Wood Technology

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Wood Technology

• January 4, 2007
• Woodworking
• Mr. Wecas

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Lumber Classifications
Hardwood
Softwood

• Broadleaved
• Deciduous
• Shed leaves at the end of a growing season

• Evergreen
• Conifers
• Cone bearing
• Needle bearing

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Grades of Lumber

• The quality or grade of lumber depends upon the
  pieces and amount of clear cuttings they contain.
• Standards are established by associations of
  lumber producers.

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Softwood Grades

• Based on American Softwood Lumber Standards PS
  20-70.
• Established by US Department of Commerce.
• Detailed rules are developed and applied by the
  various associations of lumber producers.

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Softwood Grades

• Lumber is classified into three categories
• Boards
• Dimension Lumber
• Timbers
• Each classification has several grades within it.
• Another classification is called Factory or Shop
  Lumber
• Used for doors, windows, moldings and other trim
  items.

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Softwood Lumber classifications and grades
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Hardwood Grades

• Grades for hardwood are established by the
  National Hardwood Lumber Association
• Founded in 1898
• Members include lumber producers as well as
  lumber retailers

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Hardwood Grades

• FAS (Firsts and Seconds)
• Not less than 6 in width
• Not less than 8 in length
• 83 1/3 clear cuttings
• Selects (FAS 1 Face)
• 4 wide by 6 long
• More defects on second or back face

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Hardwood Grades

• No. 1 Common
• Permits smaller pieces
• 66 2/3 clear cuttings
• No. 2 Common
• 50 clear cuttings
• No. 3 Common
• 33 1/3 clear cuttings

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Hardwood Grades

• No. 2 No. 3 common are not usually listed in
  hardwood catalogs.
• Retailers usually cut out defects and sell these
  as Shorts

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Lumber Defects
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Types of Warp

• Cup
• Edge to edge
• Bow
• End to end
• Crook
• End to end along edge
• Twist (Wind)

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Seasoning Lumber

• Green Lumber
• Fresh cut lumber
• Excessive moisture
• Must be removed before use
• Air Dried (AD)
• Simple exposure to air over a period of time
• Moisture Content reduced to 12 to 18 percent

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Seasoning Lumber

• Kiln Dried (KD)
• Lumber dried in huge ovens
• Temp and humidity carefully controlled
• Moisture content reduced to 7 to 10
• Free from internal stress
• Fewer defects from drying

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Seasoning Lumber

• Electrostatic Drying
• Microwave type ovens
• Better control of Moisture content
• Ideal for small run batches
• Faster removal of moisture
• Fewer defects
• Louisville Slugger (Baseball Bats)

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Cutting Methods

• Flat-Grained (Softwood)
• Plain Sawed (Hardwood)
• Cut from a log at angles of less than 45 degrees
• Most common means of cutting
• More likely to warp

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Cutting Methods

• Edge-grained (Softwood)
• Quarter Sawed (Hardwood)
• Cut from the log at angles of more than 45
  degrees
• More difficult to cut from log
• More waste
• Less likely to warp
• Produces attractive grain patterns

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Surface and Size

• Softwoods are surfaced on all four faces and
  edges is called S4S (Surfaced Four Sides)
• Hardwoods are purchased as
• RGH (Rough)
• S2S (Surfaced Two Sides)
• Not cut to standard width (RWL)

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Composite Board

• Hardboard
• Standard or Tempered
• Refined wood fibers and resins pressed together
  to produce a hard dense material
• 1/8, ¼, and 3/16 thick
• 4 x 8, 10, 12 or 16 lengths

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Composite Board

• Particle Board
• Wood flakes and chips bonded together with
  adhesives
• Large particles in the center for strength, small
  particles on surface for smoothness
• Base or core for plastic laminate counter tops
• Thickness from ¼ to 1 7/8
• 4 x 8 or 49 x 97

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Composite Board

• Waferboard
• Flakes about 1 ½ square
• Bonded together under heat and pressure with
  adhesive
• ¼ to ¾ thickness
• 4 x 8 sheets

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Composite Board

• Oriented Strand Board
• Similar to Waferboard
• Fibers arranged in layers at right angles to one
  another

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Plywood

• Constructed from thin veneers of wood glued
  together
• Grain direction is turned 90 degrees in
  successive layers
• Odd number of plies so that the face grain is the
  same on both sides.

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Plywood

• Varying core materials
• Veneer core
• Lumber core
• Composite core
• Thickness from 1/8 to more than 1
• Common sizes ¼, 3/8, ½, 5/8 and 3/4