Useful woodworking terms and there meanings.
The square foot (plural square feet; abbreviated ft² or sq ft) is an imperial unit. It is defined as the area of a square with length of its sides being 1 foot. A square foot is 144 square inches. Multiply the length by the width (both in inches) and divide by 144. It is the equivolent of a unit 12″ wide and 12″ long.
A board foot is one foot long, one foot wide, one inch thick (144 cubic inches).
To determine the board feet in a board:
Multiply the length, width and thickness (in inches) and divide by 144. This is your total board feet. A board 2″ by 12″ equals 2 board feet.
Multiply the width in inches by the length in feet and divide by 12. If the lumber is thicker than one inch, multiply by the thickness.
Thickness of rough sawn lumber is expressed in quarters of an inch (4/4, 5/4, 6/4, etc). The translation is easy. If a board is marked 4/4 (four quarters); going back to math class (4 divided by 4 = 1 or in this case 1″).
4/4 = 1″
5/4 = 1-1/4″
6/4 = 1-1/2″
8/4 = 2″
12/4 = 3″
Rough sawn lumber is usually 1/16″+ over the stated fraction:; however, surfaced lumber is thinner.
4/4 = 1 – 1/16″ to 1 – 1/8″ and should finish to 13/16″
5/4 = 1 – 5/16″ to 1 – 3/8″ and should finish to 1 – 1/16″
SURFACE MEASURE (S.M.)
Surface Measure (S.M.) is a unit of measure used for grading lumber. You will see this number being used in the ‘Lumber Grading’ section.
Surface Measure (S.M.) is the surface area of the board in square feet. The percentage of clear wood required for each grade is based on the surface measure (S.M.) not the board feet, thus all boards, no matter the thickness, are graded the same.
To determine S.M.:
Multiply the full width of the board by the standard length of the board and divide by 12, rounding to the nearest whole number.
Lumber grading is a function of board size and the amount of clear (defect free) surface area.
THE STANDARD GRADES
All boards are graded from the poor face. The clear face percentage for each grade is determined by measuring the width of the clear area in inches multiplied by the length of the clear area in feet. The total is referred to as cutting units.
FAS FIRSTS AND SECONDS
Minimum percentage clear: S.M. x 10 or 83 1/3% (10/12) Minimum size board: 6” x 8’
Minimum size clear cuttings: 4”x 5’ or 3” x 7’
FAS ONE FACE (F1F) AND SELECTS
Minimum size board: F1F: 6” x 8’ Sel 4” x 6’
These two grades combine the standard grades of FAS (on the better face) and No. 1 Com (on the poor face).
NO. 1 COMMON
Minimum percentage clear: S.M. x 8 or 66 2/3 % (8/12) Minimum size board: 3” x 4’
Minimum size cuttings: 3” x 3’ or 4” x 2’
NO. 2A COM
Minimum percentage clear: S.M. x 6 or 50% (6/12) Minimum size board: 3” x 4’
Minimum size cuttings: 3” x 2’
Note: When No. 2A Com. on poor face, the better face does not matter.
NO. 3A COM
Minimum percentage clear: S.M. x 4 or 33 1/3 % (4/12) Minimum size board: 3” x 4’
Minimum size cuttings: 3” x 2’
QUARTER SAWN (Q.S) LUMBER
Quarter sawn / vertical grained lumber. Most stable and strongest cut of lumber.
RIFT SAWN LUMBER
Diagonally grained lumber.
FLAT SAWN LUMBER
Lumber sawn parallel to the grain.
Warp on the face of a board from end to end.
Hollow across the face of a board.
Warp along the edge line, also known as crown.
A tight knot is usually not a problem. A loose or dead knot, surrounded by a dark ring, may fall out or may have already left a hole.
Crack going all the way through the piece of wood, commonly at the ends.
Multiple bends in a board.
Crack along the wood’s annual growth rings, not passing through the entire thickness of the wood.
Separation of grain between the growth rings, often extending along the board’s face and sometimes below its surface.
Missing wood or untrimmed bark along the edge or corner of the piece.