 8. Locate cuttings to obtain the maximum area; then, calculate the cutting area. Make sure the cuttings' sizes are not below the minimum size for the trial grade. A cutting that is 51/2 inches wide and 41/3 feet long is 61/2x41/3=281/6 cutting units. Measure cutting width using inches and fractions, and length using feet and fractions. Do not round the answer, but keep the fractions. In our example, there are two large cuttings; both meet the minimum cutting sizes of 4 inches x 2 feet or 3 inches x 3 feet. The first is 67/16 inches x 4 feet, which gives 253/4 cutting units. The second is 5 inches x 4 feet, which gives 20 cutting units. The total for these two cuttings is 453/4 cutting units which is greater than the 40 required for No. 1 Common. There is no need to take an extra cutting.
Step 9. When the piece grades No. 1 common, check the reverse side to see if the reverse is FAS grade. If so, and if a few other requirements are satisfied, then the piece is Select or FAS 1Face.
Step 10. Check to make sure that the piece qualifies for the anticipated grade in all other respects, which include the amount of wane (1/2 the length for FAS, for example), the amount of pitch outside the cuttings, and so on.
Clear cuttings are rectangular shaped areas, parallel to the edges of the lumber (not diagonal) that are free of knots on the grading face, and free of rot, pith, shake, and wane throughout the entire cutting as it is projected to the opposite face. The various cuttings cannot overlap each other. Mineral stain is admitted.
Sound cuttings are identical to clear cuttings except sound defects (such as knots, small holes, some discolorations, etc.) are admitted.
Simplified Hardwood Grades.

FAS 
No. 1 common 
No. 2 A&B Common 
No. 3A Common 
No. 3B Common 
Min. Board Width 
8 inches 
3 inches 
3 inches 
3 inches 
3 inches 
Min. Board Length 
8 feet 
4 feet 
4 feet 
4 feet 
4 feet 
Min. Cutting Size 
4"x5' 
4"x2' 
3"x2' 
3"x2' 
11/2"x2' 

3"x7' 
3"x3' 


approx. 
Basic Yield 
831/3% 
662/3% 
50% 
331/3% 
25% 
Req. Cutting Units 
SMx10 
SMx6 
SMx6 
SMx4 
SMx3 
No. of Cuttings 
SM/4 
(SM+1)/3 
SM/2 
Unlimited 
Unlimited 

(4 max) 
(5 max) 
(7 max) 


One Extra Cutting Yield 
SMx11 
SMx9 
SMx8 

