Re: Lumber grading - the very basics
8 ) Understanding of F1F basic grade requirements. F1F is the abbreviation for FAS ONE FACE. Meaning the poor side of the board must grade to #1 common and the good side of the board must grade to FAS. It may be hard to understand that lumber cut from the out side of the tree usually yields a higher grade than lumber that’s closer to the pith. As a sapling grows it side shoots lots of branches as it also continues to gain height, as it grows taller it sheds it’s lower branches. New girth growth grows over the shed branch sockets and continues to produce new wood. It’s this new growth that produces higher quality and grade than when the tree was young. In todays hurry up world, not many forest trees are allowed to remain standing long enough to produce high amounts of FAS lumber. At some point I would like to write up something about log grades and lumber that can be expected but that’s another subject for another time.
As you would expect the grade rules are the same for FAS, here’s a summary:
* Minimum board size of 6” wide x 8’ long
* Minimum cutting size of 4” wide x 5’ long or 3” wide x 7’ long
* F1F yield is SM x 10 or 83 1/3%
* Formula to calculate number of allowable cuts is SM / 4 with a maximum of 4
9) Let’s take a look at an
F1F example; the poor side is identical in respect to the number and size of clear cuttings to our #1 common example, so we already know the poor side grades to #1 common. However, note the 9’ long end grain split on the right hand side of the example, it’s not a surface check, it’s actually a split that is present on both sides of the board. For the purpose of understanding the basics and simplicity we’ll round the spit defect up to a length of one foot long. Also note the arched lines on the right hand side as characteristic of a board sawn from a log that had trapper on the small end of the log and can either be wane (bark) or missing wood. Since we already know the poor side grades to #1 common, does the good side grade to FAS?
9-1) First calculate Board Foot (BF)
Thickness 2 * Width 8 * Length 8
---------------------------------- = 10.67 BF
12
9-2) Calculate the surface measure (SM)
Width 8 * Length 8
--------------------- = 5.33 SM (5 rounded)
12
9-3) Calculate the number of cutting units (CU) contained in the example
Width 8 * Length 8 = 64 CU
9-4) Calculate number of allowable FAS cuttings to make grade
SM (5)
----- = 1.25 FAS allowable cuts (1 fraction dropped)
4
9-5) Calculate FAS CU Yield required
SM (5) * 10 = 50 FAS cutting units required
9-6) Calculate Clear Cutting Units of clear piece on the good side of the board, Width 8 * Length 7 = 56 Clear Cutting Units
As you would expect the board in this example does qualify for the F1F grade by making one cross cut at approx 1 foot from the end leaving a 8” wide 7’ long piece of lumber. FAS clear cutting yield equals 50 and the actual clear piece of lumber after our one allowable cut represents 56 clear cutting units.
